linux/fs/nilfs2/page.c
Vyacheslav Dubeyko 7f42ec3941 nilfs2: fix issue with race condition of competition between segments for dirty blocks
Many NILFS2 users were reported about strange file system corruption
(for example):

   NILFS: bad btree node (blocknr=185027): level = 0, flags = 0x0, nchildren = 768
   NILFS error (device sda4): nilfs_bmap_last_key: broken bmap (inode number=11540)

But such error messages are consequence of file system's issue that takes
place more earlier.  Fortunately, Jerome Poulin <jeromepoulin@gmail.com>
and Anton Eliasson <devel@antoneliasson.se> were reported about another
issue not so recently.  These reports describe the issue with segctor
thread's crash:

  BUG: unable to handle kernel paging request at 0000000000004c83
  IP: nilfs_end_page_io+0x12/0xd0 [nilfs2]

  Call Trace:
   nilfs_segctor_do_construct+0xf25/0x1b20 [nilfs2]
   nilfs_segctor_construct+0x17b/0x290 [nilfs2]
   nilfs_segctor_thread+0x122/0x3b0 [nilfs2]
   kthread+0xc0/0xd0
   ret_from_fork+0x7c/0xb0

These two issues have one reason.  This reason can raise third issue
too.  Third issue results in hanging of segctor thread with eating of
100% CPU.

REPRODUCING PATH:

One of the possible way or the issue reproducing was described by
Jermoe me Poulin <jeromepoulin@gmail.com>:

1. init S to get to single user mode.
2. sysrq+E to make sure only my shell is running
3. start network-manager to get my wifi connection up
4. login as root and launch "screen"
5. cd /boot/log/nilfs which is a ext3 mount point and can log when NILFS dies.
6. lscp | xz -9e > lscp.txt.xz
7. mount my snapshot using mount -o cp=3360839,ro /dev/vgUbuntu/root /mnt/nilfs
8. start a screen to dump /proc/kmsg to text file since rsyslog is killed
9. start a screen and launch strace -f -o find-cat.log -t find
/mnt/nilfs -type f -exec cat {} > /dev/null \;
10. start a screen and launch strace -f -o apt-get.log -t apt-get update
11. launch the last command again as it did not crash the first time
12. apt-get crashes
13. ps aux > ps-aux-crashed.log
13. sysrq+W
14. sysrq+E  wait for everything to terminate
15. sysrq+SUSB

Simplified way of the issue reproducing is starting kernel compilation
task and "apt-get update" in parallel.

REPRODUCIBILITY:

The issue is reproduced not stable [60% - 80%].  It is very important to
have proper environment for the issue reproducing.  The critical
conditions for successful reproducing:

(1) It should have big modified file by mmap() way.

(2) This file should have the count of dirty blocks are greater that
    several segments in size (for example, two or three) from time to time
    during processing.

(3) It should be intensive background activity of files modification
    in another thread.

INVESTIGATION:

First of all, it is possible to see that the reason of crash is not valid
page address:

  NILFS [nilfs_segctor_complete_write]:2100 bh->b_count 0, bh->b_blocknr 13895680, bh->b_size 13897727, bh->b_page 0000000000001a82
  NILFS [nilfs_segctor_complete_write]:2101 segbuf->sb_segnum 6783

Moreover, value of b_page (0x1a82) is 6786.  This value looks like segment
number.  And b_blocknr with b_size values look like block numbers.  So,
buffer_head's pointer points on not proper address value.

Detailed investigation of the issue is discovered such picture:

  [-----------------------------SEGMENT 6783-------------------------------]
  NILFS [nilfs_segctor_do_construct]:2310 nilfs_segctor_begin_construction
  NILFS [nilfs_segctor_do_construct]:2321 nilfs_segctor_collect
  NILFS [nilfs_segctor_do_construct]:2336 nilfs_segctor_assign
  NILFS [nilfs_segctor_do_construct]:2367 nilfs_segctor_update_segusage
  NILFS [nilfs_segctor_do_construct]:2371 nilfs_segctor_prepare_write
  NILFS [nilfs_segctor_do_construct]:2376 nilfs_add_checksums_on_logs
  NILFS [nilfs_segctor_do_construct]:2381 nilfs_segctor_write
  NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111149024, segbuf->sb_segnum 6783

