[f2fs-dev] [PATCH] f2fs: fix to avoid migrating empty section

[f2fs-dev] [PATCH] f2fs: fix to avoid migrating empty section

[Chao Yu via Linux-f2fs-devel]

It reports a bug from device w/ zufs:

F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
F2FS-fs (dm-64): Stopped filesystem due to reason: 4

Thread A				Thread B
- f2fs_expand_inode_data
 - f2fs_allocate_pinning_section
  - f2fs_gc_range
   - do_garbage_collect w/ segno #x
					- writepage
					 - f2fs_allocate_data_block
					  - new_curseg
					   - allocate segno #x

The root cause is: fallocate on pinning file may race w/ block allocation
as above, result in do_garbage_collect() from fallocate() may migrate
segment which is just allocated by a log, the log will update segment type
in its in-memory structure, however GC will get segment type from on-disk
SSA block, once segment type changes by log, we can detect such
inconsistency, then shutdown filesystem.

In this case, on-disk SSA shows type of segno #173822 is 1 (SUM_TYPE_NODE),
however segno #173822 was just allocated as data type segment, so in-memory
SIT shows type of segno #173822 is 0 (SUM_TYPE_DATA).

Change as below to fix this issue:
- check whether current section is empty before gc
- add sanity checks on do_garbage_collect() to avoid any race case, result
in migrating segment used by log.
- btw, it fixes misc issue in printed logs: "SSA and SIT" -> "SIT and SSA".

Fixes: 9703d69d9d15 ("f2fs: support file pinning for zoned devices")
Cc: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/gc.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index ed3acbfc83ca..a7708cf80c04 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1794,6 +1794,13 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 		struct folio *sum_folio = filemap_get_folio(META_MAPPING(sbi),
 					GET_SUM_BLOCK(sbi, segno));
 
+		if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno))) {
+			f2fs_err(sbi, "%s: segment %u is used by log",
+							__func__, segno);
+			f2fs_bug_on(sbi, 1);
+			goto skip;
+		}
+
 		if (get_valid_blocks(sbi, segno, false) == 0)
 			goto freed;
 		if (gc_type == BG_GC && __is_large_section(sbi) &&
@@ -1805,7 +1812,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 
 		sum = folio_address(sum_folio);
 		if (type != GET_SUM_TYPE((&sum->footer))) {
-			f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SSA and SIT",
+			f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SIT and SSA",
 				 segno, type, GET_SUM_TYPE((&sum->footer)));
 			f2fs_stop_checkpoint(sbi, false,
 				STOP_CP_REASON_CORRUPTED_SUMMARY);
@@ -2068,6 +2075,13 @@ int f2fs_gc_range(struct f2fs_sb_info *sbi,
 			.iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
 		};
 
+		/*
+		 * avoid migrating empty section, as it can be allocated by
+		 * log in parallel.
+		 */
+		if (!get_valid_blocks(sbi, segno, true))
+			continue;
+
 		if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno)))
 			continue;
 
-- 
2.49.0



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Re: [f2fs-dev] [PATCH] f2fs: fix to avoid migrating empty section

[Zhiguo Niu]

Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>
于2025年9月1日周一 10:08写道：
>
> It reports a bug from device w/ zufs:
>
> F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
> F2FS-fs (dm-64): Stopped filesystem due to reason: 4
>
> Thread A                                Thread B
> - f2fs_expand_inode_data
>  - f2fs_allocate_pinning_section
>   - f2fs_gc_range
>    - do_garbage_collect w/ segno #x
>                                         - writepage
>                                          - f2fs_allocate_data_block
>                                           - new_curseg
>                                            - allocate segno #x
>
> The root cause is: fallocate on pinning file may race w/ block allocation
> as above, result in do_garbage_collect() from fallocate() may migrate
> segment which is just allocated by a log, the log will update segment type
> in its in-memory structure, however GC will get segment type from on-disk
> SSA block, once segment type changes by log, we can detect such
> inconsistency, then shutdown filesystem.
>
> In this case, on-disk SSA shows type of segno #173822 is 1 (SUM_TYPE_NODE),
> however segno #173822 was just allocated as data type segment, so in-memory
> SIT shows type of segno #173822 is 0 (SUM_TYPE_DATA).
>
> Change as below to fix this issue:
> - check whether current section is empty before gc
> - add sanity checks on do_garbage_collect() to avoid any race case, result
> in migrating segment used by log.
> - btw, it fixes misc issue in printed logs: "SSA and SIT" -> "SIT and SSA".
>
> Fixes: 9703d69d9d15 ("f2fs: support file pinning for zoned devices")
> Cc: Daeho Jeong <daehojeong@google.com>
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
>  fs/f2fs/gc.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index ed3acbfc83ca..a7708cf80c04 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1794,6 +1794,13 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>                 struct folio *sum_folio = filemap_get_folio(META_MAPPING(sbi),
>                                         GET_SUM_BLOCK(sbi, segno));
>
> +               if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno))) {
> +                       f2fs_err(sbi, "%s: segment %u is used by log",
> +                                                       __func__, segno);
> +                       f2fs_bug_on(sbi, 1);
Hi Chao,
Do we need f2fs_bug_on here?  or it is enough to skip current segno
and let gc continue?
Thanks!
> +                       goto skip;
> +               }
> +
>                 if (get_valid_blocks(sbi, segno, false) == 0)
>                         goto freed;
>                 if (gc_type == BG_GC && __is_large_section(sbi) &&
> @@ -1805,7 +1812,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>
>                 sum = folio_address(sum_folio);
>                 if (type != GET_SUM_TYPE((&sum->footer))) {
> -                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SSA and SIT",
> +                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SIT and SSA",
>                                  segno, type, GET_SUM_TYPE((&sum->footer)));
>                         f2fs_stop_checkpoint(sbi, false,
>                                 STOP_CP_REASON_CORRUPTED_SUMMARY);
> @@ -2068,6 +2075,13 @@ int f2fs_gc_range(struct f2fs_sb_info *sbi,
>                         .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
>                 };
>
> +               /*
> +                * avoid migrating empty section, as it can be allocated by
> +                * log in parallel.
> +                */
> +               if (!get_valid_blocks(sbi, segno, true))
> +                       continue;
> +
>                 if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno)))
>                         continue;
>
> --
> 2.49.0
>
>
>
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel


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Re: [f2fs-dev] [PATCH] f2fs: fix to avoid migrating empty section

[Chao Yu via Linux-f2fs-devel]

On 9/3/25 08:04, Zhiguo Niu wrote:
> Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>
> 于2025年9月1日周一 10:08写道：
>>
>> It reports a bug from device w/ zufs:
>>
>> F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
>> F2FS-fs (dm-64): Stopped filesystem due to reason: 4
>>
>> Thread A                                Thread B
>> - f2fs_expand_inode_data
>>  - f2fs_allocate_pinning_section
>>   - f2fs_gc_range
>>    - do_garbage_collect w/ segno #x
>>                                         - writepage
>>                                          - f2fs_allocate_data_block
>>                                           - new_curseg
>>                                            - allocate segno #x
>>
>> The root cause is: fallocate on pinning file may race w/ block allocation
>> as above, result in do_garbage_collect() from fallocate() may migrate
>> segment which is just allocated by a log, the log will update segment type
>> in its in-memory structure, however GC will get segment type from on-disk
>> SSA block, once segment type changes by log, we can detect such
>> inconsistency, then shutdown filesystem.
>>
>> In this case, on-disk SSA shows type of segno #173822 is 1 (SUM_TYPE_NODE),
>> however segno #173822 was just allocated as data type segment, so in-memory
>> SIT shows type of segno #173822 is 0 (SUM_TYPE_DATA).
>>
>> Change as below to fix this issue:
>> - check whether current section is empty before gc
>> - add sanity checks on do_garbage_collect() to avoid any race case, result
>> in migrating segment used by log.
>> - btw, it fixes misc issue in printed logs: "SSA and SIT" -> "SIT and SSA".
>>
>> Fixes: 9703d69d9d15 ("f2fs: support file pinning for zoned devices")
>> Cc: Daeho Jeong <daehojeong@google.com>
>> Signed-off-by: Chao Yu <chao@kernel.org>
>> ---
>>  fs/f2fs/gc.c | 16 +++++++++++++++-
>>  1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index ed3acbfc83ca..a7708cf80c04 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -1794,6 +1794,13 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>                 struct folio *sum_folio = filemap_get_folio(META_MAPPING(sbi),
>>                                         GET_SUM_BLOCK(sbi, segno));
>>
>> +               if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno))) {
>> +                       f2fs_err(sbi, "%s: segment %u is used by log",
>> +                                                       __func__, segno);
>> +                       f2fs_bug_on(sbi, 1);
> Hi Chao,
> Do we need f2fs_bug_on here?  or it is enough to skip current segno
> and let gc continue?

