/* * 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/module.h> #include <linux/slab.h> #include <linux/compiler.h> #include <linux/fs.h> #include <linux/uaccess.h> #include <linux/aio.h> #include <linux/capability.h> #include <linux/kernel_stat.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/syscalls.h> #include <linux/cpuset.h> #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ #include <linux/memcontrol.h> #include "internal.h" /* * FIXME: remove all knowledge of the buffer layer from the core VM */ #include <linux/buffer_head.h> /* for generic_osync_inode */ #include <asm/mman.h> static ssize_t generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t offset, unsigned long nr_segs); /* * 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_lock (vmtruncate) * ->private_lock (__free_pte->__set_page_dirty_buffers) * ->swap_lock (exclusive_swap_page, others) * ->mapping->tree_lock * * ->i_mutex * ->i_mmap_lock (truncate->unmap_mapping_range) * * ->mmap_sem * ->i_mmap_lock * ->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_file_buffered_write) * ->mmap_sem (fault_in_pages_readable->do_page_fault) * * ->i_mutex * ->i_alloc_sem (various) * * ->inode_lock * ->sb_lock (fs/fs-writeback.c) * ->mapping->tree_lock (__sync_single_inode) * * ->i_mmap_lock * ->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) * ->inode_lock (page_remove_rmap->set_page_dirty) * ->inode_lock (zap_pte_range->set_page_dirty) * ->private_lock (zap_pte_range->__set_page_dirty_buffers) * * ->task->proc_lock * ->dcache_lock (proc_pid_lookup) */ /* * Remove 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 a write_lock on the mapping's tree_lock. */ void __remove_from_page_cache(struct page *page) { struct address_space *mapping = page->mapping; mem_cgroup_uncharge_page(page); radix_tree_delete(&mapping->page_tree, page->index); page->mapping = NULL; mapping->nrpages--; __dec_zone_page_state(page, NR_FILE_PAGES); BUG_ON(page_mapped(page)); /* * Some filesystems seem to re-dirty the page even after * the VM has canceled the dirty bit (eg ext3 journaling). * * Fix it up by doing a final dirty accounting check after * having removed the page entirely. */ if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { dec_zone_page_state(page, NR_FILE_DIRTY); dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); } } void remove_from_page_cache(struct page *page) { struct address_space *mapping = page->mapping; BUG_ON(!PageLocked(page)); write_lock_irq(&mapping->tree_lock); __remove_from_page_cache(page); write_unlock_irq(&mapping->tree_lock); } static int sync_page(void *word) { struct address_space *mapping; struct page *page; page = container_of((unsigned long *)word, struct page, flags); /* * page_mapping() is being called without PG_locked held. * Some knowledge of the state and use of the page is used to * reduce the requirements down to a memory barrier. * The danger here is of a stale page_mapping() return value * indicating a struct address_space different from the one it's * associated with when it is associated with one. * After smp_mb(), it's either the correct page_mapping() for * the page, or an old page_mapping() and the page's own * page_mapping() has gone NULL. * The ->sync_page() address_space operation must tolerate * page_mapping() going NULL. By an amazing coincidence, * this comes about because none of the users of the page * in the ->sync_page() methods make essential use of the * page_mapping(), merely passing the page down to the backing * device's unplug functions when it's non-NULL, which in turn * ignore it for all cases but swap, where only page_private(page) is * of interest. When page_mapping() does go NULL, the entire * call stack gracefully ignores the page and returns. * -- wli */ smp_mb(); mapping = page_mapping(page); if (mapping && mapping->a_ops && mapping->a_ops->sync_page) mapping->a_ops->sync_page(page); io_schedule(); return 0; } static int sync_page_killable(void *word) { sync_page(word); return fatal_signal_pending(current) ? -EINTR : 0; } /** * __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 = mapping->nrpages * 2, .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); /** * wait_on_page_writeback_range - wait for writeback to complete * @mapping: target address_space * @start: beginning page index * @end: ending page index * * Wait for writeback to complete against pages indexed by start->end * inclusive */ int wait_on_page_writeback_range(struct address_space *mapping, pgoff_t start, pgoff_t end) { struct pagevec pvec; int nr_pages; int ret = 0; pgoff_t index; if (end < start) return 0; pagevec_init(&pvec, 0); index = start; 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 (PageError(page)) ret = -EIO; } pagevec_release(&pvec); cond_resched(); } /* Check for outstanding write errors */ if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) ret = -ENOSPC; if (test_and_clear_bit(AS_EIO, &mapping->flags)) ret = -EIO; return ret; } /** * sync_page_range - write and wait on all pages in the passed range * @inode: target inode * @mapping: target address_space * @pos: beginning offset in pages to write * @count: number of bytes to write * * Write and wait upon all the pages in the passed range. This is a "data * integrity" operation. It waits upon in-flight writeout before starting and * waiting upon new writeout. If there was an IO error, return it. * * We need to re-take i_mutex during the generic_osync_inode list walk because * it is otherwise livelockable. */ int sync_page_range(struct inode *inode, struct address_space *mapping, loff_t pos, loff_t count) { pgoff_t start = pos >> PAGE_CACHE_SHIFT; pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT; int ret; if (!mapping_cap_writeback_dirty(mapping) || !count) return 0; ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1); if (ret == 0) { mutex_lock(&inode->i_mutex); ret = generic_osync_inode(inode, mapping, OSYNC_METADATA); mutex_unlock(&inode->i_mutex); } if (ret == 0) ret = wait_on_page_writeback_range(mapping, start, end); return ret; } EXPORT_SYMBOL(sync_page_range); /** * sync_page_range_nolock - write & wait on all pages in the passed range without locking * @inode: target inode * @mapping: target address_space * @pos: beginning offset in pages to write * @count: number of bytes to write * * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea * as it forces O_SYNC writers to different parts of the same file * to be serialised right until io completion. */ int sync_page_range_nolock(struct inode *inode, struct address_space *mapping, loff_t pos, loff_t count) { pgoff_t start = pos >> PAGE_CACHE_SHIFT; pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT; int ret; if (!mapping_cap_writeback_dirty(mapping) || !count) return 0; ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1); if (ret == 0) ret = generic_osync_inode(inode, mapping, OSYNC_METADATA); if (ret == 0) ret = wait_on_page_writeback_range(mapping, start, end); return ret; } EXPORT_SYMBOL(sync_page_range_nolock); /** * 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 wait_on_page_writeback_range(mapping, 0, (i_size - 1) >> PAGE_CACHE_SHIFT); } 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; } } 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 = wait_on_page_writeback_range(mapping, lstart >> PAGE_CACHE_SHIFT, lend >> PAGE_CACHE_SHIFT); if (!err) err = err2; } } return err; } /** * add_to_page_cache - add newly allocated pagecache pages * @page: page to add * @mapping: the page's address_space * @offset: page index * @gfp_mask: page allocation mode * * This function is used to add newly allocated pagecache pages; * the page is new, so we can just run SetPageLocked() against it. * The other page state flags were set by rmqueue(). * * This function does not add the page to the LRU. The caller must do that. */ int add_to_page_cache(struct page *page, struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask) { int error = mem_cgroup_cache_charge(page, current->mm, gfp_mask & ~__GFP_HIGHMEM); if (error) goto out; error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); if (error == 0) { write_lock_irq(&mapping->tree_lock); error = radix_tree_insert(&mapping->page_tree, offset, page); if (!error) { page_cache_get(page); SetPageLocked(page); page->mapping = mapping; page->index = offset; mapping->nrpages++; __inc_zone_page_state(page, NR_FILE_PAGES); } else mem_cgroup_uncharge_page(page); write_unlock_irq(&mapping->tree_lock); radix_tree_preload_end(); } else mem_cgroup_uncharge_page(page); out: return error; } EXPORT_SYMBOL(add_to_page_cache); int add_to_page_cache_lru(struct page *page, struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask) { int ret = add_to_page_cache(page, mapping, offset, gfp_mask); if (ret == 0) lru_cache_add(page); return ret; } #ifdef CONFIG_NUMA struct page *__page_cache_alloc(gfp_t gfp) { if (cpuset_do_page_mem_spread()) { int n = cpuset_mem_spread_node(); return alloc_pages_node(n, gfp, 0); } return alloc_pages(gfp, 0); } EXPORT_SYMBOL(__page_cache_alloc); #endif static int __sleep_on_page_lock(void *word) { io_schedule(); return 0; } /* * 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. */ static 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)]; } static inline void wake_up_page(struct page *page, int bit) { __wake_up_bit(page_waitqueue(page), &page->flags, bit); } 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, sync_page, TASK_UNINTERRUPTIBLE); } EXPORT_SYMBOL(wait_on_page_bit); /** * 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 * mechananism between PageLocked pages and PageWriteback pages is shared. * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. * * The first mb is necessary to safely close the critical section opened by the * TestSetPageLocked(), the second 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) { smp_mb__before_clear_bit(); if (!TestClearPageLocked(page)) BUG(); smp_mb__after_clear_bit(); 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) { if (TestClearPageReclaim(page)) rotate_reclaimable_page(page); if (!test_clear_page_writeback(page)) BUG(); smp_mb__after_clear_bit(); wake_up_page(page, PG_writeback); } EXPORT_SYMBOL(end_page_writeback); /** * __lock_page - get a lock on the page, assuming we need to sleep to get it * @page: the page to lock * * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some * random driver's requestfn sets TASK_RUNNING, we could busywait. However * chances are that on the second loop, the block layer's plug list is empty, * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. */ void __lock_page(struct page *page) { DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page, 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, sync_page_killable, TASK_KILLABLE); } /** * __lock_page_nosync - get a lock on the page, without calling sync_page() * @page: the page to lock * * Variant of lock_page that does not require the caller to hold a reference * on the page's mapping. */ void __lock_page_nosync(struct page *page) { DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock, TASK_UNINTERRUPTIBLE); } /** * find_get_page - find and get a page reference * @mapping: the address_space to search * @offset: the page index * * Is