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Diffstat (limited to 'fs/buffer.c')
| -rw-r--r-- | fs/buffer.c | 3429 |
1 files changed, 3429 insertions, 0 deletions
diff --git a/fs/buffer.c b/fs/buffer.c new file mode 100644 index 000000000..8c50a2250 --- /dev/null +++ b/fs/buffer.c @@ -0,0 +1,3429 @@ +/* + * linux/fs/buffer.c + * + * Copyright (C) 1991, 1992, 2002 Linus Torvalds + */ + +/* + * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95 + * + * Removed a lot of unnecessary code and simplified things now that + * the buffer cache isn't our primary cache - Andrew Tridgell 12/96 + * + * Speed up hash, lru, and free list operations. Use gfp() for allocating + * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM + * + * Added 32k buffer block sizes - these are required older ARM systems. - RMK + * + * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de> + */ + +#include <linux/kernel.h> +#include <linux/syscalls.h> +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/percpu.h> +#include <linux/slab.h> +#include <linux/capability.h> +#include <linux/blkdev.h> +#include <linux/file.h> +#include <linux/quotaops.h> +#include <linux/highmem.h> +#include <linux/export.h> +#include <linux/writeback.h> +#include <linux/hash.h> +#include <linux/suspend.h> +#include <linux/buffer_head.h> +#include <linux/task_io_accounting_ops.h> +#include <linux/bio.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/bitops.h> +#include <linux/mpage.h> +#include <linux/bit_spinlock.h> +#include <trace/events/block.h> + +static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); + +#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) + +void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private) +{ + bh->b_end_io = handler; + bh->b_private = private; +} +EXPORT_SYMBOL(init_buffer); + +inline void touch_buffer(struct buffer_head *bh) +{ + trace_block_touch_buffer(bh); + mark_page_accessed(bh->b_page); +} +EXPORT_SYMBOL(touch_buffer); + +void __lock_buffer(struct buffer_head *bh) +{ + wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE); +} +EXPORT_SYMBOL(__lock_buffer); + +void unlock_buffer(struct buffer_head *bh) +{ + clear_bit_unlock(BH_Lock, &bh->b_state); + smp_mb__after_atomic(); + wake_up_bit(&bh->b_state, BH_Lock); +} +EXPORT_SYMBOL(unlock_buffer); + +/* + * Returns if the page has dirty or writeback buffers. If all the buffers + * are unlocked and clean then the PageDirty information is stale. If + * any of the pages are locked, it is assumed they are locked for IO. + */ +void buffer_check_dirty_writeback(struct page *page, + bool *dirty, bool *writeback) +{ + struct buffer_head *head, *bh; + *dirty = false; + *writeback = false; + + BUG_ON(!PageLocked(page)); + + if (!page_has_buffers(page)) + return; + + if (PageWriteback(page)) + *writeback = true; + + head = page_buffers(page); + bh = head; + do { + if (buffer_locked(bh)) + *writeback = true; + + if (buffer_dirty(bh)) + *dirty = true; + + bh = bh->b_this_page; + } while (bh != head); +} +EXPORT_SYMBOL(buffer_check_dirty_writeback); + +/* + * Block until a buffer comes unlocked. This doesn't stop it + * from becoming locked again - you have to lock it yourself + * if you want to preserve its state. + */ +void __wait_on_buffer(struct buffer_head * bh) +{ + wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE); +} +EXPORT_SYMBOL(__wait_on_buffer); + +static void +__clear_page_buffers(struct page *page) +{ + ClearPagePrivate(page); + set_page_private(page, 0); + page_cache_release(page); +} + +static void buffer_io_error(struct buffer_head *bh, char *msg) +{ + char b[BDEVNAME_SIZE]; + + if (!test_bit(BH_Quiet, &bh->b_state)) + printk_ratelimited(KERN_ERR + "Buffer I/O error on dev %s, logical block %llu%s\n", + bdevname(bh->b_bdev, b), + (unsigned long long)bh->b_blocknr, msg); +} + +/* + * End-of-IO handler helper function which does not touch the bh after + * unlocking it. + * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but + * a race there is benign: unlock_buffer() only use the bh's address for + * hashing after unlocking the buffer, so it doesn't actually touch the bh + * itself. + */ +static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) +{ + if (uptodate) { + set_buffer_uptodate(bh); + } else { + /* This happens, due to failed READA attempts. */ + clear_buffer_uptodate(bh); + } + unlock_buffer(bh); +} + +/* + * Default synchronous end-of-IO handler.. Just mark it up-to-date and + * unlock the buffer. This is what ll_rw_block uses too. + */ +void end_buffer_read_sync(struct buffer_head *bh, int uptodate) +{ + __end_buffer_read_notouch(bh, uptodate); + put_bh(bh); +} +EXPORT_SYMBOL(end_buffer_read_sync); + +void end_buffer_write_sync(struct buffer_head *bh, int uptodate) +{ + if (uptodate) { + set_buffer_uptodate(bh); + } else { + buffer_io_error(bh, ", lost sync page write"); + set_buffer_write_io_error(bh); + clear_buffer_uptodate(bh); + } + unlock_buffer(bh); + put_bh(bh); +} +EXPORT_SYMBOL(end_buffer_write_sync); + +/* + * Various filesystems appear to want __find_get_block to be non-blocking. + * But it's the page lock which protects the buffers. To get around this, + * we get exclusion from try_to_free_buffers with the blockdev mapping's + * private_lock. + * + * Hack idea: for the blockdev mapping, i_bufferlist_lock contention + * may be quite high. This code could TryLock the page, and if that + * succeeds, there is no need to take private_lock. (But if + * private_lock is contended then so is mapping->tree_lock). + */ +static struct buffer_head * +__find_get_block_slow(struct block_device *bdev, sector_t block) +{ + struct inode *bd_inode = bdev->bd_inode; + struct address_space *bd_mapping = bd_inode->i_mapping; + struct buffer_head *ret = NULL; + pgoff_t index; + struct buffer_head *bh; + struct buffer_head *head; + struct page *page; + int all_mapped = 1; + + index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); + page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED); + if (!page) + goto out; + + spin_lock(&bd_mapping->private_lock); + if (!page_has_buffers(page)) + goto out_unlock; + head = page_buffers(page); + bh = head; + do { + if (!buffer_mapped(bh)) + all_mapped = 0; + else if (bh->b_blocknr == block) { + ret = bh; + get_bh(bh); + goto out_unlock; + } + bh = bh->b_this_page; + } while (bh != head); + + /* we might be here because some of the buffers on this page are + * not mapped. This is due to various races between + * file io on the block device and getblk. It gets dealt with + * elsewhere, don't buffer_error if we had some unmapped buffers + */ + if (all_mapped) { + char b[BDEVNAME_SIZE]; + + printk("__find_get_block_slow() failed. " + "block=%llu, b_blocknr=%llu\n", + (unsigned long long)block, + (unsigned long long)bh->b_blocknr); + printk("b_state=0x%08lx, b_size=%zu\n", + bh->b_state, bh->b_size); + printk("device %s blocksize: %d\n", bdevname(bdev, b), + 1 << bd_inode->i_blkbits); + } +out_unlock: + spin_unlock(&bd_mapping->private_lock); + page_cache_release(page); +out: + return ret; +} + +/* + * Kick the writeback threads then try to free up some ZONE_NORMAL memory. + */ +static void free_more_memory(void) +{ + struct zone *zone; + int nid; + + wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM); + yield(); + + for_each_online_node(nid) { + (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), + gfp_zone(GFP_NOFS), NULL, + &zone); + if (zone) + try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, + GFP_NOFS, NULL); + } +} + +/* + * I/O completion handler for block_read_full_page() - pages + * which come unlocked at the end of I/O. + */ +static void end_buffer_async_read(struct buffer_head *bh, int uptodate) +{ + unsigned long flags; + struct buffer_head *first; + struct buffer_head *tmp; + struct page *page; + int page_uptodate = 1; + + BUG_ON(!buffer_async_read(bh)); + + page = bh->b_page; + if (uptodate) { + set_buffer_uptodate(bh); + } else { + clear_buffer_uptodate(bh); + buffer_io_error(bh, ", async page read"); + SetPageError(page); + } + + /* + * Be _very_ careful from here on. Bad things can happen if + * two buffer heads end IO at almost the same time and both + * decide that the page is now completely done. + */ + first = page_buffers(page); + local_irq_save(flags); + bit_spin_lock(BH_Uptodate_Lock, &first->b_state); + clear_buffer_async_read(bh); + unlock_buffer(bh); + tmp = bh; + do { + if (!buffer_uptodate(tmp)) + page_uptodate = 0; + if (buffer_async_read(tmp)) { + BUG_ON(!buffer_locked(tmp)); + goto still_busy; + } + tmp = tmp->b_this_page; + } while (tmp != bh); + bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); + local_irq_restore(flags); + + /* + * If none of the buffers had errors and they are all + * uptodate then we can set the page uptodate. + */ + if (page_uptodate && !PageError(page)) + SetPageUptodate(page); + unlock_page(page); + return; + +still_busy: + bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); + local_irq_restore(flags); + return; +} + +/* + * Completion handler for block_write_full_page() - pages which are unlocked + * during I/O, and which have PageWriteback cleared upon I/O completion. + */ +void end_buffer_async_write(struct buffer_head *bh, int uptodate) +{ + unsigned long flags; + struct buffer_head *first; + struct buffer_head *tmp; + struct page *page; + + BUG_ON(!buffer_async_write(bh)); + + page = bh->b_page; + if (uptodate) { + set_buffer_uptodate(bh); + } else { + buffer_io_error(bh, ", lost async page write"); + set_bit(AS_EIO, &page->mapping->flags); + set_buffer_write_io_error(bh); + clear_buffer_uptodate(bh); + SetPageError(page); + } + + first = page_buffers(page); + local_irq_save(flags); + bit_spin_lock(BH_Uptodate_Lock, &first->b_state); + + clear_buffer_async_write(bh); + unlock_buffer(bh); + tmp = bh->b_this_page; + while (tmp != bh) { + if (buffer_async_write(tmp)) { + BUG_ON(!buffer_locked(tmp)); + goto still_busy; + } + tmp = tmp->b_this_page; + } + bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); + local_irq_restore(flags); + end_page_writeback(page); + return; + +still_busy: + bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); + local_irq_restore(flags); + return; +} +EXPORT_SYMBOL(end_buffer_async_write); + +/* + * If a page's buffers are under async readin (end_buffer_async_read + * completion) then there is a possibility that another thread of + * control could lock one of the buffers after it has completed + * but while some of the other buffers have not completed. This + * locked buffer would confuse end_buffer_async_read() into not unlocking + * the page. So the absence of BH_Async_Read tells end_buffer_async_read() + * that this buffer is not under async I/O. + * + * The page comes unlocked when it has no locked buffer_async buffers + * left. + * + * PageLocked prevents anyone starting new async I/O reads any of + * the buffers. + * + * PageWriteback is used to prevent simultaneous writeout of the same + * page. + * + * PageLocked prevents anyone from starting writeback of a page which is + * under read I/O (PageWriteback is only ever set against a locked page). + */ +static void mark_buffer_async_read(struct buffer_head *bh) +{ + bh->b_end_io = end_buffer_async_read; + set_buffer_async_read(bh); +} + +static void mark_buffer_async_write_endio(struct buffer_head *bh, + bh_end_io_t *handler) +{ + bh->b_end_io = handler; + set_buffer_async_write(bh); +} + +void mark_buffer_async_write(struct