Re: [f2fs-dev] [PATCH] f2fs: fix FG GC failure when file in victim is pinned

On 6/22/2026 9:46 AM, Chao Yu wrote:
> [Some people who received this message don't often get email from 
> [email protected]. Learn why this is important at https://aka.ms/ 
> LearnAboutSenderIdentification ]
> 
> [ EXTERNAL EMAIL ]
> 
> On 6/20/26 17:34, Jiucheng Xu via B4 Relay wrote:
>> From: Jiucheng Xu <[email protected]>
>>
>> When continuous write operations occur in the system, BG GC fails to
>> work. This leads to large dirty_segments and small free_segments. If
>> fallocate() is performed on a pinned file with the allocated space
>> exceeding the free_segment, FG_GC reclamation fails.
>>
>> The reason is that the file corresponding to the block in the victim is
>> pinned, causing gc_data_segment() to fail. Since the condition sec_freed
> 
> Jiucheng,
> 
> pinned file should be aligned to section size, why there is fragmented 
> blocks
> of pinfile locates in dirty sections?
> 
>> < gc_control->nr_free_secs isn't satisfied, GC stops, resulting in the
>> failure of f2fs_fallocate() allocation.
>>
>> Setting gc_control->nr_free_secs = 1 make FG GC continue searching
>> for new victim.
> 
> Maybe we can try this instead of changing f2fs_expand_inode_data() logic:
> 1. call fggc via ioctl or trigger urgent gc via sysfs
> 2. fallocate on pinfile, goto 1) if it failed
> 
> But, anyway, I suspect it's risk, if there is no normal dirty section,
> FGGC will try to call f2fs_unpin_all_sections(), then migrate dirty section
> which has pinned blocks, that will cause more damage.
> 
> Can you please figure out why pinfile is fragmented first...

Hi Chao,

Thanks for your feedback. I just do a test to simulate the Android OTA 
createCowImage failed when dirty_segments is too large.

Simple reproduction steps:
1. In my case, dirty_segments=969, free_segments=96, free space = 1.7G, 
section:segment = 1:1
2. touch a.bin
3. f2fs_io pinfile set a.bin
4. fallocate -l 1.5G a.bin

And f2fs_fallocate() returns -11.

Although the urgent mode work fine, but it is not very convenient to 
control since AOPS has a great deal of code that calls fallocate.

I have tried 5 times to fallocate(), but GC always selects the same 
victim segno. So I think it is an issue.


The trace:
f2fs_get_victim: dev = (254,0), type = No TYPE, policy = (Foreground GC, 
LFS-mode, Greedy), victim = 624, cost = 19...

f2fs_gc_end: dev = (254,0), ret = 0, seg_freed = 0, sec_freed = 0, nodes 
= 117, dents = 0, imeta = 98, free_sec:50, free_seg:50, rsv_seg:47, 
prefree_seg:47


I dump the failed victim segno, block offset in segment and related 
inode ino:
do_garbage_collect: ino=33902 segno=624 off=132

The dump of pinfile 33902 info:
main_blkaddr                            [0x    2600 : 9728]
i_inline                                [0x      61 : 97]
inline shows the file is pinned (0x60)
i_addr[0x9]                             [0x   2f7b2 : 194482]
i_addr[0xa]                             [0x   2f7b3 : 194483]
i_addr[0xb]                             [0x   2f7b4 : 194484]
...
i_addr[0x1d]                            [0x   2f7c6 : 194502]
i_addr[0x1e]                            [0x   465af : 288175]
i_addr[0x1f]                            [0x   465b0 : 288176]
...
i_addr[0x21]                            [0x   465b2 : 288178]
i_addr[0x22]                            [0x   5046d : 328813]
i_addr[0x23]                            [0x   5046e : 328814]
i_addr[0x24]                            [0x   505b6 : 329142]
i_addr[0x25]                            [0x   505b7 : 329143]
i_addr[0x26]                            [0x   505b8 : 329144]
i_addr[0x27]                            [0x   50684 : 329348]
i_addr[0x28]                            [0x   50685 : 329349]

The file is created by logcat,and looks like indeed fragmented.

Calculate the block address:
624 * 512 + 132 + 9728(main_blkaddr) = 329348

So the i_addr[0x27] = 329348 is the failed block.

Regarding "why the pinfile is fragmented" you said, we use v5.15 + 
android U. Is it that v5.15 lacks some patches for special handling of 
pinfiles?

Thanks,


> 
> Thanks,
> 
>>
>> Signed-off-by: Jiucheng Xu <[email protected]>
>> ---
>>   fs/f2fs/file.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 
>> 8acdd94272a0ced448e0ba21635d702cfec10682..3e49a73bbf3a184a314e97bff9509a66c27eac00 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -1883,7 +1883,7 @@ static int f2fs_expand_inode_data(struct inode 
>> *inode, loff_t offset,
>>                       .init_gc_type = FG_GC,
>>                       .should_migrate_blocks = false,
>>                       .err_gc_skipped = true,
>> -                     .nr_free_secs = 0 };
>> +                     .nr_free_secs = 1 };
>>       pgoff_t pg_start, pg_end;
>>       loff_t new_size;
>>       loff_t off_end;
>>
>> ---
>> base-commit: b51f606aa323d553d786ed681a213f134dc688d6
>> change-id: 20260620-origin-dev-99cdccc83800
>>
>> Best regards,
> 



_______________________________________________
Linux-f2fs-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel