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+/*
+ * 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);
+}