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* [PATCH v2] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero
@ 2021-07-19 10:14 ` Yangtao Li
  0 siblings, 0 replies; 4+ messages in thread
From: Yangtao Li @ 2021-07-19 10:14 UTC (permalink / raw)
  To: jaegeuk, chao; +Cc: linux-f2fs-devel, linux-kernel, Yangtao Li

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 <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..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


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [f2fs-dev] [PATCH v2] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero
@ 2021-07-19 10:14 ` Yangtao Li
  0 siblings, 0 replies; 4+ messages in thread
From: Yangtao Li @ 2021-07-19 10:14 UTC (permalink / raw)
  To: jaegeuk, chao; +Cc: Yangtao Li, linux-kernel, linux-f2fs-devel

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 <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..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



_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH v2] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero
  2021-07-19 10:14 ` [f2fs-dev] " Yangtao Li
@ 2021-07-20  4:08   ` Chao Yu
  -1 siblings, 0 replies; 4+ messages in thread
From: Chao Yu @ 2021-07-20  4:08 UTC (permalink / raw)
  To: Yangtao Li, jaegeuk; +Cc: linux-f2fs-devel, linux-kernel

On 2021/7/19 18:14, Yangtao Li wrote:
> 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___
>           ^

AAAABBBB___
         ^

> Thread B delete dir_entry2, and create dir_entry3.
> 
> After:
> AAAACCCCC__
>           ^

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..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;

found_valid_dirent?

>   	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)) {

if (found_valid_dirent || !bit_pos)) will be more clean?


> +				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;

found_valid_dirent = true;

Thanks,

>   	}
>   out:
>   	if (readdir_ra)
> 

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [f2fs-dev] [PATCH v2] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero
@ 2021-07-20  4:08   ` Chao Yu
  0 siblings, 0 replies; 4+ messages in thread
From: Chao Yu @ 2021-07-20  4:08 UTC (permalink / raw)
  To: Yangtao Li, jaegeuk; +Cc: linux-kernel, linux-f2fs-devel

On 2021/7/19 18:14, Yangtao Li wrote:
> 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___
>           ^

AAAABBBB___
         ^

> Thread B delete dir_entry2, and create dir_entry3.
> 
> After:
> AAAACCCCC__
>           ^

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..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;

found_valid_dirent?

>   	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)) {

if (found_valid_dirent || !bit_pos)) will be more clean?


> +				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;

found_valid_dirent = true;

Thanks,

>   	}
>   out:
>   	if (readdir_ra)
> 


_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-07-20  4:11 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-19 10:14 [PATCH v2] f2fs: Reduce the scope of setting fsck tag when de->name_len is zero Yangtao Li
2021-07-19 10:14 ` [f2fs-dev] " Yangtao Li
2021-07-20  4:08 ` Chao Yu
2021-07-20  4:08   ` [f2fs-dev] " Chao Yu

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