/*
* 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/pagevec.h>
#include <linux/blkdev.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/cpuset.h>
#include "filemap.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;
radix_tree_delete(&mapping->page_tree, page->index);
page->mapping = NULL;
mapping->nrpages--;
__dec_zone_page_state(page, NR_FILE_PAGES);
}
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;
}
/**
* __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);
static int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
loff_t end)
{
return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}
/**
* 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
* @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 = 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);
}
write_unlock_irq(&mapping->tree_lock);
radix_tree_preload_end();
}
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 fastcall 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 fastcall 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 fastcall __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);
/*
* Variant of lock_page that does not require the caller to hold a reference
* on the page's mapping.
*/
void fastcall __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, unsigned long 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_trylock_page - find and lock a page
* @mapping: the address_space to search
* @offset: the page index
*
* Same as find_get_page(), but trylock it instead of incrementing the count.
*/
struct page *find_trylock_page(struct address_space *mapping, unsigned long offset)
{
struct page *page;
read_lock_irq(&mapping->tree_lock);
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page && TestSetPageLocked(page))
page = NULL;
read_unlock_irq(&mapping->tree_lock);
return page;
}
EXPORT_SYMBOL(find_trylock_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,
unsigned long offset)
{
struct page *page;
read_lock_irq(&mapping->tree_lock);
repeat:
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);
read_lock_irq(&mapping->tree_lock);
/* Has the page been truncated while we slept? */
if (unlikely(page->mapping != mapping ||
page->index != offset)) {
unlock_page(page);
page_cache_release(page);
goto repeat;
}
}
}
read_unlock_irq(&mapping->tree_lock);
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,
unsigned long index, gfp_t gfp_mask)
{
struct page *page, *cached_page = NULL;
int err;
repeat:
page = find_lock_page(mapping, index);
if (!page) {
if (!cached_page) {
cached_page = alloc_page(gfp_mask);
if (!cached_page)
return NULL;
}
err = add_to_page_cache_lru(cached_page, mapping,
index, gfp_mask);
if (!err) {
page = cached_page;
cached_page = NULL;
} else if (err == -EEXIST)
goto repeat;
}
if (cached_page)
page_cache_release(cached_page);
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;
}
/**
* 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;
}
/**
* 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, unsigned long 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_mapping_read - generic file read routine
* @mapping: address_space to be read
* @_ra: file's readahead state
* @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.
*
* Note the struct file* is only passed for the use of readpage.
* It may be NULL.
*/
void do_generic_mapping_read(struct address_space *mapping,
struct file_ra_state *_ra,
struct file *filp,
loff_t *ppos,
read_descriptor_t *desc,
read_actor_t actor)
{
struct inode *inode = mapping->host;
unsigned long index;
unsigned long end_index;
unsigned long offset;
unsigned long last_index;
unsigned long next_index;
unsigned long prev_index;
loff_t isize;
struct page *cached_page;
int error;
struct file_ra_state ra = *_ra;
cached_page = NULL;
index = *ppos >> PAGE_CACHE_SHIFT;
next_index = index;
prev_index = ra.prev_page;
last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
isize = i_size_read(inode);
if (!isize)
goto out;
end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
for (;;) {
struct page *page;
unsigned long nr, ret;
/* nr is the maximum number of bytes to copy from this page */
nr = PAGE_CACHE_SIZE;
if (index >= end_index) {
if (index > end_index)
goto out;
nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
if (nr <= offset) {
goto out;
}
}
nr = nr - offset;
cond_resched();
if (index == next_index)
next_index = page_cache_readahead(mapping, &ra, filp,
index, last_index - index);
find_page:
page = find_get_page(mapping, index);
if (unlikely(page == NULL)) {
handle_ra_miss(mapping, &ra, index);
goto no_cached_page;
}
if (!PageUptodate(page))
goto page_not_up_to_date;
page_ok:
/* 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 (part of) the same page is read multiple times
* in succession, only mark it as accessed the first time.