there a pagecache struct page at the given (mapping, offset) tuple? * If yes, increment its refcount and return it; if no, return NULL. */ struct page * find_get_page(struct address_space *mapping, pgoff_t offset) { struct page *page; read_lock_irq(&mapping->tree_lock); page = radix_tree_lookup(&mapping->page_tree, offset); if (page) page_cache_get(page); read_unlock_irq(&mapping->tree_lock); return page; } EXPORT_SYMBOL(find_get_page); /** * find_lock_page - locate, pin and lock a pagecache page * @mapping: the address_space to search * @offset: the page index * * Locates the desired pagecache page, locks it, increments its reference * count and returns its address. * * Returns zero if the page was not present. find_lock_page() may sleep. */ struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) { struct page *page; repeat: read_lock_irq(&mapping->tree_lock); page = radix_tree_lookup(&mapping->page_tree, offset); if (page) { page_cache_get(page); if (TestSetPageLocked(page)) { read_unlock_irq(&mapping->tree_lock); __lock_page(page); /* Has the page been truncated while we slept? */ if (unlikely(page->mapping != mapping)) { unlock_page(page); page_cache_release(page); goto repeat; } VM_BUG_ON(page->index != offset); goto out; } } read_unlock_irq(&mapping->tree_lock); out: return page; } EXPORT_SYMBOL(find_lock_page); /** * find_or_create_page - locate or add a pagecache page * @mapping: the page's address_space * @index: the page's index into the mapping * @gfp_mask: page allocation mode * * Locates a page in the pagecache. If the page is not present, a new page * is allocated using @gfp_mask and is added to the pagecache and to the VM's * LRU list. The returned page is locked and has its reference count * incremented. * * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic * allocation! * * find_or_create_page() returns the desired page's address, or zero on * memory exhaustion. */ struct page *find_or_create_page(struct address_space *mapping, pgoff_t index, gfp_t gfp_mask) { struct page *page; int err; repeat: page = find_lock_page(mapping, index); if (!page) { page = __page_cache_alloc(gfp_mask); if (!page) return NULL; err = add_to_page_cache_lru(page, mapping, index, gfp_mask); if (unlikely(err)) { page_cache_release(page); page = NULL; if (err == -EEXIST) goto repeat; } } return page; } EXPORT_SYMBOL(find_or_create_page); /** * 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) { unsigned int i; unsigned int ret; read_lock_irq(&mapping->tree_lock); ret = radix_tree_gang_lookup(&mapping->page_tree, (void **)pages, start, nr_pages); for (i = 0; i < ret; i++) page_cache_get(pages[i]); read_unlock_irq(&mapping->tree_lock); 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) { unsigned int i; unsigned int ret; read_lock_irq(&mapping->tree_lock); ret = radix_tree_gang_lookup(&mapping->page_tree, (void **)pages, index, nr_pages); for (i = 0; i < ret; i++) { if (pages[i]->mapping == NULL || pages[i]->index != index) break; page_cache_get(pages[i]); index++; } read_unlock_irq(&mapping->tree_lock); return i; } 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) { unsigned int i; unsigned int ret; read_lock_irq(&mapping->tree_lock); ret = radix_tree_gang_lookup_tag(&mapping->page_tree, (void **)pages, *index, nr_pages, tag); for (i = 0; i < ret; i++) page_cache_get(pages[i]); if (ret) *index = pages[ret - 1]->index + 1; read_unlock_irq(&mapping->tree_lock); return ret; } EXPORT_SYMBOL(find_get_pages_tag); /** * grab_cache_page_nowait - returns locked page at given index in given cache * @mapping: target address_space * @index: the page index * * Same as grab_cache_page(), but do not wait if the page is unavailable. * This is intended for speculative data generators, where the data can * be regenerated if the page couldn't be grabbed. This routine should * be safe to call while holding the lock for another page. * * Clear __GFP_FS when allocating the page to avoid recursion into the fs * and deadlock against the caller's locked page. */ struct page * grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) { struct page *page = find_get_page(mapping, index); if (page) { if (!TestSetPageLocked(page)) return page; page_cache_release(page); return NULL; } page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) { page_cache_release(page); page = NULL; } return page; } EXPORT_SYMBOL(grab_cache_page_nowait); /* * 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) { if (!ra->ra_pages) return; ra->ra_pages /= 4; } /** * do_generic_file_read - generic file read routine * @filp: the file to read * @ppos: current file position * @desc: read_descriptor * @actor: read method * * 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 void do_generic_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor) { 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; 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 + desc->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)) goto page_not_up_to_date; 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... * * The actor routine returns how many bytes were actually used.. * NOTE! This may not be the same as how much of a user buffer * we filled up (we may be padding etc), so we can only update * "pos" here (the actor routine has to update the user buffer * pointers and the remaining count). */ ret = actor(desc, page, offset, nr); offset += ret; index += offset >> PAGE_CACHE_SHIFT; offset &= ~PAGE_CACHE_MASK; prev_offset = offset; page_cache_release(page); if (ret == nr && desc->count) continue; goto out; page_not_up_to_date: /* Get exclusive access to the page ... */ if (lock_page_killable(page)) goto readpage_eio; /* 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: /* 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); goto find_page; } goto readpage_error; } if (!PageUptodate(page)) { if (lock_page_killable(page)) goto readpage_eio; if (!PageUptodate(page)) { if (page->mapping == NULL) { /* * invalidate_inode_pages got it */ unlock_page(page); page_cache_release(page); goto find_page; } unlock_page(page); shrink_readahead_size_eio(filp, ra); goto readpage_eio; } unlock_page(page); } goto page_ok; readpage_eio: error = -EIO; readpage_error: /* UHHUH! A synchronous read error occurred. Report it */ desc->error = error; 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) { desc->error = -ENOMEM; goto out; } error = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); if (error) { page_cache_release(page); if (error == -EEXIST) goto find_page; desc->error = error; 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; if (filp) file_accessed(filp); } int file_read_actor(read_descriptor_t *desc, struct page *page, unsigned long offset, unsigned long size) { char *kaddr; unsigned long left, count = desc->count; if (size > count) size = count; /* * Faults on the destination of a read are common, so do it before * taking the kmap. */ if (!fault_in_pages_writeable(desc->arg.buf, size)) { kaddr = kmap_atomic(page, KM_USER0); left = __copy_to_user_inatomic(desc->arg.buf, kaddr + offset, size); kunmap_atomic(kaddr, KM_USER0); if (left == 0) goto success; } /* Do it the slow way */ kaddr = kmap(page); left = __copy_to_user(desc->arg.buf, kaddr + offset, size); kunmap(page); if (left) { size -= left; desc->error = -EFAULT; } success: desc->count = count - size; desc->written += size; desc->arg.buf += size; return size; } /* * Performs necessary checks before doing a write * @iov: io vector request * @nr_segs: number of segments in the iovec * @count: number of bytes to write * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE * * Adjust number of segments and amount of bytes to write (nr_segs should be * properly initialized first). Returns appropriate error code that caller * should return or zero in case that write should be allowed. */ int generic_segment_checks(const struct iovec *iov, unsigned long *nr_segs, size_t *count, int access_flags) { unsigned long seg; size_t cnt = 0; for (seg = 0; seg < *nr_segs; seg++) { const struct iovec *iv = &iov[seg]; /* * If any segment has a negative length, or the cumulative * length ever wraps negative then return -EINVAL. */ cnt += iv->iov_len; if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) return -EINVAL; if (access_ok(access_flags, iv->iov_base, iv->iov_len)) continue; if (seg == 0) return -EFAULT; *nr_segs = seg; cnt -= iv->iov_len; /* This segment is no good */ break; } *count = cnt; return 0; } EXPORT_SYMBOL(generic_segment_checks); /** * generic_file_aio_read - generic filesystem read routine * @iocb: kernel I/O control block * @iov: io vector request * @nr_segs: number of segments in the iovec * @pos: current file position * * This is the "read()" routine for all filesystems * that can use the page cache directly. */ ssize_t generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { struct file *filp = iocb->ki_filp; ssize_t retval; unsigned long seg; size_t count; loff_t *ppos = &iocb->ki_pos; count = 0; retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); if (retval) return retval; /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ if (filp->f_flags & O_DIRECT) { loff_t size; struct address_space *mapping; struct inode *inode; mapping = filp->f_mapping; inode = mapping->host; retval = 0; if (!count) goto out; /* skip atime */ size = i_size_read(inode); if (pos < size) { retval = generic_file_direct_IO(READ, iocb, iov, pos, nr_segs); if (retval > 0) *ppos = pos + retval; } if (likely(retval != 0)) { file_accessed(filp); goto out; } } retval = 0; if (count) { for (seg = 0; seg < nr_segs; seg++) { read_descriptor_t desc; desc.written = 0; desc.arg.buf = iov[seg].iov_base; desc.count = iov[seg].iov_len; if (desc.count == 0) continue; desc.error = 0; do_generic_file_read(filp,ppos,&desc,file_read_actor); retval += desc.written; if (desc.error) { retval = retval ?: desc.error; break; } if (desc.count > 0) break; } } out: return retval; } EXPORT_SYMBOL(generic_file_aio_read); static ssize_t do_readahead(struct address_space *mapping, struct file *filp, pgoff_t index, unsigned long nr) { if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) return -EINVAL; force_page_cache_readahead(mapping, filp, index, max_sane_readahead(nr)); return 0; } asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count) { ssize_t ret; struct file *file; ret = -EBADF; file = fget(fd); if (file) { if (file->f_mode & FMODE_READ) { struct address_space *mapping = file->f_mapping; pgoff_t start = offset >> PAGE_CACHE_SHIFT; pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; unsigned long len = end - start + 1; ret = do_readahead(mapping, file, start, len); } fput(file); } return ret; } #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) /** * 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. */ 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; struct page *page; pgoff_t size; int did_readaround = 0; int ret = 0; size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if (vmf->pgoff >= size) return VM_FAULT_SIGBUS; /* If we don't want any read-ahead, don't bother */ if (VM_RandomReadHint(vma)) goto no_cached_page; /* * Do we have something in the page cache already? */ retry_find: page = find_lock_page(mapping, vmf->pgoff); /* * For