diff options
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 2665 |
1 files changed, 2665 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c new file mode 100644 index 000000000..a863d0f9d --- /dev/null +++ b/mm/filemap.c @@ -0,0 +1,2665 @@ +/* + * linux/mm/filemap.c + * + * Copyright (C) 1994-1999 Linus Torvalds + */ + +/* + * This file handles the generic file mmap semantics used by + * most "normal" filesystems (but you don't /have/ to use this: + * the NFS filesystem used to do this differently, for example) + */ +#include <linux/export.h> +#include <linux/compiler.h> +#include <linux/fs.h> +#include <linux/uaccess.h> +#include <linux/capability.h> +#include <linux/kernel_stat.h> +#include <linux/gfp.h> +#include <linux/mm.h> +#include <linux/swap.h> +#include <linux/mman.h> +#include <linux/pagemap.h> +#include <linux/file.h> +#include <linux/uio.h> +#include <linux/hash.h> +#include <linux/writeback.h> +#include <linux/backing-dev.h> +#include <linux/pagevec.h> +#include <linux/blkdev.h> +#include <linux/security.h> +#include <linux/cpuset.h> +#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ +#include <linux/hugetlb.h> +#include <linux/memcontrol.h> +#include <linux/cleancache.h> +#include <linux/rmap.h> +#include "internal.h" + +#define CREATE_TRACE_POINTS +#include <trace/events/filemap.h> + +/* + * FIXME: remove all knowledge of the buffer layer from the core VM + */ +#include <linux/buffer_head.h> /* for try_to_free_buffers */ + +#include <asm/mman.h> + +/* + * Shared mappings implemented 30.11.1994. It's not fully working yet, + * though. + * + * Shared mappings now work. 15.8.1995 Bruno. + * + * finished 'unifying' the page and buffer cache and SMP-threaded the + * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> + * + * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> + */ + +/* + * Lock ordering: + * + * ->i_mmap_rwsem (truncate_pagecache) + * ->private_lock (__free_pte->__set_page_dirty_buffers) + * ->swap_lock (exclusive_swap_page, others) + * ->mapping->tree_lock + * + * ->i_mutex + * ->i_mmap_rwsem (truncate->unmap_mapping_range) + * + * ->mmap_sem + * ->i_mmap_rwsem + * ->page_table_lock or pte_lock (various, mainly in memory.c) + * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) + * + * ->mmap_sem + * ->lock_page (access_process_vm) + * + * ->i_mutex (generic_perform_write) + * ->mmap_sem (fault_in_pages_readable->do_page_fault) + * + * bdi->wb.list_lock + * sb_lock (fs/fs-writeback.c) + * ->mapping->tree_lock (__sync_single_inode) + * + * ->i_mmap_rwsem + * ->anon_vma.lock (vma_adjust) + * + * ->anon_vma.lock + * ->page_table_lock or pte_lock (anon_vma_prepare and various) + * + * ->page_table_lock or pte_lock + * ->swap_lock (try_to_unmap_one) + * ->private_lock (try_to_unmap_one) + * ->tree_lock (try_to_unmap_one) + * ->zone.lru_lock (follow_page->mark_page_accessed) + * ->zone.lru_lock (check_pte_range->isolate_lru_page) + * ->private_lock (page_remove_rmap->set_page_dirty) + * ->tree_lock (page_remove_rmap->set_page_dirty) + * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) + * ->inode->i_lock (page_remove_rmap->set_page_dirty) + * bdi.wb->list_lock (zap_pte_range->set_page_dirty) + * ->inode->i_lock (zap_pte_range->set_page_dirty) + * ->private_lock (zap_pte_range->__set_page_dirty_buffers) + * + * ->i_mmap_rwsem + * ->tasklist_lock (memory_failure, collect_procs_ao) + */ + +static void page_cache_tree_delete(struct address_space *mapping, + struct page *page, void *shadow) +{ + struct radix_tree_node *node; + unsigned long index; + unsigned int offset; + unsigned int tag; + void **slot; + + VM_BUG_ON(!PageLocked(page)); + + __radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot); + + if (shadow) { + mapping->nrshadows++; + /* + * Make sure the nrshadows update is committed before + * the nrpages update so that final truncate racing + * with reclaim does not see both counters 0 at the + * same time and miss a shadow entry. + */ + smp_wmb(); + } + mapping->nrpages--; + + if (!node) { + /* Clear direct pointer tags in root node */ + mapping->page_tree.gfp_mask &= __GFP_BITS_MASK; + radix_tree_replace_slot(slot, shadow); + return; + } + + /* Clear tree tags for the removed page */ + index = page->index; + offset = index & RADIX_TREE_MAP_MASK; + for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { + if (test_bit(offset, node->tags[tag])) + radix_tree_tag_clear(&mapping->page_tree, index, tag); + } + + /* Delete page, swap shadow entry */ + radix_tree_replace_slot(slot, shadow); + workingset_node_pages_dec(node); + if (shadow) + workingset_node_shadows_inc(node); + else + if (__radix_tree_delete_node(&mapping->page_tree, node)) + return; + + /* + * Track node that only contains shadow entries. + * + * Avoid acquiring the list_lru lock if already tracked. The + * list_empty() test is safe as node->private_list is + * protected by mapping->tree_lock. + */ + if (!workingset_node_pages(node) && + list_empty(&node->private_list)) { + node->private_data = mapping; + list_lru_add(&workingset_shadow_nodes, &node->private_list); + } +} + +/* + * Delete a page from the page cache and free it. Caller has to make + * sure the page is locked and that nobody else uses it - or that usage + * is safe. The caller must hold the mapping's tree_lock. + */ +void __delete_from_page_cache(struct page *page, void *shadow) +{ + struct address_space *mapping = page->mapping; + + trace_mm_filemap_delete_from_page_cache(page); + /* + * if we're uptodate, flush out into the cleancache, otherwise + * invalidate any existing cleancache entries. We can't leave + * stale data around in the cleancache once our page is gone + */ + if (PageUptodate(page) && PageMappedToDisk(page)) + cleancache_put_page(page); + else + cleancache_invalidate_page(mapping, page); + + page_cache_tree_delete(mapping, page, shadow); + + page->mapping = NULL; + /* Leave page->index set: truncation lookup relies upon it */ + + __dec_zone_page_state(page, NR_FILE_PAGES); + if (PageSwapBacked(page)) + __dec_zone_page_state(page, NR_SHMEM); + BUG_ON(page_mapped(page)); + + /* + * At this point page must be either written or cleaned by truncate. + * Dirty page here signals a bug and loss of unwritten data. + * + * This fixes dirty accounting after removing the page entirely but + * leaves PageDirty set: it has no effect for truncated page and + * anyway will be cleared before returning page into buddy allocator. + */ + if (WARN_ON_ONCE(PageDirty(page))) + account_page_cleaned(page, mapping); +} + +/** + * delete_from_page_cache - delete page from page cache + * @page: the page which the kernel is trying to remove from page cache + * + * This must be called only on pages that have been verified to be in the page + * cache and locked. It will never put the page into the free list, the caller + * has a reference on the page. + */ +void delete_from_page_cache(struct page *page) +{ + struct address_space *mapping = page->mapping; + void (*freepage)(struct page *); + + BUG_ON(!PageLocked(page)); + + freepage = mapping->a_ops->freepage; + spin_lock_irq(&mapping->tree_lock); + __delete_from_page_cache(page, NULL); + spin_unlock_irq(&mapping->tree_lock); + + if (freepage) + freepage(page); + page_cache_release(page); +} +EXPORT_SYMBOL(delete_from_page_cache); + +static int filemap_check_errors(struct address_space *mapping) +{ + int ret = 0; + /* Check for outstanding write errors */ + if (test_bit(AS_ENOSPC, &mapping->flags) && + test_and_clear_bit(AS_ENOSPC, &mapping->flags)) + ret = -ENOSPC; + if (test_bit(AS_EIO, &mapping->flags) && + test_and_clear_bit(AS_EIO, &mapping->flags)) + ret = -EIO; + return ret; +} + +/** + * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range + * @mapping: address space structure to write + * @start: offset in bytes where the range starts + * @end: offset in bytes where the range ends (inclusive) + * @sync_mode: enable synchronous operation + * + * Start writeback against all of a mapping's dirty pages that lie + * within the byte offsets <start, end> inclusive. + * + * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as + * opposed to a regular memory cleansing writeback. The difference between + * these two operations is that if a dirty page/buffer is encountered, it must + * be waited upon, and not just skipped over. + */ +int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, + loff_t end, int sync_mode) +{ + int ret; + struct writeback_control wbc = { + .sync_mode = sync_mode, + .nr_to_write = LONG_MAX, + .range_start = start, + .range_end = end, + }; + + if (!mapping_cap_writeback_dirty(mapping)) + return 0; + + ret = do_writepages(mapping, &wbc); + return ret; +} + +static inline int __filemap_fdatawrite(struct address_space *mapping, + int sync_mode) +{ + return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); +} + +int filemap_fdatawrite(struct address_space *mapping) +{ + return __filemap_fdatawrite(mapping, WB_SYNC_ALL); +} +EXPORT_SYMBOL(filemap_fdatawrite); + +int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, + loff_t end) +{ + return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); +} +EXPORT_SYMBOL(filemap_fdatawrite_range); + +/** + * filemap_flush - mostly a non-blocking flush + * @mapping: target address_space + * + * This is a mostly non-blocking flush. Not suitable for data-integrity + * purposes - I/O may not be started against all dirty pages. + */ +int filemap_flush(struct address_space *mapping) +{ + return __filemap_fdatawrite(mapping, WB_SYNC_NONE); +} +EXPORT_SYMBOL(filemap_flush); + +/** + * filemap_fdatawait_range - wait for writeback to complete + * @mapping: address space structure to wait for + * @start_byte: offset in bytes where the range starts + * @end_byte: offset in bytes where the range ends (inclusive) + * + * Walk the list of under-writeback pages of the given address space + * in the given range and wait for all of them. + */ +int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, + loff_t end_byte) +{ + pgoff_t index = start_byte >> PAGE_CACHE_SHIFT; + pgoff_t end = end_byte >> PAGE_CACHE_SHIFT; + struct pagevec pvec; + int nr_pages; + int ret2, ret = 0; + + if (end_byte < start_byte) + goto out; + + pagevec_init(&pvec, 0); + while ((index <= end) && + (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, + PAGECACHE_TAG_WRITEBACK, + min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { + unsigned i; + + for (i = 0; i < nr_pages; i++) { + struct page *page = pvec.pages[i]; + + /* until radix tree lookup accepts end_index */ + if (page->index > end) + continue; + + wait_on_page_writeback(page); + if (TestClearPageError(page)) + ret = -EIO; + } + pagevec_release(&pvec); + cond_resched(); + } +out: + ret2 = filemap_check_errors(mapping); + if (!ret) + ret = ret2; + + return ret; +} +EXPORT_SYMBOL(filemap_fdatawait_range); + +/** + * filemap_fdatawait - wait for all under-writeback pages to complete + * @mapping: address space structure to wait for + * + * Walk the list of under-writeback pages of the given address space + * and wait for all of them. + */ +int filemap_fdatawait(struct address_space *mapping) +{ + loff_t i_size = i_size_read(mapping->host); + + if (i_size == 0) + return 0; + + return filemap_fdatawait_range(mapping, 0, i_size - 1); +} +EXPORT_SYMBOL(filemap_fdatawait); + +int filemap_write_and_wait(struct address_space *mapping) +{ + int err = 0; + + if (mapping->nrpages) { + err = filemap_fdatawrite(mapping); + /* + * Even if the above returned error, the pages may be + * written partially (e.g. -ENOSPC), so we wait for it. + * But the -EIO is special case, it may indicate the worst + * thing (e.g. bug) happened, so we avoid waiting for it. + */ + if (err != -EIO) { + int err2 = filemap_fdatawait(mapping); + if (!err) + err = err2; + } + } else { + err = filemap_check_errors(mapping); + } + return err; +} +EXPORT_SYMBOL(filemap_write_and_wait); + +/** + * filemap_write_and_wait_range - write out & wait on a file range + * @mapping: the address_space for the pages + * @lstart: offset in bytes where the range starts + * @lend: offset in bytes where the range ends (inclusive) + * + * Write out and wait upon file offsets lstart->lend, inclusive. + * + * Note that `lend' is inclusive (describes the last byte to be written) so + * that this function can be used to write to the very end-of-file (end = -1). + */ +int filemap_write_and_wait_range(struct address_space *mapping, + loff_t lstart, loff_t lend) +{ + int err = 0; + + if (mapping->nrpages) { + err = __filemap_fdatawrite_range(mapping, lstart, lend, + WB_SYNC_ALL); + /* See comment of filemap_write_and_wait() */ + if (err != -EIO) { + int err2 = filemap_fdatawait_range(mapping, + lstart, lend); + if (!err) + err = err2; + } + } else { + err = filemap_check_errors(mapping); + } + return err; +} +EXPORT_SYMBOL(filemap_write_and_wait_range); + +/** + * replace_page_cache_page - replace a pagecache page with a new one + * @old: page to be replaced + * @new: page to replace with + * @gfp_mask: allocation mode + * + * This function replaces a page in the pagecache with a new one. On + * success it acquires the pagecache reference for the new page and + * drops it for the old page. Both the old and new pages must be + * locked. This function does not add the new page to the LRU, the + * caller must do that. + * + * The remove + add is atomic. The only way this function can fail is + * memory allocation failure. + */ +int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) +{ + int error; + + VM_BUG_ON_PAGE(!PageLocked(old), old); + VM_BUG_ON_PAGE(!PageLocked(new), new); + VM_BUG_ON_PAGE(new->mapping, new); + + error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); + if (!error) { + struct address_space *mapping = old->mapping; + void (*freepage)(struct page *); + + pgoff_t offset = old->index; + freepage = mapping->a_ops->freepage; + + page_cache_get(new); + new->mapping = mapping; + new->index = offset; + + spin_lock_irq(&mapping->tree_lock); + __delete_from_page_cache(old, NULL); + error = radix_tree_insert(&mapping->page_tree, offset, new); + BUG_ON(error); + mapping->nrpages++; + __inc_zone_page_state(new, NR_FILE_PAGES); + if (PageSwapBacked(new)) + __inc_zone_page_state(new, NR_SHMEM); + spin_unlock_irq(&mapping->tree_lock); + mem_cgroup_migrate(old, new, true); + radix_tree_preload_end(); + if (freepage) + freepage(old); + page_cache_release(old); + } + + return error; +} +EXPORT_SYMBOL_GPL(replace_page_cache_page); + +static int page_cache_tree_insert(struct address_space *mapping, + struct page *page, void **shadowp) +{ + struct radix_tree_node *node; + void **slot; + int error; + + error = __radix_tree_create(&mapping->page_tree, page->index, + &node, &slot); + if (error) + return error; + if (*slot) { + void *p; + + p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock); + if (!radix_tree_exceptional_entry(p)) + return -EEXIST; + if (shadowp) + *shadowp = p; + mapping->nrshadows--; + if (node) + workingset_node_shadows_dec(node); + } + radix_tree_replace_slot(slot, page); + mapping->nrpages++; + if (node) { + workingset_node_pages_inc(node); + /* + * Don't track node that contains actual pages. + * + * Avoid acquiring the list_lru lock if already + * untracked. The list_empty() test is safe as + * node->private_list is protected by + * mapping->tree_lock. + */ + if (!list_empty(&node->private_list)) + list_lru_del(&workingset_shadow_nodes, + &node->private_list); + } + return 0; +} + +static int __add_to_page_cache_locked(struct page *page, + struct address_space *mapping, + pgoff_t offset, gfp_t gfp_mask, + void **shadowp) +{ + int huge = PageHuge(page); + struct mem_cgroup *memcg; + int error; + + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(PageSwapBacked(page), page); + + if (!huge) { + error = mem_cgroup_try_charge(page, current->mm, + gfp_mask, &memcg); + if (error) + return error; + } + + error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM); + if (error) { + if (!huge) + mem_cgroup_cancel_charge(page, memcg); + return error; + } + + page_cache_get(page); + page->mapping = mapping; + page->index = offset; + + spin_lock_irq(&mapping->tree_lock); + error = page_cache_tree_insert(mapping, page, shadowp); + radix_tree_preload_end(); + if (unlikely(error)) + goto err_insert; + __inc_zone_page_state(page, NR_FILE_PAGES); + spin_unlock_irq(&mapping->tree_lock); + if (!huge) + mem_cgroup_commit_charge(page, memcg, false); + trace_mm_filemap_add_to_page_cache(page); + return 0; +err_insert: + page->mapping = NULL; + /* Leave page->index set: truncation relies upon it */ + spin_unlock_irq(&mapping->tree_lock); + if (!huge) + mem_cgroup_cancel_charge(page, memcg); + page_cache_release(page); + return error; +} + +/** + * add_to_page_cache_locked - add a locked page to the pagecache + * @page: page to add + * @mapping: the page's address_space + * @offset: page index + * @gfp_mask: page allocation mode + * + * This function is used to add a page to the pagecache. It must be locked. + * This function does not add the page to the LRU. The caller must do that. + */ +int add_to_page_cache_locked(struct page *page, struct address_space *mapping, + pgoff_t offset, gfp_t gfp_mask) +{ + return __add_to_page_cache_locked(page, mapping, offset, + gfp_mask, NULL); +} +EXPORT_SYMBOL(add_to_page_cache_locked); + +int add_to_page_cache_lru(struct page *page, struct address_space *mapping, + pgoff_t offset, gfp_t gfp_mask) +{ + void *shadow = NULL; + int ret; + + __set_page_locked(page); + ret = __add_to_page_cache_locked(page, mapping, offset, + gfp_mask, &shadow); + if (unlikely(ret)) + __clear_page_locked(page); + else { + /* + * The page might have been evicted from cache only + * recently, in which case it should be activated like + * any other repeatedly accessed page. + */ + if (shadow && workingset_refault(shadow)) { + SetPageActive(page); + workingset_activation(page); + } else + ClearPageActive(page); + lru_cache_add(page); + } + return ret; +} +EXPORT_SYMBOL_GPL(add_to_page_cache_lru); + +#ifdef CONFIG_NUMA +struct page *__page_cache_alloc(gfp_t gfp) +{ + int n; + struct page *page; + + if (cpuset_do_page_mem_spread()) { + unsigned int cpuset_mems_cookie; + do { + cpuset_mems_cookie = read_mems_allowed_begin(); + n = cpuset_mem_spread_node(); + page = alloc_pages_exact_node(n, gfp, 0); + } while (!page && read_mems_allowed_retry(cpuset_mems_cookie)); + + return page; + } + return alloc_pages(gfp, 0); +} +EXPORT_SYMBOL(__page_cache_alloc); +#endif + +/* + * In order to wait for pages to become available there must be + * waitqueues associated with pages. By using a hash table of + * waitqueues where the bucket discipline is to maintain all + * waiters on the same queue and wake all when any of the pages + * become available, and for the woken contexts to check to be + * sure the appropriate page became available, this saves space + * at a cost of "thundering herd" phenomena during rare hash + * collisions. + */ +wait_queue_head_t *page_waitqueue(struct page *page) +{ + const struct zone *zone = page_zone(page); + + return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; +} +EXPORT_SYMBOL(page_waitqueue); + +void wait_on_page_bit(struct page *page, int bit_nr) +{ + DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); + + if (test_bit(bit_nr, &page->flags)) + __wait_on_bit(page_waitqueue(page), &wait, bit_wait_io, + TASK_UNINTERRUPTIBLE); +} +EXPORT_SYMBOL(wait_on_page_bit); + +int wait_on_page_bit_killable(struct page *page, int bit_nr) +{ + DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); + + if (!test_bit(bit_nr, &page->flags)) + return 0; + + return __wait_on_bit(page_waitqueue(page), &wait, + bit_wait_io, TASK_KILLABLE); +} + +int wait_on_page_bit_killable_timeout(struct page *page, + int bit_nr, unsigned long timeout) +{ + DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); + + wait.key.timeout = jiffies + timeout; + if (!test_bit(bit_nr, &page->flags)) + return 0; + return __wait_on_bit(page_waitqueue(page), &wait, + bit_wait_io_timeout, TASK_KILLABLE); +} +EXPORT_SYMBOL_GPL(wait_on_page_bit_killable_timeout); + +/** + * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue + * @page: Page defining the wait queue of interest + * @waiter: Waiter to add to the queue + * + * Add an arbitrary @waiter to the wait queue for the nominated @page. + */ +void add_page_wait_queue(struct page *page, wait_queue_t *waiter) +{ + wait_queue_head_t *q = page_waitqueue(page); + unsigned long flags; + + spin_lock_irqsave(&q->lock, flags); + __add_wait_queue(q, waiter); + spin_unlock_irqrestore(&q->lock, flags); +} +EXPORT_SYMBOL_GPL(add_page_wait_queue); + +/** + * unlock_page - unlock a locked page + * @page: the page + * + * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). + * Also wakes sleepers in wait_on_page_writeback() because the wakeup + * mechanism between PageLocked pages and PageWriteback pages is shared. + * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. + * + * The mb is necessary to enforce ordering between the clear_bit and the read + * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). + */ +void unlock_page(struct page *page) +{ + VM_BUG_ON_PAGE(!PageLocked(page), page); + clear_bit_unlock(PG_locked, &page->flags); + smp_mb__after_atomic(); + wake_up_page(page, PG_locked); +} +EXPORT_SYMBOL(unlock_page); + +/** + * end_page_writeback - end writeback against a page + * @page: the page + */ +void end_page_writeback(struct page *page) +{ + /* + * TestClearPageReclaim could be used here but it is an atomic + * operation and overkill in this particular case. Failing to + * shuffle a page marked for immediate reclaim is too mild to + * justify taking an atomic operation penalty at the end of + * ever page writeback. + */ + if (PageReclaim(page)) { + ClearPageReclaim(page); + rotate_reclaimable_page(page); + } + + if (!test_clear_page_writeback(page)) + BUG(); + + smp_mb__after_atomic(); + wake_up_page(page, PG_writeback); +} +EXPORT_SYMBOL(end_page_writeback); + +/* + * After completing I/O on a page, call this routine to update the page + * flags appropriately + */ +void page_endio(struct page *page, int rw, int err) +{ + if (rw == READ) { + if (!err) { + SetPageUptodate(page); + } else { + ClearPageUptodate(page); + SetPageError(page); + } + unlock_page(page); + } else { /* rw == WRITE */ + if (err) { + SetPageError(page); + if (page->mapping) + mapping_set_error(page->mapping, err); + } + end_page_writeback(page); + } +} +EXPORT_SYMBOL_GPL(page_endio); + +/** + * __lock_page - get a lock on the page, assuming we need to sleep to get it + * @page: the page to lock + */ +void __lock_page(struct page *page) +{ + DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); + + __wait_on_bit_lock(page_waitqueue(page), &wait, bit_wait_io, + TASK_UNINTERRUPTIBLE); +} +EXPORT_SYMBOL(__lock_page); + +int __lock_page_killable(struct page *page) +{ + DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); + + return __wait_on_bit_lock(page_waitqueue(page), &wait, + bit_wait_io, TASK_KILLABLE); +} +EXPORT_SYMBOL_GPL(__lock_page_killable); + +/* + * Return values: + * 1 - page is locked; mmap_sem is still held. + * 0 - page is not locked. + * mmap_sem has been released (up_read()), unless flags had both + * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in + * which case mmap_sem is still held. + * + * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1 + * with the page locked and the mmap_sem unperturbed. + */ +int __lock_page_or_retry(struct page *page, struct mm_struct *mm, + unsigned int flags) +{ + if (flags & FAULT_FLAG_ALLOW_RETRY) { + /* + * CAUTION! In this case, mmap_sem is not released + * even though return 0. + */ + if (flags & FAULT_FLAG_RETRY_NOWAIT) + return 0; + + up_read(&mm->mmap_sem); + if (flags & FAULT_FLAG_KILLABLE) + wait_on_page_locked_killable(page); + else + wait_on_page_locked(page); + return 0; + } else { + if (flags & FAULT_FLAG_KILLABLE) { + int ret; + + ret = __lock_page_killable(page); + if (ret) { + up_read(&mm->mmap_sem); + return 0; + } + } else + __lock_page(page); + return 1; + } +} + +/** + * page_cache_next_hole - find the next hole (not-present entry) + * @mapping: mapping + * @index: index + * @max_scan: maximum range to search + * + * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the + * lowest indexed hole. + * + * Returns: the index of the hole if found, otherwise returns an index + * outside of the set specified (in which case 'return - index >= + * max_scan' will be true). In rare cases of index wrap-around, 0 will + * be returned. + * + * page_cache_next_hole may be called under rcu_read_lock. However, + * like radix_tree_gang_lookup, this will not atomically search a + * snapshot of the tree at a single point in time. For example, if a + * hole is created at index 5, then subsequently a hole is created at + * index 10, page_cache_next_hole covering both indexes may return 10 + * if called under rcu_read_lock. + */ +pgoff_t page_cache_next_hole(struct address_space *mapping, + pgoff_t index, unsigned long max_scan) +{ + unsigned long i; + + for (i = 0; i < max_scan; i++) { + struct page *page; + + page = radix_tree_lookup(&mapping->page_tree, index); + if (!page || radix_tree_exceptional_entry(page)) + break; + index++; + if (index == 0) + break; + } + + return index; +} +EXPORT_SYMBOL(page_cache_next_hole); + +/** + * page_cache_prev_hole - find the prev hole (not-present entry) + * @mapping: mapping + * @index: index + * @max_scan: maximum range to search + * + * Search backwards in the range [max(index-max_scan+1, 0), index] for + * the first hole. + * + * Returns: the index of the hole if found, otherwise returns an index + * outside of the set specified (in which case 'index - return >= + * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX + * will be returned. + * + * page_cache_prev_hole may be called under rcu_read_lock. However, + * like radix_tree_gang_lookup, this will not atomically search a + * snapshot of the tree at a single point in time. For example, if a + * hole is created at index 10, then subsequently a hole is created at + * index 5, page_cache_prev_hole covering both indexes may return 5 if + * called under rcu_read_lock. + */ +pgoff_t page_cache_prev_hole(struct address_space *mapping, + pgoff_t index, unsigned long max_scan) +{ + unsigned long i; + + for (i = 0; i < max_scan; i++) { + struct page *page; + + page = radix_tree_lookup(&mapping->page_tree, index); + if (!page || radix_tree_exceptional_entry(page)) + break; + index--; + if (index == ULONG_MAX) + break; + } + + return index; +} +EXPORT_SYMBOL(page_cache_prev_hole); + +/** + * find_get_entry - find and get a page cache entry + * @mapping: the address_space to