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: _
Before:
AAAABBBB___
^
Thread B delete dir_entry2, and create dir_entry3.
After:
AAAACCCCC__
^
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 & b) before bit_pos moves to first
valid dir_entry.
Signed-off-by: Yangtao Li <[email protected]>
---
fs/f2fs/dir.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 456651682daf..3e2a61a3600c 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 find_valid_dentry = 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 (!(ctx->pos % d->max != 0 && find_valid_dentry ==
false)) {
+ 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;
+ find_valid_dentry = true;
}
out:
if (readdir_ra)
--
2.32.0
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