*/
if (prev_index != index)
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;
page_cache_release(page);
if (ret == nr && desc->count)
continue;
goto out;
page_not_up_to_date:
/* Get exclusive access to the page ... */
lock_page(page);
/* 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)) {
lock_page(page);
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);
error = -EIO;
shrink_readahead_size_eio(filp, &ra);
goto readpage_error;
}
unlock_page(page);
}
/*
* i_size must be checked after we have done ->readpage.
*
* Checking i_size after the readpage 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;
goto page_ok;
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..
*/
if (!cached_page) {
cached_page = page_cache_alloc_cold(mapping);
if (!cached_page) {
desc->error = -ENOMEM;
goto out;
}
}
error = add_to_page_cache_lru(cached_page, mapping,
index, GFP_KERNEL);
if (error) {
if (error == -EEXIST)
goto find_page;
desc->error = error;
goto out;
}
page = cached_page;
cached_page = NULL;
goto readpage;
}
out:
*_ra = ra;
*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
if (cached_page)
page_cache_release(cached_page);
if (filp)
file_accessed(filp);
}
EXPORT_SYMBOL(do_generic_mapping_read);
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;
}
/**
* 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;
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.
*/
count += iv->iov_len;
if (unlikely((ssize_t)(count|iv->iov_len) < 0))
return -EINVAL;
if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
continue;
if (seg == 0)
return -EFAULT;
nr_segs = seg;
count -= iv->iov_len; /* This segment is no good */
break;
}
/* 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 && !is_sync_kiocb(iocb))
retval = -EIOCBQUEUED;
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;
}
}
}
out:
return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);
int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
{
ssize_t written;
unsigned long count = desc->count;
struct file *file = desc->arg.data;
if (size > count)
size = count;
written = file->f_op->sendpage(file, page, offset,
size, &file->f_pos, size<count);
if (written < 0) {
desc->error = written;
written = 0;
}
desc->count = count - written;
desc->written += written;
return written;
}
ssize_t generic_file_sendfile(struct file *in_file, loff_t *ppos,
size_t count, read_actor_t actor, void *target)
{
read_descriptor_t desc;
if (!count)
return 0;
desc.written = 0;
desc.count = count;
desc.arg.data = target;
desc.error = 0;
do_generic_file_read(in_file, ppos, &desc, actor);
if (desc.written)
return desc.written;
return desc.error;
}
EXPORT_SYMBOL(generic_file_sendfile);
static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
unsigned long 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;
unsigned long start = offset >> PAGE_CACHE_SHIFT;
unsigned long 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
static int FASTCALL(page_cache_read(struct file * file, unsigned long offset));
/**
* 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 fastcall page_cache_read(struct file * file, unsigned long 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_nopage - read in file data for page fault handling
* @area: the applicable vm_area
* @address: target address to read in
* @type: returned with VM_FAULT_{MINOR,MAJOR} if not %NULL
*
* filemap_nopage() 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.
*/
struct page *filemap_nopage(struct vm_area_struct *area,
unsigned long address, int *type)
{
int error;
struct file *file = area->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;
unsigned long size, pgoff;
int did_readaround = 0, majmin = VM_FAULT_MINOR;
pgoff = ((address-area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;
retry_all:
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (pgoff >= size)
goto outside_data_content;
/* If we don't want any read-ahead, don't bother */
if (VM_RandomReadHint(area))
goto no_cached_page;
/*
* The readahead code wants to be told about each and every page
* so it can build and shrink its windows appropriately
*
* For sequential accesses, we use the generic readahead logic.
*/
if (VM_SequentialReadHint(area))
page_cache_readahead(mapping, ra, file, pgoff, 1);
/*
* Do we have something in the page cache already?
*/
retry_find:
page = find_get_page(mapping, pgoff);
if (!page) {
unsigned long ra_pages;
if (VM_SequentialReadHint(area)) {
handle_ra_miss(mapping, ra, pgoff);
goto no_cached_page;
}
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 > ra->mmap_hit + 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) {
majmin = 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 (pgoff > ra_pages / 2)
start = pgoff - ra_pages / 2;
do_page_cache_readahead(mapping, file, start, ra_pages);
}
page = find_get_page(mapping, pgoff);
if (!page)
goto no_cached_page;
}
if (!did_readaround)
ra->mmap_hit++;
/*
* Ok, found a page in the page cache, now we need to check
* that it's up-to-date.