buffer_head *bh) +{ + mark_buffer_async_write_endio(bh, end_buffer_async_write); +} +EXPORT_SYMBOL(mark_buffer_async_write); + + +/* + * fs/buffer.c contains helper functions for buffer-backed address space's + * fsync functions. A common requirement for buffer-based filesystems is + * that certain data from the backing blockdev needs to be written out for + * a successful fsync(). For example, ext2 indirect blocks need to be + * written back and waited upon before fsync() returns. + * + * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), + * inode_has_buffers() and invalidate_inode_buffers() are provided for the + * management of a list of dependent buffers at ->i_mapping->private_list. + * + * Locking is a little subtle: try_to_free_buffers() will remove buffers + * from their controlling inode's queue when they are being freed. But + * try_to_free_buffers() will be operating against the *blockdev* mapping + * at the time, not against the S_ISREG file which depends on those buffers. + * So the locking for private_list is via the private_lock in the address_space + * which backs the buffers. Which is different from the address_space + * against which the buffers are listed. So for a particular address_space, + * mapping->private_lock does *not* protect mapping->private_list! In fact, + * mapping->private_list will always be protected by the backing blockdev's + * ->private_lock. + * + * Which introduces a requirement: all buffers on an address_space's + * ->private_list must be from the same address_space: the blockdev's. + * + * address_spaces which do not place buffers at ->private_list via these + * utility functions are free to use private_lock and private_list for + * whatever they want. The only requirement is that list_empty(private_list) + * be true at clear_inode() time. + * + * FIXME: clear_inode should not call invalidate_inode_buffers(). The + * filesystems should do that. invalidate_inode_buffers() should just go + * BUG_ON(!list_empty). + * + * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should + * take an address_space, not an inode. And it should be called + * mark_buffer_dirty_fsync() to clearly define why those buffers are being + * queued up. + * + * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the + * list if it is already on a list. Because if the buffer is on a list, + * it *must* already be on the right one. If not, the filesystem is being + * silly. This will save a ton of locking. But first we have to ensure + * that buffers are taken *off* the old inode's list when they are freed + * (presumably in truncate). That requires careful auditing of all + * filesystems (do it inside bforget()). It could also be done by bringing + * b_inode back. + */ + +/* + * The buffer's backing address_space's private_lock must be held + */ +static void __remove_assoc_queue(struct buffer_head *bh) +{ + list_del_init(&bh->b_assoc_buffers); + WARN_ON(!bh->b_assoc_map); + if (buffer_write_io_error(bh)) + set_bit(AS_EIO, &bh->b_assoc_map->flags); + bh->b_assoc_map = NULL; +} + +int inode_has_buffers(struct inode *inode) +{ + return !list_empty(&inode->i_data.private_list); +} + +/* + * osync is designed to support O_SYNC io. It waits synchronously for + * all already-submitted IO to complete, but does not queue any new + * writes to the disk. + * + * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as + * you dirty the buffers, and then use osync_inode_buffers to wait for + * completion. Any other dirty buffers which are not yet queued for + * write will not be flushed to disk by the osync. + */ +static int osync_buffers_list(spinlock_t *lock, struct list_head *list) +{ + struct buffer_head *bh; + struct list_head *p; + int err = 0; + + spin_lock(lock); +repeat: + list_for_each_prev(p, list) { + bh = BH_ENTRY(p); + if (buffer_locked(bh)) { + get_bh(bh); + spin_unlock(lock); + wait_on_buffer(bh); + if (!buffer_uptodate(bh)) + err = -EIO; + brelse(bh); + spin_lock(lock); + goto repeat; + } + } + spin_unlock(lock); + return err; +} + +static void do_thaw_one(struct super_block *sb, void *unused) +{ + char b[BDEVNAME_SIZE]; + while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) + printk(KERN_WARNING "Emergency Thaw on %s\n", + bdevname(sb->s_bdev, b)); +} + +static void do_thaw_all(struct work_struct *work) +{ + iterate_supers(do_thaw_one, NULL); + kfree(work); + printk(KERN_WARNING "Emergency Thaw complete\n"); +} + +/** + * emergency_thaw_all -- forcibly thaw every frozen filesystem + * + * Used for emergency unfreeze of all filesystems via SysRq + */ +void emergency_thaw_all(void) +{ + struct work_struct *work; + + work = kmalloc(sizeof(*work), GFP_ATOMIC); + if (work) { + INIT_WORK(work, do_thaw_all); + schedule_work(work); + } +} + +/** + * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers + * @mapping: the mapping which wants those buffers written + * + * Starts I/O against the buffers at mapping->private_list, and waits upon + * that I/O. + * + * Basically, this is a convenience function for fsync(). + * @mapping is a file or directory which needs those buffers to be written for + * a successful fsync(). + */ +int sync_mapping_buffers(struct address_space *mapping) +{ + struct address_space *buffer_mapping = mapping->private_data; + + if (buffer_mapping == NULL || list_empty(&mapping->private_list)) + return 0; + + return fsync_buffers_list(&buffer_mapping->private_lock, + &mapping->private_list); +} +EXPORT_SYMBOL(sync_mapping_buffers); + +/* + * Called when we've recently written block `bblock', and it is known that + * `bblock' was for a buffer_boundary() buffer. This means that the block at + * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's + * dirty, schedule it for IO. So that indirects merge nicely with their data. + */ +void write_boundary_block(struct block_device *bdev, + sector_t bblock, unsigned blocksize) +{ + struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); + if (bh) { + if (buffer_dirty(bh)) + ll_rw_block(WRITE, 1, &bh); + put_bh(bh); + } +} + +void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) +{ + struct address_space *mapping = inode->i_mapping; + struct address_space *buffer_mapping = bh->b_page->mapping; + + mark_buffer_dirty(bh); + if (!mapping->private_data) { + mapping->private_data = buffer_mapping; + } else { + BUG_ON(mapping->private_data != buffer_mapping); + } + if (!bh->b_assoc_map) { + spin_lock(&buffer_mapping->private_lock); + list_move_tail(&bh->b_assoc_buffers, + &mapping->private_list); + bh->b_assoc_map = mapping; + spin_unlock(&buffer_mapping->private_lock); + } +} +EXPORT_SYMBOL(mark_buffer_dirty_inode); + +/* + * Mark the page dirty, and set it dirty in the radix tree, and mark the inode + * dirty. + * + * If warn is true, then emit a warning if the page is not uptodate and has + * not been truncated. + */ +static void __set_page_dirty(struct page *page, + struct address_space *mapping, int warn) +{ + unsigned long flags; + + spin_lock_irqsave(&mapping->tree_lock, flags); + if (page->mapping) { /* Race with truncate? */ + WARN_ON_ONCE(warn && !PageUptodate(page)); + account_page_dirtied(page, mapping); + radix_tree_tag_set(&mapping->page_tree, + page_index(page), PAGECACHE_TAG_DIRTY); + } + spin_unlock_irqrestore(&mapping->tree_lock, flags); + __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); +} + +/* + * Add a page to the dirty page list. + * + * It is a sad fact of life that this function is called from several places + * deeply under spinlocking. It may not sleep. + * + * If the page has buffers, the uptodate buffers are set dirty, to preserve + * dirty-state coherency between the page and the buffers. It the page does + * not have buffers then when they are later attached they will all be set + * dirty. + * + * The buffers are dirtied before the page is dirtied. There's a small race + * window in which a writepage caller may see the page cleanness but not the + * buffer dirtiness. That's fine. If this code were to set the page dirty + * before the buffers, a concurrent writepage caller could clear the page dirty + * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean + * page on the dirty page list. + * + * We use private_lock to lock against try_to_free_buffers while using the + * page's buffer list. Also use this to protect against clean buffers being + * added to the page after it was set dirty. + * + * FIXME: may need to call ->reservepage here as well. That's rather up to the + * address_space though. + */ +int __set_page_dirty_buffers(struct page *page) +{ + int newly_dirty; + struct address_space *mapping = page_mapping(page); + + if (unlikely(!mapping)) + return !TestSetPageDirty(page); + + spin_lock(&mapping->private_lock); + if (page_has_buffers(page)) { + struct buffer_head *head = page_buffers(page); + struct buffer_head *bh = head; + + do { + set_buffer_dirty(bh); + bh = bh->b_this_page; + } while (bh != head); + } + newly_dirty = !TestSetPageDirty(page); + spin_unlock(&mapping->private_lock); + + if (newly_dirty) + __set_page_dirty(page, mapping, 1); + return newly_dirty; +} +EXPORT_SYMBOL(__set_page_dirty_buffers); + +/* + * Write out and wait upon a list of buffers. + * + * We have conflicting pressures: we want to make sure that all + * initially dirty buffers get waited on, but that any subsequently + * dirtied buffers don't. After all, we don't want fsync to last + * forever if somebody is actively writing to the file. + * + * Do this in two main stages: first we copy dirty buffers to a + * temporary inode list, queueing the writes as we go. Then we clean + * up, waiting for those writes to complete. + * + * During this second stage, any subsequent updates to the file may end + * up refiling the buffer on the original inode's dirty list again, so + * there is a chance we will end up with a buffer queued for write but + * not yet completed on that list. So, as a final cleanup we go through + * the osync code to catch these locked, dirty buffers without requeuing + * any newly dirty buffers for write. + */ +static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) +{ + struct buffer_head *bh; + struct list_head tmp; + struct address_space *mapping; + int err = 0, err2; + struct blk_plug plug; + + INIT_LIST_HEAD(&tmp); + blk_start_plug(&plug); + + spin_lock(lock); + while (!list_empty(list)) { + bh = BH_ENTRY(list->next); + mapping = bh->b_assoc_map; + __remove_assoc_queue(bh); + /* Avoid race with mark_buffer_dirty_inode() which does + * a lockless check and we rely on seeing the dirty bit */ + smp_mb(); + if (buffer_dirty(bh) || buffer_locked(bh)) { + list_add(&bh->b_assoc_buffers, &tmp); + bh->b_assoc_map = mapping; + if (buffer_dirty(bh)) { + get_bh(bh); + spin_unlock(lock); + /* + * Ensure any pending I/O completes so that + * write_dirty_buffer() actually writes the + * current contents - it is a noop if I/O is + * still in flight on potentially older + * contents. + */ + write_dirty_buffer(bh, WRITE_SYNC); + + /* + * Kick off IO for the previous mapping. Note + * that we will not run the very last mapping, + * wait_on_buffer() will do that for us + * through sync_buffer(). + */ + brelse(bh); + spin_lock(lock); + } + } + } + + spin_unlock(lock); + blk_finish_plug(&plug); + spin_lock(lock); + + while (!list_empty(&tmp)) { + bh = BH_ENTRY(tmp.prev); + get_bh(bh); + mapping = bh->b_assoc_map; + __remove_assoc_queue(bh); + /* Avoid race with mark_buffer_dirty_inode() which does + * a lockless check and