  [-----------------------------SEGMENT 6784-------------------------------]
  NILFS [nilfs_segctor_do_construct]:2310 nilfs_segctor_begin_construction
  NILFS [nilfs_segctor_do_construct]:2321 nilfs_segctor_collect
  NILFS [nilfs_lookup_dirty_data_buffers]:782 bh->b_count 1, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824
  NILFS [nilfs_lookup_dirty_data_buffers]:783 bh->b_assoc_buffers.next ffff8802174a6798, bh->b_assoc_buffers.prev ffff880221cffee8
  NILFS [nilfs_segctor_do_construct]:2336 nilfs_segctor_assign
  NILFS [nilfs_segctor_do_construct]:2367 nilfs_segctor_update_segusage
  NILFS [nilfs_segctor_do_construct]:2371 nilfs_segctor_prepare_write
  NILFS [nilfs_segctor_do_construct]:2376 nilfs_add_checksums_on_logs
  NILFS [nilfs_segctor_do_construct]:2381 nilfs_segctor_write
  NILFS [nilfs_segbuf_submit_bh]:575 bh->b_count 1, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824
  NILFS [nilfs_segbuf_submit_bh]:576 segbuf->sb_segnum 6784
  NILFS [nilfs_segbuf_submit_bh]:577 bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880218bcdf50
  NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111150080, segbuf->sb_segnum 6784, segbuf->sb_nbio 0
  [----------] ditto
  NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111164416, segbuf->sb_segnum 6784, segbuf->sb_nbio 15

  [-----------------------------SEGMENT 6785-------------------------------]
  NILFS [nilfs_segctor_do_construct]:2310 nilfs_segctor_begin_construction
  NILFS [nilfs_segctor_do_construct]:2321 nilfs_segctor_collect
  NILFS [nilfs_lookup_dirty_data_buffers]:782 bh->b_count 2, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824
  NILFS [nilfs_lookup_dirty_data_buffers]:783 bh->b_assoc_buffers.next ffff880219277e80, bh->b_assoc_buffers.prev ffff880221cffc88
  NILFS [nilfs_segctor_do_construct]:2367 nilfs_segctor_update_segusage
  NILFS [nilfs_segctor_do_construct]:2371 nilfs_segctor_prepare_write
  NILFS [nilfs_segctor_do_construct]:2376 nilfs_add_checksums_on_logs
  NILFS [nilfs_segctor_do_construct]:2381 nilfs_segctor_write
  NILFS [nilfs_segbuf_submit_bh]:575 bh->b_count 2, bh->b_page ffffea000709b000, page->index 0, i_ino 1033103, i_size 25165824
  NILFS [nilfs_segbuf_submit_bh]:576 segbuf->sb_segnum 6785
  NILFS [nilfs_segbuf_submit_bh]:577 bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880222cc7ee8
  NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111165440, segbuf->sb_segnum 6785, segbuf->sb_nbio 0
  [----------] ditto
  NILFS [nilfs_segbuf_submit_bio]:464 bio->bi_sector 111177728, segbuf->sb_segnum 6785, segbuf->sb_nbio 12

  NILFS [nilfs_segctor_do_construct]:2399 nilfs_segctor_wait
  NILFS [nilfs_segbuf_wait]:676 segbuf->sb_segnum 6783
  NILFS [nilfs_segbuf_wait]:676 segbuf->sb_segnum 6784
  NILFS [nilfs_segbuf_wait]:676 segbuf->sb_segnum 6785

  NILFS [nilfs_segctor_complete_write]:2100 bh->b_count 0, bh->b_blocknr 13895680, bh->b_size 13897727, bh->b_page 0000000000001a82

  BUG: unable to handle kernel paging request at 0000000000001a82
  IP: [<ffffffffa024d0f2>] nilfs_end_page_io+0x12/0xd0 [nilfs2]

Usually, for every segment we collect dirty files in list.  Then, dirty
blocks are gathered for every dirty file, prepared for write and
submitted by means of nilfs_segbuf_submit_bh() call.  Finally, it takes
place complete write phase after calling nilfs_end_bio_write() on the
block layer.  Buffers/pages are marked as not dirty on final phase and
processed files removed from the list of dirty files.

It is possible to see that we had three prepare_write and submit_bio
phases before segbuf_wait and complete_write phase.  Moreover, segments
compete between each other for dirty blocks because on every iteration
of segments processing dirty buffer_heads are added in several lists of
payload_buffers:

  [SEGMENT 6784]: bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880218bcdf50
  [SEGMENT 6785]: bh->b_assoc_buffers.next ffff880218a0d5f8, bh->b_assoc_buffers.prev ffff880222cc7ee8

The next pointer is the same but prev pointer has changed.  It means
that buffer_head has next pointer from one list but prev pointer from
another.  Such modification can be made several times.  And, finally, it
can be resulted in various issues: (1) segctor hanging, (2) segctor
crashing, (3) file system metadata corruption.

