在 3/12/2025 12:03 PM, Chao Yu 写道:
>
> On 3/12/25 11:19, Chunhai Guo wrote:
>> 在 1/20/2025 7:45 PM, Chao Yu 写道:
>>> On 1/19/25 22:08, Chunhai Guo wrote:
>>>> fstrim may miss candidates that need to be discarded, as shown in the
>>>> examples below.
>>>>
>>>> The root cause is that when cpc->reason is set with CP_DISCARD,
>>>> add_discard_addrs() expects that ckpt_valid_map and cur_valid_map have
>>>> been synced by seg_info_to_raw_sit() [1], and it tries to find the
>>>> candidates based on ckpt_valid_map and discard_map. However,
>>>> seg_info_to_raw_sit() does not actually run before
>>>> f2fs_exist_trim_candidates(), resulting in the failure.
>>>>
>>>> The code logic can be simplified for all cases by finding all the
>>>> discard blocks based only on discard_map. This might result in more
>>>> discard blocks being sent for the segment during the first checkpoint
>>>> after mounting, which were originally expected to be sent only in
>>>> fstrim. Regardless, these discard blocks should eventually be sent, and
>>>> the simplified code makes sense in this context.
>>>>
>>>> root# cp testfile /f2fs_mountpoint
>>>>
>>>> root# f2fs_io fiemap 0 1 /f2fs_mountpoint/testfile
>>>> Fiemap: offset = 0 len = 1
>>>> logical addr. physical addr. length flags
>>>> 0 0000000000000000 0000000406a00000 000000003d800000 00001000
>>>>
>>>> root# rm /f2fs_mountpoint/testfile
>>>>
>>>> root# fstrim -v -o 0x406a00000 -l 1024M /f2fs_mountpoint -- no candidate
>>>> is found
>>>> /f2fs_mountpoint: 0 B (0 bytes) trimmed
>>>>
>>>> Relevant code process of the root cause:
>>>> f2fs_trim_fs()
>>>> f2fs_write_checkpoint()
>>>> ...
>>>> if (cpc->reason & CP_DISCARD) {
>>>> if (!f2fs_exist_trim_candidates(sbi, cpc)) {
>>>> unblock_operations(sbi);
>>>> goto out; // No candidates are found here, and it
>>>> exits.
>>>> }
>>>> ...
>>>> }
>>>>
>>>> [1] Please refer to commit d7bc2484b8d4 ("f2fs: fix small discards not
>>>> to issue redundantly") for the relationship between
>>>> seg_info_to_raw_sit() and add_discard_addrs().
>>>>
>>>> Fixes: 25290fa5591d ("f2fs: return fs_trim if there is no candidate")
>>>> Signed-off-by: Chunhai Guo <guochun...@vivo.com>
>>>> ---
>>>> v1:
>>>> https://lore.kernel.org/linux-f2fs-devel/20250102101310.580277-1-guochun...@vivo.com/
>>>> v1->v2: Find all the discard blocks based only on discard_map in
>>>> add_discard_addrs().
>>>> ---
>>>> fs/f2fs/segment.c | 5 +----
>>>> 1 file changed, 1 insertion(+), 4 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>> index 13ee73a3c481..25ea892a42dd 100644
>>>> --- a/fs/f2fs/segment.c
>>>> +++ b/fs/f2fs/segment.c
>>>> @@ -2074,8 +2074,6 @@ static bool add_discard_addrs(struct f2fs_sb_info
>>>> *sbi, struct cp_control *cpc,
>>>> {
>>>> int entries = SIT_VBLOCK_MAP_SIZE / sizeof(unsigned long);
>>>> struct seg_entry *se = get_seg_entry(sbi, cpc->trim_start);
>>>> - unsigned long *cur_map = (unsigned long *)se->cur_valid_map;
>>>> - unsigned long *ckpt_map = (unsigned long *)se->ckpt_valid_map;
>>>> unsigned long *discard_map = (unsigned long *)se->discard_map;
>>>> unsigned long *dmap = SIT_I(sbi)->tmp_map;
>>>> unsigned int start = 0, end = -1;
>>>> @@ -2100,8 +2098,7 @@ static bool add_discard_addrs(struct f2fs_sb_info
>>>> *sbi, struct cp_control *cpc,
>>>>
>>>> /* SIT_VBLOCK_MAP_SIZE should be multiple of sizeof(unsigned long) */
>>>> for (i = 0; i < entries; i++)
>>>> - dmap[i] = force ? ~ckpt_map[i] & ~discard_map[i] :
>>>> - (cur_map[i] ^ ckpt_map[i]) & ckpt_map[i];
>>>> + dmap[i] = ~discard_map[i];
>>> discard is critical, we need more sanity check here, maybe:
>>>
>>> /* never issue discard to valid data's block address */
>>> f2fs_bug_on(sbi, (cur_map[i] ^ discard_map[i]) & cur_map[i]);
>>>
>>> Can you please check this?
>> Sure. I have added the BUG_ON check and performed the following tests
>> without issue:
>> 1. Ran xfstests and fsstress in the QEMU environment.
>>
>> 2. Ran monkey and reboot tests on ARM64 Android devices with the 6.6 kernel.
> Thanks, so it looks fine now, can you please update the patch w/ above
> f2fs_bug_on check?
OK. I will sent the v3 patch.
Thanks,
> Thanks,
>
>> Thanks,
>>
>>
>>> Thanks,
>>>
>>>> while (force || SM_I(sbi)->dcc_info->nr_discards <=
>>>> SM_I(sbi)->dcc_info->max_discards) {
>>
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