we rely on seeing the dirty bit */ + smp_mb(); + if (buffer_dirty(bh)) { + list_add(&bh->b_assoc_buffers, + &mapping->private_list); + bh->b_assoc_map = mapping; + } + spin_unlock(lock); + wait_on_buffer(bh); + if (!buffer_uptodate(bh)) + err = -EIO; + brelse(bh); + spin_lock(lock); + } + + spin_unlock(lock); + err2 = osync_buffers_list(lock, list); + if (err) + return err; + else + return err2; +} + +/* + * Invalidate any and all dirty buffers on a given inode. We are + * probably unmounting the fs, but that doesn't mean we have already + * done a sync(). Just drop the buffers from the inode list. + * + * NOTE: we take the inode's blockdev's mapping's private_lock. Which + * assumes that all the buffers are against the blockdev. Not true + * for reiserfs. + */ +void invalidate_inode_buffers(struct inode *inode) +{ + if (inode_has_buffers(inode)) { + struct address_space *mapping = &inode->i_data; + struct list_head *list = &mapping->private_list; + struct address_space *buffer_mapping = mapping->private_data; + + spin_lock(&buffer_mapping->private_lock); + while (!list_empty(list)) + __remove_assoc_queue(BH_ENTRY(list->next)); + spin_unlock(&buffer_mapping->private_lock); + } +} +EXPORT_SYMBOL(invalidate_inode_buffers); + +/* + * Remove any clean buffers from the inode's buffer list. This is called + * when we're trying to free the inode itself. Those buffers can pin it. + * + * Returns true if all buffers were removed. + */ +int remove_inode_buffers(struct inode *inode) +{ + int ret = 1; + + if (inode_has_buffers(inode)) { + struct address_space *mapping = &inode->i_data; + struct list_head *list = &mapping->private_list; + struct address_space *buffer_mapping = mapping->private_data; + + spin_lock(&buffer_mapping->private_lock); + while (!list_empty(list)) { + struct buffer_head *bh = BH_ENTRY(list->next); + if (buffer_dirty(bh)) { + ret = 0; + break; + } + __remove_assoc_queue(bh); + } + spin_unlock(&buffer_mapping->private_lock); + } + return ret; +} + +/* + * Create the appropriate buffers when given a page for data area and + * the size of each buffer.. Use the bh->b_this_page linked list to + * follow the buffers created. Return NULL if unable to create more + * buffers. + * + * The retry flag is used to differentiate async IO (paging, swapping) + * which may not fail from ordinary buffer allocations. + */ +struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, + int retry) +{ + struct buffer_head *bh, *head; + long offset; + +try_again: + head = NULL; + offset = PAGE_SIZE; + while ((offset -= size) >= 0) { + bh = alloc_buffer_head(GFP_NOFS); + if (!bh) + goto no_grow; + + bh->b_this_page = head; + bh->b_blocknr = -1; + head = bh; + + bh->b_size = size; + + /* Link the buffer to its page */ + set_bh_page(bh, page, offset); + } + return head; +/* + * In case anything failed, we just free everything we got. + */ +no_grow: + if (head) { + do { + bh = head; + head = head->b_this_page; + free_buffer_head(bh); + } while (head); + } + + /* + * Return failure for non-async IO requests. Async IO requests + * are not allowed to fail, so we have to wait until buffer heads + * become available. But we don't want tasks sleeping with + * partially complete buffers, so all were released above. + */ + if (!retry) + return NULL; + + /* We're _really_ low on memory. Now we just + * wait for old buffer heads to become free due to + * finishing IO. Since this is an async request and + * the reserve list is empty, we're sure there are + * async buffer heads in use. + */ + free_more_memory(); + goto try_again; +} +EXPORT_SYMBOL_GPL(alloc_page_buffers); + +static inline void +link_dev_buffers(struct page *page, struct buffer_head *head) +{ + struct buffer_head *bh, *tail; + + bh = head; + do { + tail = bh; + bh = bh->b_this_page; + } while (bh); + tail->b_this_page = head; + attach_page_buffers(page, head); +} + +static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size) +{ + sector_t retval = ~((sector_t)0); + loff_t sz = i_size_read(bdev->bd_inode); + + if (sz) { + unsigned int sizebits = blksize_bits(size); + retval = (sz >> sizebits); + } + return retval; +} + +/* + * Initialise the state of a blockdev page's buffers. + */ +static sector_t +init_page_buffers(struct page *page, struct block_device *bdev, + sector_t block, int size) +{ + struct buffer_head *head = page_buffers(page); + struct buffer_head *bh = head; + int uptodate = PageUptodate(page); + sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size); + + do { + if (!buffer_mapped(bh)) { + init_buffer(bh, NULL, NULL); + bh->b_bdev = bdev; + bh->b_blocknr = block; + if (uptodate) + set_buffer_uptodate(bh); + if (block < end_block) + set_buffer_mapped(bh); + } + block++; + bh = bh->b_this_page; + } while (bh != head); + + /* + * Caller needs to validate requested block against end of device. + */ + return end_block; +} + +/* + * Create the page-cache page that contains the requested block. + * + * This is used purely for blockdev mappings. + */ +static int +grow_dev_page(struct block_device *bdev, sector_t block, + pgoff_t index, int size, int sizebits, gfp_t gfp) +{ + struct inode *inode = bdev->bd_inode; + struct page *page; + struct buffer_head *bh; + sector_t end_block; + int ret = 0; /* Will call free_more_memory() */ + gfp_t gfp_mask; + + gfp_mask = (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS) | gfp; + + /* + * XXX: __getblk_slow() can not really deal with failure and + * will endlessly loop on improvised global reclaim. Prefer + * looping in the allocator rather than here, at least that + * code knows what it's doing. + */ + gfp_mask |= __GFP_NOFAIL; + + page = find_or_create_page(inode->i_mapping, index, gfp_mask); + if (!page) + return ret; + + BUG_ON(!PageLocked(page)); + + if (page_has_buffers(page)) { + bh = page_buffers(page); + if (bh->b_size == size) { + end_block = init_page_buffers(page, bdev, + (sector_t)index << sizebits, + size); + goto done; + } + if (!try_to_free_buffers(page)) + goto failed; + } + + /* + * Allocate some buffers for this page + */ + bh = alloc_page_buffers(page, size, 0); + if (!bh) + goto failed; + + /* + * Link the page to the buffers and initialise them. Take the + * lock to be atomic wrt __find_get_block(), which does not + * run under the page lock. + */ + spin_lock(&inode->i_mapping->private_lock); + link_dev_buffers(page, bh); + end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits, + size); + spin_unlock(&inode->i_mapping->private_lock); +done: + ret = (block < end_block) ? 1 : -ENXIO; +failed: + unlock_page(page); + page_cache_release(page); + return ret; +} + +/* + * Create buffers for the specified block device block's page. If + * that page was dirty, the buffers are set dirty also. + */ +static int +grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp) +{ + pgoff_t index; + int sizebits; + + sizebits = -1; + do { + sizebits++; + } while ((size << sizebits) < PAGE_SIZE); + + index = block >> sizebits; + + /* + * Check for a block which wants to lie outside our maximum possible + * pagecache index. (this comparison is done using sector_t types). + */ + if (unlikely(index != block >> sizebits)) { + char b[BDEVNAME_SIZE]; + + printk(KERN_ERR "%s: requested out-of-range block %llu for " + "device %s\n", + __func__, (unsigned long long)block, + bdevname(bdev, b)); + return -EIO; + } + + /* Create a page with the proper size buffers.. */ + return grow_dev_page(bdev, block, index, size, sizebits, gfp); +} + +struct buffer_head * +__getblk_slow(struct block_device *bdev, sector_t block, + unsigned size, gfp_t gfp) +{ + /* Size must be multiple of hard sectorsize */ + if (unlikely(size & (bdev_logical_block_size(bdev)-1) || + (size < 512 || size > PAGE_SIZE))) { + printk(KERN_ERR "getblk(): invalid block size %d requested\n", + size); + printk(KERN_ERR "logical block size: %d\n", + bdev_logical_block_size(bdev)); + + dump_stack(); + return NULL; + } + + for (;;) { + struct buffer_head *bh; + int ret; + + bh = __find_get_block(bdev, block, size); + if (bh) + return bh; + + ret = grow_buffers(bdev, block, size, gfp); + if (ret < 0) + return NULL; + if (ret == 0) + free_more_memory(); + } +} +EXPORT_SYMBOL(__getblk_slow); + +/* + * The relationship between dirty buffers and dirty pages: + * + * Whenever a page has any dirty buffers, the page's dirty bit is set, and + * the page is tagged dirty in its radix tree. + * + * At all times, the dirtiness of the buffers represents the dirtiness of + * subsections of the page. If the page has buffers, the page dirty bit is + * merely a hint about the true dirty state. + * + * When a page is set dirty in its entirety, all its buffers are marked dirty + * (if the page has buffers). + * + * When a buffer is marked dirty, its page is dirtied, but the page's other + * buffers are not. + * + * Also. When blockdev buffers are explicitly read with bread(), they + * individually become uptodate. But their backing page remains not + * uptodate - even if all of its buffers are uptodate. A subsequent + * block_read_full_page() against that page will discover all the uptodate + * buffers, will set the page uptodate and will perform no I/O. + */ + +/** + * mark_buffer_dirty - mark a buffer_head as needing writeout + * @bh: the buffer_head to mark dirty + * + * mark_buffer_dirty() will set the dirty bit against the buffer, then set its + * backing page dirty, then tag the page as dirty in its address_space's radix + * tree and then attach the address_space's inode to its superblock's dirty + * inode list. + * + * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, + * mapping->tree_lock and mapping->host->i_lock. + */ +void mark_buffer_dirty(struct buffer_head *bh) +{ + WARN_ON_ONCE(!buffer_uptodate(bh)); + + trace_block_dirty_buffer(bh); + + /* + * Very *carefully* optimize the it-is-already-dirty case. + * + * Don't let the final "is it dirty" escape to before we + * perhaps modified the buffer. + */ + if (buffer_dirty(bh)) { + smp_mb(); + if (buffer_dirty(bh)) + return; + } + + if (!test_set_buffer_dirty(bh)) { + struct page *page = bh->b_page; + if (!TestSetPageDirty(page)) { + struct address_space *mapping = page_mapping(page); + if (mapping) + __set_page_dirty(page, mapping, 0); + } + } +} +EXPORT_SYMBOL(mark_buffer_dirty); + +/* + * Decrement a buffer_head's reference count. If all buffers against a page + * have zero reference count, are clean and unlocked, and if the page is clean + * and unlocked then try_to_free_buffers() may strip the buffers from the page + * in preparation for freeing it (sometimes, rarely, buffers are removed from + * a page but it ends up not being freed, and buffers may later be reattached). + */ +void __brelse(struct buffer_head * buf) +{ + if (atomic_read(&buf->b_count)) { + put_bh(buf); + return; + } + WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); +} +EXPORT_SYMBOL(__brelse); + +/* + * bforget() is like brelse(), except it discards any + * potentially dirty data. + */ +void __bforget(struct buffer_head *bh) +{ + clear_buffer_dirty(bh); + if (bh->b_assoc_map) { + struct address_space *buffer_mapping = bh->b_page->mapping; + + spin_lock(&buffer_mapping->private_lock); + list_del_init(&bh->b_assoc_buffers); + bh->b_assoc_map = NULL; + spin_unlock(&buffer_mapping->private_lock); + } + __brelse(bh); +} +EXPORT_SYMBOL(__bforget); + +static struct buffer_head *__bread_slow(struct buffer_head *bh) +{ + lock_buffer(bh); + if (buffer_uptodate(bh)) { + unlock_buffer(bh); + return bh; + } else { + get_bh(bh); + bh->b_end_io = end_buffer_read_sync; + submit_bh(READ, bh); + wait_on_buffer(bh); + if (buffer_uptodate(bh)) + return bh; + } + brelse(bh); + return NULL; +} + +/* + * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). + * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their + * refcount elevated by one when they're in an LRU. A buffer can only appear + * once in a particular CPU's LRU. A single buffer can be present in multiple + * CPU's LRUs at the same time. + * + * This is a transparent caching front-end to sb_bread(), sb_getblk() and + * sb_find_get_block(). + * + * The LRUs themselves only need locking against invalidate_bh_lrus. We use + * a local interrupt disable for that. + */ + +#define BH_LRU_SIZE 16 + +struct bh_lru { + struct buffer_head *bhs[BH_LRU_SIZE]; +}; + +static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; + +#ifdef CONFIG_SMP +#define bh_lru_lock() local_irq_disable() +#define bh_lru_unlock() local_irq_enable() +#else +#define bh_lru_lock() preempt_disable() +#define bh_lru_unlock() preempt_enable() +#endif + +static inline void check_irqs_on(void) +{ +#ifdef irqs_disabled + BUG_ON(irqs_disabled()); +#endif +} + +/* + * The LRU management algorithm is dopey-but-simple. Sorry. + */ +static void bh_lru_install(struct buffer_head *bh) +{ + struct buffer_head *evictee = NULL; + + check_irqs_on(); + bh_lru_lock(); + if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { + struct buffer_head *bhs[BH_LRU_SIZE]; + int in; + int out = 0; + + get_bh(bh); + bhs[out++] = bh; + for (in = 0; in < BH_LRU_SIZE; in++) { + struct buffer_head *bh2 = + __this_cpu_read(bh_lrus.bhs[in]); + + if (bh2 == bh) { + __brelse(bh2); + } else { + if (out >= BH_LRU_SIZE) { + BUG_ON(evictee != NULL); + evictee = bh2; + } else { + bhs[out++] = bh2; + } + } + } + while (out < BH_LRU_SIZE) + bhs[out++] = NULL; + memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); + } + bh_lru_unlock(); + + if (evictee) + __brelse(evictee); +} + +/* + * Look up the bh in this cpu's LRU. If it's there, move it to the head. + */ +static struct buffer_head * +lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) +{ + struct buffer_head *ret = NULL; + unsigned int i; + + check_irqs_on(); + bh_lru_lock(); + for (i = 0; i < BH_LRU_SIZE; i++) { + struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); + + if (bh && bh->b_blocknr == block && bh->b_bdev == bdev && + bh->b_size == size) { + if (i) { + while (i) { + __this_cpu_write(bh_lrus.bhs[i], + __this_cpu_read(bh_lrus.bhs[i - 1])); + i--; + } + __this_cpu_write(bh_lrus.bhs[0], bh); + } + get_bh(bh); + ret = bh; + break; + } + } + bh_lru_unlock(); + return ret; +} + +/* + * Perform a pagecache lookup for the matching buffer. If it's there, refresh + * it in the LRU and mark it as accessed. If it is not present then return + * NULL + */ +struct buffer_head * +__find_get_block(struct block_device *bdev, sector_t block, unsigned size) +{ + struct buffer_head *bh = lookup_bh_lru(bdev, block, size); + + if (bh == NULL) { + /* __find_get_block_slow will mark the page accessed */ + bh = __find_get_block_slow(bdev, block); + if (bh) + bh_lru_install(bh); + } else + touch_buffer(bh); + + return bh; +} +EXPORT_SYMBOL(__find_get_block); + +/* + * __getblk_gfp() will locate (and, if necessary, create) the buffer_head + * which corresponds to the passed block_device, block and size. The + * returned buffer has its reference count incremented. + * + * __getblk_gfp() will lock up the machine if grow_dev_page's + * try_to_free_buffers() attempt is failing. FIXME, perhaps? + */ +struct buffer_head * +__getblk_gfp(struct block_device *bdev, sector_t block, + unsigned size, gfp_t gfp) +{ + struct buffer_head *bh = __find_get_block(bdev, block, size); + + might_sleep(); + if (bh == NULL) + bh = __getblk_slow(bdev, block, size, gfp); + return bh; +} +EXPORT_SYMBOL(__getblk_gfp); + +/* + * Do async read-ahead on a buffer.. + */ +void __breadahead(struct block_device *bdev, sector_t block, unsigned size) +{ + struct buffer_head *bh = __getblk(bdev, block, size); + if (likely(bh)) { + ll_rw_block(READA, 1, &bh); + brelse(bh); + } +} +EXPORT_SYMBOL(__breadahead); + +/** + * __bread_gfp() - reads a specified block and returns the bh + * @bdev: the block_device to read from + * @block: number of block + * @size: size (in bytes) to read + * @gfp: page allocation flag + * + * Reads a specified block, and returns buffer head that contains it. + * The page cache can be allocated from non-movable area + * not to prevent page migration if you set gfp to zero. + * It returns NULL if the block was unreadable. + */ +struct buffer_head * +__bread_gfp(struct block_device *bdev, sector_t block, + unsigned size, gfp_t gfp) +{ + struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp); + + if (likely(bh) && !buffer_uptodate(bh)) + bh = __bread_slow(bh); + return bh; +} +EXPORT_SYMBOL(__bread_gfp); + +/* + * invalidate_bh_lrus() is called rarely - but not only at unmount. + * This doesn't race because it runs in each cpu either in irq + * or with preempt disabled. + */ +static void invalidate_bh_lru(void *arg) +{ + struct bh_lru *b = &get_cpu_var(bh_lrus); + int i; + + for (i = 0; i < BH_LRU_SIZE; i++) { + brelse(b->bhs[i]); + b->bhs[i] = NULL; + } + put_cpu_var(bh_lrus); +} + +static bool has_bh_in_lru(int cpu, void *dummy) +{ + struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); + int i; + + for (i = 0; i < BH_LRU_SIZE; i++) { + if (b->bhs[i]) + return 1; + } + + return 0; +} + +void invalidate_bh_lrus(void) +{ + on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL); +} +EXPORT_SYMBOL_GPL(invalidate_bh_lrus); + +void set_bh_page(struct buffer_head *bh, + struct page *page, unsigned long offset) +{ + bh->b_page = page; + BUG_ON(offset >= PAGE_SIZE); + if (PageHighMem(page)) + /* + * This catches illegal uses and preserves the offset: + */ + bh->b_data = (char *)(0 + offset); + else + bh->b_data = page_address(page) + offset; +} +EXPORT_SYMBOL(set_bh_page); + +/* + * Called when truncating a buffer on a page completely. + */ + +/* Bits that are cleared during an invalidate */ +#define BUFFER_FLAGS_DISCARD \ + (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \ + 1 << BH_Delay | 1 << BH_Unwritten) + +static void discard_buffer(struct buffer_head * bh) +{ + unsigned long b_state, b_state_old; + + lock_buffer(bh); + clear_buffer_dirty(bh); + bh->b_bdev = NULL; + b_state = bh->b_state; + for (;;) { + b_state_old = cmpxchg(&bh->b_state, b_state, + (b_state & ~BUFFER_FLAGS_DISCARD)); + if (b_state_old == b_state) + break; + b_state = b_state_old; + } + unlock_buffer(bh); +} + +/** + * block_invalidatepage - invalidate part or all of a buffer-backed page + * + * @page: the page which is affected + * @offset: start of the range to invalidate + * @length: length of the range to invalidate + * + * block_invalidatepage() is called when all or part of the page has become + * invalidated by a truncate operation. + * + * block_invalidatepage() does not have to release all buffers, but it must + * ensure that no dirty buffer is left outside @offset and that no I/O + * is underway against any of the blocks which are outside the truncation + * point. Because the caller is about to free (and possibly reuse) those + * blocks on-disk. + */ +void block_invalidatepage(struct page *page, unsigned int offset, + unsigned int length) +{ + struct buffer_head *head, *bh, *next; + unsigned int curr_off = 0; + unsigned int stop = length + offset; + + BUG_ON(!PageLocked(page)); + if (!page_has_buffers(page)) + goto out; + + /* + * Check for overflow + */ + BUG_ON(stop > PAGE_CACHE_SIZE || stop < length); + + head = page_buffers(page); + bh = head; + do { + unsigned int next_off = curr_off + bh->b_size; + next = bh->b_this_page; + + /* + * Are we still fully in range ? + */ + if (next_off > stop) + goto out; + + /* + * is this block fully invalidated? + */ + if (offset <= curr_off) + discard_buffer(bh); + curr_off = next_off; + bh = next; + } while (bh != head); + + /* + * We release buffers only if the entire page is being invalidated. + * The get_block cached value has been unconditionally invalidated, + * so real IO is not possible anymore. + */ + if (offset == 0) + try_to_release_page(page, 0); +out: + return; +} +EXPORT_SYMBOL(block_invalidatepage); + + +/* + * We attach and possibly dirty the buffers atomically wrt + * __set_page_dirty_buffers() via private_lock. try_to_free_buffers + * is already excluded via the page lock. + */ +void create_empty_buffers(struct page *page, + unsigned long blocksize, unsigned long b_state) +{ + struct buffer_head *bh, *head, *tail; + + head = alloc_page_buffers(page, blocksize, 1); + bh = head; + do { + bh->b_state |= b_state; + tail = bh; + bh = bh->b_this_page; + } while (bh); + tail->b_this_page = head; + + spin_lock(&page->mapping->private_lock); + if (PageUptodate(page) || PageDirty(page)) { + bh = head; + do { + if (PageDirty(page)) + set_buffer_dirty(bh); + if (PageUptodate(page)) + set_buffer_uptodate(bh); + bh = bh->b_this_page; + } while (bh != head); + } + attach_page_buffers(page, head); + spin_unlock(&page->mapping->private_lock); +} +EXPORT_SYMBOL(create_empty_buffers); + +/* + * We are taking a block for data and we don't want any output from any + * buffer-cache aliases starting from return from that function and + * until the moment when something will explicitly mark the buffer + * dirty (hopefully that will not happen until we will free that block ;-) + * We don't even need to mark it not-uptodate - nobody can expect + * anything from a newly allocated buffer anyway. We used to used + * unmap_buffer() for such invalidation, but that was wrong. We definitely + * don't want to mark the alias unmapped, for example - it would confuse + * anyone who might pick it with bread() afterwards... + * + * Also.. Note that bforget() doesn't lock the buffer. So there can + * be writeout I/O going on against recently-freed buffers. We don't + * wait on that I/O in bforget() - it's more efficient to wait on the I/O + * only if we really need to. That happens here. + */ +void unmap_underlying_metadata(struct block_device *bdev, sector_t block) +{ + struct buffer_head *old_bh; + + might_sleep(); + + old_bh = __find_get_block_slow(bdev, block); + if (old_bh) { + clear_buffer_dirty(old_bh); + wait_on_buffer(old_bh); + clear_buffer_req(old_bh); + __brelse(old_bh); + } +} +EXPORT_SYMBOL(unmap_underlying_metadata); + +/* + * Size is a power-of-two in the range 512..PAGE_SIZE, + * and the case we care about most is PAGE_SIZE. + * + * So this *could* possibly be written with those + * constraints in mind (relevant mostly if some + * architecture has a slow bit-scan instruction) + */ +static inline int block_size_bits(unsigned int blocksize) +{ + return ilog2(blocksize); +} + +static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state) +{ + BUG_ON(!PageLocked(page)); + + if (!page_has_buffers(page)) + create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state); + return page_buffers(page); +} + +/* + * NOTE! All mapped/uptodate combinations are valid: + * + * Mapped Uptodate Meaning + * + * No No "unknown" - must do get_block() + * No Yes "hole" - zero-filled + * Yes No "allocated" - allocated on disk, not read in + * Yes Yes "valid" - allocated and up-to-date in memory. + * + * "Dirty" is valid only with the last case (mapped+uptodate). + */ + +/* + * While block_write_full_page is writing back the dirty buffers under + * the page lock, whoever dirtied the buffers may decide to clean them + * again at any time. We handle that by only looking at the buffer + * state inside lock_buffer(). + * + * If block_write_full_page() is called for regular writeback + * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a + * locked buffer. This only can happen if someone has written the buffer + * directly, with submit_bh(). At the address_space level PageWriteback + * prevents this contention from occurring. + * + * If block_write_full_page() is called with wbc->sync_mode == + * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this + * causes the writes to be flagged as synchronous writes. + */ +static int __block_write_full_page(struct inode *inode, struct page *page, + get_block_t *get_block, struct writeback_control *wbc, + bh_end_io_t *handler) +{ + int err; + sector_t block; + sector_t last_block; + struct buffer_head *bh, *head; + unsigned int blocksize, bbits; + int nr_underway = 0; + int write_op = (wbc->sync_mode == WB_SYNC_ALL ? + WRITE_SYNC : WRITE); + + head = create_page_buffers(page, inode, + (1 << BH_Dirty)|(1 << BH_Uptodate)); + + /* + * Be very careful. We have no exclusion from __set_page_dirty_buffers + * here, and the (potentially unmapped) buffers may become dirty at + * any time. If a buffer becomes dirty here after we've inspected it + * then we just miss that fact, and the page stays dirty. + * + * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; + * handle that here by just cleaning them. + */ + + bh = head; + blocksize = bh->b_size; + bbits = block_size_bits(blocksize); + + block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); + last_block = (i_size_read(inode) - 1) >> bbits; + + /* + * Get all the dirty buffers mapped to disk addresses and + * handle any aliases from the underlying blockdev's mapping. + */ + do { + if (block > last_block) { + /* + * mapped buffers outside i_size will occur, because + * this page can be outside i_size when there is a + * truncate in progress. + */ + /* + * The buffer was zeroed by block_write_full_page() + */ + clear_buffer_dirty(bh); + set_buffer_uptodate(bh); + } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && + buffer_dirty(bh)) { + WARN_ON(bh->b_size != blocksize); + err = get_block(inode, block, bh, 1); + if (err) + goto recover; + clear_buffer_delay(bh); + if (buffer_new(bh)) { + /* blockdev mappings never come here */ + clear_buffer_new(bh); + unmap_underlying_metadata(bh->b_bdev, + bh->b_blocknr); + } + } + bh = bh->b_this_page; + block++; + } while (bh != head); + + do { + if (!buffer_mapped(bh)) + continue; + /* + * If it's a fully non-blocking write attempt and we cannot + * lock the buffer then redirty the page. Note that this can + * potentially cause a busy-wait loop from writeback threads + * and kswapd activity, but those code paths have their own + * higher-level throttling. + */ + if (wbc->sync_mode != WB_SYNC_NONE) { + lock_buffer(bh); + } else if (!trylock_buffer(bh)) { + redirty_page_for_writepage(wbc, page); + continue; + } + if (test_clear_buffer_dirty(bh)) { + mark_buffer_async_write_endio(bh, handler); + } else { + unlock_buffer(bh); + } + } while ((bh = bh->b_this_page) != head); + + /* + * The page and its buffers are protected by PageWriteback(), so we can + * drop the bh refcounts early. + */ + BUG_ON(PageWriteback(page)); + set_page_writeback(page); + + do { + struct buffer_head *next = bh->b_this_page; + if (buffer_async_write(bh)) { + submit_bh(write_op, bh); + nr_underway++; + } + bh = next; + } while (bh != head); + unlock_page(page); + + err = 0; +done: + if (nr_underway == 0) { + /* + * The page was marked dirty, but the buffers were + * clean. Someone wrote them back by hand with + * ll_rw_block/submit_bh. A rare case. + */ + end_page_writeback(page); + + /* + * The page and buffer_heads can be released at any time from + * here on. + */ + } + return err; + +recover: + /* + * ENOSPC, or some other error. We may already have added some + * blocks to the file, so we need to write these out to avoid + * exposing stale data. + * The page is currently locked and not marked for writeback + */ + bh = head; + /* Recovery: lock and submit the mapped buffers */ + do { + if (buffer_mapped(bh) && buffer_dirty(bh) && + !buffer_delay(bh)) { + lock_buffer(bh); + mark_buffer_async_write_endio(bh, handler); + } else { + /* + * The buffer may have been set dirty during + * attachment to a dirty page. + */ + clear_buffer_dirty(bh); + } + } while ((bh = bh->b_this_page) != head); + SetPageError(page); + BUG_ON(PageWriteback(page)); + mapping_set_error(page->mapping, err); + set_page_writeback(page); + do { + struct buffer_head *next = bh->b_this_page; + if (buffer_async_write(bh)) { + clear_buffer_dirty(bh); + submit_bh(write_op, bh); + nr_underway++; + } + bh = next; + } while (bh != head); + unlock_page(page); + goto done; +} + +/* + * If a page has any new buffers, zero them out here, and mark them uptodate + * and dirty so they'll be written out (in order to prevent uninitialised + * block data from leaking). And clear the new bit. + */ +void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) +{ + unsigned int block_start, block_end; + struct buffer_head *head, *bh; + + BUG_ON(!PageLocked(page)); + if (!page_has_buffers(page)) + return; + + bh = head = page_buffers(page); + block_start = 0; + do { + block_end = block_start + bh->b_size; + + if (buffer_new(bh)) { + if (block_end > from && block_start < to) { + if (!PageUptodate(page)) { + unsigned start, size; + + start = max(from, block_start); + size = min(to, block_end) - start; + + zero_user(page, start, size); + set_buffer_uptodate(bh); + } + + clear_buffer_new(bh); + mark_buffer_dirty(bh); + } + } + + block_start = block_end; + bh = bh->b_this_page; + } while (bh != head); +} +EXPORT_SYMBOL(page_zero_new_buffers); + +int __block_write_begin(struct page *page, loff_t pos, unsigned len, + get_block_t *get_block) +{ + unsigned from = pos & (PAGE_CACHE_SIZE - 1); + unsigned to = from + len; + struct inode *inode = page->mapping->host; + unsigned block_start, block_end; + sector_t block; + int err = 0; + unsigned blocksize, bbits; + struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; + + BUG_ON(!PageLocked(page)); + BUG_ON(from > PAGE_CACHE_SIZE); + BUG_ON(to > PAGE_CACHE_SIZE); + BUG_ON(from > to); + + head = create_page_buffers(page, inode, 0); + blocksize = head->b_size; + bbits = block_size_bits(blocksize); + + block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); + + for(bh = head, block_start = 0; bh != head || !block_start; + block++, block_start=block_end, bh = bh->b_this_page) { + block_end = block_start + blocksize; + if (block_end <= from || block_start >= to) { + if (PageUptodate(page)) { + if (!buffer_uptodate(bh)) + set_buffer_uptodate(bh); + } + continue; + } + if (buffer_new(bh)) + clear_buffer_new(bh); + if (!buffer_mapped(bh)) { + WARN_ON(bh->b_size != blocksize); + err = get_block(inode, block, bh, 1); + if (err) + break; + if (buffer_new(bh)) { + unmap_underlying_metadata(bh->b_bdev, + bh->b_blocknr); + if (PageUptodate(page)) { + clear_buffer_new(bh); + set_buffer_uptodate(bh); + mark_buffer_dirty(bh); + continue; + } + if (block_end > to || block_start < from) + zero_user_segments(page, + to, block_end, + block_start, from); + continue; + } + } + if (PageUptodate(page)) { + if (!buffer_uptodate(bh)) + set_buffer_uptodate(bh); + continue; + } + if (!buffer_uptodate(bh) && !buffer_delay(bh) && + !buffer_unwritten(bh) && + (block_start < from || block_end > to)) { + ll_rw_block(READ, 1, &bh); + *wait_bh++=bh; + } + } + /* + * If we issued read requests - let them complete. + */ + while(wait_bh > wait) { + wait_on_buffer(*--wait_bh); + if (!buffer_uptodate(*wait_bh)) + err = -EIO; + } + if (unlikely(err)) + page_zero_new_buffers(page, from, to); + return err; +} +EXPORT_SYMBOL(__block_write_begin); + +static int __block_commit_write(struct inode *inode, struct page *page, + unsigned from, unsigned to) +{ + unsigned block_start, block_end; + int partial = 0; + unsigned blocksize; + struct buffer_head *bh, *head; + + bh = head = page_buffers(page); + blocksize = bh->b_size; + + block_start = 0; + do { + block_end = block_start + blocksize; + if (block_end <= from || block_start >= to) { + if (!buffer_uptodate(bh)) + partial = 1; + } else { + set_buffer_uptodate(bh); + mark_buffer_dirty(bh); + } + clear_buffer_new(bh); + + block_start = block_end; + bh = bh->b_this_page; + } while (bh != head); + + /* + * If this is a partial write which happened to make all buffers + * uptodate then we can optimize away a bogus readpage() for + * the next read(). Here we 'discover' whether the page went + * uptodate as a result of this (potentially partial) write. + */ + if (!partial) + SetPageUptodate(page); + return 0; +} + +/* + * block_write_begin takes care of the basic task of block allocation and + * bringing partial write blocks uptodate first. + * + * The filesystem needs to handle block truncation upon failure. + */ +int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, + unsigned flags, struct page **pagep, get_block_t *get_block) +{ + pgoff_t index = pos >> PAGE_CACHE_SHIFT; + struct page *page; + int status; + + page = grab_cache_page_write_begin(mapping, index, flags); + if (!page) + return -ENOMEM; + + status = __block_write_begin(page, pos, len, get_block); + if (unlikely(status)) { + unlock_page(page); + page_cache_release(page); + page = NULL; + } + + *pagep = page; + return status; +} +EXPORT_SYMBOL(block_write_begin); + +int block_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + struct inode *inode = mapping->host; + unsigned start; + + start = pos & (PAGE_CACHE_SIZE - 1); + + if (unlikely(copied < len)) { + /* + * The buffers that were written will now be uptodate, so we + * don't have to worry about a readpage reading them and + * overwriting a partial write. However if we have encountered + * a short write and only partially written into a buffer, it + * will not be marked uptodate, so a readpage might come in and + * destroy our partial write. + * + * Do the simplest thing, and just treat any short write to a + * non uptodate page as a zero-length write, and force the + * caller to redo the whole thing. + */ + if (!PageUptodate(page)) + copied = 0; + + page_zero_new_buffers(page, start+copied, start+len); + } + flush_dcache_page(page); + + /* This could be a short (even 0-length) commit */ + __block_commit_write(inode, page, start, start+copied); + + return copied; +} +EXPORT_SYMBOL(block_write_end); + +int generic_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + struct inode *inode = mapping->host; + loff_t old_size = inode->i_size; + int i_size_changed = 0; + + copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); + + /* + * No need to use i_size_read() here, the i_size + * cannot change under us because we hold i_mutex. + * + * But it's important to update i_size while still holding page lock: + * page writeout could otherwise come in and zero beyond i_size. + */ + if (pos+copied > inode->i_size) { + i_size_write(inode, pos+copied); + i_size_changed = 1; + } + + unlock_page(page); + page_cache_release(page); + + if (old_size < pos) + pagecache_isize_extended(inode, old_size, pos); + /* + * Don't mark the inode dirty under page lock. First, it unnecessarily + * makes the holding time