diff options
author | Yangtao Li <frank.li@vivo.com> | 2021-08-04 11:29:46 +0800 |
---|---|---|
committer | Jaegeuk Kim <jaegeuk@kernel.org> | 2021-08-04 15:51:21 -0700 |
commit | d4bf15a7ce172d186d400d606adf4f34a59130d6 (patch) | |
tree | 58b34fab1de46230b3d8ee30892c5905a8dcbf38 /fs/f2fs/dir.c | |
parent | 91803392c732c43b5cf440e885ea89be7f5fecef (diff) |
f2fs: reduce the scope of setting fsck tag when de->name_len is zero
I recently found a case where de->name_len is 0 in f2fs_fill_dentries()
easily reproduced, and finally set the fsck flag.
Thread A Thread B
- f2fs_readdir
- f2fs_read_inline_dir
- ctx->pos = d.max
- f2fs_add_dentry
- f2fs_add_inline_entry
- do_convert_inline_dir
- f2fs_add_regular_entry
- f2fs_readdir
- f2fs_fill_dentries
- set_sbi_flag(sbi, SBI_NEED_FSCK)
Process A opens the folder, and has been reading without closing it.
During this period, Process B created a file under the folder (occupying
multiple f2fs_dir_entry, exceeding the d.max of the inline dir). After
creation, process A uses the d.max of inline dir to read it again, and
it will read that de->name_len is 0.
And Chao pointed out that w/o inline conversion, the race condition still
can happen as below:
dir_entry1: A
dir_entry2: B
dir_entry3: C
free slot: _
ctx->pos: ^
Thread A is traversing directory,
ctx-pos moves to below position after readdir() by thread A:
AAAABBBB___
^
Then thread B delete dir_entry2, and create dir_entry3.
Thread A calls readdir() to lookup dirents starting from middle
of new dirent slots as below:
AAAACCCCCC_
^
In these scenarios, the file system is not damaged, and it's hard to
avoid it. But we can bypass tagging FSCK flag if:
a) bit_pos (:= ctx->pos % d->max) is non-zero and
b) before bit_pos moves to first valid dir_entry.
Fixes: ddf06b753a85 ("f2fs: fix to trigger fsck if dirent.name_len is zero")
Signed-off-by: Yangtao Li <frank.li@vivo.com>
[Chao: clean up description]
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs/f2fs/dir.c')
-rw-r--r-- | fs/f2fs/dir.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 456651682daf..c250bf46ef5e 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -1000,6 +1000,7 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, struct f2fs_sb_info *sbi = F2FS_I_SB(d->inode); struct blk_plug plug; bool readdir_ra = sbi->readdir_ra == 1; + bool found_valid_dirent = false; int err = 0; bit_pos = ((unsigned long)ctx->pos % d->max); @@ -1014,13 +1015,15 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, de = &d->dentry[bit_pos]; if (de->name_len == 0) { + if (found_valid_dirent || !bit_pos) { + printk_ratelimited( + "%sF2FS-fs (%s): invalid namelen(0), ino:%u, run fsck to fix.", + KERN_WARNING, sbi->sb->s_id, + le32_to_cpu(de->ino)); + set_sbi_flag(sbi, SBI_NEED_FSCK); + } bit_pos++; ctx->pos = start_pos + bit_pos; - printk_ratelimited( - "%sF2FS-fs (%s): invalid namelen(0), ino:%u, run fsck to fix.", - KERN_WARNING, sbi->sb->s_id, - le32_to_cpu(de->ino)); - set_sbi_flag(sbi, SBI_NEED_FSCK); continue; } @@ -1063,6 +1066,7 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d, f2fs_ra_node_page(sbi, le32_to_cpu(de->ino)); ctx->pos = start_pos + bit_pos; + found_valid_dirent = true; } out: if (readdir_ra) |