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OpenCloudOS-Kernel/mm/filemap.c

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/*
* linux/mm/filemap.c
*
* Copyright (C) 1994-1999 Linus Torvalds
*/
/*
* This file handles the generic file mmap semantics used by
* most "normal" filesystems (but you don't /have/ to use this:
* the NFS filesystem used to do this differently, for example)
*/
#include <linux/export.h>
#include <linux/compiler.h>
#include <linux/dax.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/capability.h>
#include <linux/kernel_stat.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/hash.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/security.h>
#include <linux/cpuset.h>
#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
#include <linux/hugetlb.h>
#include <linux/memcontrol.h>
#include <linux/cleancache.h>
#include <linux/rmap.h>
#include "internal.h"
#define CREATE_TRACE_POINTS
#include <trace/events/filemap.h>
/*
* FIXME: remove all knowledge of the buffer layer from the core VM
*/
#include <linux/buffer_head.h> /* for try_to_free_buffers */
#include <asm/mman.h>
/*
* Shared mappings implemented 30.11.1994. It's not fully working yet,
* though.
*
* Shared mappings now work. 15.8.1995 Bruno.
*
* finished 'unifying' the page and buffer cache and SMP-threaded the
* page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
*
* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
*/
/*
* Lock ordering:
*
* ->i_mmap_rwsem (truncate_pagecache)
* ->private_lock (__free_pte->__set_page_dirty_buffers)
* ->swap_lock (exclusive_swap_page, others)
* ->mapping->tree_lock
*
* ->i_mutex
* ->i_mmap_rwsem (truncate->unmap_mapping_range)
*
* ->mmap_sem
* ->i_mmap_rwsem
* ->page_table_lock or pte_lock (various, mainly in memory.c)
* ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
*
* ->mmap_sem
* ->lock_page (access_process_vm)
*
* ->i_mutex (generic_perform_write)
* ->mmap_sem (fault_in_pages_readable->do_page_fault)
*
* bdi->wb.list_lock
* sb_lock (fs/fs-writeback.c)
* ->mapping->tree_lock (__sync_single_inode)
*
* ->i_mmap_rwsem
* ->anon_vma.lock (vma_adjust)
*
* ->anon_vma.lock
* ->page_table_lock or pte_lock (anon_vma_prepare and various)
*
* ->page_table_lock or pte_lock
* ->swap_lock (try_to_unmap_one)
* ->private_lock (try_to_unmap_one)
* ->tree_lock (try_to_unmap_one)
* ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
* ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
* ->private_lock (page_remove_rmap->set_page_dirty)
* ->tree_lock (page_remove_rmap->set_page_dirty)
* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
* ->inode->i_lock (page_remove_rmap->set_page_dirty)
* ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
* bdi.wb->list_lock (zap_pte_range->set_page_dirty)
* ->inode->i_lock (zap_pte_range->set_page_dirty)
* ->private_lock (zap_pte_range->__set_page_dirty_buffers)
*
* ->i_mmap_rwsem
* ->tasklist_lock (memory_failure, collect_procs_ao)
*/
static int page_cache_tree_insert(struct address_space *mapping,
struct page *page, void **shadowp)
{
struct radix_tree_node *node;
void **slot;
int error;
error = __radix_tree_create(&mapping->page_tree, page->index, 0,
&node, &slot);
if (error)
return error;
if (*slot) {
void *p;
p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
if (!radix_tree_exceptional_entry(p))
return -EEXIST;
mapping->nrexceptional--;
if (!dax_mapping(mapping)) {
if (shadowp)
*shadowp = p;
} else {
/* DAX can replace empty locked entry with a hole */
WARN_ON_ONCE(p !=
dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
/* Wakeup waiters for exceptional entry lock */
dax_wake_mapping_entry_waiter(mapping, page->index, p,
true);
}
}
__radix_tree_replace(&mapping->page_tree, node, slot, page,
workingset_update_node, mapping);
mapping->nrpages++;
return 0;
}
static void page_cache_tree_delete(struct address_space *mapping,
struct page *page, void *shadow)
{
int i, nr;
/* hugetlb pages are represented by one entry in the radix tree */
nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageTail(page), page);
VM_BUG_ON_PAGE(nr != 1 && shadow, page);
for (i = 0; i < nr; i++) {
struct radix_tree_node *node;
void **slot;
__radix_tree_lookup(&mapping->page_tree, page->index + i,
&node, &slot);
VM_BUG_ON_PAGE(!node && nr != 1, page);
radix_tree_clear_tags(&mapping->page_tree, node, slot);
__radix_tree_replace(&mapping->page_tree, node, slot, shadow,
workingset_update_node, mapping);
}
if (shadow) {
mapping->nrexceptional += nr;
/*
* Make sure the nrexceptional update is committed before
* the nrpages update so that final truncate racing
* with reclaim does not see both counters 0 at the
* same time and miss a shadow entry.
*/
smp_wmb();
}
mapping->nrpages -= nr;
}
/*
* Delete a page from the page cache and free it. Caller has to make
* sure the page is locked and that nobody else uses it - or that usage
* is safe. The caller must hold the mapping's tree_lock.
*/
void __delete_from_page_cache(struct page *page, void *shadow)
{
struct address_space *mapping = page->mapping;
int nr = hpage_nr_pages(page);
trace_mm_filemap_delete_from_page_cache(page);
/*
* if we're uptodate, flush out into the cleancache, otherwise
* invalidate any existing cleancache entries. We can't leave
* stale data around in the cleancache once our page is gone
*/
if (PageUptodate(page) && PageMappedToDisk(page))
cleancache_put_page(page);
else
cleancache_invalidate_page(mapping, page);
VM_BUG_ON_PAGE(PageTail(page), page);
VM_BUG_ON_PAGE(page_mapped(page), page);
if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
int mapcount;
pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
current->comm, page_to_pfn(page));
dump_page(page, "still mapped when deleted");
dump_stack();
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
mapcount = page_mapcount(page);
if (mapping_exiting(mapping) &&
page_count(page) >= mapcount + 2) {
/*
* All vmas have already been torn down, so it's
* a good bet that actually the page is unmapped,
* and we'd prefer not to leak it: if we're wrong,
* some other bad page check should catch it later.
*/
page_mapcount_reset(page);
page_ref_sub(page, mapcount);
}
}
page_cache_tree_delete(mapping, page, shadow);
page->mapping = NULL;
/* Leave page->index set: truncation lookup relies upon it */
/* hugetlb pages do not participate in page cache accounting. */
if (!PageHuge(page))
__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
if (PageSwapBacked(page)) {
__mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
if (PageTransHuge(page))
__dec_node_page_state(page, NR_SHMEM_THPS);
} else {
VM_BUG_ON_PAGE(PageTransHuge(page) && !PageHuge(page), page);
}
/*
* At this point page must be either written or cleaned by truncate.
* Dirty page here signals a bug and loss of unwritten data.
*
* This fixes dirty accounting after removing the page entirely but
* leaves PageDirty set: it has no effect for truncated page and
* anyway will be cleared before returning page into buddy allocator.
*/
if (WARN_ON_ONCE(PageDirty(page)))
account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
}
/**
* delete_from_page_cache - delete page from page cache
* @page: the page which the kernel is trying to remove from page cache
*
* This must be called only on pages that have been verified to be in the page
* cache and locked. It will never put the page into the free list, the caller
* has a reference on the page.
*/
void delete_from_page_cache(struct page *page)
{
struct address_space *mapping = page_mapping(page);
unsigned long flags;
void (*freepage)(struct page *);
BUG_ON(!PageLocked(page));
freepage = mapping->a_ops->freepage;
spin_lock_irqsave(&mapping->tree_lock, flags);
__delete_from_page_cache(page, NULL);
spin_unlock_irqrestore(&mapping->tree_lock, flags);
if (freepage)
freepage(page);
if (PageTransHuge(page) && !PageHuge(page)) {
page_ref_sub(page, HPAGE_PMD_NR);
VM_BUG_ON_PAGE(page_count(page) <= 0, page);
} else {
put_page(page);
}
}
EXPORT_SYMBOL(delete_from_page_cache);
int filemap_check_errors(struct address_space *mapping)
{
int ret = 0;
/* Check for outstanding write errors */
if (test_bit(AS_ENOSPC, &mapping->flags) &&
test_and_clear_bit(AS_ENOSPC, &mapping->flags))
ret = -ENOSPC;
if (test_bit(AS_EIO, &mapping->flags) &&
test_and_clear_bit(AS_EIO, &mapping->flags))
ret = -EIO;
return ret;
}
EXPORT_SYMBOL(filemap_check_errors);
/**
* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
* @mapping: address space structure to write
* @start: offset in bytes where the range starts
* @end: offset in bytes where the range ends (inclusive)
* @sync_mode: enable synchronous operation
*
* Start writeback against all of a mapping's dirty pages that lie
* within the byte offsets <start, end> inclusive.
*
* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
* opposed to a regular memory cleansing writeback. The difference between
* these two operations is that if a dirty page/buffer is encountered, it must
* be waited upon, and not just skipped over.