Zhiguo,

I think we should never select in-use segment as GC victim, so I add a
f2fs_bug_on() here to detect any potential bugs. Let's see what will we
find w/ this.

Thanks,

> Thanks!
>> +                       goto skip;
>> +               }
>> +
>>                 if (get_valid_blocks(sbi, segno, false) == 0)
>>                         goto freed;
>>                 if (gc_type == BG_GC && __is_large_section(sbi) &&
>> @@ -1805,7 +1812,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>
>>                 sum = folio_address(sum_folio);
>>                 if (type != GET_SUM_TYPE((&sum->footer))) {
>> -                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SSA and SIT",
>> +                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SIT and SSA",
>>                                  segno, type, GET_SUM_TYPE((&sum->footer)));
>>                         f2fs_stop_checkpoint(sbi, false,
>>                                 STOP_CP_REASON_CORRUPTED_SUMMARY);
>> @@ -2068,6 +2075,13 @@ int f2fs_gc_range(struct f2fs_sb_info *sbi,
>>                         .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
>>                 };
>>
>> +               /*
>> +                * avoid migrating empty section, as it can be allocated by
>> +                * log in parallel.
>> +                */
>> +               if (!get_valid_blocks(sbi, segno, true))
>> +                       continue;
>> +
>>                 if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno)))
>>                         continue;
>>
>> --
>> 2.49.0
>>
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel



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Re: [f2fs-dev] [PATCH] f2fs: fix to avoid migrating empty section

[Zhiguo Niu]

