On 06/21, Chao Yu wrote:
> If there is millions of discard entries cached in rb tree, each
> sanity check of it can cause very long latency as held cmd_lock
> blocking other lock grabbers.
>
> In other aspect, we have enabled the check very long time, as
> we see, there is no such inconsistent condition caused by bugs.
>
> But still we do not choose to kill it directly, instead, adding
> an flag to disable the check now, if there is related code change,
> we can reuse it to detect bugs.
>
> Signed-off-by: Yunlei He <heyun...@huawei.com>
> Signed-off-by: Chao Yu <yuch...@huawei.com>
> ---
> fs/f2fs/f2fs.h | 1 +
> fs/f2fs/segment.c | 10 +++++++---
> 2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 49c687173923..412e907920c2 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -309,6 +309,7 @@ struct discard_cmd_control {
> atomic_t issing_discard; /* # of issing discard */
> atomic_t discard_cmd_cnt; /* # of cached cmd count */
> struct rb_root root; /* root of discard rb-tree */
> + bool rbtree_check; /* config for consistence check
> */
> };
>
> /* for the list of fsync inodes, used only during recovery */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 6dbdf2c48fba..8c1d6c546fa0 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1199,8 +1199,9 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
> mutex_lock(&dcc->cmd_lock);
> if (list_empty(pend_list))
> goto next;
> - f2fs_bug_on(sbi,
> - !f2fs_check_rb_tree_consistence(sbi, &dcc->root));
> + if (dcc->rbtree_check)
unlikely()?
> + f2fs_bug_on(sbi, !f2fs_check_rb_tree_consistence(sbi,
> + &dcc->root));
> blk_start_plug(&plug);
> list_for_each_entry_safe(dc, tmp, pend_list, list) {
> f2fs_bug_on(sbi, dc->state != D_PREP);
> @@ -1752,6 +1753,7 @@ static int create_discard_cmd_control(struct
> f2fs_sb_info *sbi)
> dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
> dcc->undiscard_blks = 0;
> dcc->root = RB_ROOT;
> + dcc->rbtree_check = false;
>
> init_waitqueue_head(&dcc->discard_wait_queue);
> SM_I(sbi)->dcc_info = dcc;
> @@ -2381,7 +2383,9 @@ static void __issue_discard_cmd_range(struct
> f2fs_sb_info *sbi,
> issued = 0;
>
> mutex_lock(&dcc->cmd_lock);
> - f2fs_bug_on(sbi, !f2fs_check_rb_tree_consistence(sbi, &dcc->root));
> + if (dcc->rbtree_check)
unlikely()?
> + f2fs_bug_on(sbi, !f2fs_check_rb_tree_consistence(sbi,
> + &dcc->root));
>
> dc = (struct discard_cmd *)f2fs_lookup_rb_tree_ret(&dcc->root,
> NULL, start,
> --
> 2.18.0.rc1
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