*/
int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
loff_t end, int sync_mode)
{
int ret;
struct writeback_control wbc = {
.sync_mode = sync_mode,
.nr_to_write = LONG_MAX,
.range_start = start,
.range_end = end,
};
if (!mapping_cap_writeback_dirty(mapping))
return 0;
wbc_attach_fdatawrite_inode(&wbc, mapping->host);
ret = do_writepages(mapping, &wbc);
wbc_detach_inode(&wbc);
return ret;
}
static inline int __filemap_fdatawrite(struct address_space *mapping,
int sync_mode)
{
return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
}
int filemap_fdatawrite(struct address_space *mapping)
{
return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite);
int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
loff_t end)
{
return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite_range);
/**
* filemap_flush - mostly a non-blocking flush
* @mapping: target address_space
*
* This is a mostly non-blocking flush. Not suitable for data-integrity
* purposes - I/O may not be started against all dirty pages.
*/
int filemap_flush(struct address_space *mapping)
{
return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
}
EXPORT_SYMBOL(filemap_flush);
static int __filemap_fdatawait_range(struct address_space *mapping,
loff_t start_byte, loff_t end_byte)
{
pgoff_t index = start_byte >> PAGE_SHIFT;
pgoff_t end = end_byte >> PAGE_SHIFT;
struct pagevec pvec;
int nr_pages;
int ret = 0;
if (end_byte < start_byte)
goto out;
pagevec_init(&pvec, 0);
while ((index <= end) &&
(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_WRITEBACK,
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
unsigned i;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
/* until radix tree lookup accepts end_index */
if (page->index > end)
continue;
wait_on_page_writeback(page);
if (TestClearPageError(page))
ret = -EIO;
}
pagevec_release(&pvec);
cond_resched();
}
out:
return ret;
}
/**
* filemap_fdatawait_range - wait for writeback to complete
* @mapping: address space structure to wait for
* @start_byte: offset in bytes where the range starts
* @end_byte: offset in bytes where the range ends (inclusive)
*
* Walk the list of under-writeback pages of the given address space
* in the given range and wait for all of them. Check error status of
* the address space and return it.
*
* Since the error status of the address space is cleared by this function,
* callers are responsible for checking the return value and handling and/or
* reporting the error.
*/
int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
loff_t end_byte)
{
int ret, ret2;
ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
ret2 = filemap_check_errors(mapping);
if (!ret)
ret = ret2;
return ret;
}
EXPORT_SYMBOL(filemap_fdatawait_range);
/**
* filemap_fdatawait_keep_errors - wait for writeback without clearing errors
* @mapping: address space structure to wait for
*
* Walk the list of under-writeback pages of the given address space
* and wait for all of them. Unlike filemap_fdatawait(), this function
* does not clear error status of the address space.
*
* Use this function if callers don't handle errors themselves. Expected
* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
* fsfreeze(8)
*/
void filemap_fdatawait_keep_errors(struct address_space *mapping)
{
loff_t i_size = i_size_read(mapping->host);
if (i_size == 0)
return;
__filemap_fdatawait_range(mapping, 0, i_size - 1);
}
/**
* filemap_fdatawait - wait for all under-writeback pages to complete
* @mapping: address space structure to wait for
*
* Walk the list of under-writeback pages of the given address space
* and wait for all of them. Check error status of the address space
* and return it.
*
* Since the error status of the address space is cleared by this function,
* callers are responsible for checking the return value and handling and/or
* reporting the error.
*/
int filemap_fdatawait(struct address_space *mapping)
{
loff_t i_size = i_size_read(mapping->host);
if (i_size == 0)
return 0;
return filemap_fdatawait_range(mapping, 0, i_size - 1);
}
EXPORT_SYMBOL(filemap_fdatawait);
int filemap_write_and_wait(struct address_space *mapping)
{
int err = 0;
if ((!dax_mapping(mapping) && mapping->nrpages) ||
(dax_mapping(mapping) && mapping->nrexceptional)) {
err = filemap_fdatawrite(mapping);
/*
* Even if the above returned error, the pages may be
* written partially (e.g. -ENOSPC), so we wait for it.
* But the -EIO is special case, it may indicate the worst
* thing (e.g. bug) happened, so we avoid waiting for it.
*/
if (err != -EIO) {
int err2 = filemap_fdatawait(mapping);
if (!err)
err = err2;
}
} else {
err = filemap_check_errors(mapping);
}
return err;
}
EXPORT_SYMBOL(filemap_write_and_wait);
/**
* filemap_write_and_wait_range - write out & wait on a file range
* @mapping: the address_space for the pages
* @lstart: offset in bytes where the range starts
* @lend: offset in bytes where the range ends (inclusive)
*
* Write out and wait upon file offsets lstart->lend, inclusive.
*
* Note that `lend' is inclusive (describes the last byte to be written) so
* that this function can be used to write to the very end-of-file (end = -1).
*/
int filemap_write_and_wait_range(struct address_space *mapping,
loff_t lstart, loff_t lend)
{
int err = 0;
if ((!dax_mapping(mapping) && mapping->nrpages) ||
(dax_mapping(mapping) && mapping->nrexceptional)) {
err = __filemap_fdatawrite_range(mapping, lstart, lend,
WB_SYNC_ALL);
/* See comment of filemap_write_and_wait() */
if (err != -EIO) {
int err2 = filemap_fdatawait_range(mapping,
lstart, lend);
if (!err)
err = err2;
}
} else {
err = filemap_check_errors(mapping);
}
return err;
}
EXPORT_SYMBOL(filemap_write_and_wait_range);
/**
* replace_page_cache_page - replace a pagecache page with a new one
* @old: page to be replaced
* @new: page to replace with
* @gfp_mask: allocation mode
*
* This function replaces a page in the pagecache with a new one. On
* success it acquires the pagecache reference for the new page and
* drops it for the old page. Both the old and new pages must be
* locked. This function does not add the new page to the LRU, the
* caller must do that.
*
* The remove + add is atomic. The only way this function can fail is
* memory allocation failure.
*/
int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
{
int error;
VM_BUG_ON_PAGE(!PageLocked(old), old);
VM_BUG_ON_PAGE(!PageLocked(new), new);
VM_BUG_ON_PAGE(new->mapping, new);
error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
if (!error) {
struct address_space *mapping = old->mapping;
void (*freepage)(struct page *);
unsigned long flags;
pgoff_t offset = old->index;
freepage = mapping->a_ops->freepage;
get_page(new);
new->mapping = mapping;
new->index = offset;
spin_lock_irqsave(&mapping->tree_lock, flags);
__delete_from_page_cache(old, NULL);
error = page_cache_tree_insert(mapping, new, NULL);
BUG_ON(error);
/*
* hugetlb pages do not participate in page cache accounting.
*/
if (!PageHuge(new))
__inc_node_page_state(new, NR_FILE_PAGES);
if (PageSwapBacked(new))
__inc_node_page_state(new, NR_SHMEM);
spin_unlock_irqrestore(&mapping->tree_lock, flags);
mem_cgroup_migrate(old, new);
radix_tree_preload_end();
if (freepage)
freepage(old);
put_page(old);
}
return error;
}
EXPORT_SYMBOL_GPL(replace_page_cache_page);
static int __add_to_page_cache_locked(struct page *page,
struct address_space *mapping,
pgoff_t offset, gfp_t gfp_mask,
void **shadowp)
{
int huge = PageHuge(page);
struct mem_cgroup *memcg;
int error;
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapBacked(page), page);
if (!huge) {
error = mem_cgroup_try_charge(page, current->mm,
gfp_mask, &memcg, false);
if (error)
return error;
}
error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
if (error) {
if (!huge)
mem_cgroup_cancel_charge(page, memcg, false);
return error;
}
get_page(page);
page->mapping = mapping;
page->index = offset;
spin_lock_irq(&mapping->tree_lock);
error = page_cache_tree_insert(mapping, page, shadowp);
radix_tree_preload_end();
if (unlikely(error))
goto err_insert;
/* hugetlb pages do not participate in page cache accounting. */
if (!huge)
__inc_node_page_state(page, NR_FILE_PAGES);
spin_unlock_irq(&mapping->tree_lock);
if (!huge)
mem_cgroup_commit_charge(page, memcg, false, false);
trace_mm_filemap_add_to_page_cache(page);
return 0;
err_insert:
page->mapping = NULL;
/* Leave page->index set: truncation relies upon it */
spin_unlock_irq(&mapping->tree_lock);
if (!huge)
mem_cgroup_cancel_charge(page, memcg, false);
put_page(page);
return error;
}
/**
* add_to_page_cache_locked - add a locked page to the pagecache
* @page: page to add
* @mapping: the page's address_space
* @offset: page index
* @gfp_mask: page allocation mode
*
* This function is used to add a page to the pagecache. It must be locked.
* This function does not add the page to the LRU. The caller must do that.
