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- /*
- * 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)
- * ->memcg->move_lock (page_remove_rmap->mem_cgroup_begin_page_stat)
- * 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 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 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 (!node) {
- /*
- * We need a node to properly account shadow
- * entries. Don't plant any without. XXX
- */
- shadow = NULL;
- }
- 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 and
- * mem_cgroup_begin_page_stat().
- */
- void __delete_from_page_cache(struct page *page, void *shadow,
- struct mem_cgroup *memcg)
- {
- 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 */
- /* hugetlb pages do not participate in page cache accounting. */
- if (!PageHuge(page))
- __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, memcg,
- inode_to_wb(mapping->host));
- }
- /**
- * 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;
- struct mem_cgroup *memcg;
- unsigned long flags;
- void (*freepage)(struct page *);
- BUG_ON(!PageLocked(page));
- freepage = mapping->a_ops->freepage;
- memcg = mem_cgroup_begin_page_stat(page);
- spin_lock_irqsave(&mapping->tree_lock, flags);
- __delete_from_page_cache(page, NULL, memcg);
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
- mem_cgroup_end_page_stat(memcg);
- 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;
- wbc_attach_fdatawrite_inode(&wbc, mapping->host);
- ret = do_writepages(mapping, &wbc);
- wbc_detach_inode(&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);
- static 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 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:
- return ret;
- }
- /**
- * 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. Check error status of
- * the address space and return it.
- *
- * Since the error status of the address space is cleared by this function,
- * callers are responsible for checking the return value and handling and/or
- * reporting the error.
- */
- int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
- loff_t end_byte)
- {
- int ret, ret2;
- ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
- ret2 = filemap_check_errors(mapping);
- if (!ret)
- ret = ret2;
- return ret;
- }
- EXPORT_SYMBOL(filemap_fdatawait_range);
- /**
- * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
- * @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. Unlike filemap_fdatawait(), this function
- * does not clear error status of the address space.
- *
- * Use this function if callers don't handle errors themselves. Expected
- * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
- * fsfreeze(8)
- */
- void filemap_fdatawait_keep_errors(struct address_space *mapping)
- {
- loff_t i_size = i_size_read(mapping->host);
- if (i_size == 0)
- return;
- __filemap_fdatawait_range(mapping, 0, i_size - 1);
- }
- /**
- * 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. Check error status of the address space
- * and return it.
- *
- * Since the error status of the address space is cleared by this function,
- * callers are responsible for checking the return value and handling and/or
- * reporting the error.
- */
- 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_RECLAIM_MASK);
- if (!error) {
- struct address_space *mapping = old->mapping;
- void (*freepage)(struct page *);
- struct mem_cgroup *memcg;
- unsigned long flags;
- pgoff_t offset = old->index;
- freepage = mapping->a_ops->freepage;
- page_cache_get(new);
- new->mapping = mapping;
- new->index = offset;
- memcg = mem_cgroup_begin_page_stat(old);
- spin_lock_irqsave(&mapping->tree_lock, flags);
- __delete_from_page_cache(old, NULL, memcg);
- error = page_cache_tree_insert(mapping, new, NULL);
- BUG_ON(error);
- /*
- * hugetlb pages do not participate in page cache accounting.
- */
- if (!PageHuge(new))
- __inc_zone_page_state(new, NR_FILE_PAGES);
- if (PageSwapBacked(new))
- __inc_zone_page_state(new, NR_SHMEM);
- spin_unlock_irqrestore(&mapping->tree_lock, flags);
- mem_cgroup_end_page_stat(memcg);
- mem_cgroup_replace_page(old, new);
- radix_tree_preload_end();
- if (freepage)
- freepage(old);
- page_cache_release(old);
- }
- return error;
- }
- EXPORT_SYMBOL_GPL(replace_page_cache_page);
- 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_RECLAIM_MASK);
- 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;
- /* hugetlb pages do not participate in page cache accounting. */
- if (!huge)
- __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_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) {
- struct address_space *mapping;
- SetPageError(page);
- mapping = page_mapping(page);
- if (mapping)
- mapping_set_error(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);
- 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:
- if (fatal_signal_pending(current)) {
- error = -EINTR;
- goto out;
- }
- 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)) {
- /*
- * See comment in do_read_cache_page on why
- * wait_on_page_locked is used to avoid unnecessarily
- * serialisations and why it's safe.
- */
- wait_on_page_locked_killable(page);
- if (PageUptodate(page))
- goto page_ok;
- 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,
- mapping_gfp_constraint(mapping, 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, gfp_t gfp_mask)
- {
- struct address_space *mapping = file->f_mapping;
- struct page *page;
- int ret;
- do {
- page = __page_cache_alloc(gfp_mask|__GFP_COLD);
- if (!page)
- return -ENOMEM;
- ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
- 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)
- {
- 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->start = max_t(long, 0, offset - ra->ra_pages / 2);
- ra->size = ra->ra_pages;
- ra->async_size = ra->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, vmf->gfp_mask);
- /*
- * 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);
- file_update_time(vma->vm_file);
- 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 *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;
- 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);
- }
- filler:
- err = filler(data, page);
- if (err < 0) {
- page_cache_release(page);
- return ERR_PTR(err);
- }
- page = wait_on_page_read(page);
- if (IS_ERR(page))
- return page;
- goto out;
- }
- if (PageUptodate(page))
- goto out;
- /*
- * Page is not up to date and may be locked due one of the following
- * case a: Page is being filled and the page lock is held
- * case b: Read/write error clearing the page uptodate status
- * case c: Truncation in progress (page locked)
- * case d: Reclaim in progress
- *
- * Case a, the page will be up to date when the page is unlocked.
- * There is no need to serialise on the page lock here as the page
- * is pinned so the lock gives no additional protection. Even if the
- * the page is truncated, the data is still valid if PageUptodate as
- * it's a race vs truncate race.
- * Case b, the page will not be up to date
- * Case c, the page may be truncated but in itself, the data may still
- * be valid after IO completes as it's a read vs truncate race. The
- * operation must restart if the page is not uptodate on unlock but
- * otherwise serialising on page lock to stabilise the mapping gives
- * no additional guarantees to the caller as the page lock is
- * released before return.
- * Case d, similar to truncation. If reclaim holds the page lock, it
- * will be a race with remove_mapping that determines if the mapping
- * is valid on unlock but otherwise the data is valid and there is
- * no need to serialise with page lock.
- *
- * As the page lock gives no additional guarantee, we optimistically
- * wait on the page to be unlocked and check if it's up to date and
- * use the page if it is. Otherwise, the page lock is required to
- * distinguish between the different cases. The motivation is that we
- * avoid spurious serialisations and wakeups when multiple processes
- * wait on the same page for IO to complete.
- */
- wait_on_page_locked(page);
- if (PageUptodate(page))
- goto out;
- /* Distinguish between all the cases under the safety of the lock */
- lock_page(page);
- /* Case c or d, restart the operation */
- if (!page->mapping) {
- unlock_page(page);
- page_cache_release(page);
- goto repeat;
- }
- /* Someone else locked and filled the page in a very small window */
- if (PageUptodate(page)) {
- unlock_page(page);
- goto out;
- }
- goto filler;
- 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;
- }
- if (fatal_signal_pending(current)) {
- status = -EINTR;
- 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);
- } 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_privs(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_RECLAIM & __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);
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