of page lock longer. Second, it forces lock + * ordering of page lock and transaction start for journaling + * filesystems. + */ + if (i_size_changed) + mark_inode_dirty(inode); + + return copied; +} +EXPORT_SYMBOL(generic_write_end); + +/* + * block_is_partially_uptodate checks whether buffers within a page are + * uptodate or not. + * + * Returns true if all buffers which correspond to a file portion + * we want to read are uptodate. + */ +int block_is_partially_uptodate(struct page *page, unsigned long from, + unsigned long count) +{ + unsigned block_start, block_end, blocksize; + unsigned to; + struct buffer_head *bh, *head; + int ret = 1; + + if (!page_has_buffers(page)) + return 0; + + head = page_buffers(page); + blocksize = head->b_size; + to = min_t(unsigned, PAGE_CACHE_SIZE - from, count); + to = from + to; + if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) + return 0; + + bh = head; + block_start = 0; + do { + block_end = block_start + blocksize; + if (block_end > from && block_start < to) { + if (!buffer_uptodate(bh)) { + ret = 0; + break; + } + if (block_end >= to) + break; + } + block_start = block_end; + bh = bh->b_this_page; + } while (bh != head); + + return ret; +} +EXPORT_SYMBOL(block_is_partially_uptodate); + +/* + * Generic "read page" function for block devices that have the normal + * get_block functionality. This is most of the block device filesystems. + * Reads the page asynchronously --- the unlock_buffer() and + * set/clear_buffer_uptodate() functions propagate buffer state into the + * page struct once IO has completed. + */ +int block_read_full_page(struct page *page, get_block_t *get_block) +{ + struct inode *inode = page->mapping->host; + sector_t iblock, lblock; + struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; + unsigned int blocksize, bbits; + int nr, i; + int fully_mapped = 1; + + head = create_page_buffers(page, inode, 0); + blocksize = head->b_size; + bbits = block_size_bits(blocksize); + + iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); + lblock = (i_size_read(inode)+blocksize-1) >> bbits; + bh = head; + nr = 0; + i = 0; + + do { + if (buffer_uptodate(bh)) + continue; + + if (!buffer_mapped(bh)) { + int err = 0; + + fully_mapped = 0; + if (iblock < lblock) { + WARN_ON(bh->b_size != blocksize); + err = get_block(inode, iblock, bh, 0); + if (err) + SetPageError(page); + } + if (!buffer_mapped(bh)) { + zero_user(page, i * blocksize, blocksize); + if (!err) + set_buffer_uptodate(bh); + continue; + } + /* + * get_block() might have updated the buffer + * synchronously + */ + if (buffer_uptodate(bh)) + continue; + } + arr[nr++] = bh; + } while (i++, iblock++, (bh = bh->b_this_page) != head); + + if (fully_mapped) + SetPageMappedToDisk(page); + + if (!nr) { + /* + * All buffers are uptodate - we can set the page uptodate + * as well. But not if get_block() returned an error. + */ + if (!PageError(page)) + SetPageUptodate(page); + unlock_page(page); + return 0; + } + + /* Stage two: lock the buffers */ + for (i = 0; i < nr; i++) { + bh = arr[i]; + lock_buffer(bh); + mark_buffer_async_read(bh); + } + + /* + * Stage 3: start the IO. Check for uptodateness + * inside the buffer lock in case another process reading + * the underlying blockdev brought it uptodate (the sct fix). + */ + for (i = 0; i < nr; i++) { + bh = arr[i]; + if (buffer_uptodate(bh)) + end_buffer_async_read(bh, 1); + else + submit_bh(READ, bh); + } + return 0; +} +EXPORT_SYMBOL(block_read_full_page); + +/* utility function for filesystems that need to do work on expanding + * truncates. Uses filesystem pagecache writes to allow the filesystem to + * deal with the hole. + */ +int generic_cont_expand_simple(struct inode *inode, loff_t size) +{ + struct address_space *mapping = inode->i_mapping; + struct page *page; + void *fsdata; + int err; + + err = inode_newsize_ok(inode, size); + if (err) + goto out; + + err = pagecache_write_begin(NULL, mapping, size, 0, + AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, + &page, &fsdata); + if (err) + goto out; + + err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); + BUG_ON(err > 0); + +out: + return err; +} +EXPORT_SYMBOL(generic_cont_expand_simple); + +static int cont_expand_zero(struct file *file, struct address_space *mapping, + loff_t pos, loff_t *bytes) +{ + struct inode *inode = mapping->host; + unsigned blocksize = 1 << inode->i_blkbits; + struct page *page; + void *fsdata; + pgoff_t index, curidx; + loff_t curpos; + unsigned zerofrom, offset, len; + int err = 0; + + index = pos >> PAGE_CACHE_SHIFT; + offset = pos & ~PAGE_CACHE_MASK; + + while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { + zerofrom = curpos & ~PAGE_CACHE_MASK; + if (zerofrom & (blocksize-1)) { + *bytes |= (blocksize-1); + (*bytes)++; + } + len = PAGE_CACHE_SIZE - zerofrom; + + err = pagecache_write_begin(file, mapping, curpos, len, + AOP_FLAG_UNINTERRUPTIBLE, + &page, &fsdata); + if (err) + goto out; + zero_user(page, zerofrom, len); + err = pagecache_write_end(file, mapping, curpos, len, len, + page, fsdata); + if (err < 0) + goto out; + BUG_ON(err != len); + err = 0; + + balance_dirty_pages_ratelimited(mapping); + + if (unlikely(fatal_signal_pending(current))) { + err = -EINTR; + goto out; + } + } + + /* page covers the boundary, find the boundary offset */ + if (index == curidx) { + zerofrom = curpos & ~PAGE_CACHE_MASK; + /* if we will expand the thing last block will be filled */ + if (offset <= zerofrom) { + goto out; + } + if (zerofrom & (blocksize-1)) { + *bytes |= (blocksize-1); + (*bytes)++; + } + len = offset - zerofrom; + + err = pagecache_write_begin(file, mapping, curpos, len, + AOP_FLAG_UNINTERRUPTIBLE, + &page, &fsdata); + if (err) + goto out; + zero_user(page, zerofrom, len); + err = pagecache_write_end(file, mapping, curpos, len, len, + page, fsdata); + if (err < 0) + goto out; + BUG_ON(err != len); + err = 0; + } +out: + return err; +} + +/* + * For moronic filesystems that do not allow holes in file. + * We may have to extend the file. + */ +int cont_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata, + get_block_t *get_block, loff_t *bytes) +{ + struct inode *inode = mapping->host; + unsigned blocksize = 1 << inode->i_blkbits; + unsigned zerofrom; + int err; + + err = cont_expand_zero(file, mapping, pos, bytes); + if (err) + return err; + + zerofrom = *bytes & ~PAGE_CACHE_MASK; + if (pos+len > *bytes && zerofrom & (blocksize-1)) { + *bytes |= (blocksize-1); + (*bytes)++; + } + + return block_write_begin(mapping, pos, len, flags, pagep, get_block); +} +EXPORT_SYMBOL(cont_write_begin); + +int block_commit_write(struct page *page, unsigned from, unsigned to) +{ + struct inode *inode = page->mapping->host; + __block_commit_write(inode,page,from,to); + return 0; +} +EXPORT_SYMBOL(block_commit_write); + +/* + * block_page_mkwrite() is not allowed to change the file size as it gets + * called from a page fault handler when a page is first dirtied. Hence we must + * be careful to check for EOF conditions here. We set the page up correctly + * for a written page which means we get ENOSPC checking when writing into + * holes and correct delalloc and unwritten extent mapping on filesystems that + * support these features. + * + * We are not allowed to take the i_mutex here so we have to play games to + * protect against truncate races as the page could now be beyond EOF. Because + * truncate writes the inode size before removing pages, once we have the + * page lock we can determine safely if the page is beyond EOF. If it is not + * beyond EOF, then the page is guaranteed safe against truncation until we + * unlock the page. + * + * Direct callers of this function should protect against filesystem freezing + * using sb_start_write() - sb_end_write() functions. + */ +int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, + get_block_t get_block) +{ + struct page *page = vmf->page; + struct inode *inode = file_inode(vma->vm_file); + unsigned long end; + loff_t size; + int ret; + + lock_page(page); + size = i_size_read(inode); + if ((page->mapping != inode->i_mapping) || + (page_offset(page) > size)) { + /* We overload EFAULT to mean page got truncated */ + ret = -EFAULT; + goto out_unlock; + } + + /* page is wholly or partially inside EOF */ + if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) + end = size & ~PAGE_CACHE_MASK; + else + end = PAGE_CACHE_SIZE; + + ret = __block_write_begin(page, 0, end, get_block); + if (!ret) + ret = block_commit_write(page, 0, end); + + if (unlikely(ret < 0)) + goto out_unlock; + set_page_dirty(page); + wait_for_stable_page(page); + return 0; +out_unlock: + unlock_page(page); + return ret; +} +EXPORT_SYMBOL(__block_page_mkwrite); + +int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, + get_block_t get_block) +{ + int ret; + struct super_block *sb = file_inode(vma->vm_file)->i_sb; + + sb_start_pagefault(sb); + + /* + * Update file times before taking page lock. We may end up failing the + * fault so this update may be superfluous but who really cares... + */ + vma_file_update_time(vma); + + ret = __block_page_mkwrite(vma, vmf, get_block); + sb_end_pagefault(sb); + return block_page_mkwrite_return(ret); +} +EXPORT_SYMBOL(block_page_mkwrite); + +/* + * nobh_write_begin()'s prereads are special: the buffer_heads are freed + * immediately, while under the page lock. So it needs a special end_io + * handler which does not touch the bh after unlocking it. + */ +static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) +{ + __end_buffer_read_notouch(bh, uptodate); +} + +/* + * Attach the singly-linked list of buffers created by nobh_write_begin, to + * the page (converting it to circular linked list and taking care of page + * dirty races). + */ +static void attach_nobh_buffers(struct page *page, struct buffer_head *head) +{ + struct buffer_head *bh; + + BUG_ON(!PageLocked(page)); + + spin_lock(&page->mapping->private_lock); + bh = head; + do { + if (PageDirty(page)) + set_buffer_dirty(bh); + if (!bh->b_this_page) + bh->b_this_page = head; + bh = bh->b_this_page; + } while (bh != head); + attach_page_buffers(page, head); + spin_unlock(&page->mapping->private_lock); +} + +/* + * On entry, the page is fully not uptodate. + * On exit the page is fully uptodate in the areas outside (from,to) + * The filesystem needs to handle block truncation upon failure. + */ +int nobh_write_begin(struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata, + get_block_t *get_block) +{ + struct inode *inode = mapping->host; + const unsigned blkbits = inode->i_blkbits; + const unsigned blocksize = 1 << blkbits; + struct buffer_head *head, *bh; + struct page *page; + pgoff_t index; + unsigned from, to; + unsigned block_in_page; + unsigned block_start, block_end; + sector_t block_in_file; + int nr_reads = 0; + int ret = 0; + int is_mapped_to_disk = 1; + + index = pos >> PAGE_CACHE_SHIFT; + from = pos & (PAGE_CACHE_SIZE - 1); + to = from + len; + + page = grab_cache_page_write_begin(mapping, index, flags); + if (!page) + return -ENOMEM; + *pagep = page; + *fsdata = NULL; + + if (page_has_buffers(page)) { + ret = __block_write_begin(page, pos, len, get_block); + if (unlikely(ret)) + goto out_release; + return ret; + } + + if (PageMappedToDisk(page)) + return 0; + + /* + * Allocate buffers so that we can keep track of state, and potentially + * attach them to the page if an error occurs. In the common case of + * no error, they will just be freed again