*/
int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
pgoff_t offset, gfp_t gfp_mask)
{
return __add_to_page_cache_locked(page, mapping, offset,
gfp_mask, NULL);
}
EXPORT_SYMBOL(add_to_page_cache_locked);
int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
pgoff_t offset, gfp_t gfp_mask)
{
void *shadow = NULL;
int ret;
__SetPageLocked(page);
ret = __add_to_page_cache_locked(page, mapping, offset,
gfp_mask, &shadow);
if (unlikely(ret))
__ClearPageLocked(page);
else {
/*
* The page might have been evicted from cache only
* recently, in which case it should be activated like
* any other repeatedly accessed page.
* The exception is pages getting rewritten; evicting other
* data from the working set, only to cache data that will
* get overwritten with something else, is a waste of memory.
*/
if (!(gfp_mask & __GFP_WRITE) &&
shadow && workingset_refault(shadow)) {
SetPageActive(page);
workingset_activation(page);
} else
ClearPageActive(page);
lru_cache_add(page);
}
return ret;
}
EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
#ifdef CONFIG_NUMA
struct page *__page_cache_alloc(gfp_t gfp)
{
int n;
struct page *page;
if (cpuset_do_page_mem_spread()) {
unsigned int cpuset_mems_cookie;
do {
cpuset_mems_cookie = read_mems_allowed_begin();
n = cpuset_mem_spread_node();
page = __alloc_pages_node(n, gfp, 0);
} while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
return page;
}
return alloc_pages(gfp, 0);
}
EXPORT_SYMBOL(__page_cache_alloc);
#endif
/*
* In order to wait for pages to become available there must be
* waitqueues associated with pages. By using a hash table of
* waitqueues where the bucket discipline is to maintain all
* waiters on the same queue and wake all when any of the pages
* become available, and for the woken contexts to check to be
* sure the appropriate page became available, this saves space
* at a cost of "thundering herd" phenomena during rare hash
* collisions.
*/
#define PAGE_WAIT_TABLE_BITS 8
#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
static wait_queue_head_t *page_waitqueue(struct page *page)
{
return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
}
void __init pagecache_init(void)
{
int i;
for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
init_waitqueue_head(&page_wait_table[i]);
page_writeback_init();
}
struct wait_page_key {
struct page *page;
int bit_nr;
int page_match;
};
struct wait_page_queue {
struct page *page;
int bit_nr;
wait_queue_t wait;
};
static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
{
struct wait_page_key *key = arg;
struct wait_page_queue *wait_page
= container_of(wait, struct wait_page_queue, wait);
if (wait_page->page != key->page)
return 0;
key->page_match = 1;
if (wait_page->bit_nr != key->bit_nr)
return 0;
if (test_bit(key->bit_nr, &key->page->flags))
return 0;
return autoremove_wake_function(wait, mode, sync, key);
}
static void wake_up_page_bit(struct page *page, int bit_nr)
{
wait_queue_head_t *q = page_waitqueue(page);
struct wait_page_key key;
unsigned long flags;
key.page = page;
key.bit_nr = bit_nr;
key.page_match = 0;
spin_lock_irqsave(&q->lock, flags);
__wake_up_locked_key(q, TASK_NORMAL, &key);
/*
* It is possible for other pages to have collided on the waitqueue
* hash, so in that case check for a page match. That prevents a long-
* term waiter
*
* It is still possible to miss a case here, when we woke page waiters
* and removed them from the waitqueue, but there are still other
* page waiters.
*/
if (!waitqueue_active(q) || !key.page_match) {
ClearPageWaiters(page);
/*
* It's possible to miss clearing Waiters here, when we woke
* our page waiters, but the hashed waitqueue has waiters for
* other pages on it.
*
* That's okay, it's a rare case. The next waker will clear it.
*/
}
spin_unlock_irqrestore(&q->lock, flags);
}
static void wake_up_page(struct page *page, int bit)
{
if (!PageWaiters(page))
return;
wake_up_page_bit(page, bit);
}
static inline int wait_on_page_bit_common(wait_queue_head_t *q,
struct page *page, int bit_nr, int state, bool lock)
{
struct wait_page_queue wait_page;
wait_queue_t *wait = &wait_page.wait;
int ret = 0;
init_wait(wait);
wait->func = wake_page_function;
wait_page.page = page;
wait_page.bit_nr = bit_nr;
for (;;) {
spin_lock_irq(&q->lock);
if (likely(list_empty(&wait->task_list))) {
if (lock)
__add_wait_queue_tail_exclusive(q, wait);
else
__add_wait_queue(q, wait);
SetPageWaiters(page);
}
set_current_state(state);
spin_unlock_irq(&q->lock);
if (likely(test_bit(bit_nr, &page->flags))) {
io_schedule();
if (unlikely(signal_pending_state(state, current))) {
ret = -EINTR;
break;
}
}
if (lock) {
if (!test_and_set_bit_lock(bit_nr, &page->flags))
break;
} else {
if (!test_bit(bit_nr, &page->flags))
break;
}
}
finish_wait(q, wait);
/*
* A signal could leave PageWaiters set. Clearing it here if
* !waitqueue_active would be possible (by open-coding finish_wait),
* but still fail to catch it in the case of wait hash collision. We
* already can fail to clear wait hash collision cases, so don't
* bother with signals either.
*/
return ret;
}
void wait_on_page_bit(struct page *page, int bit_nr)
{
wait_queue_head_t *q = page_waitqueue(page);
wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
}
EXPORT_SYMBOL(wait_on_page_bit);
int wait_on_page_bit_killable(struct page *page, int bit_nr)
{
wait_queue_head_t *q = page_waitqueue(page);
return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
}
/**
* add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
* @page: Page defining the wait queue of interest
* @waiter: Waiter to add to the queue
*
* Add an arbitrary @waiter to the wait queue for the nominated @page.
*/
void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
{
wait_queue_head_t *q = page_waitqueue(page);
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
__add_wait_queue(q, waiter);
SetPageWaiters(page);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(add_page_wait_queue);
#ifndef clear_bit_unlock_is_negative_byte
/*
* PG_waiters is the high bit in the same byte as PG_lock.
*
* On x86 (and on many other architectures), we can clear PG_lock and
* test the sign bit at the same time. But if the architecture does
* not support that special operation, we just do this all by hand
* instead.
*
* The read of PG_waiters has to be after (or concurrently with) PG_locked
* being cleared, but a memory barrier should be unneccssary since it is
* in the same byte as PG_locked.
*/
static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
{
clear_bit_unlock(nr, mem);
/* smp_mb__after_atomic(); */
return test_bit(PG_waiters, mem);
}
#endif
/**
* unlock_page - unlock a locked page
* @page: the page
*
* Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
* Also wakes sleepers in wait_on_page_writeback() because the wakeup
* mechanism between PageLocked pages and PageWriteback pages is shared.
* But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
*
* Note that this depends on PG_waiters being the sign bit in the byte
* that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
* clear the PG_locked bit and test PG_waiters at the same time fairly
* portably (architectures that do LL/SC can test any bit, while x86 can
* test the sign bit).
*/
void unlock_page(struct page *page)
{
BUILD_BUG_ON(PG_waiters != 7);
page = compound_head(page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
wake_up_page_bit(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);
/**
* end_page_writeback - end writeback against a page
* @page: the page
*/
void end_page_writeback(struct page *page)
{
/*
* TestClearPageReclaim could be used here but it is an atomic
* operation and overkill in this particular case. Failing to
* shuffle a page marked for immediate reclaim is too mild to
* justify taking an atomic operation penalty at the end of
* ever page writeback.
*/
if (PageReclaim(page)) {
ClearPageReclaim(page);
rotate_reclaimable_page(page);
}
if (!test_clear_page_writeback(page))
BUG();
smp_mb__after_atomic();
wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);
/*
* After completing I/O on a page, call this routine to update the page
* flags appropriately
*/
void page_endio(struct page *page, bool is_write, int err)
{
if (!is_write) {
if (!err) {
SetPageUptodate(page);
} else {
ClearPageUptodate(page);
SetPageError(page);
}
unlock_page(page);
} else {
if (err) {
struct address_space *mapping;
SetPageError(page);
mapping = page_mapping(page);
if (mapping)
mapping_set_error(mapping, err);
}
end_page_writeback(page);
}
}
EXPORT_SYMBOL_GPL(page_endio);
/**
* __lock_page - get a lock on the page, assuming we need to sleep to get it
* @__page: the page to lock
*/
void __lock_page(struct page *__page)
{
struct page *page = compound_head(__page);
wait_queue_head_t *q = page_waitqueue(page);
wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
}
EXPORT_SYMBOL(__lock_page);
int __lock_page_killable(struct page *__page)
{
struct page *page = compound_head(__page);
wait_queue_head_t *q = page_waitqueue(page);
return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
}
EXPORT_SYMBOL_GPL(__lock_page_killable);
/*
* Return values:
* 1 - page is locked; mmap_sem is still held.
* 0 - page is not locked.
* mmap_sem has been released (up_read()), unless flags had both
* FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
* which case mmap_sem is still held.
*
* If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
* with the page locked and the mmap_sem unperturbed.
*/
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags)
{
if (flags & FAULT_FLAG_ALLOW_RETRY) {
/*
* CAUTION! In this case, mmap_sem is not released
* even though return 0.