sequential accesses, we use the generic readahead logic. */ if (VM_SequentialReadHint(vma)) { if (!page) { page_cache_sync_readahead(mapping, ra, file, vmf->pgoff, 1); page = find_lock_page(mapping, vmf->pgoff); if (!page) goto no_cached_page; } if (PageReadahead(page)) { page_cache_async_readahead(mapping, ra, file, page, vmf->pgoff, 1); } } if (!page) { unsigned long ra_pages; 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) goto no_cached_page; /* * To keep the pgmajfault counter straight, we need to * check did_readaround, as this is an inner loop. */ if (!did_readaround) { ret = VM_FAULT_MAJOR; count_vm_event(PGMAJFAULT); } did_readaround = 1; ra_pages = max_sane_readahead(file->f_ra.ra_pages); if (ra_pages) { pgoff_t start = 0; if (vmf->pgoff > ra_pages / 2) start = vmf->pgoff - ra_pages / 2; do_page_cache_readahead(mapping, file, start, ra_pages); } page = find_lock_page(mapping, vmf->pgoff); if (!page) goto no_cached_page; } if (!did_readaround) ra->mmap_miss--; /* * 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; /* Must recheck i_size under page lock */ size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if (unlikely(vmf->pgoff >= size)) { unlock_page(page); page_cache_release(page); return VM_FAULT_SIGBUS; } /* * Found the page and have a reference on it. */ mark_page_accessed(page); ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT; 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, vmf->pgoff); /* * 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: /* IO error path */ if (!did_readaround) { ret = VM_FAULT_MAJOR; count_vm_event(PGMAJFAULT); } /* * 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); struct vm_operations_struct generic_file_vm_ops = { .fault = filemap_fault, }; /* 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; vma->vm_flags |= VM_CAN_NONLINEAR; 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 *__read_cache_page(struct address_space *mapping, pgoff_t index, int (*filler)(void *,struct page*), void *data) { struct page *page; int err; repeat: page = find_get_page(mapping, index); if (!page) { page = page_cache_alloc_cold(mapping); if (!page) return ERR_PTR(-ENOMEM); err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); 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); } } return page; } /** * read_cache_page_async - 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: destination for read data * * Same as read_cache_page, but don't wait for page to become unlocked * after submitting it to the filler. * * Read into the page cache. If a page already exists, and PageUptodate() is * not set, try to fill the page but don't wait for it to become unlocked. * * If the page does not get brought uptodate, return -EIO. */ struct page *read_cache_page_async(struct address_space *mapping, pgoff_t index, int (*filler)(void *,struct page*), void *data) { struct page *page; int err; retry: page = __read_cache_page(mapping, index, filler, data); 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); } out: mark_page_accessed(page); return page; } EXPORT_SYMBOL(read_cache_page_async); /** * 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: destination for read data * * Read into the page cache. If a page already exists, and PageUptodate() is * not set, try to fill the page then 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) { struct page *page; page = read_cache_page_async(mapping, index, filler, data); if (IS_ERR(page)) goto out; wait_on_page_locked(page); if (!PageUptodate(page)) { page_cache_release(page); page = ERR_PTR(-EIO); } out: return page; } EXPORT_SYMBOL(read_cache_page); /* * The logic we want is * * if suid or (sgid and xgrp) * remove privs */ int should_remove_suid(struct dentry *dentry) { mode_t mode = dentry->d_inode->i_mode; int kill = 0; /* suid always must be killed */ if (unlikely(mode & S_ISUID)) kill = ATTR_KILL_SUID; /* * sgid without any exec bits is just a mandatory locking mark; leave * it alone. If some exec bits are set, it's a real sgid; kill it. */ if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) kill |= ATTR_KILL_SGID; if (unlikely(kill && !capable(CAP_FSETID))) return kill; return 0; } EXPORT_SYMBOL(should_remove_suid); static int __remove_suid(struct dentry *dentry, int kill) { struct iattr newattrs; newattrs.ia_valid = ATTR_FORCE | kill; return notify_change(dentry, &newattrs); } int remove_suid(struct dentry *dentry) { int killsuid = should_remove_suid(dentry); int killpriv = security_inode_need_killpriv(dentry); int error = 0; if (killpriv < 0) return killpriv; if (killpriv) error = security_inode_killpriv(dentry); if (!error && killsuid) error = __remove_suid(dentry, killsuid); return error; } EXPORT_SYMBOL(remove_suid); static size_t __iovec_copy_from_user_inatomic(char *vaddr, const struct iovec *iov, size_t base, size_t bytes) { size_t copied = 0, left = 0; while (bytes) { char __user *buf = iov->iov_base + base; int copy = min(bytes, iov->iov_len - base); base = 0; left = __copy_from_user_inatomic_nocache(vaddr, buf, copy); copied += copy; bytes -= copy; vaddr += copy; iov++; if (unlikely(left)) break; } return copied - left; } /* * Copy as much as we can into the page and return the number of bytes which * were sucessfully copied. If a fault is encountered then return the number of * bytes which were copied. */ size_t iov_iter_copy_from_user_atomic(struct page *page, struct iov_iter *i, unsigned long offset, size_t bytes) { char *kaddr; size_t copied; BUG_ON(!in_atomic()); kaddr = kmap_atomic(page, KM_USER0); if (likely(i->nr_segs == 1)) { int left; char __user *buf = i->iov->iov_base + i->iov_offset; left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes); copied = bytes - left; } else { copied = __iovec_copy_from_user_inatomic(kaddr + offset, i->iov, i->iov_offset, bytes); } kunmap_atomic(kaddr, KM_USER0); return copied; } EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); /* * This has the same sideeffects and return value as * iov_iter_copy_from_user_atomic(). * The difference is that it attempts to resolve faults. * Page must not be locked. */ size_t iov_iter_copy_from_user(struct page *page, struct iov_iter *i, unsigned long offset, size_t bytes) { char *kaddr; size_t copied; kaddr = kmap(page); if (likely(i->nr_segs == 1)) { int left; char __user *buf = i->iov->iov_base + i->iov_offset; left = __copy_from_user_nocache(kaddr + offset, buf, bytes); copied = bytes - left; } else { copied = __iovec_copy_from_user_inatomic(kaddr + offset, i->iov, i->iov_offset, bytes); } kunmap(page); return copied; } EXPORT_SYMBOL(iov_iter_copy_from_user); void iov_iter_advance(struct iov_iter *i, size_t bytes) { BUG_ON(i->count < bytes); if (likely(i->nr_segs == 1)) { i->iov_offset += bytes; i->count -= bytes; } else { const struct iovec *iov = i->iov; size_t base = i->iov_offset; /* * The !iov->iov_len check ensures we skip over unlikely * zero-length segments (without overruning the iovec). */ while (bytes || unlikely(!iov->iov_len && i->count)) { int copy; copy = min(bytes, iov->iov_len - base); BUG_ON(!i->count || i->count < copy); i->count -= copy; bytes -= copy; base += copy; if (iov->iov_len == base) { iov++; base = 0; } } i->iov = iov; i->iov_offset = base; } } EXPORT_SYMBOL(iov_iter_advance); /* * Fault in the first iovec of the given iov_iter, to a maximum length * of bytes. Returns 0 on success, or non-zero if the memory could not be * accessed (ie. because it is an invalid address). * * writev-intensive code may want this to prefault several iovecs -- that * would be possible (callers must not rely on the fact that _only_ the * first iovec will be faulted with the current implementation). */ int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) { char __user *buf = i->iov->iov_base + i->iov_offset; bytes = min(bytes, i->iov->iov_len - i->iov_offset); return fault_in_pages_readable(buf, bytes); } EXPORT_SYMBOL(iov_iter_fault_in_readable); /* * Return the count of just the current iov_iter segment. */ size_t iov_iter_single_seg_count(struct iov_iter *i) { const struct iovec *iov = i->iov; if (i->nr_segs == 1) return i->count; else return min(i->count, iov->iov_len - i->iov_offset); } EXPORT_SYMBOL(iov_iter_single_seg_count); /* * 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 int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) { struct inode *inode = file->f_mapping->host; unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; if (unlikely(*pos < 0)) return -EINVAL; if (!isblk) { /* FIXME: this is for backwards compatibility with 2.4 */ if (file->f_flags & O_APPEND) *pos = i_size_read(inode); if (limit != RLIM_INFINITY) { if (*pos >= limit) { send_sig(SIGXFSZ, current, 0); return -EFBIG; } if (*count > limit - (typeof(limit))*pos) { *count = limit - (typeof(limit))*pos; } } } /* * LFS rule */ if (unlikely(*pos + *count > MAX_NON_LFS && !(file->f_flags & O_LARGEFILE))) { if (*pos >= MAX_NON_LFS) { return -EFBIG; } if (*count > MAX_NON_LFS - (unsigned long)*pos) { *count = 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 (likely(!isblk)) { if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { if (*count || *pos > inode->i_sb->s_maxbytes) { return -EFBIG; } /* zero-length writes at ->s_maxbytes are OK */ } if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) *count = inode->i_sb->s_maxbytes - *pos; } else { #ifdef CONFIG_BLOCK loff_t isize; if (bdev_read_only(I_BDEV(inode))) return -EPERM; isize = i_size_read(inode); if (*pos >= isize) { if (*count || *pos > isize) return -ENOSPC; } if (*pos + *count > isize) *count = isize - *pos; #else return -EPERM; #endif } return 0; } 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; if (aops->write_begin) { return aops->write_begin(file, mapping, pos, len, flags, pagep, fsdata); } else { int ret; pgoff_t index = pos >> PAGE_CACHE_SHIFT; unsigned offset = pos & (PAGE_CACHE_SIZE - 1); struct inode *inode = mapping->host; struct page *page; again: page = __grab_cache_page(mapping, index); *pagep = page; if (!page) return -ENOMEM; if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) { /* * There is no way to resolve a short write situation * for a !Uptodate page (except by double copying in * the caller done by generic_perform_write_2copy). * * Instead, we have to bring it uptodate here. */ ret = aops->readpage(file, page); page_cache_release(page); if (ret) { if (ret == AOP_TRUNCATED_PAGE) goto again; return ret; } goto again; } ret = aops->prepare_write(file, page, offset, offset+len); if (ret) { unlock_page(page); page_cache_release(page); if (pos + len > inode->i_size) vmtruncate(inode, inode->i_size); } return ret; } } 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; int ret; if (aops->write_end) { mark_page_accessed(page); ret = aops->write_end(file, mapping, pos, len, copied, page, fsdata); } else { unsigned offset = pos & (PAGE_CACHE_SIZE - 1); struct inode *inode = mapping->host; flush_dcache_page(page); ret = aops->commit_write(file, page, offset, offset+len); unlock_page(page); mark_page_accessed(page); page_cache_release(page); if (ret < 0) { if (pos + len > inode->i_size) vmtruncate(inode, inode->i_size); } else if (ret > 0) ret = min_t(size_t, copied, ret); else ret = copied; } return