*/
if (!PageUptodate(page))
goto page_not_uptodate;
success:
/*
* Found the page and have a reference on it.
*/
mark_page_accessed(page);
if (type)
*type = majmin;
return page;
outside_data_content:
/*
* An external ptracer can access pages that normally aren't
* accessible..
*/
if (area->vm_mm == current->mm)
return NOPAGE_SIGBUS;
/* Fall through to the non-read-ahead case */
no_cached_page:
/*
* We're only likely to ever get here if MADV_RANDOM is in
* effect.
*/
error = page_cache_read(file, pgoff);
grab_swap_token();
/*
* 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 NOPAGE_OOM;
return NOPAGE_SIGBUS;
page_not_uptodate:
if (!did_readaround) {
majmin = VM_FAULT_MAJOR;
count_vm_event(PGMAJFAULT);
}
lock_page(page);
/* Did it get unhashed while we waited for it? */
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
goto retry_all;
}
/* Did somebody else get it up-to-date? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
error = mapping->a_ops->readpage(file, page);
if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
} else if (error == AOP_TRUNCATED_PAGE) {
page_cache_release(page);
goto retry_find;
}
/*
* 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.
*/
lock_page(page);
/* Somebody truncated the page on us? */
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
goto retry_all;
}
/* Somebody else successfully read it in? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
ClearPageError(page);
error = mapping->a_ops->readpage(file, page);
if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
} else if (error == AOP_TRUNCATED_PAGE) {
page_cache_release(page);
goto retry_find;
}
/*
* Things didn't work out. Return zero to tell the
* mm layer so, possibly freeing the page cache page first.
*/
shrink_readahead_size_eio(file, ra);
page_cache_release(page);
return NOPAGE_SIGBUS;
}
EXPORT_SYMBOL(filemap_nopage);
static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
int nonblock)
{
struct address_space *mapping = file->f_mapping;
struct page *page;
int error;
/*
* Do we have something in the page cache already?
*/
retry_find:
page = find_get_page(mapping, pgoff);
if (!page) {
if (nonblock)
return NULL;
goto no_cached_page;
}
/*
* Ok, found a page in the page cache, now we need to check
* that it's up-to-date.
*/
if (!PageUptodate(page)) {
if (nonblock) {
page_cache_release(page);
return NULL;
}
goto page_not_uptodate;
}
success:
/*
* Found the page and have a reference on it.
*/
mark_page_accessed(page);
return page;
no_cached_page:
error = page_cache_read(file, 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.
*/
return NULL;
page_not_uptodate:
lock_page(page);
/* Did it get truncated while we waited for it? */
if (!page->mapping) {
unlock_page(page);
goto err;
}
/* Did somebody else get it up-to-date? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
error = mapping->a_ops->readpage(file, page);
if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
} else if (error == AOP_TRUNCATED_PAGE) {
page_cache_release(page);
goto retry_find;
}
/*
* 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.
*/
lock_page(page);
/* Somebody truncated the page on us? */
if (!page->mapping) {
unlock_page(page);
goto err;
}
/* Somebody else successfully read it in? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
ClearPageError(page);
error = mapping->a_ops->readpage(file, page);
if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
} else if (error == AOP_TRUNCATED_PAGE) {
page_cache_release(page);
goto retry_find;
}
/*
* Things didn't work out. Return zero to tell the
* mm layer so, possibly freeing the page cache page first.
