Messages in this thread Patch in this message | | | From | Yangtao Li <> | Subject | [PATCH v3] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero | Date | Tue, 20 Jul 2021 15:06:33 +0800 |
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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: ^
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 <frank.li@vivo.com> --- 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..bfe942733b5e 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) -- 2.32.0
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