ret; } EXPORT_SYMBOL(pagecache_write_end); ssize_t generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, unsigned long *nr_segs, loff_t pos, loff_t *ppos, size_t count, size_t ocount) { struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; ssize_t written; if (count != ocount) *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs); if (written > 0) { loff_t end = pos + written; if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { i_size_write(inode, end); mark_inode_dirty(inode); } *ppos = end; } /* * Sync the fs metadata but not the minor inode changes and * of course not the data as we did direct DMA for the IO. * i_mutex is held, which protects generic_osync_inode() from * livelocking. AIO O_DIRECT ops attempt to sync metadata here. */ if ((written >= 0 || written == -EIOCBQUEUED) && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { int err = generic_osync_inode(inode, mapping, OSYNC_METADATA); if (err < 0) written = err; } 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(struct address_space *mapping, pgoff_t index) { int status; struct page *page; repeat: page = find_lock_page(mapping, index); if (likely(page)) return page; page = page_cache_alloc(mapping); if (!page) return NULL; status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); if (unlikely(status)) { page_cache_release(page); if (status == -EEXIST) goto repeat; return NULL; } return page; } EXPORT_SYMBOL(__grab_cache_page); static ssize_t generic_perform_write_2copy(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; struct inode *inode = mapping->host; long status = 0; ssize_t written = 0; do { struct page *src_page; struct page *page; pgoff_t index; /* Pagecache index for current page */ unsigned long offset; /* Offset into pagecache page */ unsigned long bytes; /* Bytes to write to page */ size_t copied; /* Bytes copied from user */ offset = (pos & (PAGE_CACHE_SIZE - 1)); index = pos >> PAGE_CACHE_SHIFT; bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, iov_iter_count(i)); /* * a non-NULL src_page indicates that we're doing the * copy via get_user_pages and kmap. */ src_page = NULL; /* * 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; } page = __grab_cache_page(mapping, index); if (!page) { status = -ENOMEM; break; } /* * non-uptodate pages cannot cope with short copies, and we * cannot take a pagefault with the destination page locked. * So pin the source page to copy it. */ if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) { unlock_page(page); src_page = alloc_page(GFP_KERNEL); if (!src_page) { page_cache_release(page); status = -ENOMEM; break; } /* * Cannot get_user_pages with a page locked for the * same reason as we can't take a page fault with a * page locked (as explained below). */ copied = iov_iter_copy_from_user(src_page, i, offset, bytes); if (unlikely(copied == 0)) { status = -EFAULT; page_cache_release(page); page_cache_release(src_page); break; } bytes = copied; lock_page(page); /* * Can't handle the page going uptodate here, because * that means we would use non-atomic usercopies, which * zero out the tail of the page, which can cause * zeroes to become transiently visible. We could just * use a non-zeroing copy, but the APIs aren't too * consistent. */ if (unlikely(!page->mapping || PageUptodate(page))) { unlock_page(page); page_cache_release(page); page_cache_release(src_page); continue; } } status = a_ops->prepare_write(file, page, offset, offset+bytes); if (unlikely(status)) goto fs_write_aop_error; if (!src_page) { /* * Must not enter the pagefault handler here, because * we hold the page lock, so we might recursively * deadlock on the same lock, or get an ABBA deadlock * against a different lock, or against the mmap_sem * (which nests outside the page lock). So increment * preempt count, and use _atomic usercopies. * * The page is uptodate so we are OK to encounter a * short copy: if unmodified parts of the page are * marked dirty and written out to disk, it doesn't * really matter. */ pagefault_disable(); copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); pagefault_enable(); } else { void *src, *dst; src = kmap_atomic(src_page, KM_USER0); dst = kmap_atomic(page, KM_USER1); memcpy(dst + offset, src + offset, bytes); kunmap_atomic(dst, KM_USER1); kunmap_atomic(src, KM_USER0); copied = bytes; } flush_dcache_page(page); status = a_ops->commit_write(file, page, offset, offset+bytes); if (unlikely(status < 0)) goto fs_write_aop_error; if (unlikely(status > 0)) /* filesystem did partial write */ copied = min_t(size_t, copied, status); unlock_page(page); mark_page_accessed(page); page_cache_release(page); if (src_page) page_cache_release(src_page); iov_iter_advance(i, copied); pos += copied; written += copied; balance_dirty_pages_ratelimited(mapping); cond_resched(); continue; fs_write_aop_error: unlock_page(page); page_cache_release(page); if (src_page) page_cache_release(src_page); /* * prepare_write() may have instantiated a few blocks * outside i_size. Trim these off again. Don't need * i_size_read because we hold i_mutex. */ if (pos + bytes > inode->i_size) vmtruncate(inode, inode->i_size); break; } while (iov_iter_count(i)); return written ? written : status; } static 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 (segment_eq(get_fs(), KERNEL_DS)) flags |= AOP_FLAG_UNINTERRUPTIBLE; do { struct page *page; pgoff_t index; /* Pagecache index for current 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)); index = pos >> PAGE_CACHE_SHIFT; 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)) break; pagefault_disable(); copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); pagefault_enable(); 