search + * @offset: the page cache index + * + * Looks up the page cache slot at @mapping & @offset. If there is a + * page cache page, it is returned with an increased refcount. + * + * If the slot holds a shadow entry of a previously evicted page, or a + * swap entry from shmem/tmpfs, it is returned. + * + * Otherwise, %NULL is returned. + */ +struct page *find_get_entry(struct address_space *mapping, pgoff_t offset) +{ + void **pagep; + struct page *page; + + rcu_read_lock(); +repeat: + page = NULL; + pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); + if (pagep) { + page = radix_tree_deref_slot(pagep); + if (unlikely(!page)) + goto out; + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) + goto repeat; + /* + * A shadow entry of a recently evicted page, + * or a swap entry from shmem/tmpfs. Return + * it without attempting to raise page count. + */ + goto out; + } + if (!page_cache_get_speculative(page)) + goto repeat; + + /* + * Has the page moved? + * This is part of the lockless pagecache protocol. See + * include/linux/pagemap.h for details. + */ + if (unlikely(page != *pagep)) { + page_cache_release(page); + goto repeat; + } + } +out: + rcu_read_unlock(); + + return page; +} +EXPORT_SYMBOL(find_get_entry); + +/** + * find_lock_entry - locate, pin and lock a page cache entry + * @mapping: the address_space to search + * @offset: the page cache index + * + * Looks up the page cache slot at @mapping & @offset. If there is a + * page cache page, it is returned locked and with an increased + * refcount. + * + * If the slot holds a shadow entry of a previously evicted page, or a + * swap entry from shmem/tmpfs, it is returned. + * + * Otherwise, %NULL is returned. + * + * find_lock_entry() may sleep. + */ +struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset) +{ + struct page *page; + +repeat: + page = find_get_entry(mapping, offset); + if (page && !radix_tree_exception(page)) { + lock_page(page); + /* Has the page been truncated? */ + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + page_cache_release(page); + goto repeat; + } + VM_BUG_ON_PAGE(page->index != offset, page); + } + return page; +} +EXPORT_SYMBOL(find_lock_entry); + +/** + * pagecache_get_page - find and get a page reference + * @mapping: the address_space to search + * @offset: the page index + * @fgp_flags: PCG flags + * @gfp_mask: gfp mask to use for the page cache data page allocation + * + * Looks up the page cache slot at @mapping & @offset. + * + * PCG flags modify how the page is returned. + * + * FGP_ACCESSED: the page will be marked accessed + * FGP_LOCK: Page is return locked + * FGP_CREAT: If page is not present then a new page is allocated using + * @gfp_mask and added to the page cache and the VM's LRU + * list. The page is returned locked and with an increased + * refcount. Otherwise, %NULL is returned. + * + * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even + * if the GFP flags specified for FGP_CREAT are atomic. + * + * If there is a page cache page, it is returned with an increased refcount. + */ +struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, + int fgp_flags, gfp_t gfp_mask) +{ + struct page *page; + +repeat: + page = find_get_entry(mapping, offset); + if (radix_tree_exceptional_entry(page)) + page = NULL; + if (!page) + goto no_page; + + if (fgp_flags & FGP_LOCK) { + if (fgp_flags & FGP_NOWAIT) { + if (!trylock_page(page)) { + page_cache_release(page); + return NULL; + } + } else { + lock_page(page); + } + + /* Has the page been truncated? */ + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + page_cache_release(page); + goto repeat; + } + VM_BUG_ON_PAGE(page->index != offset, page); + } + + if (page && (fgp_flags & FGP_ACCESSED)) + mark_page_accessed(page); + +no_page: + if (!page && (fgp_flags & FGP_CREAT)) { + int err; + if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping)) + gfp_mask |= __GFP_WRITE; + if (fgp_flags & FGP_NOFS) + gfp_mask &= ~__GFP_FS; + + page = __page_cache_alloc(gfp_mask); + if (!page) + return NULL; + + if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK))) + fgp_flags |= FGP_LOCK; + + /* Init accessed so avoid atomic mark_page_accessed later */ + if (fgp_flags & FGP_ACCESSED) + __SetPageReferenced(page); + + err = add_to_page_cache_lru(page, mapping, offset, + gfp_mask & GFP_RECLAIM_MASK); + if (unlikely(err)) { + page_cache_release(page); + page = NULL; + if (err == -EEXIST) + goto repeat; + } + } + + return page; +} +EXPORT_SYMBOL(pagecache_get_page); + +/** + * find_get_entries - gang pagecache lookup + * @mapping: The address_space to search + * @start: The starting page cache index + * @nr_entries: The maximum number of entries + * @entries: Where the resulting entries are placed + * @indices: The cache indices corresponding to the entries in @entries + * + * find_get_entries() will search for and return a group of up to + * @nr_entries entries in the mapping. The entries are placed at + * @entries. find_get_entries() takes a reference against any actual + * pages it returns. + * + * The search returns a group of mapping-contiguous page cache entries + * with ascending indexes. There may be holes in the indices due to + * not-present pages. + * + * Any shadow entries of evicted pages, or swap entries from + * shmem/tmpfs, are included in the returned array. + * + * find_get_entries() returns the number of pages and shadow entries + * which were found. + */ +unsigned find_get_entries(struct address_space *mapping, + pgoff_t start, unsigned int nr_entries, + struct page **entries, pgoff_t *indices) +{ + void **slot; + unsigned int ret = 0; + struct radix_tree_iter iter; + + if (!nr_entries) + return 0; + + rcu_read_lock(); +restart: + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { + struct page *page; +repeat: + page = radix_tree_deref_slot(slot); + if (unlikely(!page)) + continue; + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) + goto restart; + /* + * A shadow entry of a recently evicted page, + * or a swap entry from shmem/tmpfs. Return + * it without attempting to raise page count. + */ + goto export; + } + if (!page_cache_get_speculative(page)) + goto repeat; + + /* Has the page moved? */ + if (unlikely(page != *slot)) { + page_cache_release(page); + goto repeat; + } +export: + indices[ret] = iter.index; + entries[ret] = page; + if (++ret == nr_entries) + break; + } + rcu_read_unlock(); + return ret; +} + +/** + * find_get_pages - gang pagecache lookup + * @mapping: The address_space to search + * @start: The starting page index + * @nr_pages: The maximum number of pages + * @pages: Where the resulting pages are placed + * + * find_get_pages() will search for and return a group of up to + * @nr_pages pages in the mapping. The pages are placed at @pages. + * find_get_pages() takes a reference against the returned pages. + * + * The search returns a group of mapping-contiguous pages with ascending + * indexes. There may be holes in the indices due to not-present pages. + * + * find_get_pages() returns the number of pages which were found. + */ +unsigned find_get_pages(struct address_space *mapping, pgoff_t start, + unsigned int nr_pages, struct page **pages) +{ + struct radix_tree_iter iter; + void **slot; + unsigned ret = 0; + + if (unlikely(!nr_pages)) + return 0; + + rcu_read_lock(); +restart: + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { + struct page *page; +repeat: + page = radix_tree_deref_slot(slot); + if (unlikely(!page)) + continue; + + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) { + /* + * Transient condition which can only trigger + * when entry at index 0 moves out of or back + * to root: none yet gotten, safe to restart. + */ + WARN_ON(iter.index); + goto restart; + } + /* + * A shadow entry of a recently evicted page, + * or a swap entry from shmem/tmpfs. Skip + * over it. + */ + continue; + } + + if (!page_cache_get_speculative(page)) + goto repeat; + + /* Has the page moved? */ + if (unlikely(page != *slot)) { + page_cache_release(page); + goto repeat; + } + + pages[ret] = page; + if (++ret == nr_pages) + break; + } + + rcu_read_unlock(); + return ret; +} + +/** + * find_get_pages_contig - gang contiguous pagecache lookup + * @mapping: The address_space to search + * @index: The starting page index + * @nr_pages: The maximum number of pages + * @pages: Where the resulting pages are placed + * + * find_get_pages_contig() works exactly like find_get_pages(), except + * that the returned number of pages are guaranteed to be contiguous. + * + * find_get_pages_contig() returns the number of pages which were found. + */ +unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, + unsigned int nr_pages, struct page **pages) +{ + struct radix_tree_iter iter; + void **slot; + unsigned int ret = 0; + + if (unlikely(!nr_pages)) + return 0; + + rcu_read_lock(); +restart: + radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) { + struct