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Message-ID: <2b8f7a88-5204-a4ea-9f80-1056abb30d98@kernel.org>
Date: Wed, 7 Aug 2019 22:06:17 +0800
From: Chao Yu <chao@...nel.org>
To: Sahitya Tummala <stummala@...eaurora.org>,
Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <yuchao0@...wei.com>,
linux-f2fs-devel@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH v4] f2fs: Fix indefinite loop in f2fs_gc()
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@...eaurora.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@...wei.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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