diff options
| author | Shuqi Zhang <zhangshuqi3@huawei.com> | 2022-08-31 10:24:40 +0800 |
|---|---|---|
| committer | Jaegeuk Kim <jaegeuk@kernel.org> | 2022-10-04 13:31:42 -0700 |
| commit | 9b7eadd9bd3a0cc24533a23d83c46430a0ea60ff (patch) | |
| tree | 9ddbf0e17456a34c6473161679d2aacbb38ed7ca /fs/f2fs/data.c | |
| parent | 173cdf2c32b4b02474006d87648383244c0a6db9 (diff) | |
| download | linux-9b7eadd9bd3a0cc24533a23d83c46430a0ea60ff.tar.gz | |
f2fs: fix wrong dirty page count when race between mmap and fallocate.
This is a BUG_ON issue as follows when running xfstest-generic-503:
WARNING: CPU: 21 PID: 1385 at fs/f2fs/inode.c:762 f2fs_evict_inode+0x847/0xaa0
Modules linked in:
CPU: 21 PID: 1385 Comm: umount Not tainted 5.19.0-rc5+ #73
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
Call Trace:
evict+0x129/0x2d0
dispose_list+0x4f/0xb0
evict_inodes+0x204/0x230
generic_shutdown_super+0x5b/0x1e0
kill_block_super+0x29/0x80
kill_f2fs_super+0xe6/0x140
deactivate_locked_super+0x44/0xc0
deactivate_super+0x79/0x90
cleanup_mnt+0x114/0x1a0
__cleanup_mnt+0x16/0x20
task_work_run+0x98/0x100
exit_to_user_mode_prepare+0x3d0/0x3e0
syscall_exit_to_user_mode+0x12/0x30
do_syscall_64+0x42/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
Function flow analysis when BUG occurs:
f2fs_fallocate mmap
do_page_fault
pte_spinlock // ---lock_pte
do_wp_page
wp_page_shared
pte_unmap_unlock // unlock_pte
do_page_mkwrite
f2fs_vm_page_mkwrite
down_read(invalidate_lock)
lock_page
if (PageMappedToDisk(page))
goto out;
// set_page_dirty --NOT RUN
out: up_read(invalidate_lock);
finish_mkwrite_fault // unlock_pte
f2fs_collapse_range
down_write(i_mmap_sem)
truncate_pagecache
unmap_mapping_pages
i_mmap_lock_write // down_write(i_mmap_rwsem)
......
zap_pte_range
pte_offset_map_lock // ---lock_pte
set_page_dirty
f2fs_dirty_data_folio
if (!folio_test_dirty(folio)) {
fault_dirty_shared_page
set_page_dirty
f2fs_dirty_data_folio
if (!folio_test_dirty(folio)) {
filemap_dirty_folio
f2fs_update_dirty_folio // ++
}
unlock_page
filemap_dirty_folio
f2fs_update_dirty_folio // page count++
}
pte_unmap_unlock // --unlock_pte
i_mmap_unlock_write // up_write(i_mmap_rwsem)
truncate_inode_pages
up_write(i_mmap_sem)
When race happens between mmap-do_page_fault-wp_page_shared and
fallocate-truncate_pagecache-zap_pte_range, the zap_pte_range calls
function set_page_dirty without page lock. Besides, though
truncate_pagecache has immap and pte lock, wp_page_shared calls
fault_dirty_shared_page without any. In this case, two threads race
in f2fs_dirty_data_folio function. Page is set to dirty only ONCE,
but the count is added TWICE by calling filemap_dirty_folio.
Thus the count of dirty page cannot accord with the real dirty pages.
Following is the solution to in case of race happens without any lock.
Since folio_test_set_dirty in filemap_dirty_folio is atomic, judge return
value will not be at risk of race.
Signed-off-by: Shuqi Zhang <zhangshuqi3@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs/f2fs/data.c')
| -rw-r--r-- | fs/f2fs/data.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 0869fbbb5516..87524d3dce22 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -3697,8 +3697,7 @@ static bool f2fs_dirty_data_folio(struct address_space *mapping, folio_mark_uptodate(folio); BUG_ON(folio_test_swapcache(folio)); - if (!folio_test_dirty(folio)) { - filemap_dirty_folio(mapping, folio); + if (filemap_dirty_folio(mapping, folio)) { f2fs_update_dirty_folio(inode, folio); return true; } |