*/
if (flags & FAULT_FLAG_RETRY_NOWAIT)
return 0;
up_read(&mm->mmap_sem);
if (flags & FAULT_FLAG_KILLABLE)
wait_on_page_locked_killable(page);
else
wait_on_page_locked(page);
return 0;
} else {
if (flags & FAULT_FLAG_KILLABLE) {
int ret;
ret = __lock_page_killable(page);
if (ret) {
up_read(&mm->mmap_sem);
return 0;
}
} else
__lock_page(page);
return 1;
}
}
/**
* page_cache_next_hole - find the next hole (not-present entry)
* @mapping: mapping
* @index: index
* @max_scan: maximum range to search
*
* Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
* lowest indexed hole.
*
* Returns: the index of the hole if found, otherwise returns an index
* outside of the set specified (in which case 'return - index >=
* max_scan' will be true). In rare cases of index wrap-around, 0 will
* be returned.
*
* page_cache_next_hole may be called under rcu_read_lock. However,
* like radix_tree_gang_lookup, this will not atomically search a
* snapshot of the tree at a single point in time. For example, if a
* hole is created at index 5, then subsequently a hole is created at
* index 10, page_cache_next_hole covering both indexes may return 10
* if called under rcu_read_lock.
*/
pgoff_t page_cache_next_hole(struct address_space *mapping,
pgoff_t index, unsigned long max_scan)
{
unsigned long i;
for (i = 0; i < max_scan; i++) {
struct page *page;
page = radix_tree_lookup(&mapping->page_tree, index);
if (!page || radix_tree_exceptional_entry(page))
break;
index++;
if (index == 0)
break;
}
return index;
}
EXPORT_SYMBOL(page_cache_next_hole);
/**
* page_cache_prev_hole - find the prev hole (not-present entry)
* @mapping: mapping
* @index: index
* @max_scan: maximum range to search
*
* Search backwards in the range [max(index-max_scan+1, 0), index] for
* the first hole.
*
* Returns: the index of the hole if found, otherwise returns an index
* outside of the set specified (in which case 'index - return >=
* max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
* will be returned.
*
* page_cache_prev_hole may be called under rcu_read_lock. However,
* like radix_tree_gang_lookup, this will not atomically search a
* snapshot of the tree at a single point in time. For example, if a
* hole is created at index 10, then subsequently a hole is created at
* index 5, page_cache_prev_hole covering both indexes may return 5 if
* called under rcu_read_lock.
*/
pgoff_t page_cache_prev_hole(struct address_space *mapping,
pgoff_t index, unsigned long max_scan)
{
unsigned long i;
for (i = 0; i < max_scan; i++) {
struct page *page;
page = radix_tree_lookup(&mapping->page_tree, index);
if (!page || radix_tree_exceptional_entry(page))
break;
index--;
if (index == ULONG_MAX)
break;
}
return index;
}
EXPORT_SYMBOL(page_cache_prev_hole);
/**
* find_get_entry - find and get a page cache entry
* @mapping: the address_space to search
* @offset: the page cache index
*
* Looks up the page cache slot at @mapping & @offset. If there is a
* page cache page, it is returned with an increased refcount.
*
* If the slot holds a shadow entry of a previously evicted page, or a
* swap entry from shmem/tmpfs, it is returned.
*
* Otherwise, %NULL is returned.
*/
struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
{
void **pagep;
struct page *head, *page;
rcu_read_lock();
repeat:
page = NULL;
pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
if (pagep) {
page = radix_tree_deref_slot(pagep);
if (unlikely(!page))
goto out;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page))
goto repeat;
/*
* A shadow entry of a recently evicted page,
* or a swap entry from shmem/tmpfs. Return
* it without attempting to raise page count.
*/
goto out;
}
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/*
* Has the page moved?
* This is part of the lockless pagecache protocol. See
* include/linux/pagemap.h for details.
*/
if (unlikely(page != *pagep)) {
put_page(head);
goto repeat;
}
}
out:
rcu_read_unlock();
return page;
}
EXPORT_SYMBOL(find_get_entry);
/**
* find_lock_entry - locate, pin and lock a page cache entry
* @mapping: the address_space to search
* @offset: the page cache index
*
* Looks up the page cache slot at @mapping & @offset. If there is a
* page cache page, it is returned locked and with an increased
* refcount.
*
* If the slot holds a shadow entry of a previously evicted page, or a
* swap entry from shmem/tmpfs, it is returned.
*
* Otherwise, %NULL is returned.
*
* find_lock_entry() may sleep.
*/
struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
{
struct page *page;
repeat:
page = find_get_entry(mapping, offset);
if (page && !radix_tree_exception(page)) {
lock_page(page);
/* Has the page been truncated? */
if (unlikely(page_mapping(page) != mapping)) {
unlock_page(page);
put_page(page);
goto repeat;
}
VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
}
return page;
}
EXPORT_SYMBOL(find_lock_entry);
/**
* pagecache_get_page - find and get a page reference
* @mapping: the address_space to search
* @offset: the page index
* @fgp_flags: PCG flags
* @gfp_mask: gfp mask to use for the page cache data page allocation
*
* Looks up the page cache slot at @mapping & @offset.
*
* PCG flags modify how the page is returned.
*
* FGP_ACCESSED: the page will be marked accessed
* FGP_LOCK: Page is return locked
* FGP_CREAT: If page is not present then a new page is allocated using
* @gfp_mask and added to the page cache and the VM's LRU
* list. The page is returned locked and with an increased
* refcount. Otherwise, %NULL is returned.
*
* If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
* if the GFP flags specified for FGP_CREAT are atomic.
*
* If there is a page cache page, it is returned with an increased refcount.
*/
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
int fgp_flags, gfp_t gfp_mask)
{
struct page *page;
repeat:
page = find_get_entry(mapping, offset);
if (radix_tree_exceptional_entry(page))
page = NULL;
if (!page)
goto no_page;
if (fgp_flags & FGP_LOCK) {
if (fgp_flags & FGP_NOWAIT) {
if (!trylock_page(page)) {
put_page(page);
return NULL;
}
} else {
lock_page(page);
}
/* Has the page been truncated? */
if (unlikely(page->mapping != mapping)) {
unlock_page(page);
put_page(page);
goto repeat;
}
VM_BUG_ON_PAGE(page->index != offset, page);
}
if (page && (fgp_flags & FGP_ACCESSED))
mark_page_accessed(page);
no_page:
if (!page && (fgp_flags & FGP_CREAT)) {
int err;
if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
gfp_mask |= __GFP_WRITE;
if (fgp_flags & FGP_NOFS)
gfp_mask &= ~__GFP_FS;
page = __page_cache_alloc(gfp_mask);
if (!page)
return NULL;
if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
fgp_flags |= FGP_LOCK;
/* Init accessed so avoid atomic mark_page_accessed later */
if (fgp_flags & FGP_ACCESSED)
__SetPageReferenced(page);
err = add_to_page_cache_lru(page, mapping, offset,
gfp_mask & GFP_RECLAIM_MASK);
if (unlikely(err)) {
put_page(page);
page = NULL;
if (err == -EEXIST)
goto repeat;
}
}
return page;
}
EXPORT_SYMBOL(pagecache_get_page);
/**
* find_get_entries - gang pagecache lookup
* @mapping: The address_space to search
* @start: The starting page cache index
* @nr_entries: The maximum number of entries
* @entries: Where the resulting entries are placed
* @indices: The cache indices corresponding to the entries in @entries
*
* find_get_entries() will search for and return a group of up to
* @nr_entries entries in the mapping. The entries are placed at
* @entries. find_get_entries() takes a reference against any actual
* pages it returns.
*
* The search returns a group of mapping-contiguous page cache entries
* with ascending indexes. There may be holes in the indices due to
* not-present pages.
*
* Any shadow entries of evicted pages, or swap entries from
* shmem/tmpfs, are included in the returned array.
*
* find_get_entries() returns the number of pages and shadow entries
* which were found.
*/
unsigned find_get_entries(struct address_space *mapping,
pgoff_t start, unsigned int nr_entries,
struct page **entries, pgoff_t *indices)
{
void **slot;
unsigned int ret = 0;
struct radix_tree_iter iter;
if (!nr_entries)
return 0;
rcu_read_lock();
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
continue;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
slot = radix_tree_iter_retry(&iter);
continue;
}
/*
* A shadow entry of a recently evicted page, a swap
* entry from shmem/tmpfs or a DAX entry. Return it
* without attempting to raise page count.
*/
goto export;
}
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(head);
goto repeat;
}
export:
indices[ret] = iter.index;
entries[ret] = page;
if (++ret == nr_entries)
break;
}
rcu_read_unlock();
return ret;
}
/**
* find_get_pages - gang pagecache lookup
* @mapping: The address_space to search
* @start: The starting page index
* @nr_pages: The maximum number of pages
* @pages: Where the resulting pages are placed
*
* find_get_pages() will search for and return a group of up to
* @nr_pages pages in the mapping. The pages are placed at @pages.
* find_get_pages() takes a reference against the returned pages.