page *page; +repeat: + page = radix_tree_deref_slot(slot); + /* The hole, there no reason to continue */ + if (unlikely(!page)) + break; + + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) { + /* + * Transient condition which can only trigger + * when entry at index 0 moves out of or back + * to root: none yet gotten, safe to restart. + */ + goto restart; + } + /* + * A shadow entry of a recently evicted page, + * or a swap entry from shmem/tmpfs. Stop + * looking for contiguous pages. + */ + break; + } + + if (!page_cache_get_speculative(page)) + goto repeat; + + /* Has the page moved? */ + if (unlikely(page != *slot)) { + page_cache_release(page); + goto repeat; + } + + /* + * must check mapping and index after taking the ref. + * otherwise we can get both false positives and false + * negatives, which is just confusing to the caller. + */ + if (page->mapping == NULL || page->index != iter.index) { + page_cache_release(page); + break; + } + + pages[ret] = page; + if (++ret == nr_pages) + break; + } + rcu_read_unlock(); + return ret; +} +EXPORT_SYMBOL(find_get_pages_contig); + +/** + * find_get_pages_tag - find and return pages that match @tag + * @mapping: the address_space to search + * @index: the starting page index + * @tag: the tag index + * @nr_pages: the maximum number of pages + * @pages: where the resulting pages are placed + * + * Like find_get_pages, except we only return pages which are tagged with + * @tag. We update @index to index the next page for the traversal. + */ +unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, + int tag, unsigned int nr_pages, struct page **pages) +{ + struct radix_tree_iter iter; + void **slot; + unsigned ret = 0; + + if (unlikely(!nr_pages)) + return 0; + + rcu_read_lock(); +restart: + radix_tree_for_each_tagged(slot, &mapping->page_tree, + &iter, *index, tag) { + struct page *page; +repeat: + page = radix_tree_deref_slot(slot); + if (unlikely(!page)) + continue; + + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) { + /* + * Transient condition which can only trigger + * when entry at index 0 moves out of or back + * to root: none yet gotten, safe to restart. + */ + goto restart; + } + /* + * A shadow entry of a recently evicted page. + * + * Those entries should never be tagged, but + * this tree walk is lockless and the tags are + * looked up in bulk, one radix tree node at a + * time, so there is a sizable window for page + * reclaim to evict a page we saw tagged. + * + * Skip over it. + */ + continue; + } + + if (!page_cache_get_speculative(page)) + goto repeat; + + /* Has the page moved? */ + if (unlikely(page != *slot)) { + page_cache_release(page); + goto repeat; + } + + pages[ret] = page; + if (++ret == nr_pages) + break; + } + + rcu_read_unlock(); + + if (ret) + *index = pages[ret - 1]->index + 1; + + return ret; +} +EXPORT_SYMBOL(find_get_pages_tag); + +/* + * CD/DVDs are error prone. When a medium error occurs, the driver may fail + * a _large_ part of the i/o request. Imagine the worst scenario: + * + * ---R__________________________________________B__________ + * ^ reading here ^ bad block(assume 4k) + * + * read(R) => miss => readahead(R...B) => media error => frustrating retries + * => failing the whole request => read(R) => read(R+1) => + * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => + * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => + * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... + * + * It is going insane. Fix it by quickly scaling down the readahead size. + */ +static void shrink_readahead_size_eio(struct file *filp, + struct file_ra_state *ra) +{ + ra->ra_pages /= 4; +} + +/** + * do_generic_file_read - generic file read routine + * @filp: the file to read + * @ppos: current file position + * @iter: data destination + * @written: already copied + * + * This is a generic file read routine, and uses the + * mapping->a_ops->readpage() function for the actual low-level stuff. + * + * This is really ugly. But the goto's actually try to clarify some + * of the logic when it comes to error handling etc. + */ +static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos, + struct iov_iter *iter, ssize_t written) +{ + struct address_space *mapping = filp->f_mapping; + struct inode *inode = mapping->host; + struct file_ra_state *ra = &filp->f_ra; + pgoff_t index; + pgoff_t last_index; + pgoff_t prev_index; + unsigned long offset; /* offset into pagecache page */ + unsigned int prev_offset; + int error = 0; + + index = *ppos >> PAGE_CACHE_SHIFT; + prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; + prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); + last_index = (*ppos + iter->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; + offset = *ppos & ~PAGE_CACHE_MASK; + + for (;;) { + struct page *page; + pgoff_t end_index; + loff_t isize; + unsigned long nr, ret; + + cond_resched(); +find_page: + page = find_get_page(mapping, index); + if (!page) { + page_cache_sync_readahead(mapping, + ra, filp, + index, last_index - index); + page = find_get_page(mapping, index); + if (unlikely(page == NULL)) + goto no_cached_page; + } + if (PageReadahead(page)) { + page_cache_async_readahead(mapping, + ra, filp, page, + index, last_index - index); + } + if (!PageUptodate(page)) { + if (inode->i_blkbits == PAGE_CACHE_SHIFT || + !mapping->a_ops->is_partially_uptodate) + goto page_not_up_to_date; + if (!trylock_page(page)) + goto page_not_up_to_date; + /* Did it get truncated before we got the lock? */ + if (!page->mapping) + goto page_not_up_to_date_locked; + if (!mapping->a_ops->is_partially_uptodate(page, + offset, iter->count)) + goto page_not_up_to_date_locked; + unlock_page(page); + } +page_ok: + /* + * i_size must be checked after we know the page is Uptodate. + * + * Checking i_size after the check allows us to calculate + * the correct value for "nr", which means the zero-filled + * part of the page is not copied back to userspace (unless + * another truncate extends the file - this is desired though). + */ + + isize = i_size_read(inode); + end_index = (isize - 1) >> PAGE_CACHE_SHIFT; + if (unlikely(!isize || index > end_index)) { + page_cache_release(page); + goto out; + } + + /* nr is the maximum number of bytes to copy from this page */ + nr = PAGE_CACHE_SIZE; + if (index == end_index) { + nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; + if (nr <= offset) { + page_cache_release(page); + goto out; + } + } + nr = nr - offset; + + /* If users can be writing to this page using arbitrary + * virtual addresses, take care about potential aliasing + * before reading the page on the kernel side. + */ + if (mapping_writably_mapped(mapping)) + flush_dcache_page(page); + + /* + * When a sequential read accesses a page several times, + * only mark it as accessed the first time. + */ + if (prev_index != index || offset != prev_offset) + mark_page_accessed(page); + prev_index = index; + + /* + * Ok, we have the page, and it's up-to-date, so + * now we can copy it to user space... + */ + + ret = copy_page_to_iter(page, offset, nr, iter); + offset += ret; + index += offset >> PAGE_CACHE_SHIFT; + offset &= ~PAGE_CACHE_MASK; + prev_offset = offset; + + page_cache_release(page); + written += ret; + if (!iov_iter_count(iter)) + goto out; + if (ret < nr) { + error = -EFAULT; + goto out; + } + continue; + +page_not_up_to_date: + /* Get exclusive access to the page ... */ + error = lock_page_killable(page); + if (unlikely(error)) + goto readpage_error; + +page_not_up_to_date_locked: + /* Did it get truncated before we got the lock? */ + if (!page->mapping) { + unlock_page(page); + page_cache_release(page); + continue; + } + + /* Did somebody else fill it already? */ + if (PageUptodate(page)) { + unlock_page(page); + goto page_ok; + } + +readpage: + /* + * A previous I/O error may have been due to temporary + * failures, eg. multipath errors. + * PG_error will be set again if readpage fails. + */ + ClearPageError(page); + /* Start the actual read. The read will unlock the page. */ + error = mapping->a_ops->readpage(filp, page); + + if (unlikely(error)) { + if (error == AOP_TRUNCATED_PAGE) { + page_cache_release(page); + error = 0; + goto find_page; + } + goto readpage_error; + } + + if (!PageUptodate(page)) { + error = lock_page_killable(page); + if (unlikely(error)) + goto readpage_error; + if (!PageUptodate(page)) { + if (page->mapping == NULL) { + /* + * invalidate_mapping_pages got it + */ + unlock_page(page); + page_cache_release(page); + goto find_page; + } + unlock_page(page); + shrink_readahead_size_eio(filp, ra); + error = -EIO; + goto readpage_error; + } + unlock_page(page); + } + + goto page_ok; + +readpage_error: + /* UHHUH! A synchronous read error occurred. Report it */ + page_cache_release(page); + goto out; + +no_cached_page: + /* + * Ok, it wasn't cached, so we need to create a new + * page.. + */ + page = page_cache_alloc_cold(mapping); + if (!page) { + error = -ENOMEM; + goto out; + } + error = add_to_page_cache_lru(page, mapping, + index, GFP_KERNEL); + if (error) { + page_cache_release(page); + if (error == -EEXIST) { + error = 0; + goto find_page; + } + goto out; + } + goto readpage; + } + +out: + ra->prev_pos = prev_index; + ra->prev_pos <<= PAGE_CACHE_SHIFT; + ra->prev_pos |= prev_offset; + + *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; + file_accessed(filp); + return written ? written : error; +} + +/** + * generic_file_read_iter - generic filesystem read routine + * @iocb: kernel I/O control block + * @iter: destination for the data read + * + * This is the "read_iter()" routine for all filesystems + * that can use the page cache directly. + */ +ssize_t +generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) +{ + struct file *file = iocb->ki_filp; + ssize_t retval = 0; + loff_t *ppos = &iocb->ki_pos; + loff_t pos = *ppos; + + if (iocb->ki_flags & IOCB_DIRECT) { + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + size_t count = iov_iter_count(iter); + loff_t size; + + if (!count) + goto out; /* skip atime */ + size = i_size_read(inode); + retval = filemap_write_and_wait_range(mapping, pos, + pos + count - 1); + if (!retval) { + struct iov_iter data = *iter; + retval = mapping->a_ops->direct_IO(iocb, &data, pos); + } + + if (retval > 0) { + *ppos = pos + retval; + iov_iter_advance(iter, retval); + } + + /* + * Btrfs can have a short DIO read if we encounter + * compressed extents, so if there was an error, or if + * we've already read everything we wanted to, or if + * there was a short read because we hit EOF, go ahead + * and return. Otherwise fallthrough to buffered io for + * the rest of the read. Buffered reads will not work for + * DAX files, so don't bother trying. + */ + if (retval < 0 || !iov_iter_count(iter) || *ppos >= size || + IS_DAX(inode)) { + file_accessed(file); + goto out; + } + } + + retval = do_generic_file_read(file, ppos, iter, retval); +out: + return retval; +} +EXPORT_SYMBOL(generic_file_read_iter); + +#ifdef CONFIG_MMU +/** + * page_cache_read - adds requested page to the page cache if not already there + * @file: file to read + * @offset: page index + * + * This adds the requested page to the page cache if it isn't already there, + * and schedules an I/O to read in its contents from disk. + */ +static int page_cache_read(struct file *file, pgoff_t offset) +{ + struct address_space *mapping = file->f_mapping; + struct page *page; + int ret; + + do { + page = page_cache_alloc_cold(mapping); + if (!page) + return -ENOMEM; + + ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); + if (ret == 0) + ret = mapping->a_ops->readpage(file, page); + else if (ret == -EEXIST) + ret = 0; /* losing race to add is OK */ + + page_cache_release(page); + + } while (ret == AOP_TRUNCATED_PAGE); + + return ret; +} + +#define MMAP_LOTSAMISS (100) + +/* + * Synchronous readahead happens when we don't even find + * a page in the page cache at all. + */ +static void do_sync_mmap_readahead(struct vm_area_struct *vma, + struct file_ra_state *ra, + struct file *file, + pgoff_t offset) +{ + unsigned long ra_pages; + struct address_space *mapping = file->f_mapping; + + /* If we don't want any read-ahead, don't bother */ + if (vma->vm_flags & VM_RAND_READ) + return; + if (!ra->ra_pages) + return; + + if (vma->vm_flags & VM_SEQ_READ) { + page_cache_sync_readahead(mapping, ra, file, offset, + ra->ra_pages); + return; + } + + /* Avoid banging the cache line if not needed */ + if (ra->mmap_miss < MMAP_LOTSAMISS * 10) + ra->mmap_miss++; + + /* + * Do we miss much more than hit in this file? If so, + * stop bothering with read-ahead. It will only hurt. + */ + if (ra->mmap_miss > MMAP_LOTSAMISS) + return; + + /* + * mmap read-around + */ + ra_pages = max_sane_readahead(ra->ra_pages); + ra->start = max_t(long, 0, offset - ra_pages / 2); + ra->size = ra_pages; + ra->async_size = ra_pages / 4; + ra_submit(ra, mapping, file); +} + +/* + * Asynchronous readahead happens when we find the page and PG_readahead, + * so we want to possibly extend the readahead further.. + */ +static void do_async_mmap_readahead(struct vm_area_struct *vma, + struct file_ra_state *ra, + struct file *file, + struct page *page, + pgoff_t offset) +{ + struct address_space *mapping = file->f_mapping; + + /* If we don't want any read-ahead, don't bother */ + if (vma->vm_flags & VM_RAND_READ) + return; + if (ra->mmap_miss > 0) + ra->mmap_miss--; + if (PageReadahead(page)) + page_cache_async_readahead(mapping, ra, file, + page, offset, ra->ra_pages); +} + +/** + * filemap_fault - read in file data for page fault handling + * @vma: vma in which the fault was taken + * @vmf: struct vm_fault containing details of the fault + * + * filemap_fault() is invoked via the vma operations vector for a + * mapped memory region to read in file data during a page fault. + * + * The goto's are kind of ugly, but this streamlines the normal case of having + * it in the page cache, and handles the special cases reasonably without + * having a lot of duplicated code. + * + * vma->vm_mm->mmap_sem must be held on entry. + * + * If our return value has VM_FAULT_RETRY set, it's because + * lock_page_or_retry() returned 0. + * The mmap_sem has usually been released in this case. + * See __lock_page_or_retry() for the exception. + * + * If our return value does not have VM_FAULT_RETRY set, the mmap_sem + * has not been released. + * + * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set. + */ +int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + int error; + struct file *file = vma->vm_file; + struct address_space *mapping = file->f_mapping; + struct file_ra_state *ra = &file->f_ra; + struct inode *inode = mapping->host; + pgoff_t offset = vmf->pgoff; + struct page *page; + loff_t size; + int ret = 0; + + size = round_up(i_size_read(inode), PAGE_CACHE_SIZE); + if (offset >= size >> PAGE_CACHE_SHIFT) + return VM_FAULT_SIGBUS; + + /* + * Do we have something in the page cache already? + */ + page = find_get_page(mapping, offset); + if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { + /* + * We found the page, so try async readahead before + * waiting for the lock. + */ + do_async_mmap_readahead(vma, ra, file, page, offset); + } else if (!page) { + /* No page in the page cache at all */ + do_sync_mmap_readahead(vma, ra, file, offset); + count_vm_event(PGMAJFAULT); + mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); + ret = VM_FAULT_MAJOR; +retry_find: + page = find_get_page(mapping, offset); + if (!page) + goto no_cached_page; + } + + if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) { + page_cache_release(page); + return ret | VM_FAULT_RETRY; + } + + /* Did it get truncated? */ + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + put_page(page); + goto retry_find; + } + VM_BUG_ON_PAGE(page->index != offset, page); + + /* + * We have a locked page in the page cache, now we need to check + * that it's up-to-date. If not, it is going to be due to an error. + */ + if (unlikely(!PageUptodate(page))) + goto page_not_uptodate; + + /* + * Found the page and have a reference on it. + * We must recheck i_size under page lock. + */ + size = round_up(i_size_read(inode), PAGE_CACHE_SIZE); + if (unlikely(offset >= size >> PAGE_CACHE_SHIFT)) { + unlock_page(page); + page_cache_release(page); + return VM_FAULT_SIGBUS; + } + + vmf->page = page; + return ret | VM_FAULT_LOCKED; + +no_cached_page: + /* + * We're only likely to ever get here if MADV_RANDOM is in + * effect. + */ + error = page_cache_read(file, offset); + + /* + * The page we want has now been added to the page cache. + * In the unlikely event that someone removed it in the + * meantime, we'll just come back here and read it again. + */ + if (error >= 0) + goto retry_find; + + /* + * An error return from page_cache_read can result if the + * system is low on memory, or a problem occurs while trying + * to schedule I/O. + */ + if (error == -ENOMEM) + return VM_FAULT_OOM; + return VM_FAULT_SIGBUS; + +page_not_uptodate: + /* + * Umm, take care of errors if the page isn't up-to-date. + * Try to re-read it _once_. We do this synchronously, + * because there really aren't any performance issues here + * and we need to check for errors. + */ + ClearPageError(page); + error = mapping->a_ops->readpage(file, page); + if (!error) { + wait_on_page_locked(page); + if (!PageUptodate(page)) + error = -EIO; + } + page_cache_release(page); + + if (!error || error == AOP_TRUNCATED_PAGE) + goto retry_find; + + /* Things didn't work out. Return zero to tell the mm layer so. */ + shrink_readahead_size_eio(file, ra); + return VM_FAULT_SIGBUS; +} +EXPORT_SYMBOL(filemap_fault); + +void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + struct radix_tree_iter iter; + void **slot; + struct file *file = vma->vm_file; + struct address_space *mapping = file->f_mapping; + loff_t size; + struct page *page; + unsigned long address = (unsigned long) vmf->virtual_address; + unsigned long addr; + pte_t *pte; + + rcu_read_lock(); + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, vmf->pgoff) { + if (iter.index > vmf->max_pgoff) + break; +repeat: + page = radix_tree_deref_slot(slot); + if (unlikely(!page)) + goto next; + if (radix_tree_exception(page)) { + if (radix_tree_deref_retry(page)) + break; + else + goto next; + } + + if (!page_cache_get_speculative(page)) + goto repeat; + + /* Has the page moved? */ + if (unlikely(page != *slot)) { + page_cache_release(page); + goto repeat; + } + + if (!PageUptodate(page) || + PageReadahead(page) || + PageHWPoison(page)) + goto skip; + if (!trylock_page(page)) + goto skip; + + if (page->mapping != mapping || !PageUptodate(page)) + goto unlock; + + size = round_up(i_size_read(mapping->host), PAGE_CACHE_SIZE); + if (page->index >= size >> PAGE_CACHE_SHIFT) + goto unlock; + + pte = vmf->pte + page->index - vmf->pgoff; + if (!pte_none(*pte)) + goto unlock; + + if (file->f_ra.mmap_miss > 0) + file->f_ra.mmap_miss--; + addr = address + (page->index - vmf->pgoff) * PAGE_SIZE; + do_set_pte(vma, addr, page, pte, false, false); + unlock_page(page); + goto next; +unlock: + unlock_page(page); +skip: + page_cache_release(page); +next: + if (iter.index == vmf->max_pgoff) + break; + } + rcu_read_unlock(); +} +EXPORT_SYMBOL(filemap_map_pages); + +int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + struct page *page = vmf->page; + struct inode *inode = file_inode(vma->vm_file); + int ret = VM_FAULT_LOCKED; + + sb_start_pagefault(inode->i_sb); + vma_file_update_time(vma); + lock_page(page); + if (page->mapping != inode->i_mapping) { + unlock_page(page); + ret = VM_FAULT_NOPAGE; + goto out; + } + /* + * We mark the page dirty already here so that when freeze is in + * progress, we are guaranteed that writeback during freezing will + * see the dirty page and writeprotect it again. + */ + set_page_dirty(page); + wait_for_stable_page(page); +out: + sb_end_pagefault(inode->i_sb); + return ret; +} +EXPORT_SYMBOL(filemap_page_mkwrite); + +const struct vm_operations_struct generic_file_vm_ops = { + .fault = filemap_fault, + .map_pages = filemap_map_pages, + .page_mkwrite = filemap_page_mkwrite, +}; + +/* This is used for a general mmap of a disk file */ + +int generic_file_mmap(struct file * file, struct vm_area_struct * vma) +{ + struct address_space *mapping = file->f_mapping; + + if (!mapping->a_ops->readpage) + return -ENOEXEC; + file_accessed(file); + vma->vm_ops = &generic_file_vm_ops; + return 0; +} + +/* + * This is for filesystems which do not implement ->writepage. + */ +int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) +{ + if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) + return -EINVAL; + return generic_file_mmap(file, vma); +} +#else +int generic_file_mmap(struct file * file, struct vm_area_struct * vma) +{ + return -ENOSYS; +} +int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) +{ + return -ENOSYS; +} +#endif /* CONFIG_MMU */ + +EXPORT_SYMBOL(generic_file_mmap); +EXPORT_SYMBOL(generic_file_readonly_mmap); + +static struct page *wait_on_page_read(struct page *page) +{ + if (!IS_ERR(page)) { + wait_on_page_locked(page); + if (!PageUptodate(page)) { + page_cache_release(page); + page = ERR_PTR(-EIO); + } + } + return page; +} + +static struct page *__read_cache_page(struct address_space *mapping, + pgoff_t index, + int (*filler)(void *, struct page *), + void *data, + gfp_t gfp) +{ + struct page *page; + int err; +repeat: + page = find_get_page(mapping, index); + if (!page) { + page = __page_cache_alloc(gfp | __GFP_COLD); + if (!page) + return ERR_PTR(-ENOMEM); + err = add_to_page_cache_lru(page, mapping, index, gfp); + if (unlikely(err)) { + page_cache_release(page); + if (err == -EEXIST) + goto repeat; + /* Presumably ENOMEM for radix tree node */ + return ERR_PTR(err); + } + err = filler(data, page); + if (err < 0) { + page_cache_release(page); + page = ERR_PTR(err); + } else { + page = wait_on_page_read(page); + } + } + return page; +} + +static struct page *do_read_cache_page(struct address_space *mapping, + pgoff_t index, + int (*filler)(void *, struct page *), + void *data, + gfp_t gfp) + +{ + struct page *page; + int err; + +retry: + page = __read_cache_page(mapping, index, filler, data, gfp); + if (IS_ERR(page)) + return page; + if (PageUptodate(page)) + goto out; + + lock_page(page); + if (!page->mapping) { + unlock_page(page); + page_cache_release(page); + goto retry; + } + if (PageUptodate(page)) { + unlock_page(page); + goto out; + } + err = filler(data, page); + if (err < 0) { + page_cache_release(page); + return ERR_PTR(err); + } else { + page = wait_on_page_read(page); + if (IS_ERR(page)) + return page; + } +out: + mark_page_accessed(page); + return page; +} + +/** + * read_cache_page - read into page cache, fill it if needed + * @mapping: the page's address_space + * @index: the page index + * @filler: function to perform the read + * @data: first arg to filler(data, page) function, often left as NULL + * + * Read into the page cache. If a page already exists, and PageUptodate() is + * not set, try to fill the page and wait for it to become unlocked. + * + * If the page does not get brought uptodate, return -EIO. + */ +struct page *read_cache_page(struct address_space *mapping, + pgoff_t index, + int (*filler)(void *, struct page *), + void *data) +{ + return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); +} +EXPORT_SYMBOL(read_cache_page); + +/** + * read_cache_page_gfp - read into page cache, using specified page allocation flags. + * @mapping: the page's address_space + * @index: the page index + * @gfp: the page allocator flags to use if allocating + * + * This is the same as "read_mapping_page(mapping, index, NULL)", but with + * any new page allocations done using the specified allocation flags. + * + * If the page does not get brought uptodate, return -EIO. + */ +struct page *read_cache_page_gfp(struct address_space *mapping, + pgoff_t index, + gfp_t gfp) +{ + filler_t *filler = (filler_t *)mapping->a_ops->readpage; + + return do_read_cache_page(mapping, index, filler, NULL, gfp); +} +EXPORT_SYMBOL(read_cache_page_gfp); + +/* + * Performs necessary checks before doing a write + * + * Can adjust writing position or amount of bytes to write. + * Returns appropriate error code that caller should return or + * zero in case that write should be allowed. + */ +inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) +{ + struct file *file = iocb->ki_filp; + struct inode *inode = file->f_mapping->host; + unsigned long limit = rlimit(RLIMIT_FSIZE); + loff_t pos; + + if (!iov_iter_count(from)) + return 0; + + /* FIXME: this is for backwards compatibility with 2.4 */ + if (iocb->ki_flags & IOCB_APPEND) + iocb->ki_pos = i_size_read(inode); + + pos = iocb->ki_pos; + + if (limit != RLIM_INFINITY) { + if (iocb->ki_pos >= limit) { + send_sig(SIGXFSZ, current, 0); + return -EFBIG; + } + iov_iter_truncate(from, limit - (unsigned long)pos); + } + + /* + * LFS rule + */ + if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS && + !(file->f_flags & O_LARGEFILE))) { + if (pos >= MAX_NON_LFS) + return -EFBIG; + iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos); + } + + /* + * Are we about to exceed the fs block limit ? + * + * If we have written data it becomes a short write. If we have + * exceeded without writing data we send a signal and return EFBIG. + * Linus frestrict idea will clean these up nicely.. + */ + if (unlikely(pos >= inode->i_sb->s_maxbytes)) + return -EFBIG; + + iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos); + return iov_iter_count(from); +} +EXPORT_SYMBOL(generic_write_checks); + +int pagecache_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata) +{ + const struct address_space_operations *aops = mapping->a_ops; + + return aops->write_begin(file, mapping, pos, len, flags, + pagep, fsdata); +} +EXPORT_SYMBOL(pagecache_write_begin); + +int pagecache_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + const struct address_space_operations *aops = mapping->a_ops; + + return aops->write_end(file, mapping, pos, len, copied, page, fsdata); +} +EXPORT_SYMBOL(pagecache_write_end); + +ssize_t +generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos) +{ + struct file *file = iocb->ki_filp; + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + ssize_t written; + size_t write_len; + pgoff_t end; + struct iov_iter data; + + write_len = iov_iter_count(from); + end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; + + written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); + if (written) + goto out; + + /* + * After a write we want buffered reads to be sure to go to disk to get + * the new data. We invalidate clean cached page from the region we're + * about to write. We do this *before* the