*/
err:
page_cache_release(page);
return NULL;
}
int filemap_populate(struct vm_area_struct *vma, unsigned long addr,
unsigned long len, pgprot_t prot, unsigned long pgoff,
int nonblock)
{
struct file *file = vma->vm_file;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
unsigned long size;
struct mm_struct *mm = vma->vm_mm;
struct page *page;
int err;
if (!nonblock)
force_page_cache_readahead(mapping, vma->vm_file,
pgoff, len >> PAGE_CACHE_SHIFT);
repeat:
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (pgoff + (len >> PAGE_CACHE_SHIFT) > size)
return -EINVAL;
page = filemap_getpage(file, pgoff, nonblock);
/* XXX: This is wrong, a filesystem I/O error may have happened. Fix that as
* done in shmem_populate calling shmem_getpage */
if (!page && !nonblock)
return -ENOMEM;
if (page) {
err = install_page(mm, vma, addr, page, prot);
if (err) {
page_cache_release(page);
return err;
}
} else if (vma->vm_flags & VM_NONLINEAR) {
/* No page was found just because we can't read it in now (being
* here implies nonblock != 0), but the page may exist, so set
* the PTE to fault it in later. */
err = install_file_pte(mm, vma, addr, pgoff, prot);
if (err)
return err;
}
len -= PAGE_SIZE;
addr += PAGE_SIZE;
pgoff++;
if (len)
goto repeat;
return 0;
}
EXPORT_SYMBOL(filemap_populate);
struct vm_operations_struct generic_file_vm_ops = {
.nopage = filemap_nopage,
.populate = filemap_populate,
};
/* 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 inline struct page *__read_cache_page(struct address_space *mapping,
unsigned long index,
int (*filler)(void *,struct page*),
void *data)
{
struct page *page, *cached_page = NULL;
int err;
repeat:
page = find_get_page(mapping, index);
if (!page) {
if (!cached_page) {
cached_page = page_cache_alloc_cold(mapping);
if (!cached_page)
return ERR_PTR(-ENOMEM);
}
err = add_to_page_cache_lru(cached_page, mapping,
index, GFP_KERNEL);
if (err == -EEXIST)
goto repeat;
if (err < 0) {
/* Presumably ENOMEM for radix tree node */
page_cache_release(cached_page);
return ERR_PTR(err);
}
page = cached_page;
cached_page = NULL;
err = filler(data, page);
if (err < 0) {
page_cache_release(page);
page = ERR_PTR(err);
}
}
if (cached_page)
page_cache_release(cached_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: destination for read data
*
* Read into the page cache. If a page already exists,
* and PageUptodate() is not set, try to fill the page.
*/
struct page *read_cache_page(struct address_space *mapping,
unsigned long 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))
goto out;
mark_page_accessed(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);
page = ERR_PTR(err);
}
out:
return page;
}
EXPORT_SYMBOL(read_cache_page);
/*
* If the page was newly created, increment its refcount and add it to the
* caller's lru-buffering pagevec. This function is specifically for
* generic_file_write().
*/
static inline struct page *
__grab_cache_page(struct address_space *mapping, unsigned long index,
struct page **cached_page, struct pagevec *lru_pvec)
{
int err;
struct page *page;
repeat:
page = find_lock_page(mapping, index);
if (!page) {
if (!*cached_page) {
*cached_page = page_cache_alloc(mapping);
if (!*cached_page)
return NULL;
}
err = add_to_page_cache(*cached_page, mapping,
index, GFP_KERNEL);
if (err == -EEXIST)
goto repeat;
if (err == 0) {
page = *cached_page;
page_cache_get(page);
if (!pagevec_add(lru_pvec, page))
__pagevec_lru_add(lru_pvec);
*cached_page = NULL;
}
}
return 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);
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 kill = should_remove_suid(dentry);
if (unlikely(kill))
return __remove_suid(dentry, kill);
return 0;
}
EXPORT_SYMBOL(remove_suid);
size_t
__filemap_copy_from_user_iovec_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;
}
/*
* 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) {
send_sig(SIGXFSZ, current, 0);
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) {
send_sig(SIGXFSZ, current, 0);
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);
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.
*/
if (written >= 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
if (err < 0)
written = err;
}
if (written == count && !is_sync_kiocb(iocb))
written = -EIOCBQUEUED;
return written;
}
EXPORT_SYMBOL(generic_file_direct_write);
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;
long status = 0;
struct page *page;
struct page *cached_page = NULL;
size_t bytes;
struct pagevec lru_pvec;
const struct iovec *cur_iov = iov; /* current iovec */
size_t iov_base = 0; /* offset in the current iovec */
char __user *buf;
pagevec_init(&lru_pvec, 0);
/*
* handle partial DIO write. Adjust cur_iov if needed.