*
* The search returns a group of mapping-contiguous pages with ascending
* indexes. There may be holes in the indices due to not-present pages.
*
* find_get_pages() returns the number of pages which were found.
*/
unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
unsigned int nr_pages, struct page **pages)
{
struct radix_tree_iter iter;
void **slot;
unsigned ret = 0;
if (unlikely(!nr_pages))
return 0;
rcu_read_lock();
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
continue;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
slot = radix_tree_iter_retry(&iter);
continue;
}
/*
* A shadow entry of a recently evicted page,
* or a swap entry from shmem/tmpfs. Skip
* over it.
*/
continue;
}
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(head);
goto repeat;
}
pages[ret] = page;
if (++ret == nr_pages)
break;
}
rcu_read_unlock();
return ret;
}
/**
* find_get_pages_contig - gang contiguous pagecache lookup
* @mapping: The address_space to search
* @index: The starting page index
* @nr_pages: The maximum number of pages
* @pages: Where the resulting pages are placed
*
* find_get_pages_contig() works exactly like find_get_pages(), except
* that the returned number of pages are guaranteed to be contiguous.
*
* find_get_pages_contig() returns the number of pages which were found.
*/
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
unsigned int nr_pages, struct page **pages)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!nr_pages))
return 0;
rcu_read_lock();
radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
/* The hole, there no reason to continue */
if (unlikely(!page))
break;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
slot = radix_tree_iter_retry(&iter);
continue;
}
/*
* A shadow entry of a recently evicted page,
* or a swap entry from shmem/tmpfs. Stop
* looking for contiguous pages.
*/
break;
}
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(head);
goto repeat;
}
/*
* must check mapping and index after taking the ref.
* otherwise we can get both false positives and false
* negatives, which is just confusing to the caller.
*/
if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
put_page(page);
break;
}
pages[ret] = page;
if (++ret == nr_pages)
break;
}
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(find_get_pages_contig);
/**
* find_get_pages_tag - find and return pages that match @tag
* @mapping: the address_space to search
* @index: the starting page index
* @tag: the tag index
* @nr_pages: the maximum number of pages
* @pages: where the resulting pages are placed
*
* Like find_get_pages, except we only return pages which are tagged with
* @tag. We update @index to index the next page for the traversal.
*/
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
int tag, unsigned int nr_pages, struct page **pages)
{
struct radix_tree_iter iter;
void **slot;
unsigned ret = 0;
if (unlikely(!nr_pages))
return 0;
rcu_read_lock();
radix_tree_for_each_tagged(slot, &mapping->page_tree,
&iter, *index, tag) {
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
continue;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
slot = radix_tree_iter_retry(&iter);
continue;
}
/*
* A shadow entry of a recently evicted page.
*
* Those entries should never be tagged, but
* this tree walk is lockless and the tags are
* looked up in bulk, one radix tree node at a
* time, so there is a sizable window for page
* reclaim to evict a page we saw tagged.
*
* Skip over it.
*/
continue;
}
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(head);
goto repeat;
}
pages[ret] = page;
if (++ret == nr_pages)
break;
}
rcu_read_unlock();
if (ret)
*index = pages[ret - 1]->index + 1;
return ret;
}
EXPORT_SYMBOL(find_get_pages_tag);
/**
* find_get_entries_tag - find and return entries that match @tag
* @mapping: the address_space to search
* @start: the starting page cache index
* @tag: the tag index
* @nr_entries: the maximum number of entries
* @entries: where the resulting entries are placed
* @indices: the cache indices corresponding to the entries in @entries
*
* Like find_get_entries, except we only return entries which are tagged with
* @tag.
*/
unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
int tag, unsigned int nr_entries,
struct page **entries, pgoff_t *indices)
{
void **slot;
unsigned int ret = 0;
struct radix_tree_iter iter;
if (!nr_entries)
return 0;
rcu_read_lock();
radix_tree_for_each_tagged(slot, &mapping->page_tree,
&iter, start, tag) {
struct page *head, *page;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
continue;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
slot = radix_tree_iter_retry(&iter);
continue;
}
/*
* A shadow entry of a recently evicted page, a swap
* entry from shmem/tmpfs or a DAX entry. Return it
* without attempting to raise page count.
*/
goto export;
}
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(head);
goto repeat;
}
export:
indices[ret] = iter.index;
entries[ret] = page;
if (++ret == nr_entries)
break;
}
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(find_get_entries_tag);
/*
* CD/DVDs are error prone. When a medium error occurs, the driver may fail
* a _large_ part of the i/o request. Imagine the worst scenario:
*
* ---R__________________________________________B__________
* ^ reading here ^ bad block(assume 4k)
*
* read(R) => miss => readahead(R...B) => media error => frustrating retries
* => failing the whole request => read(R) => read(R+1) =>
* readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
* readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
* readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
*
* It is going insane. Fix it by quickly scaling down the readahead size.
*/
static void shrink_readahead_size_eio(struct file *filp,
struct file_ra_state *ra)
{
ra->ra_pages /= 4;
}
/**
* do_generic_file_read - generic file read routine
* @filp: the file to read
* @ppos: current file position
* @iter: data destination
* @written: already copied
*
* This is a generic file read routine, and uses the
* mapping->a_ops->readpage() function for the actual low-level stuff.
*
* This is really ugly. But the goto's actually try to clarify some
* of the logic when it comes to error handling etc.
*/
static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
struct iov_iter *iter, ssize_t written)
{
struct address_space *mapping = filp->f_mapping;
struct inode *inode = mapping->host;
struct file_ra_state *ra = &filp->f_ra;
pgoff_t index;
pgoff_t last_index;
pgoff_t prev_index;
unsigned long offset; /* offset into pagecache page */
unsigned int prev_offset;
int error = 0;
if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
return 0;
iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
index = *ppos >> PAGE_SHIFT;
prev_index = ra->prev_pos >> PAGE_SHIFT;
prev_offset = ra->prev_pos & (PAGE_SIZE-1);
last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
offset = *ppos & ~PAGE_MASK;
for (;;) {
struct page *page;
pgoff_t end_index;
loff_t isize;
unsigned long nr, ret;
cond_resched();
find_page:
if (fatal_signal_pending(current)) {
error = -EINTR;
goto out;
}
page = find_get_page(mapping, index);
if (!page) {
page_cache_sync_readahead(mapping,
ra, filp,
index, last_index - index);
page = find_get_page(mapping, index);
if (unlikely(page == NULL))
goto no_cached_page;
}
if (PageReadahead(page)) {
page_cache_async_readahead(mapping,
ra, filp, page,
index, last_index - index);
}
if (!PageUptodate(page)) {
/*
* See comment in do_read_cache_page on why
* wait_on_page_locked is used to avoid unnecessarily
* serialisations and why it's safe.
*/
error = wait_on_page_locked_killable(page);
if (unlikely(error))
goto readpage_error;
if (PageUptodate(page))
goto page_ok;
if (inode->i_blkbits == PAGE_SHIFT ||
!mapping->a_ops->is_partially_uptodate)
goto page_not_up_to_date;
/* pipes can't handle partially uptodate pages */
if (unlikely(iter->type & ITER_PIPE))
goto page_not_up_to_date;
if (!trylock_page(page))
goto page_not_up_to_date;
/* Did it get truncated before we got the lock? */
if (!page->mapping)
goto page_not_up_to_date_locked;
if (!mapping->a_ops->is_partially_uptodate(page,
offset, iter->count))
goto page_not_up_to_date_locked;
unlock_page(page);
}
page_ok:
/*
* i_size must be checked after we know the page is Uptodate.
*
* Checking i_size after the check allows us to calculate
* the correct value for "nr", which means the zero-filled
* part of the page is not copied back to userspace (unless
* another truncate extends the file - this is desired though).
*/
isize = i_size_read(inode);
end_index = (isize - 1) >> PAGE_SHIFT;
if (unlikely(!isize || index > end_index)) {
put_page(page);
goto out;
}
/* nr is the maximum number of bytes to copy from this page */
nr = PAGE_SIZE;
if (index == end_index) {
nr = ((isize - 1) & ~PAGE_MASK) + 1;
if (nr <= offset) {
put_page(page);
goto out;
}
}
nr = nr - offset;
/* If users can be writing to this page using arbitrary
* virtual addresses, take care about potential aliasing
* before reading the page on the kernel side.
*/
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
/*
* When a sequential read accesses a page several times,
* only mark it as accessed the first time.
*/
if (prev_index != index || offset != prev_offset)
mark_page_accessed(page);
prev_index = index;
/*
* Ok, we have the page, and it's up-to-date, so
* now we can copy it to user space...
*/
ret = copy_page_to_iter(page, offset, nr, iter);
offset += ret;
index += offset >> PAGE_SHIFT;
offset &= ~PAGE_MASK;
prev_offset = offset;
put_page(page);
written += ret;
if (!iov_iter_count(iter))
goto out;
if (ret < nr) {
error = -EFAULT;
goto out;
}
continue;
page_not_up_to_date:
/* Get exclusive access to the page ... */
error = lock_page_killable(page);
if (unlikely(error))
goto readpage_error;
page_not_up_to_date_locked:
/* Did it get truncated before we got the lock? */
if (!page->mapping) {
unlock_page(page);
put_page(page);
continue;
}
/* Did somebody else fill it already? */
if (PageUptodate(page)) {
unlock_page(page);
goto page_ok;
}
readpage:
/*
* A previous I/O error may have been due to temporary
* failures, eg. multipath errors.