write so that we can return + * without clobbering -EIOCBQUEUED from ->direct_IO(). + */ + if (mapping->nrpages) { + written = invalidate_inode_pages2_range(mapping, + pos >> PAGE_CACHE_SHIFT, end); + /* + * If a page can not be invalidated, return 0 to fall back + * to buffered write. + */ + if (written) { + if (written == -EBUSY) + return 0; + goto out; + } + } + + data = *from; + written = mapping->a_ops->direct_IO(iocb, &data, pos); + + /* + * Finally, try again to invalidate clean pages which might have been + * cached by non-direct readahead, or faulted in by get_user_pages() + * if the source of the write was an mmap'ed region of the file + * we're writing. Either one is a pretty crazy thing to do, + * so we don't support it 100%. If this invalidation + * fails, tough, the write still worked... + */ + if (mapping->nrpages) { + invalidate_inode_pages2_range(mapping, + pos >> PAGE_CACHE_SHIFT, end); + } + + if (written > 0) { + pos += written; + iov_iter_advance(from, written); + if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { + i_size_write(inode, pos); + mark_inode_dirty(inode); + } + iocb->ki_pos = pos; + } +out: + return written; +} +EXPORT_SYMBOL(generic_file_direct_write); + +/* + * Find or create a page at the given pagecache position. Return the locked + * page. This function is specifically for buffered writes. + */ +struct page *grab_cache_page_write_begin(struct address_space *mapping, + pgoff_t index, unsigned flags) +{ + struct page *page; + int fgp_flags = FGP_LOCK|FGP_ACCESSED|FGP_WRITE|FGP_CREAT; + + if (flags & AOP_FLAG_NOFS) + fgp_flags |= FGP_NOFS; + + page = pagecache_get_page(mapping, index, fgp_flags, + mapping_gfp_mask(mapping)); + if (page) + wait_for_stable_page(page); + + return page; +} +EXPORT_SYMBOL(grab_cache_page_write_begin); + +ssize_t generic_perform_write(struct file *file, + struct iov_iter *i, loff_t pos) +{ + struct address_space *mapping = file->f_mapping; + const struct address_space_operations *a_ops = mapping->a_ops; + long status = 0; + ssize_t written = 0; + unsigned int flags = 0; + + /* + * Copies from kernel address space cannot fail (NFSD is a big user). + */ + if (!iter_is_iovec(i)) + flags |= AOP_FLAG_UNINTERRUPTIBLE; + + do { + struct page *page; + unsigned long offset; /* Offset into pagecache page */ + unsigned long bytes; /* Bytes to write to page */ + size_t copied; /* Bytes copied from user */ + void *fsdata; + + offset = (pos & (PAGE_CACHE_SIZE - 1)); + bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, + iov_iter_count(i)); + +again: + /* + * Bring in the user page that we will copy from _first_. + * Otherwise there's a nasty deadlock on copying from the + * same page as we're writing to, without it being marked + * up-to-date. + * + * Not only is this an optimisation, but it is also required + * to check that the address is actually valid, when atomic + * usercopies are used, below. + */ + if (unlikely(iov_iter_fault_in_readable(i, bytes))) { + status = -EFAULT; + break; + } + + status = a_ops->write_begin(file, mapping, pos, bytes, flags, + &page, &fsdata); + if (unlikely(status < 0)) + break; + + if (mapping_writably_mapped(mapping)) + flush_dcache_page(page); + + copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); + flush_dcache_page(page); + + status = a_ops->write_end(file, mapping, pos, bytes, copied, + page, fsdata); + if (unlikely(status < 0)) + break; + copied = status; + + cond_resched(); + + iov_iter_advance(i, copied); + if (unlikely(copied == 0)) { + /* + * If we were unable to copy any data at all, we must + * fall back to a single segment length write. + * + * If we didn't fallback here, we could livelock + * because not all segments in the iov can be copied at + * once without a pagefault. + */ + bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, + iov_iter_single_seg_count(i)); + goto again; + } + pos += copied; + written += copied; + + balance_dirty_pages_ratelimited(mapping); + if (fatal_signal_pending(current)) { + status = -EINTR; + break; + } + } while (iov_iter_count(i)); + + return written ? written : status; +} +EXPORT_SYMBOL(generic_perform_write); + +/** + * __generic_file_write_iter - write data to a file + * @iocb: IO state structure (file, offset, etc.) + * @from: iov_iter with data to write + * + * This function does all the work needed for actually writing data to a + * file. It does all basic checks, removes SUID from the file, updates + * modification times and calls proper subroutines depending on whether we + * do direct IO or a standard buffered write. + * + * It expects i_mutex to be grabbed unless we work on a block device or similar + * object which does not need locking at all. + * + * This function does *not* take care of syncing data in case of O_SYNC write. + * A caller has to handle it. This is mainly due to the fact that we want to + * avoid syncing under i_mutex. + */ +ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) +{ + struct file *file = iocb->ki_filp; + struct address_space * mapping = file->f_mapping; + struct inode *inode = mapping->host; + ssize_t written = 0; + ssize_t err; + ssize_t status; + + /* We can write back this queue in page reclaim */ + current->backing_dev_info = inode_to_bdi(inode); + err = file_remove_suid(file); + if (err) + goto out; + + err = file_update_time(file); + if (err) + goto out; + + if (iocb->ki_flags & IOCB_DIRECT) { + loff_t pos, endbyte; + + written = generic_file_direct_write(iocb, from, iocb->ki_pos); + /* + * If the write stopped short of completing, fall back to + * buffered writes. Some filesystems do this for writes to + * holes, for example. For DAX files, a buffered write will + * not succeed (even if it did, DAX does not handle dirty + * page-cache pages correctly). + */ + if (written < 0 || !iov_iter_count(from) || IS_DAX(inode)) + goto out; + + status = generic_perform_write(file, from, pos = iocb->ki_pos); + /* + * If generic_perform_write() returned a synchronous error + * then we want to return the number of bytes which were + * direct-written, or the error code if that was zero. Note + * that this differs from normal direct-io semantics, which + * will return -EFOO even if some bytes were written. + */ + if (unlikely(status < 0)) { + err = status; + goto out; + } + /* + * We need to ensure that the page cache pages are written to + * disk and invalidated to preserve the expected O_DIRECT + * semantics. + */ + endbyte = pos + status - 1; + err = filemap_write_and_wait_range(mapping, pos, endbyte); + if (err == 0) { + iocb->ki_pos = endbyte + 1; + written += status; + invalidate_mapping_pages(mapping, + pos >> PAGE_CACHE_SHIFT, + endbyte >> PAGE_CACHE_SHIFT); + } else { + /* + * We don't know how much we wrote, so just return + * the number of bytes which were direct-written + */ + } + } else { + written = generic_perform_write(file, from, iocb->ki_pos); + if (likely(written > 0)) + iocb->ki_pos += written; + } +out: + current->backing_dev_info = NULL; + return written ? written : err; +} +EXPORT_SYMBOL(__generic_file_write_iter); + +/** + * generic_file_write_iter - write data to a file + * @iocb: IO state structure + * @from: iov_iter with data to write + * + * This is a wrapper around __generic_file_write_iter() to be used by most + * filesystems. It takes care of syncing the file in case of O_SYNC file + * and acquires i_mutex as needed. + */ +ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) +{ + struct file *file = iocb->ki_filp; + struct inode *inode = file->f_mapping->host; + ssize_t ret; + + mutex_lock(&inode->i_mutex); + ret = generic_write_checks(iocb, from); + if (ret > 0) + ret = __generic_file_write_iter(iocb, from); + mutex_unlock(&inode->i_mutex); + + if (ret > 0) { + ssize_t err; + + err = generic_write_sync(file, iocb->ki_pos - ret, ret); + if (err < 0) + ret = err; + } + return ret; +} +EXPORT_SYMBOL(generic_file_write_iter); + +/** + * try_to_release_page() - release old fs-specific metadata on a page + * + * @page: the page which the kernel is trying to free + * @gfp_mask: memory allocation flags (and I/O mode) + * + * The address_space is to try to release any data against the page + * (presumably at page->private). If the release was successful, return `1'. + * Otherwise return zero. + * + * This may also be called if PG_fscache is set on a page, indicating that the + * page is known to the local caching routines. + * + * The @gfp_mask argument specifies whether I/O may be performed to release + * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). + * + */ +int try_to_release_page(struct page *page, gfp_t gfp_mask) +{ + struct address_space * const mapping = page->mapping; + + BUG_ON(!PageLocked(page)); + if (PageWriteback(page)) + return 0; + + if (mapping && mapping->a_ops->releasepage) + return mapping->a_ops->releasepage(page, gfp_mask); + return try_to_free_buffers(page); +} + +EXPORT_SYMBOL(try_to_release_page); |