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; } ssize_t generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos, loff_t *ppos, size_t count, ssize_t written) { struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; const struct address_space_operations *a_ops = mapping->a_ops; struct inode *inode = mapping->host; ssize_t status; struct iov_iter i; iov_iter_init(&i, iov, nr_segs, count, written); if (a_ops->write_begin) status = generic_perform_write(file, &i, pos); else status = generic_perform_write_2copy(file, &i, pos); if (likely(status >= 0)) { written += status; *ppos = pos + status; /* * For now, when the user asks for O_SYNC, we'll actually give * O_DSYNC */ if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) { if (!a_ops->writepage || !is_sync_kiocb(iocb)) status = generic_osync_inode(inode, mapping, OSYNC_METADATA|OSYNC_DATA); } } /* * If we get here for O_DIRECT writes then we must have fallen through * to buffered writes (block instantiation inside i_size). So we sync * the file data here, to try to honour O_DIRECT expectations. */ if (unlikely(file->f_flags & O_DIRECT) && written) status = filemap_write_and_wait(mapping); return written ? written : status; } EXPORT_SYMBOL(generic_file_buffered_write); static ssize_t __generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t *ppos) { struct file *file = iocb->ki_filp; struct address_space * mapping = file->f_mapping; size_t ocount; /* original count */ size_t count; /* after file limit checks */ struct inode *inode = mapping->host; loff_t pos; ssize_t written; ssize_t err; ocount = 0; err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); if (err) return err; count = ocount; pos = *ppos; vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); /* We can write back this queue in page reclaim */ current->backing_dev_info = mapping->backing_dev_info; written = 0; err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); if (err) goto out; if (count == 0) goto out; err = remove_suid(file->f_path.dentry); if (err) goto out; file_update_time(file); /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ if (unlikely(file->f_flags & O_DIRECT)) { loff_t endbyte; ssize_t written_buffered; written = generic_file_direct_write(iocb, iov, &nr_segs, pos, ppos, count, ocount); if (written < 0 || written == count) goto out; /* * direct-io write to a hole: fall through to buffered I/O * for completing the rest of the request. */ pos += written; count -= written; written_buffered = generic_file_buffered_write(iocb, iov, nr_segs, pos, ppos, count, written); /* * If generic_file_buffered_write() retuned 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 (written_buffered < 0) { err = written_buffered; 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 + written_buffered - written - 1; err = do_sync_mapping_range(file->f_mapping, pos, endbyte, SYNC_FILE_RANGE_WAIT_BEFORE| SYNC_FILE_RANGE_WRITE| SYNC_FILE_RANGE_WAIT_AFTER); if (err == 0) { written = written_buffered; 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_file_buffered_write(iocb, iov, nr_segs, pos, ppos, count, written); } out: current->backing_dev_info = NULL; return written ? written : err; } ssize_t generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; ssize_t ret; BUG_ON(iocb->ki_pos != pos); ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, &iocb->ki_pos); if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { ssize_t err; err = sync_page_range_nolock(inode, mapping, pos, ret); if (err < 0) ret = err; } return ret; } EXPORT_SYMBOL(generic_file_aio_write_nolock); ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; struct inode *inode = mapping->host; ssize_t ret; BUG_ON(iocb->ki_pos != pos); mutex_lock(&inode->i_mutex); ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, &iocb->ki_pos); mutex_unlock(&inode->i_mutex); if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) { ssize_t err; err = sync_page_range(inode, mapping, pos, ret); if (err < 0) ret = err; } return ret; } EXPORT_SYMBOL(generic_file_aio_write); /* * Called under i_mutex for writes to S_ISREG files. Returns -EIO if something * went wrong during pagecache shootdown. */ static ssize_t generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t offset, unsigned long nr_segs) { struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; ssize_t retval; size_t write_len; pgoff_t end = 0; /* silence gcc */ /* * If it's a write, unmap all mmappings of the file up-front. This * will cause any pte dirty bits to be propagated into the pageframes * for the subsequent filemap_write_and_wait(). */ if (rw == WRITE) { write_len = iov_length(iov, nr_segs); end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT; if (mapping_mapped(mapping)) unmap_mapping_range(mapping, offset, write_len, 0); } retval = filemap_write_and_wait(mapping); if (retval) 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 * -EIO without clobbering -EIOCBQUEUED from ->direct_IO(). */ if (rw == WRITE && mapping->nrpages) { retval = invalidate_inode_pages2_range(mapping, offset >> PAGE_CACHE_SHIFT, end); if (retval) goto out; } retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs); /* * 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 (rw == WRITE && mapping->nrpages) { invalidate_inode_pages2_range(mapping, offset >> PAGE_CACHE_SHIFT, end); } out: return retval; } /** * 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. * * 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). * * NOTE: @gfp_mask may go away, and this function may become non-blocking. */ 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);