* PG_error will be set again if readpage fails.
*/
ClearPageError(page);
/* Start the actual read. The read will unlock the page. */
error = mapping->a_ops->readpage(filp, page);
if (unlikely(error)) {
if (error == AOP_TRUNCATED_PAGE) {
put_page(page);
error = 0;
goto find_page;
}
goto readpage_error;
}
if (!PageUptodate(page)) {
error = lock_page_killable(page);
if (unlikely(error))
goto readpage_error;
if (!PageUptodate(page)) {
if (page->mapping == NULL) {
/*
* invalidate_mapping_pages got it
*/
unlock_page(page);
put_page(page);
goto find_page;
}
unlock_page(page);
shrink_readahead_size_eio(filp, ra);
error = -EIO;
goto readpage_error;
}
unlock_page(page);
}
goto page_ok;
readpage_error:
/* UHHUH! A synchronous read error occurred. Report it */
put_page(page);
goto out;
no_cached_page:
/*
* Ok, it wasn't cached, so we need to create a new
* page..
*/
page = page_cache_alloc_cold(mapping);
if (!page) {
error = -ENOMEM;
goto out;
}
error = add_to_page_cache_lru(page, mapping, index,
mapping_gfp_constraint(mapping, GFP_KERNEL));
if (error) {
put_page(page);
if (error == -EEXIST) {
error = 0;
goto find_page;
}
goto out;
}
goto readpage;
}
out:
ra->prev_pos = prev_index;
ra->prev_pos <<= PAGE_SHIFT;
ra->prev_pos |= prev_offset;
*ppos = ((loff_t)index << PAGE_SHIFT) + offset;
file_accessed(filp);
return written ? written : error;
}
/**
* generic_file_read_iter - generic filesystem read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the "read_iter()" routine for all filesystems
* that can use the page cache directly.
*/
ssize_t
generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
ssize_t retval = 0;
size_t count = iov_iter_count(iter);
if (!count)
goto out; /* skip atime */
if (iocb->ki_flags & IOCB_DIRECT) {
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
struct iov_iter data = *iter;
loff_t size;
size = i_size_read(inode);
retval = filemap_write_and_wait_range(mapping, iocb->ki_pos,
iocb->ki_pos + count - 1);
if (retval < 0)
goto out;
file_accessed(file);
retval = mapping->a_ops->direct_IO(iocb, &data);
if (retval >= 0) {
iocb->ki_pos += retval;
iov_iter_advance(iter, retval);
}
/*
* Btrfs can have a short DIO read if we encounter
* compressed extents, so if there was an error, or if
* we've already read everything we wanted to, or if
* there was a short read because we hit EOF, go ahead
* and return. Otherwise fallthrough to buffered io for
* the rest of the read. Buffered reads will not work for
* DAX files, so don't bother trying.
*/
if (retval < 0 || !iov_iter_count(iter) || iocb->ki_pos >= size ||
IS_DAX(inode))
goto out;
}
retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);
out:
return retval;
}
EXPORT_SYMBOL(generic_file_read_iter);
#ifdef CONFIG_MMU
/**
* page_cache_read - adds requested page to the page cache if not already there
* @file: file to read
* @offset: page index
* @gfp_mask: memory allocation flags
*
* This adds the requested page to the page cache if it isn't already there,
* and schedules an I/O to read in its contents from disk.
*/
static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
{
struct address_space *mapping = file->f_mapping;
struct page *page;
int ret;
do {
page = __page_cache_alloc(gfp_mask|__GFP_COLD);
if (!page)
return -ENOMEM;
ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
if (ret == 0)
ret = mapping->a_ops->readpage(file, page);
else if (ret == -EEXIST)
ret = 0; /* losing race to add is OK */
put_page(page);
} while (ret == AOP_TRUNCATED_PAGE);
return ret;
}
#define MMAP_LOTSAMISS (100)
/*
* Synchronous readahead happens when we don't even find
* a page in the page cache at all.
*/
static void do_sync_mmap_readahead(struct vm_area_struct *vma,
struct file_ra_state *ra,
struct file *file,
pgoff_t offset)
{
struct address_space *mapping = file->f_mapping;
/* If we don't want any read-ahead, don't bother */
if (vma->vm_flags & VM_RAND_READ)
return;
if (!ra->ra_pages)
return;
if (vma->vm_flags & VM_SEQ_READ) {
page_cache_sync_readahead(mapping, ra, file, offset,
ra->ra_pages);
return;
}
/* Avoid banging the cache line if not needed */
if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
ra->mmap_miss++;
/*
* Do we miss much more than hit in this file? If so,
* stop bothering with read-ahead. It will only hurt.
*/
if (ra->mmap_miss > MMAP_LOTSAMISS)
return;
/*
* mmap read-around
*/
ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
ra->size = ra->ra_pages;
ra->async_size = ra->ra_pages / 4;
ra_submit(ra, mapping, file);
}
/*
* Asynchronous readahead happens when we find the page and PG_readahead,
* so we want to possibly extend the readahead further..
*/
static void do_async_mmap_readahead(struct vm_area_struct *vma,
struct file_ra_state *ra,
struct file *file,
struct page *page,
pgoff_t offset)
{
struct address_space *mapping = file->f_mapping;
/* If we don't want any read-ahead, don't bother */
if (vma->vm_flags & VM_RAND_READ)
return;
if (ra->mmap_miss > 0)
ra->mmap_miss--;
if (PageReadahead(page))
page_cache_async_readahead(mapping, ra, file,
page, offset, ra->ra_pages);
}
/**
* filemap_fault - read in file data for page fault handling
* @vmf: struct vm_fault containing details of the fault
*
* filemap_fault() is invoked via the vma operations vector for a
* mapped memory region to read in file data during a page fault.
*
* The goto's are kind of ugly, but this streamlines the normal case of having
* it in the page cache, and handles the special cases reasonably without
* having a lot of duplicated code.
*
* vma->vm_mm->mmap_sem must be held on entry.
*
* If our return value has VM_FAULT_RETRY set, it's because
* lock_page_or_retry() returned 0.
* The mmap_sem has usually been released in this case.
* See __lock_page_or_retry() for the exception.
*
* If our return value does not have VM_FAULT_RETRY set, the mmap_sem
* has not been released.
*
* We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
*/
int filemap_fault(struct vm_fault *vmf)
{
int error;
struct file *file = vmf->vma->vm_file;
struct address_space *mapping = file->f_mapping;
struct file_ra_state *ra = &file->f_ra;
struct inode *inode = mapping->host;
pgoff_t offset = vmf->pgoff;
struct page *page;
loff_t size;
int ret = 0;
size = round_up(i_size_read(inode), PAGE_SIZE);
if (offset >= size >> PAGE_SHIFT)
return VM_FAULT_SIGBUS;
/*
* Do we have something in the page cache already?
*/
page = find_get_page(mapping, offset);
if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
/*
* We found the page, so try async readahead before
* waiting for the lock.
*/
do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
} else if (!page) {
/* No page in the page cache at all */
do_sync_mmap_readahead(vmf->vma, ra, file, offset);
count_vm_event(PGMAJFAULT);
mem_cgroup_count_vm_event(vmf->vma->vm_mm, PGMAJFAULT);
ret = VM_FAULT_MAJOR;
retry_find:
page = find_get_page(mapping, offset);
if (!page)
goto no_cached_page;
}
if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
put_page(page);
return ret | VM_FAULT_RETRY;
}
/* Did it get truncated? */
if (unlikely(page->mapping != mapping)) {
unlock_page(page);
put_page(page);
goto retry_find;
}
VM_BUG_ON_PAGE(page->index != offset, page);
/*
* We have a locked page in the page cache, now we need to check
* that it's up-to-date. If not, it is going to be due to an error.
*/
if (unlikely(!PageUptodate(page)))
goto page_not_uptodate;
/*
* Found the page and have a reference on it.
* We must recheck i_size under page lock.
*/
size = round_up(i_size_read(inode), PAGE_SIZE);
if (unlikely(offset >= size >> PAGE_SHIFT)) {
unlock_page(page);
put_page(page);
return VM_FAULT_SIGBUS;
}
vmf->page = page;
return ret | VM_FAULT_LOCKED;
no_cached_page:
/*
* We're only likely to ever get here if MADV_RANDOM is in
* effect.
*/
error = page_cache_read(file, offset, vmf->gfp_mask);
/*
* The page we want has now been added to the page cache.
* In the unlikely event that someone removed it in the
* meantime, we'll just come back here and read it again.
*/
if (error >= 0)
goto retry_find;
/*
* An error return from page_cache_read can result if the
* system is low on memory, or a problem occurs while trying
* to schedule I/O.
