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

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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