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SubjectRe: [f2fs-dev] [PATCH v4] f2fs: Fix indefinite loop in f2fs_gc()
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Hi Sahitya,

On 2019/9/17 13:33, Sahitya Tummala wrote:
> Hi Chao,
>
> On Fri, Sep 06, 2019 at 07:00:32PM +0800, Chao Yu wrote:
>> Hi Sahitya,
>>
>> Luckily, I can reproduce this issue with generic/269, and have sent another
>> patch for the issue, could you please check that one?
>>
>
> Thanks for the fix. The issue could not get reproduced yet, so could not make
> much progress on the customer case.

Alright, let me know if you get any clue or make progress on this issue.

Thanks,

>
> thanks,
>
>> Thanks,
>>
>> On 2019/8/7 22:06, Chao Yu wrote:
>>> On 2019-8-7 21:40, Sahitya Tummala wrote:
>>>> Policy - Foreground GC, LFS and greedy GC mode.
>>>>
>>>> Under this policy, f2fs_gc() loops forever to GC as it doesn't have
>>>> enough free segements to proceed and thus it keeps calling gc_more
>>>> for the same victim segment. This can happen if the selected victim
>>>> segment could not be GC'd due to failed blkaddr validity check i.e.
>>>> is_alive() returns false for the blocks set in current validity map.
>>>>
>>>> Fix this by keeping track of such invalid segments and skip those
>>>> segments for selection in get_victim_by_default() to avoid endless
>>>> GC loop under such error scenarios. Currently, add this logic under
>>>> CONFIG_F2FS_CHECK_FS to be able to root cause the issue in debug
>>>> version.
>>>>
>>>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
>>>> ---
>>>> v4: Cover all logic with CONFIG_F2FS_CHECK_FS
>>>>
>>>> fs/f2fs/gc.c | 31 +++++++++++++++++++++++++++++--
>>>> fs/f2fs/segment.c | 14 +++++++++++++-
>>>> fs/f2fs/segment.h | 3 +++
>>>> 3 files changed, 45 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>> index 8974672..cbcacbd 100644
>>>> --- a/fs/f2fs/gc.c
>>>> +++ b/fs/f2fs/gc.c
>>>> @@ -382,6 +382,16 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
>>>> nsearched++;
>>>> }
>>>>
>>>> +#ifdef CONFIG_F2FS_CHECK_FS
>>>> + /*
>>>> + * skip selecting the invalid segno (that is failed due to block
>>>> + * validity check failure during GC) to avoid endless GC loop in
>>>> + * such cases.
>>>> + */
>>>> + if (test_bit(segno, sm->invalid_segmap))
>>>> + goto next;
>>>> +#endif
>>>> +
>>>> secno = GET_SEC_FROM_SEG(sbi, segno);
>>>>
>>>> if (sec_usage_check(sbi, secno))
>>>> @@ -602,8 +612,15 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>> {
>>>> struct page *node_page;
>>>> nid_t nid;
>>>> - unsigned int ofs_in_node;
>>>> + unsigned int ofs_in_node, segno;
>>>> block_t source_blkaddr;
>>>> + unsigned long offset;
>>>> +#ifdef CONFIG_F2FS_CHECK_FS
>>>> + struct sit_info *sit_i = SIT_I(sbi);
>>>> +#endif
>>>> +
>>>> + segno = GET_SEGNO(sbi, blkaddr);
>>>> + offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);
>>>>
>>>> nid = le32_to_cpu(sum->nid);
>>>> ofs_in_node = le16_to_cpu(sum->ofs_in_node);
>>>> @@ -627,8 +644,18 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>> source_blkaddr = datablock_addr(NULL, node_page, ofs_in_node);