*/
if (error == -ENOMEM)
return VM_FAULT_OOM;
return VM_FAULT_SIGBUS;
page_not_uptodate:
/*
* Umm, take care of errors if the page isn't up-to-date.
* Try to re-read it _once_. We do this synchronously,
* because there really aren't any performance issues here
* and we need to check for errors.
*/
ClearPageError(page);
error = mapping->a_ops->readpage(file, page);
if (!error) {
wait_on_page_locked(page);
if (!PageUptodate(page))
error = -EIO;
}
put_page(page);
if (!error || error == AOP_TRUNCATED_PAGE)
goto retry_find;
/* Things didn't work out. Return zero to tell the mm layer so. */
shrink_readahead_size_eio(file, ra);
return VM_FAULT_SIGBUS;
}
EXPORT_SYMBOL(filemap_fault);
void filemap_map_pages(struct vm_fault *vmf,
pgoff_t start_pgoff, pgoff_t end_pgoff)
{
struct radix_tree_iter iter;
void **slot;
struct file *file = vmf->vma->vm_file;
struct address_space *mapping = file->f_mapping;
pgoff_t last_pgoff = start_pgoff;
loff_t size;
struct page *head, *page;
rcu_read_lock();
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
start_pgoff) {
if (iter.index > end_pgoff)
break;
repeat:
page = radix_tree_deref_slot(slot);
if (unlikely(!page))
goto next;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page)) {
slot = radix_tree_iter_retry(&iter);
continue;
}
goto next;
}
head = compound_head(page);
if (!page_cache_get_speculative(head))
goto repeat;
/* The page was split under us? */
if (compound_head(page) != head) {
put_page(head);
goto repeat;
}
/* Has the page moved? */
if (unlikely(page != *slot)) {
put_page(head);
goto repeat;
}
if (!PageUptodate(page) ||
PageReadahead(page) ||
PageHWPoison(page))
goto skip;
if (!trylock_page(page))
goto skip;
if (page->mapping != mapping || !PageUptodate(page))
goto unlock;
size = round_up(i_size_read(mapping->host), PAGE_SIZE);
if (page->index >= size >> PAGE_SHIFT)
goto unlock;
if (file->f_ra.mmap_miss > 0)
file->f_ra.mmap_miss--;
vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
if (vmf->pte)
vmf->pte += iter.index - last_pgoff;
last_pgoff = iter.index;
if (alloc_set_pte(vmf, NULL, page))
goto unlock;
unlock_page(page);
goto next;
unlock:
unlock_page(page);
skip:
put_page(page);
next:
/* Huge page is mapped? No need to proceed. */
if (pmd_trans_huge(*vmf->pmd))
break;
if (iter.index == end_pgoff)
break;
}
rcu_read_unlock();
}
EXPORT_SYMBOL(filemap_map_pages);
int filemap_page_mkwrite(struct vm_fault *vmf)
{
struct page *page = vmf->page;
struct inode *inode = file_inode(vmf->vma->vm_file);
int ret = VM_FAULT_LOCKED;
sb_start_pagefault(inode->i_sb);
file_update_time(vmf->vma->vm_file);
lock_page(page);
if (page->mapping != inode->i_mapping) {
unlock_page(page);
ret = VM_FAULT_NOPAGE;
goto out;
}
/*
* We mark the page dirty already here so that when freeze is in
* progress, we are guaranteed that writeback during freezing will
* see the dirty page and writeprotect it again.
*/
set_page_dirty(page);
wait_for_stable_page(page);
out:
sb_end_pagefault(inode->i_sb);
return ret;
}
EXPORT_SYMBOL(filemap_page_mkwrite);
const struct vm_operations_struct generic_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = filemap_page_mkwrite,
};
/* This is used for a general mmap of a disk file */
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
struct address_space *mapping = file->f_mapping;
if (!mapping->a_ops->readpage)
return -ENOEXEC;
file_accessed(file);
vma->vm_ops = &generic_file_vm_ops;
return 0;
}
/*
* This is for filesystems which do not implement ->writepage.
*/
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
return -EINVAL;
return generic_file_mmap(file, vma);
}
#else
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
return -ENOSYS;
}
int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
{
return -ENOSYS;
}
#endif /* CONFIG_MMU */
EXPORT_SYMBOL(generic_file_mmap);
EXPORT_SYMBOL(generic_file_readonly_mmap);
static struct page *wait_on_page_read(struct page *page)
{
if (!IS_ERR(page)) {
wait_on_page_locked(page);
if (!PageUptodate(page)) {
put_page(page);
page = ERR_PTR(-EIO);
}
}
return page;
}
static struct page *do_read_cache_page(struct address_space *mapping,
pgoff_t index,
int (*filler)(void *, struct page *),
void *data,
gfp_t gfp)
{
struct page *page;
int err;
repeat:
page = find_get_page(mapping, index);
if (!page) {
page = __page_cache_alloc(gfp | __GFP_COLD);
if (!page)
return ERR_PTR(-ENOMEM);
err = add_to_page_cache_lru(page, mapping, index, gfp);
if (unlikely(err)) {
put_page(page);
if (err == -EEXIST)
goto repeat;
/* Presumably ENOMEM for radix tree node */
return ERR_PTR(err);
}
filler:
err = filler(data, page);
if (err < 0) {
put_page(page);
return ERR_PTR(err);
}
page = wait_on_page_read(page);
if (IS_ERR(page))
return page;
goto out;
}
if (PageUptodate(page))
goto out;
/*
* Page is not up to date and may be locked due one of the following
* case a: Page is being filled and the page lock is held
* case b: Read/write error clearing the page uptodate status
* case c: Truncation in progress (page locked)
* case d: Reclaim in progress
*
* Case a, the page will be up to date when the page is unlocked.
* There is no need to serialise on the page lock here as the page
* is pinned so the lock gives no additional protection. Even if the
* the page is truncated, the data is still valid if PageUptodate as
* it's a race vs truncate race.
* Case b, the page will not be up to date
* Case c, the page may be truncated but in itself, the data may still
* be valid after IO completes as it's a read vs truncate race. The
* operation must restart if the page is not uptodate on unlock but
* otherwise serialising on page lock to stabilise the mapping gives
* no additional guarantees to the caller as the page lock is
* released before return.
* Case d, similar to truncation. If reclaim holds the page lock, it
* will be a race with remove_mapping that determines if the mapping
* is valid on unlock but otherwise the data is valid and there is
* no need to serialise with page lock.
*
* As the page lock gives no additional guarantee, we optimistically
* wait on the page to be unlocked and check if it's up to date and
* use the page if it is. Otherwise, the page lock is required to
* distinguish between the different cases. The motivation is that we
* avoid spurious serialisations and wakeups when multiple processes
* wait on the same page for IO to complete.
*/
wait_on_page_locked(page);
if (PageUptodate(page))
goto out;
/* Distinguish between all the cases under the safety of the lock */
lock_page(page);
/* Case c or d, restart the operation */
if (!page->mapping) {
unlock_page(page);
put_page(page);
goto repeat;
}
/* Someone else locked and filled the page in a very small window */
if (PageUptodate(page)) {
unlock_page(page);
goto out;
}
goto filler;
out:
mark_page_accessed(page);
return page;
}
/**
* read_cache_page - read into page cache, fill it if needed
* @mapping: the page's address_space
* @index: the page index
* @filler: function to perform the read
* @data: first arg to filler(data, page) function, often left as NULL
*
* Read into the page cache. If a page already exists, and PageUptodate() is
* not set, try to fill the page and wait for it to become unlocked.
*
* If the page does not get brought uptodate, return -EIO.
*/
struct page *read_cache_page(struct address_space *mapping,
pgoff_t index,
int (*filler)(void *, struct page *),
void *data)
{
return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
}
EXPORT_SYMBOL(read_cache_page);
/**
* read_cache_page_gfp - read into page cache, using specified page allocation flags.
* @mapping: the page's address_space
* @index: the page index
* @gfp: the page allocator flags to use if allocating
*
* This is the same as "read_mapping_page(mapping, index, NULL)", but with
* any new page allocations done using the specified allocation flags.
*
* If the page does not get brought uptodate, return -EIO.
*/
struct page *read_cache_page_gfp(struct address_space *mapping,
pgoff_t index,
gfp_t gfp)
{
filler_t *filler = (filler_t *)mapping->a_ops->readpage;
return do_read_cache_page(mapping, index, filler, NULL, gfp);
}
EXPORT_SYMBOL(read_cache_page_gfp);
/*
* Performs necessary checks before doing a write
*
* Can adjust writing position or amount of bytes to write.
* Returns appropriate error code that caller should return or
* zero in case that write should be allowed.
*/
inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
unsigned long limit = rlimit(RLIMIT_FSIZE);
loff_t pos;
if (!iov_iter_count(from))
return 0;
/* FIXME: this is for backwards compatibility with 2.4 */
if (iocb->ki_flags & IOCB_APPEND)
iocb->ki_pos = i_size_read(inode);
pos = iocb->ki_pos;
if (limit != RLIM_INFINITY) {
if (iocb->ki_pos >= limit) {
send_sig(SIGXFSZ, current, 0);
return -EFBIG;
}
iov_iter_truncate(from, limit - (unsigned long)pos);
}
/*
* LFS rule
*/
if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
!(file->f_flags & O_LARGEFILE))) {
if (pos >= MAX_NON_LFS)
return -EFBIG;
iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
}
/*
* Are we about to exceed the fs block limit ?