*/
if (likely(nr_segs == 1))
buf = iov->iov_base + written;
else {
filemap_set_next_iovec(&cur_iov, &iov_base, written);
buf = cur_iov->iov_base + iov_base;
}
do {
unsigned long index;
unsigned long offset;
size_t copied;
offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
index = pos >> PAGE_CACHE_SHIFT;
bytes = PAGE_CACHE_SIZE - offset;
/* Limit the size of the copy to the caller's write size */
bytes = min(bytes, count);
/*
* Limit the size of the copy to that of the current segment,
* because fault_in_pages_readable() doesn't know how to walk
* segments.
*/
bytes = min(bytes, cur_iov->iov_len - iov_base);
/*
* 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.
*/
fault_in_pages_readable(buf, bytes);
page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
if (!page) {
status = -ENOMEM;
break;
}
if (unlikely(bytes == 0)) {
status = 0;
copied = 0;
goto zero_length_segment;
}
status = a_ops->prepare_write(file, page, offset, offset+bytes);
if (unlikely(status)) {
loff_t isize = i_size_read(inode);
if (status != AOP_TRUNCATED_PAGE)
unlock_page(page);
page_cache_release(page);
if (status == AOP_TRUNCATED_PAGE)
continue;
/*
* prepare_write() may have instantiated a few blocks
* outside i_size. Trim these off again.
*/
if (pos + bytes > isize)
vmtruncate(inode, isize);
break;
}
if (likely(nr_segs == 1))
copied = filemap_copy_from_user(page, offset,
buf, bytes);
else
copied = filemap_copy_from_user_iovec(page, offset,
cur_iov, iov_base, bytes);
flush_dcache_page(page);
status = a_ops->commit_write(file, page, offset, offset+bytes);
if (status == AOP_TRUNCATED_PAGE) {
page_cache_release(page);
continue;
}
zero_length_segment:
if (likely(copied >= 0)) {
if (!status)
status = copied;
if (status >= 0) {
written += status;
count -= status;
pos += status;
buf += status;
if (unlikely(nr_segs > 1)) {
filemap_set_next_iovec(&cur_iov,
&iov_base, status);
if (count)
buf = cur_iov->iov_base +
iov_base;
} else {
iov_base += status;
}
}
}
if (unlikely(copied != bytes))
if (status >= 0)
status = -EFAULT;
unlock_page(page);
mark_page_accessed(page);
page_cache_release(page);
if (status < 0)
break;
balance_dirty_pages_ratelimited(mapping);
cond_resched();
} while (count);
*ppos = pos;
if (cached_page)
page_cache_release(cached_page);
/*
* For now, when the user asks for O_SYNC, we'll actually give O_DSYNC
*/
if (likely(status >= 0)) {
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);
pagevec_lru_add(&lru_pvec);
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;
unsigned long seg;
loff_t pos;
ssize_t written;
ssize_t err;
ocount = 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.
*/
ocount += iv->iov_len;
if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
return -EINVAL;
if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
continue;
if (seg == 0)
return -EFAULT;
nr_segs = seg;
ocount -= iv->iov_len; /* This segment is no good */
break;
}
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_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_file_range(file, 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 = 0;
/*
* 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);
if (mapping_mapped(mapping))
unmap_mapping_range(mapping, offset, write_len, 0);
}
retval = filemap_write_and_wait(mapping);
if (retval == 0) {
retval = mapping->a_ops->direct_IO(rw, iocb, iov,
offset, nr_segs);
if (rw == WRITE && mapping->nrpages) {
pgoff_t end = (offset + write_len - 1)
>> PAGE_CACHE_SHIFT;
int err = invalidate_inode_pages2_range(mapping,
offset >> PAGE_CACHE_SHIFT, end);
if (err)
retval = err;
}
}
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);