FIX:
This patch adds:

(1) setting of BH_Async_Write flag in nilfs_segctor_prepare_write()
    for every proccessed dirty block;

(2) checking of BH_Async_Write flag in
    nilfs_lookup_dirty_data_buffers() and
    nilfs_lookup_dirty_node_buffers();

(3) clearing of BH_Async_Write flag in nilfs_segctor_complete_write(),
    nilfs_abort_logs(), nilfs_forget_buffer(), nilfs_clear_dirty_page().

Reported-by: Jerome Poulin <jeromepoulin@gmail.com>
Reported-by: Anton Eliasson <devel@antoneliasson.se>
Cc: Paul Fertser <fercerpav@gmail.com>
Cc: ARAI Shun-ichi <hermes@ceres.dti.ne.jp>
Cc: Piotr Szymaniak <szarpaj@grubelek.pl>
Cc: Juan Barry Manuel Canham <Linux@riotingpacifist.net>
Cc: Zahid Chowdhury <zahid.chowdhury@starsolutions.com>
Cc: Elmer Zhang <freeboy6716@gmail.com>
Cc: Kenneth Langga <klangga@gmail.com>
Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-09-30 14:31:02 -07:00

588 lines
15 KiB
C

/*
* page.c - buffer/page management specific to NILFS
*
* Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* Written by Ryusuke Konishi <ryusuke@osrg.net>,
* Seiji Kihara <kihara@osrg.net>.
*/
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/swap.h>
#include <linux/bitops.h>
#include <linux/page-flags.h>
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/pagevec.h>
#include <linux/gfp.h>
#include "nilfs.h"
#include "page.h"
#include "mdt.h"
#define NILFS_BUFFER_INHERENT_BITS \
((1UL << BH_Uptodate) | (1UL << BH_Mapped) | (1UL << BH_NILFS_Node) | \
(1UL << BH_NILFS_Volatile) | (1UL << BH_NILFS_Checked))
static struct buffer_head *
__nilfs_get_page_block(struct page *page, unsigned long block, pgoff_t index,
int blkbits, unsigned long b_state)
{
unsigned long first_block;
struct buffer_head *bh;
if (!page_has_buffers(page))
create_empty_buffers(page, 1 << blkbits, b_state);
first_block = (unsigned long)index << (PAGE_CACHE_SHIFT - blkbits);
bh = nilfs_page_get_nth_block(page, block - first_block);
touch_buffer(bh);
wait_on_buffer(bh);
return bh;
}
struct buffer_head *nilfs_grab_buffer(struct inode *inode,
struct address_space *mapping,
unsigned long blkoff,
unsigned long b_state)
{
int blkbits = inode->i_blkbits;
pgoff_t index = blkoff >> (PAGE_CACHE_SHIFT - blkbits);
struct page *page;
struct buffer_head *bh;
page = grab_cache_page(mapping, index);
if (unlikely(!page))
return NULL;
bh = __nilfs_get_page_block(page, blkoff, index, blkbits, b_state);
if (unlikely(!bh)) {
unlock_page(page);
page_cache_release(page);
return NULL;
}
return bh;
}
/**
* nilfs_forget_buffer - discard dirty state
* @inode: owner inode of the buffer
* @bh: buffer head of the buffer to be discarded
*/
void nilfs_forget_buffer(struct buffer_head *bh)
{
struct page *page = bh->b_page;
lock_buffer(bh);
clear_buffer_nilfs_volatile(bh);
clear_buffer_nilfs_checked(bh);
clear_buffer_nilfs_redirected(bh);
clear_buffer_async_write(bh);
clear_buffer_dirty(bh);
if (nilfs_page_buffers_clean(page))
__nilfs_clear_page_dirty(page);
clear_buffer_uptodate(bh);
clear_buffer_mapped(bh);
bh->b_blocknr = -1;
ClearPageUptodate(page);
ClearPageMappedToDisk(page);
unlock_buffer(bh);
brelse(bh);
}
/**
* nilfs_copy_buffer -- copy buffer data and flags
* @dbh: destination buffer
* @sbh: source buffer
*/
void nilfs_copy_buffer(struct buffer_head *dbh, struct buffer_head *sbh)
{
void *kaddr0, *kaddr1;
unsigned long bits;
struct page *spage = sbh->b_page, *dpage = dbh->b_page;
struct buffer_head *bh;
kaddr0 = kmap_atomic(spage);
kaddr1 = kmap_atomic(dpage);
memcpy(kaddr1 + bh_offset(dbh), kaddr0 + bh_offset(sbh), sbh->b_size);