Chao Yu <chao@kernel.org> 于2025年9月3日周三 09:33写道：
>
> On 9/3/25 08:04, Zhiguo Niu wrote:
> > Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>
> > 于2025年9月1日周一 10:08写道：
> >>
> >> It reports a bug from device w/ zufs:
> >>
> >> F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
> >> F2FS-fs (dm-64): Stopped filesystem due to reason: 4
> >>
> >> Thread A                                Thread B
> >> - f2fs_expand_inode_data
> >>  - f2fs_allocate_pinning_section
> >>   - f2fs_gc_range
> >>    - do_garbage_collect w/ segno #x
> >>                                         - writepage
> >>                                          - f2fs_allocate_data_block
> >>                                           - new_curseg
> >>                                            - allocate segno #x
> >>
> >> The root cause is: fallocate on pinning file may race w/ block allocation
> >> as above, result in do_garbage_collect() from fallocate() may migrate
> >> segment which is just allocated by a log, the log will update segment type
> >> in its in-memory structure, however GC will get segment type from on-disk
> >> SSA block, once segment type changes by log, we can detect such
> >> inconsistency, then shutdown filesystem.
> >>
> >> In this case, on-disk SSA shows type of segno #173822 is 1 (SUM_TYPE_NODE),
> >> however segno #173822 was just allocated as data type segment, so in-memory
> >> SIT shows type of segno #173822 is 0 (SUM_TYPE_DATA).
> >>
> >> Change as below to fix this issue:
> >> - check whether current section is empty before gc
> >> - add sanity checks on do_garbage_collect() to avoid any race case, result
> >> in migrating segment used by log.
> >> - btw, it fixes misc issue in printed logs: "SSA and SIT" -> "SIT and SSA".
> >>
> >> Fixes: 9703d69d9d15 ("f2fs: support file pinning for zoned devices")
> >> Cc: Daeho Jeong <daehojeong@google.com>
> >> Signed-off-by: Chao Yu <chao@kernel.org>
> >> ---
> >>  fs/f2fs/gc.c | 16 +++++++++++++++-
> >>  1 file changed, 15 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> >> index ed3acbfc83ca..a7708cf80c04 100644
> >> --- a/fs/f2fs/gc.c
> >> +++ b/fs/f2fs/gc.c
> >> @@ -1794,6 +1794,13 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >>                 struct folio *sum_folio = filemap_get_folio(META_MAPPING(sbi),
> >>                                         GET_SUM_BLOCK(sbi, segno));
> >>
> >> +               if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno))) {
> >> +                       f2fs_err(sbi, "%s: segment %u is used by log",
> >> +                                                       __func__, segno);
> >> +                       f2fs_bug_on(sbi, 1);
> > Hi Chao,
> > Do we need f2fs_bug_on here?  or it is enough to skip current segno
> > and let gc continue?
>
> Zhiguo,
>
> I think we should never select in-use segment as GC victim, so I add a
> f2fs_bug_on() here to detect any potential bugs. Let's see what will we
> find w/ this.
Hi Chao,
Got it and thanks for this.
>
> Thanks,
>
> > Thanks!
> >> +                       goto skip;
> >> +               }
> >> +
> >>                 if (get_valid_blocks(sbi, segno, false) == 0)
> >>                         goto freed;
> >>                 if (gc_type == BG_GC && __is_large_section(sbi) &&
> >> @@ -1805,7 +1812,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
> >>
> >>                 sum = folio_address(sum_folio);
> >>                 if (type != GET_SUM_TYPE((&sum->footer))) {
> >> -                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SSA and SIT",
> >> +                       f2fs_err(sbi, "Inconsistent segment (%u) type [%d, %d] in SIT and SSA",
> >>                                  segno, type, GET_SUM_TYPE((&sum->footer)));
> >>                         f2fs_stop_checkpoint(sbi, false,
> >>                                 STOP_CP_REASON_CORRUPTED_SUMMARY);
> >> @@ -2068,6 +2075,13 @@ int f2fs_gc_range(struct f2fs_sb_info *sbi,
> >>                         .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
> >>                 };
> >>
> >> +               /*
> >> +                * avoid migrating empty section, as it can be allocated by
> >> +                * log in parallel.
> >> +                */
> >> +               if (!get_valid_blocks(sbi, segno, true))
> >> +                       continue;
> >> +
> >>                 if (is_cursec(sbi, GET_SEC_FROM_SEG(sbi, segno)))
> >>                         continue;
> >>
> >> --
> >> 2.49.0
> >>
> >>
> >>
> >> _______________________________________________
> >> Linux-f2fs-devel mailing list
> >> Linux-f2fs-devel@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>


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Re: [f2fs-dev] [PATCH] f2fs: fix to avoid migrating empty section

[patchwork-bot+f2fs--- via Linux-f2fs-devel]

Hello:

This patch was applied to jaegeuk/f2fs.git (dev)
by Jaegeuk Kim <jaegeuk@kernel.org>:

On Mon,  1 Sep 2025 10:04:15 +0800 you wrote:
> It reports a bug from device w/ zufs:
> 
> F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
> F2FS-fs (dm-64): Stopped filesystem due to reason: 4
> 
> Thread A				Thread B
> - f2fs_expand_inode_data
>  - f2fs_allocate_pinning_section
>   - f2fs_gc_range
>    - do_garbage_collect w/ segno #x
> 					- writepage
> 					 - f2fs_allocate_data_block
> 					  - new_curseg
> 					   - allocate segno #x
> 
> [...]

Here is the summary with links:
  - [f2fs-dev] f2fs: fix to avoid migrating empty section
    https://git.kernel.org/jaegeuk/f2fs/c/d625a2b08c08

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html




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