*
* If we have written data it becomes a short write. If we have
* exceeded without writing data we send a signal and return EFBIG.
* Linus frestrict idea will clean these up nicely..
*/
if (unlikely(pos >= inode->i_sb->s_maxbytes))
return -EFBIG;
iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
return iov_iter_count(from);
}
EXPORT_SYMBOL(generic_write_checks);
int pagecache_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
const struct address_space_operations *aops = mapping->a_ops;
return aops->write_begin(file, mapping, pos, len, flags,
pagep, fsdata);
}
EXPORT_SYMBOL(pagecache_write_begin);
int pagecache_write_end(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata)
{
const struct address_space_operations *aops = mapping->a_ops;
return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
}
EXPORT_SYMBOL(pagecache_write_end);
ssize_t
generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
loff_t pos = iocb->ki_pos;
ssize_t written;
size_t write_len;
pgoff_t end;
struct iov_iter data;
write_len = iov_iter_count(from);
end = (pos + write_len - 1) >> PAGE_SHIFT;
written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
if (written)
goto out;
/*
* After a write we want buffered reads to be sure to go to disk to get
* the new data. We invalidate clean cached page from the region we're
* about to write. We do this *before* the write so that we can return
* without clobbering -EIOCBQUEUED from ->direct_IO().
*/
if (mapping->nrpages) {
written = invalidate_inode_pages2_range(mapping,
pos >> PAGE_SHIFT, end);
/*
* If a page can not be invalidated, return 0 to fall back
* to buffered write.
*/
if (written) {
if (written == -EBUSY)
return 0;
goto out;
}
}
data = *from;
written = mapping->a_ops->direct_IO(iocb, &data);
/*
* Finally, try again to invalidate clean pages which might have been
* cached by non-direct readahead, or faulted in by get_user_pages()
* if the source of the write was an mmap'ed region of the file
* we're writing. Either one is a pretty crazy thing to do,
* so we don't support it 100%. If this invalidation
* fails, tough, the write still worked...
*/
if (mapping->nrpages) {
invalidate_inode_pages2_range(mapping,
pos >> PAGE_SHIFT, end);
}
if (written > 0) {
pos += written;
iov_iter_advance(from, written);
if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
i_size_write(inode, pos);
mark_inode_dirty(inode);
}
iocb->ki_pos = pos;
}
out:
return written;
}
EXPORT_SYMBOL(generic_file_direct_write);
/*
* Find or create a page at the given pagecache position. Return the locked
* page. This function is specifically for buffered writes.
*/
struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags)
{
struct page *page;
int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
if (flags & AOP_FLAG_NOFS)
fgp_flags |= FGP_NOFS;
page = pagecache_get_page(mapping, index, fgp_flags,
mapping_gfp_mask(mapping));
if (page)
wait_for_stable_page(page);
return page;
}
EXPORT_SYMBOL(grab_cache_page_write_begin);
ssize_t generic_perform_write(struct file *file,
struct iov_iter *i, loff_t pos)
{
struct address_space *mapping = file->f_mapping;
const struct address_space_operations *a_ops = mapping->a_ops;
long status = 0;
ssize_t written = 0;
unsigned int flags = 0;
/*
* Copies from kernel address space cannot fail (NFSD is a big user).
*/
if (!iter_is_iovec(i))
flags |= AOP_FLAG_UNINTERRUPTIBLE;
do {
struct page *page;
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
size_t copied; /* Bytes copied from user */
void *fsdata;
offset = (pos & (PAGE_SIZE - 1));
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_count(i));
again:
/*
* Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
*
* Not only is this an optimisation, but it is also required
* to check that the address is actually valid, when atomic
* usercopies are used, below.
*/
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
status = -EFAULT;
break;
}
if (fatal_signal_pending(current)) {
status = -EINTR;
break;
}
status = a_ops->write_begin(file, mapping, pos, bytes, flags,
&page, &fsdata);
if (unlikely(status < 0))
break;
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
flush_dcache_page(page);
status = a_ops->write_end(file, mapping, pos, bytes, copied,
page, fsdata);
if (unlikely(status < 0))
break;
copied = status;
cond_resched();
iov_iter_advance(i, copied);
if (unlikely(copied == 0)) {
/*
* If we were unable to copy any data at all, we must
* fall back to a single segment length write.
*
* If we didn't fallback here, we could livelock
* because not all segments in the iov can be copied at
* once without a pagefault.
*/
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_single_seg_count(i));
goto again;
}
pos += copied;
written += copied;
balance_dirty_pages_ratelimited(mapping);
} while (iov_iter_count(i));
return written ? written : status;
}
EXPORT_SYMBOL(generic_perform_write);
/**
* __generic_file_write_iter - write data to a file
* @iocb: IO state structure (file, offset, etc.)
* @from: iov_iter with data to write
*
* This function does all the work needed for actually writing data to a
* file. It does all basic checks, removes SUID from the file, updates
* modification times and calls proper subroutines depending on whether we
* do direct IO or a standard buffered write.
*
* It expects i_mutex to be grabbed unless we work on a block device or similar
* object which does not need locking at all.
*
* This function does *not* take care of syncing data in case of O_SYNC write.
* A caller has to handle it. This is mainly due to the fact that we want to
* avoid syncing under i_mutex.
*/
ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct address_space * mapping = file->f_mapping;
struct inode *inode = mapping->host;
ssize_t written = 0;
ssize_t err;
ssize_t status;
/* We can write back this queue in page reclaim */
current->backing_dev_info = inode_to_bdi(inode);
err = file_remove_privs(file);
if (err)
goto out;
err = file_update_time(file);
if (err)
goto out;
if (iocb->ki_flags & IOCB_DIRECT) {
loff_t pos, endbyte;
written = generic_file_direct_write(iocb, from);
/*
* If the write stopped short of completing, fall back to
* buffered writes. Some filesystems do this for writes to
* holes, for example. For DAX files, a buffered write will
* not succeed (even if it did, DAX does not handle dirty
* page-cache pages correctly).
*/
if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
goto out;
status = generic_perform_write(file, from, pos = iocb->ki_pos);
/*
* If generic_perform_write() returned a synchronous error
* then we want to return the number of bytes which were
* direct-written, or the error code if that was zero. Note
* that this differs from normal direct-io semantics, which
* will return -EFOO even if some bytes were written.
*/
if (unlikely(status < 0)) {
err = status;
goto out;
}
/*
* We need to ensure that the page cache pages are written to
* disk and invalidated to preserve the expected O_DIRECT
* semantics.
*/
endbyte = pos + status - 1;
err = filemap_write_and_wait_range(mapping, pos, endbyte);
if (err == 0) {
iocb->ki_pos = endbyte + 1;
written += status;
invalidate_mapping_pages(mapping,
pos >> PAGE_SHIFT,
endbyte >> PAGE_SHIFT);
} else {
/*
* We don't know how much we wrote, so just return
* the number of bytes which were direct-written
*/
}
} else {
written = generic_perform_write(file, from, iocb->ki_pos);
if (likely(written > 0))
iocb->ki_pos += written;
}
out:
current->backing_dev_info = NULL;
return written ? written : err;
}
EXPORT_SYMBOL(__generic_file_write_iter);
/**
* generic_file_write_iter - write data to a file
* @iocb: IO state structure
* @from: iov_iter with data to write
*
* This is a wrapper around __generic_file_write_iter() to be used by most
* filesystems. It takes care of syncing the file in case of O_SYNC file
* and acquires i_mutex as needed.
*/
ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
ssize_t ret;
inode_lock(inode);
ret = generic_write_checks(iocb, from);
if (ret > 0)
ret = __generic_file_write_iter(iocb, from);
inode_unlock(inode);
if (ret > 0)
ret = generic_write_sync(iocb, ret);
return ret;
}
EXPORT_SYMBOL(generic_file_write_iter);
/**
* try_to_release_page() - release old fs-specific metadata on a page
*
* @page: the page which the kernel is trying to free
* @gfp_mask: memory allocation flags (and I/O mode)
*
* The address_space is to try to release any data against the page
* (presumably at page->private). If the release was successful, return `1'.
* Otherwise return zero.
*
* This may also be called if PG_fscache is set on a page, indicating that the
* page is known to the local caching routines.
*
* The @gfp_mask argument specifies whether I/O may be performed to release
* this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
*
*/
int try_to_release_page(struct page *page, gfp_t gfp_mask)
{
struct address_space * const mapping = page->mapping;
BUG_ON(!PageLocked(page));
if (PageWriteback(page))
return 0;
if (mapping && mapping->a_ops->releasepage)
return mapping->a_ops->releasepage(page, gfp_mask);
return try_to_free_buffers(page);
}
EXPORT_SYMBOL(try_to_release_page);
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