without ever being attached + * to the page (which is all OK, because we're under the page lock). + * + * Be careful: the buffer linked list is a NULL terminated one, rather + * than the circular one we're used to. + */ + head = alloc_page_buffers(page, blocksize, 0); + if (!head) { + ret = -ENOMEM; + goto out_release; + } + + block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); + + /* + * We loop across all blocks in the page, whether or not they are + * part of the affected region. This is so we can discover if the + * page is fully mapped-to-disk. + */ + for (block_start = 0, block_in_page = 0, bh = head; + block_start < PAGE_CACHE_SIZE; + block_in_page++, block_start += blocksize, bh = bh->b_this_page) { + int create; + + block_end = block_start + blocksize; + bh->b_state = 0; + create = 1; + if (block_start >= to) + create = 0; + ret = get_block(inode, block_in_file + block_in_page, + bh, create); + if (ret) + goto failed; + if (!buffer_mapped(bh)) + is_mapped_to_disk = 0; + if (buffer_new(bh)) + unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); + if (PageUptodate(page)) { + set_buffer_uptodate(bh); + continue; + } + if (buffer_new(bh) || !buffer_mapped(bh)) { + zero_user_segments(page, block_start, from, + to, block_end); + continue; + } + if (buffer_uptodate(bh)) + continue; /* reiserfs does this */ + if (block_start < from || block_end > to) { + lock_buffer(bh); + bh->b_end_io = end_buffer_read_nobh; + submit_bh(READ, bh); + nr_reads++; + } + } + + if (nr_reads) { + /* + * The page is locked, so these buffers are protected from + * any VM or truncate activity. Hence we don't need to care + * for the buffer_head refcounts. + */ + for (bh = head; bh; bh = bh->b_this_page) { + wait_on_buffer(bh); + if (!buffer_uptodate(bh)) + ret = -EIO; + } + if (ret) + goto failed; + } + + if (is_mapped_to_disk) + SetPageMappedToDisk(page); + + *fsdata = head; /* to be released by nobh_write_end */ + + return 0; + +failed: + BUG_ON(!ret); + /* + * Error recovery is a bit difficult. We need to zero out blocks that + * were newly allocated, and dirty them to ensure they get written out. + * Buffers need to be attached to the page at this point, otherwise + * the handling of potential IO errors during writeout would be hard + * (could try doing synchronous writeout, but what if that fails too?) + */ + attach_nobh_buffers(page, head); + page_zero_new_buffers(page, from, to); + +out_release: + unlock_page(page); + page_cache_release(page); + *pagep = NULL; + + return ret; +} +EXPORT_SYMBOL(nobh_write_begin); + +int nobh_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + struct inode *inode = page->mapping->host; + struct buffer_head *head = fsdata; + struct buffer_head *bh; + BUG_ON(fsdata != NULL && page_has_buffers(page)); + + if (unlikely(copied < len) && head) + attach_nobh_buffers(page, head); + if (page_has_buffers(page)) + return generic_write_end(file, mapping, pos, len, + copied, page, fsdata); + + SetPageUptodate(page); + set_page_dirty(page); + if (pos+copied > inode->i_size) { + i_size_write(inode, pos+copied); + mark_inode_dirty(inode); + } + + unlock_page(page); + page_cache_release(page); + + while (head) { + bh = head; + head = head->b_this_page; + free_buffer_head(bh); + } + + return copied; +} +EXPORT_SYMBOL(nobh_write_end); + +/* + * nobh_writepage() - based on block_full_write_page() except + * that it tries to operate without attaching bufferheads to + * the page. + */ +int nobh_writepage(struct page *page, get_block_t *get_block, + struct writeback_control *wbc) +{ + struct inode * const inode = page->mapping->host; + loff_t i_size = i_size_read(inode); + const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; + unsigned offset; + int ret; + + /* Is the page fully inside i_size? */ + if (page->index < end_index) + goto out; + + /* Is the page fully outside i_size? (truncate in progress) */ + offset = i_size & (PAGE_CACHE_SIZE-1); + if (page->index >= end_index+1 || !offset) { + /* + * The page may have dirty, unmapped buffers. For example, + * they may have been added in ext3_writepage(). Make them + * freeable here, so the page does not leak. + */ +#if 0 + /* Not really sure about this - do we need this ? */ + if (page->mapping->a_ops->invalidatepage) + page->mapping->a_ops->invalidatepage(page, offset); +#endif + unlock_page(page); + return 0; /* don't care */ + } + + /* + * The page straddles i_size. It must be zeroed out on each and every + * writepage invocation because it may be mmapped. "A file is mapped + * in multiples of the page size. For a file that is not a multiple of + * the page size, the remaining memory is zeroed when mapped, and + * writes to that region are not written out to the file." + */ + zero_user_segment(page, offset, PAGE_CACHE_SIZE); +out: + ret = mpage_writepage(page, get_block, wbc); + if (ret == -EAGAIN) + ret = __block_write_full_page(inode, page, get_block, wbc, + end_buffer_async_write); + return ret; +} +EXPORT_SYMBOL(nobh_writepage); + +int nobh_truncate_page(struct address_space *mapping, + loff_t from, get_block_t *get_block) +{ + pgoff_t index = from >> PAGE_CACHE_SHIFT; + unsigned offset = from & (PAGE_CACHE_SIZE-1); + unsigned blocksize; + sector_t iblock; + unsigned length, pos; + struct inode *inode = mapping->host; + struct page *page; + struct buffer_head map_bh; + int err; + + blocksize = 1 << inode->i_blkbits; + length = offset & (blocksize - 1); + + /* Block boundary? Nothing to do */ + if (!length) + return 0; + + length = blocksize - length; + iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); + + page = grab_cache_page(mapping, index); + err = -ENOMEM; + if (!page) + goto out; + + if (page_has_buffers(page)) { +has_buffers: + unlock_page(page); + page_cache_release(page); + return block_truncate_page(mapping, from, get_block); + } + + /* Find the buffer that contains "offset" */ + pos = blocksize; + while (offset >= pos) { + iblock++; + pos += blocksize; + } + + map_bh.b_size = blocksize; + map_bh.b_state = 0; + err = get_block(inode, iblock, &map_bh, 0); + if (err) + goto unlock; + /* unmapped? It's a hole - nothing to do */ + if (!buffer_mapped(&map_bh)) + goto unlock; + + /* Ok, it's mapped. Make sure it's up-to-date */ + if (!PageUptodate(page)) { + err = mapping->a_ops->readpage(NULL, page); + if (err) { + page_cache_release(page); + goto out; + } + lock_page(page); + if (!PageUptodate(page)) { + err = -EIO; + goto unlock; + } + if (page_has_buffers(page)) + goto has_buffers; + } + zero_user(page, offset, length); + set_page_dirty(page); + err = 0; + +unlock: + unlock_page(page); + page_cache_release(page); +out: + return err; +} +EXPORT_SYMBOL(nobh_truncate_page); + +int block_truncate_page(struct address_space *mapping, + loff_t from, get_block_t *get_block) +{ + pgoff_t index = from >> PAGE_CACHE_SHIFT; + unsigned offset = from & (PAGE_CACHE_SIZE-1); + unsigned blocksize; + sector_t iblock; + unsigned length, pos; + struct inode *inode = mapping->host; + struct page *page; + struct buffer_head *bh; + int err; + + blocksize = 1 << inode->i_blkbits; + length = offset & (blocksize - 1); + + /* Block boundary? Nothing to do */ + if (!length) + return 0; + + length = blocksize - length; + iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); + + page = grab_cache_page(mapping, index); + err = -ENOMEM; + if (!page) + goto out; + + if (!page_has_buffers(page)) + create_empty_buffers(page, blocksize, 0); + + /* Find the buffer that contains "offset" */ + bh = page_buffers(page); + pos = blocksize; + while (offset >= pos) { + bh = bh->b_this_page; + iblock++; + pos += blocksize; + } + + err = 0; + if (!buffer_mapped(bh)) { + WARN_ON(bh->b_size != blocksize); + err = get_block(inode, iblock, bh, 0); + if (err) + goto unlock; + /* unmapped? It's a hole - nothing to do */ + if (!buffer_mapped(bh)) + goto unlock; + } + + /* Ok, it's mapped. Make sure it's up-to-date */ + if (PageUptodate(page)) + set_buffer_uptodate(bh); + + if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { + err = -EIO; + ll_rw_block(READ, 1, &bh); + wait_on_buffer(bh); + /* Uhhuh. Read error. Complain and punt. */ + if (!buffer_uptodate(bh)) + goto unlock; + } + + zero_user(page, offset, length); + mark_buffer_dirty(bh); + err = 0; + +unlock: + unlock_page(page); + page_cache_release(page); +out: + return err; +} +EXPORT_SYMBOL(block_truncate_page); + +/* + * The generic ->writepage function for buffer-backed address_spaces + */ +int block_write_full_page(struct page *page, get_block_t *get_block, + struct writeback_control *wbc) +{ + struct inode * const inode = page->mapping->host; + loff_t i_size = i_size_read(inode); + const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; + unsigned offset; + + /* Is the page fully inside i_size? */ + if (page->index < end_index) + return __block_write_full_page(inode, page, get_block, wbc, + end_buffer_async_write); + + /* Is the page fully outside i_size? (truncate in progress) */ + offset = i_size & (PAGE_CACHE_SIZE-1); + if (page->index >= end_index+1 || !offset) { + /* + * The page may have dirty, unmapped buffers. For example, + * they may have been added in ext3_writepage(). Make them + * freeable here, so the page does not leak. + */ + do_invalidatepage(page, 0, PAGE_CACHE_SIZE); + unlock_page(page); + return 0; /* don't care */ + } + + /* + * The page straddles i_size. It must be zeroed out on each and every + * writepage invocation because it may be mmapped. "A file is mapped + * in multiples of the page size. For a file that is not a multiple of + * the page size, the remaining memory is zeroed when mapped, and + * writes to that region are not written out to the file." + */ + zero_user_segment(page, offset, PAGE_CACHE_SIZE); + return __block_write_full_page(inode, page, get_block, wbc, + end_buffer_async_write); +} +EXPORT_SYMBOL(block_write_full_page); + +sector_t generic_block_bmap(struct address_space *mapping, sector_t block, + get_block_t *get_block) +{ + struct buffer_head tmp; + struct inode *inode = mapping->host; + tmp.b_state = 0; + tmp.b_blocknr = 0; + tmp.b_size = 1 << inode->i_blkbits; + get_block(inode, block, &tmp, 0); + return tmp.b_blocknr; +} +EXPORT_SYMBOL(generic_block_bmap); + +static void end_bio_bh_io_sync(struct bio *bio, int err) +{ + struct buffer_head *bh = bio->bi_private; + + if (err == -EOPNOTSUPP) { + set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); + } + + if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) + set_bit(BH_Quiet, &bh->b_state); + + bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); + bio_put(bio); +} + +/* + * This allows us to do IO even on the odd last sectors + * of a device, even if the block size is some multiple + * of the physical sector size. + * + * We'll just truncate the bio to the size of the device, + * and clear the end of the buffer head manually. + * + * Truly out-of-range accesses will turn into actual IO + * errors, this only handles the "we need to be able to + * do IO at the final sector" case. + */ +void guard_bio_eod(int rw, struct bio *bio) +{ + sector_t maxsector; + struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1]; + unsigned truncated_bytes; + + maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9; + if (!maxsector) + return; + + /* + * If the *whole* IO is past the end of the device, + * let it through, and the IO layer will turn it into + * an EIO. + */ + if (unlikely(bio->bi_iter.bi_sector >= maxsector)) + return; + + maxsector -= bio->bi_iter.bi_sector; + if (likely((bio->bi_iter.bi_size >> 9) <= maxsector)) + return; + + /* Uhhuh. We've got a bio that straddles the device size! */ + truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9); + + /* Truncate the bio.. */ + bio->bi_iter.bi_size -= truncated_bytes; + bvec->bv_len -= truncated_bytes; + + /* ..and clear the end of the buffer for reads */ + if ((rw & RW_MASK) == READ) { + zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len, + truncated_bytes); + } +} + +int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags) +{ + struct bio *bio; + int ret = 0; + + BUG_ON(!buffer_locked(bh)); + BUG_ON(!buffer_mapped(bh)); + BUG_ON(!bh->b_end_io); + BUG_ON(buffer_delay(bh)); + BUG_ON(buffer_unwritten(bh)); + + /* + * Only clear out a write error when rewriting + */ + if (test_set_buffer_req(bh) && (rw & WRITE)) + clear_buffer_write_io_error(bh); + + /* + * from here on down, it's all bio -- do the initial mapping, + * submit_bio -> generic_make_request may further map this bio around + */ + bio = bio_alloc(GFP_NOIO, 1); + + bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9); + bio->bi_bdev = bh->b_bdev; + bio->bi_io_vec[0].bv_page = bh->b_page; + bio->bi_io_vec[0].bv_len = bh->b_size; + bio->bi_io_vec[0].bv_offset = bh_offset(bh); + + bio->bi_vcnt = 1; + bio->bi_iter.bi_size = bh->b_size; + + bio->bi_end_io = end_bio_bh_io_sync; + bio->bi_private = bh; + bio->bi_flags |= bio_flags; + + /* Take care of bh's that straddle the end of the device */ + guard_bio_eod(rw, bio); + + if (buffer_meta(bh)) + rw |= REQ_META; + if (buffer_prio(bh)) + rw |= REQ_PRIO; + + bio_get(bio); + submit_bio(rw, bio); + + if (bio_flagged(bio, BIO_EOPNOTSUPP)) + ret = -EOPNOTSUPP; + + bio_put(bio); + return ret; +} +EXPORT_SYMBOL_GPL(_submit_bh); + +int submit_bh(int rw, struct buffer_head *bh) +{ + return _submit_bh(rw, bh, 0); +} +EXPORT_SYMBOL(submit_bh); + +/** + * ll_rw_block: low-level access to block devices (DEPRECATED) + * @rw: whether to %READ or %WRITE or maybe %READA (readahead) + * @nr: number of &struct buffer_heads in the array + * @bhs: array of pointers to &struct buffer_head + * + * ll_rw_block() takes an array of pointers to &struct buffer_heads, and + * requests an I/O operation on them, either a %READ or a %WRITE. The third + * %READA option is described in the documentation for generic_make_request() + * which ll_rw_block() calls. + * + * This function drops any buffer that it cannot get a lock on (with the + * BH_Lock state bit), any buffer that appears to be clean when doing a write + * request, and any buffer that appears to be up-to-date when doing read + * request. Further it marks as clean buffers that are processed for + * writing (the buffer cache won't assume that they are actually clean + * until the buffer gets unlocked). + * + * ll_rw_block sets b_end_io to simple completion handler that marks + * the buffer up-to-date (if appropriate), unlocks the buffer and wakes + * any waiters. + * + * All of the buffers must be for the same device, and must also be a + * multiple of the current approved size for the device. + */ +void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) +{ + int i; + + for (i = 0; i < nr; i++) { + struct buffer_head *bh = bhs[i]; + + if (!trylock_buffer(bh)) + continue; + if (rw == WRITE) { + if (test_clear_buffer_dirty(bh)) { + bh->b_end_io = end_buffer_write_sync; + get_bh(bh); + submit_bh(WRITE, bh); + continue; + } + } else { + if (!buffer_uptodate(bh)) { + bh->b_end_io = end_buffer_read_sync; + get_bh(bh); + submit_bh(rw, bh); + continue; + } + } + unlock_buffer(bh); + } +} +EXPORT_SYMBOL(ll_rw_block); + +void write_dirty_buffer(struct buffer_head *bh, int rw) +{ + lock_buffer(bh); + if (!test_clear_buffer_dirty(bh)) { + unlock_buffer(bh); + return; + } + bh->b_end_io = end_buffer_write_sync; + get_bh(bh); + submit_bh(rw, bh); +} +EXPORT_SYMBOL(write_dirty_buffer); + +/* + * For a data-integrity writeout, we need to wait upon any in-progress I/O + * and then start new I/O and then wait upon it. The caller must have a ref on + * the buffer_head. + */ +int __sync_dirty_buffer(struct buffer_head *bh, int rw) +{ + int ret = 0; + + WARN_ON(atomic_read(&bh->b_count) < 1); + lock_buffer(bh); + if (test_clear_buffer_dirty(bh)) { + get_bh(bh); + bh->b_end_io = end_buffer_write_sync; + ret = submit_bh(rw, bh); + wait_on_buffer(bh); + if (!ret && !buffer_uptodate(bh)) + ret = -EIO; + } else { + unlock_buffer(bh); + } + return ret; +} +EXPORT_SYMBOL(__sync_dirty_buffer); + +int sync_dirty_buffer(struct buffer_head *bh) +{ + return __sync_dirty_buffer(bh, WRITE_SYNC); +} +EXPORT_SYMBOL(sync_dirty_buffer); + +/* + * try_to_free_buffers() checks if all the buffers on this particular page + * are unused, and releases them if so. + * + * Exclusion against try_to_free_buffers may be obtained by either + * locking the page or by holding its mapping's private_lock. + * + * If the page is dirty but all the buffers are clean then we need to + * be sure to mark the page clean as well. This is because the page + * may be against a block device, and a later reattachment of buffers + * to a dirty page will set *all* buffers dirty. Which would corrupt + * filesystem data on the same device. + * + * The same applies to regular filesystem pages: if all the buffers are + * clean then we set the page clean and proceed. To do that, we require + * total exclusion from __set_page_dirty_buffers(). That is obtained with + * private_lock. + * + * try_to_free_buffers() is non-blocking. + */ +static inline int buffer_busy(struct buffer_head *bh) +{ + return atomic_read(&bh->b_count) | + (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); +} + +static int +drop_buffers(struct page *page, struct buffer_head **buffers_to_free) +{ + struct buffer_head *head = page_buffers(page); + struct buffer_head *bh; + + bh = head; + do { + if (buffer_write_io_error(bh) && page->mapping) + set_bit(AS_EIO, &page->mapping->flags); + if (buffer_busy(bh)) + goto failed; + bh = bh->b_this_page; + } while (bh != head); + + do { + struct buffer_head *next = bh->b_this_page; + + if (bh->b_assoc_map) + __remove_assoc_queue(bh); + bh = next; + } while (bh != head); + *buffers_to_free = head; + __clear_page_buffers(page); + return 1; +failed: + return 0; +} + +int try_to_free_buffers(struct page *page) +{ + struct address_space * const mapping = page->mapping; + struct buffer_head *buffers_to_free = NULL; + int ret = 0; + + BUG_ON(!PageLocked(page)); + if (PageWriteback(page)) + return 0; + + if (mapping == NULL) { /* can this still happen? */ + ret = drop_buffers(page, &buffers_to_free); + goto out; + } + + spin_lock(&mapping->private_lock); + ret = drop_buffers(page, &buffers_to_free); + + /* + * If the filesystem writes its buffers by hand (eg ext3) + * then we can have clean buffers against a dirty page. We + * clean the page here; otherwise the VM will never notice + * that the filesystem did any IO at all. + * + * Also, during truncate, discard_buffer will have marked all + * the page's buffers clean. We discover that here and clean + * the page also. + * + * private_lock must be held over this entire operation in order + * to synchronise against __set_page_dirty_buffers and prevent the + * dirty bit from being lost. + */ + if (ret && TestClearPageDirty(page)) + account_page_cleaned(page, mapping); + spin_unlock(&mapping->private_lock); +out: + if (buffers_to_free) { + struct buffer_head *bh = buffers_to_free; + + do { + struct buffer_head *next = bh->b_this_page; + free_buffer_head(bh); + bh = next; + } while (bh != buffers_to_free); + } + return ret; +} +EXPORT_SYMBOL(try_to_free_buffers); + +/* + * There are no bdflush tunables left. But distributions are + * still running obsolete flush daemons, so we terminate them here. + * + * Use of bdflush() is deprecated and will be removed in a future kernel. + * The `flush-X' kernel threads fully replace bdflush daemons and this call. + */ +SYSCALL_DEFINE2(bdflush, int, func, long, data) +{ + static int msg_count; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (msg_count < 5) { + msg_count++; + printk(KERN_INFO + "warning: process `%s' used the obsolete bdflush" + " system call\n", current->comm); + printk(KERN_INFO "Fix your initscripts?\n"); + } + + if (func == 1) + do_exit(0); + return 0; +} + +/* + * Buffer-head allocation + */ +static struct kmem_cache *bh_cachep __read_mostly; + +/* + * Once the number of bh's in the machine exceeds this level, we start + * stripping them in writeback. + */ +static unsigned long max_buffer_heads; + +int buffer_heads_over_limit; + +struct bh_accounting { + int nr; /* Number of live bh's */ + int ratelimit; /* Limit cacheline bouncing */ +}; + +static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; + +static void recalc_bh_state(void) +{ + int i; + int tot = 0; + + if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) + return; + __this_cpu_write(bh_accounting.ratelimit, 0); + for_each_online_cpu(i) + tot += per_cpu(bh_accounting, i).nr; + buffer_heads_over_limit = (tot > max_buffer_heads); +} + +struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) +{ + struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); + if (ret) { + INIT_LIST_HEAD(&ret->b_assoc_buffers); + preempt_disable(); + __this_cpu_inc(bh_accounting.nr); + recalc_bh_state(); + preempt_enable(); + } + return ret; +} +EXPORT_SYMBOL(alloc_buffer_head); + +void free_buffer_head(struct buffer_head *bh) +{ + BUG_ON(!list_empty(&bh->b_assoc_buffers)); + kmem_cache_free(bh_cachep, bh); + preempt_disable(); + __this_cpu_dec(bh_accounting.nr); + recalc_bh_state(); + preempt_enable(); +} +EXPORT_SYMBOL(free_buffer_head); + +static void buffer_exit_cpu(int cpu) +{ + int i; + struct bh_lru *b = &per_cpu(bh_lrus, cpu); + + for (i = 0; i < BH_LRU_SIZE; i++) { + brelse(b->bhs[i]); + b->bhs[i] = NULL; + } + this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); + per_cpu(bh_accounting, cpu).nr = 0; +} + +static int buffer_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) + buffer_exit_cpu((unsigned long)hcpu); + return NOTIFY_OK; +} + +/** + * bh_uptodate_or_lock - Test whether the buffer is uptodate + * @bh: struct buffer_head + * + * Return true if the buffer is up-to-date and false, + * with the buffer locked, if not. + */ +int bh_uptodate_or_lock(struct buffer_head *bh) +{ + if (!buffer_uptodate(bh)) { + lock_buffer(bh); + if (!buffer_uptodate(bh)) + return 0; + unlock_buffer(bh); + } + return 1; +} +EXPORT_SYMBOL(bh_uptodate_or_lock); + +/** + * bh_submit_read - Submit a locked buffer for reading + * @bh: struct buffer_head + * + * Returns zero on success and -EIO on error. + */ +int bh_submit_read(struct buffer_head *bh) +{ + BUG_ON(!buffer_locked(bh)); + + if (buffer_uptodate(bh)) { + unlock_buffer(bh); + return 0; + } + + get_bh(bh); + bh->b_end_io = end_buffer_read_sync; + submit_bh(READ, bh); + wait_on_buffer(bh); + if (buffer_uptodate(bh)) + return 0; + return -EIO; +} +EXPORT_SYMBOL(bh_submit_read); + +void __init buffer_init(void) +{ + unsigned long nrpages; + + bh_cachep = kmem_cache_create("buffer_head", + sizeof(struct buffer_head), 0, + (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| + SLAB_MEM_SPREAD), + NULL); + + /* + * Limit the bh occupancy to 10% of ZONE_NORMAL + */ + nrpages = (nr_free_buffer_pages() * 10) / 100; + max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); + hotcpu_notifier(buffer_cpu_notify, 0); +} |