>>>> f2fs_put_page(node_page, 1);
>>>>
>>>> - if (source_blkaddr != blkaddr)
>>>> + if (source_blkaddr != blkaddr) {
>>>> +#ifdef CONFIG_F2FS_CHECK_FS
>>>
>>> unsigned int segno = GET_SEGNO(sbi, blkaddr);
>>> unsigned int offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);
>>>
>>> Should be local, otherwise it looks good to me, I think Jaegeuk can help to fix
>>> this while merging.
>>>
>>> Reviewed-by: Chao Yu <yuchao0@huawei.com>
>>>
>>> Thanks,
>>>
>>>> + if (unlikely(check_valid_map(sbi, segno, offset))) {
>>>> + if (!test_and_set_bit(segno, sit_i->invalid_segmap)) {
>>>> + f2fs_err(sbi, "mismatched blkaddr %u (source_blkaddr %u) in seg %u\n",
>>>> + blkaddr, source_blkaddr, segno);
>>>> + f2fs_bug_on(sbi, 1);
>>>> + }
>>>> + }
>>>> +#endif
>>>> return false;
>>>> + }
>>>> return true;
>>>> }
>>>>
>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>> index a661ac3..ee795b1 100644
>>>> --- a/fs/f2fs/segment.c
>>>> +++ b/fs/f2fs/segment.c
>>>> @@ -806,6 +806,9 @@ static void __remove_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
>>>> enum dirty_type dirty_type)
>>>> {
>>>> struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
>>>> +#ifdef CONFIG_F2FS_CHECK_FS
>>>> + struct sit_info *sit_i = SIT_I(sbi);
>>>> +#endif
>>>>
>>>> if (test_and_clear_bit(segno, dirty_i->dirty_segmap[dirty_type]))
>>>> dirty_i->nr_dirty[dirty_type]--;
>>>> @@ -817,9 +820,13 @@ static void __remove_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno,
>>>> if (test_and_clear_bit(segno, dirty_i->dirty_segmap[t]))
>>>> dirty_i->nr_dirty[t]--;
>>>>
>>>> - if (get_valid_blocks(sbi, segno, true) == 0)
>>>> + if (get_valid_blocks(sbi, segno, true) == 0) {
>>>> clear_bit(GET_SEC_FROM_SEG(sbi, segno),
>>>> dirty_i->victim_secmap);
>>>> +#ifdef CONFIG_F2FS_CHECK_FS
>>>> + clear_bit(segno, sit_i->invalid_segmap);
>>>> +#endif
>>>> + }
>>>> }
>>>> }
>>>>
>>>> @@ -4015,6 +4022,10 @@ static int build_sit_info(struct f2fs_sb_info *sbi)
>>>> sit_i->sit_bitmap_mir = kmemdup(src_bitmap, bitmap_size, GFP_KERNEL);
>>>> if (!sit_i->sit_bitmap_mir)
>>>> return -ENOMEM;
>>>> +
>>>> + sit_i->invalid_segmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
>>>> + if (!sit_i->invalid_segmap)
>>>> + return -ENOMEM;
>>>> #endif
>>>>
>>>> /* init SIT information */
>>>> @@ -4517,6 +4528,7 @@ static void destroy_sit_info(struct f2fs_sb_info *sbi)
>>>> kvfree(sit_i->sit_bitmap);
>>>> #ifdef CONFIG_F2FS_CHECK_FS
>>>> kvfree(sit_i->sit_bitmap_mir);
>>>> + kvfree(sit_i->invalid_segmap);
>>>> #endif
>>>> kvfree(sit_i);
>>>> }
>>>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
>>>> index b746028..9370d53 100644
>>>> --- a/fs/f2fs/segment.h
>>>> +++ b/fs/f2fs/segment.h
>>>> @@ -229,6 +229,9 @@ struct sit_info {
>>>> char *sit_bitmap; /* SIT bitmap pointer */
>>>> #ifdef CONFIG_F2FS_CHECK_FS
>>>> char *sit_bitmap_mir; /* SIT bitmap mirror */
>>>> +
>>>> + /* bitmap of segments to be ignored by GC in case of errors */
>>>> + unsigned long *invalid_segmap;
>>>> #endif
>>>> unsigned int bitmap_size; /* SIT bitmap size */
>>>>
>>>>
>>> .
>>>
>

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