kunmap_atomic(kaddr1);
kunmap_atomic(kaddr0);
dbh->b_state = sbh->b_state & NILFS_BUFFER_INHERENT_BITS;
dbh->b_blocknr = sbh->b_blocknr;
dbh->b_bdev = sbh->b_bdev;
bh = dbh;
bits = sbh->b_state & ((1UL << BH_Uptodate) | (1UL << BH_Mapped));
while ((bh = bh->b_this_page) != dbh) {
lock_buffer(bh);
bits &= bh->b_state;
unlock_buffer(bh);
}
if (bits & (1UL << BH_Uptodate))
SetPageUptodate(dpage);
else
ClearPageUptodate(dpage);
if (bits & (1UL << BH_Mapped))
SetPageMappedToDisk(dpage);
else
ClearPageMappedToDisk(dpage);
}
/**
* nilfs_page_buffers_clean - check if a page has dirty buffers or not.
* @page: page to be checked
*
* nilfs_page_buffers_clean() returns zero if the page has dirty buffers.
* Otherwise, it returns non-zero value.
*/
int nilfs_page_buffers_clean(struct page *page)
{
struct buffer_head *bh, *head;
bh = head = page_buffers(page);
do {
if (buffer_dirty(bh))
return 0;
bh = bh->b_this_page;
} while (bh != head);
return 1;
}
void nilfs_page_bug(struct page *page)
{
struct address_space *m;
unsigned long ino;
if (unlikely(!page)) {
printk(KERN_CRIT "NILFS_PAGE_BUG(NULL)\n");
return;
}
m = page->mapping;
ino = m ? m->host->i_ino : 0;
printk(KERN_CRIT "NILFS_PAGE_BUG(%p): cnt=%d index#=%llu flags=0x%lx "
"mapping=%p ino=%lu\n",
page, atomic_read(&page->_count),
(unsigned long long)page->index, page->flags, m, ino);
if (page_has_buffers(page)) {
struct buffer_head *bh, *head;
int i = 0;
bh = head = page_buffers(page);
do {
printk(KERN_CRIT
" BH[%d] %p: cnt=%d block#=%llu state=0x%lx\n",
i++, bh, atomic_read(&bh->b_count),
(unsigned long long)bh->b_blocknr, bh->b_state);
bh = bh->b_this_page;
} while (bh != head);
}
}
/**
* nilfs_copy_page -- copy the page with buffers
* @dst: destination page
* @src: source page
* @copy_dirty: flag whether to copy dirty states on the page's buffer heads.
*
* This function is for both data pages and btnode pages. The dirty flag
* should be treated by caller. The page must not be under i/o.
* Both src and dst page must be locked
*/
static void nilfs_copy_page(struct page *dst, struct page *src, int copy_dirty)
{
struct buffer_head *dbh, *dbufs, *sbh, *sbufs;
unsigned long mask = NILFS_BUFFER_INHERENT_BITS;
BUG_ON(PageWriteback(dst));
sbh = sbufs = page_buffers(src);
if (!page_has_buffers(dst))
create_empty_buffers(dst, sbh->b_size, 0);
if (copy_dirty)
mask |= (1UL << BH_Dirty);
dbh = dbufs = page_buffers(dst);
do {
lock_buffer(sbh);
lock_buffer(dbh);
dbh->b_state = sbh->b_state & mask;
dbh->b_blocknr = sbh->b_blocknr;
dbh->b_bdev = sbh->b_bdev;
sbh = sbh->b_this_page;
dbh = dbh->b_this_page;
} while (dbh != dbufs);
copy_highpage(dst, src);
if (PageUptodate(src) && !PageUptodate(dst))
SetPageUptodate(dst);
else if (!PageUptodate(src) && PageUptodate(dst))
ClearPageUptodate(dst);
if (PageMappedToDisk(src) && !PageMappedToDisk(dst))
SetPageMappedToDisk(dst);
else if (!PageMappedToDisk(src) && PageMappedToDisk(dst))
ClearPageMappedToDisk(dst);
do {
unlock_buffer(sbh);
unlock_buffer(dbh);
sbh = sbh->b_this_page;
dbh = dbh->b_this_page;
} while (dbh != dbufs);
}
int nilfs_copy_dirty_pages(struct address_space *dmap,
struct address_space *smap)
{
struct pagevec pvec;
unsigned int i;
pgoff_t index = 0;
int err = 0;
pagevec_init(&pvec, 0);
repeat:
if (!pagevec_lookup_tag(&pvec, smap, &index, PAGECACHE_TAG_DIRTY,
PAGEVEC_SIZE))
return 0;
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i], *dpage;
lock_page(page);
if (unlikely(!PageDirty(page)))
NILFS_PAGE_BUG(page, "inconsistent dirty state");
dpage = grab_cache_page(dmap, page->index);
if (unlikely(!dpage)) {
/* No empty page is added to the page cache */
err = -ENOMEM;
unlock_page(page);
break;
}
if (unlikely(!page_has_buffers(page)))
NILFS_PAGE_BUG(page,
"found empty page in dat page cache");
nilfs_copy_page(dpage, page, 1);
__set_page_dirty_nobuffers(dpage);
unlock_page(dpage);
page_cache_release(dpage);
unlock_page(page);
}
pagevec_release(&pvec);
cond_resched();
if (likely(!err))
goto repeat;
return err;
}
/**
* nilfs_copy_back_pages -- copy back pages to original cache from shadow cache
* @dmap: destination page cache
* @smap: source page cache
*
* No pages must no be added to the cache during this process.
* This must be ensured by the caller.
*/
void nilfs_copy_back_pages(struct address_space *dmap,
struct address_space *smap)
{
struct pagevec pvec;
unsigned int i, n;
pgoff_t index = 0;
int err;
pagevec_init(&pvec, 0);
repeat:
n = pagevec_lookup(&pvec, smap, index, PAGEVEC_SIZE);
if (!n)
return;
index = pvec.pages[n - 1]->index + 1;
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i], *dpage;
pgoff_t offset = page->index;
lock_page(page);
dpage = find_lock_page(dmap, offset);
if (dpage) {
/* override existing page on the destination cache */
WARN_ON(PageDirty(dpage));
nilfs_copy_page(dpage, page, 0);
unlock_page(dpage);
page_cache_release(dpage);
} else {
struct page *page2;
/* move the page to the destination cache */
spin_lock_irq(&smap->tree_lock);
page2 = radix_tree_delete(&smap->page_tree, offset);
WARN_ON(page2 != page);
smap->nrpages--;
spin_unlock_irq(&smap->tree_lock);
spin_lock_irq(&dmap->tree_lock);
err = radix_tree_insert(&dmap->page_tree, offset, page);
if (unlikely(err < 0)) {
WARN_ON(err == -EEXIST);
page->mapping = NULL;
page_cache_release(page); /* for cache */
} else {
page->mapping = dmap;
dmap->nrpages++;
if (PageDirty(page))
radix_tree_tag_set(&dmap->page_tree,
offset,
PAGECACHE_TAG_DIRTY);
}
spin_unlock_irq(&dmap->tree_lock);
}
unlock_page(page);
}
pagevec_release(&pvec);
cond_resched();
goto repeat;
}
/**
* nilfs_clear_dirty_pages - discard dirty pages in address space
* @mapping: address space with dirty pages for discarding
* @silent: suppress [true] or print [false] warning messages
*/
void nilfs_clear_dirty_pages(struct address_space *mapping, bool silent)
{
struct pagevec pvec;
unsigned int i;
pgoff_t index = 0;
pagevec_init(&pvec, 0);
while (pagevec_lookup_tag(&pvec, mapping, &index, PAGECACHE_TAG_DIRTY,
PAGEVEC_SIZE)) {
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
lock_page(page);
nilfs_clear_dirty_page(page, silent);
unlock_page(page);
}
pagevec_release(&pvec);
cond_resched();
}
}
/**
* nilfs_clear_dirty_page - discard dirty page
* @page: dirty page that will be discarded
* @silent: suppress [true] or print [false] warning messages
*/
void nilfs_clear_dirty_page(struct page *page, bool silent)
{
struct inode *inode = page->mapping->host;
struct super_block *sb = inode->i_sb;
BUG_ON(!PageLocked(page));
if (!silent) {
nilfs_warning(sb, __func__,
"discard page: offset %lld, ino %lu",
page_offset(page), inode->i_ino);
}
ClearPageUptodate(page);
ClearPageMappedToDisk(page);
if (page_has_buffers(page)) {
struct buffer_head *bh, *head;
bh = head = page_buffers(page);
do {
lock_buffer(bh);
if (!silent) {
nilfs_warning(sb, __func__,
"discard block %llu, size %zu",
(u64)bh->b_blocknr, bh->b_size);
}
clear_buffer_async_write(bh);
clear_buffer_dirty(bh);
clear_buffer_nilfs_volatile(bh);
clear_buffer_nilfs_checked(bh);
clear_buffer_nilfs_redirected(bh);
clear_buffer_uptodate(bh);
clear_buffer_mapped(bh);
unlock_buffer(bh);
} while (bh = bh->b_this_page, bh != head);
}
__nilfs_clear_page_dirty(page);
}
unsigned nilfs_page_count_clean_buffers(struct page *page,
unsigned from, unsigned to)
{
unsigned block_start, block_end;
struct buffer_head *bh, *head;
unsigned nc = 0;
for (bh = head = page_buffers(page), block_start = 0;
bh != head || !block_start;
block_start = block_end, bh = bh->b_this_page) {
block_end = block_start + bh->b_size;
if (block_end > from && block_start < to && !buffer_dirty(bh))
nc++;
}
return nc;
}
void nilfs_mapping_init(struct address_space *mapping, struct inode *inode,
struct backing_dev_info *bdi)
{
mapping->host = inode;
mapping->flags = 0;
mapping_set_gfp_mask(mapping, GFP_NOFS);
mapping->private_data = NULL;
mapping->backing_dev_info = bdi;
mapping->a_ops = &empty_aops;
}
/*
* NILFS2 needs clear_page_dirty() in the following two cases:
*
* 1) For B-tree node pages and data pages of the dat/gcdat, NILFS2 clears
* page dirty flags when it copies back pages from the shadow cache
* (gcdat->{i_mapping,i_btnode_cache}) to its original cache
* (dat->{i_mapping,i_btnode_cache}).
*
* 2) Some B-tree operations like insertion or deletion may dispose buffers
* in dirty state, and this needs to cancel the dirty state of their pages.
*/
int __nilfs_clear_page_dirty(struct page *page)
{
struct address_space *mapping = page->mapping;
if (mapping) {
spin_lock_irq(&mapping->tree_lock);
if (test_bit(PG_dirty, &page->flags)) {
radix_tree_tag_clear(&mapping->page_tree,
page_index(page),
PAGECACHE_TAG_DIRTY);
spin_unlock_irq(&mapping->tree_lock);
return clear_page_dirty_for_io(page);
}
spin_unlock_irq(&mapping->tree_lock);
return 0;
}
return TestClearPageDirty(page);
}
/**
* nilfs_find_uncommitted_extent - find extent of uncommitted data
* @inode: inode
* @start_blk: start block offset (in)
* @blkoff: start offset of the found extent (out)
*
* This function searches an extent of buffers marked "delayed" which
* starts from a block offset equal to or larger than @start_blk. If
* such an extent was found, this will store the start offset in
* @blkoff and return its length in blocks. Otherwise, zero is
* returned.
*/
unsigned long nilfs_find_uncommitted_extent(struct inode *inode,
sector_t start_blk,
sector_t *blkoff)
{
unsigned int i;
pgoff_t index;
unsigned int nblocks_in_page;
unsigned long length = 0;
sector_t b;
struct pagevec pvec;
struct page *page;
if (inode->i_mapping->nrpages == 0)
return 0;
index = start_blk >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
nblocks_in_page = 1U << (PAGE_CACHE_SHIFT - inode->i_blkbits);
pagevec_init(&pvec, 0);
repeat:
pvec.nr = find_get_pages_contig(inode->i_mapping, index, PAGEVEC_SIZE,
pvec.pages);
if (pvec.nr == 0)
return length;
if (length > 0 && pvec.pages[0]->index > index)
goto out;
b = pvec.pages[0]->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
i = 0;
do {
page = pvec.pages[i];
lock_page(page);
if (page_has_buffers(page)) {
struct buffer_head *bh, *head;
bh = head = page_buffers(page);
do {
if (b < start_blk)
continue;
if (buffer_delay(bh)) {
if (length == 0)
*blkoff = b;
length++;
} else if (length > 0) {
goto out_locked;
}
} while (++b, bh = bh->b_this_page, bh != head);
} else {
if (length > 0)
goto out_locked;
b += nblocks_in_page;
}
unlock_page(page);
} while (++i < pagevec_count(&pvec));
index = page->index + 1;
pagevec_release(&pvec);
cond_resched();
goto repeat;
out_locked:
unlock_page(page);
out:
pagevec_release(&pvec);
return length;
}