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Subject[PATCH 3/3] f2fs: wait discard IO completion without cmd_lock held
Date
From: Chao Yu <yuchao0@huawei.com>

Wait discard IO completion outside cmd_lock to avoid long latency
of holding cmd_lock in IO busy scenario.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
fs/f2fs/segment.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 2b11119d9071..2b926db0588b 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1005,17 +1005,34 @@ static void __wait_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
struct list_head *wait_list = &(dcc->wait_list);
struct discard_cmd *dc, *tmp;
+ bool need_wait;
+
+next:
+ need_wait = false;

mutex_lock(&dcc->cmd_lock);
list_for_each_entry_safe(dc, tmp, wait_list, list) {
- if (!wait_cond || dc->state == D_DONE) {
- if (dc->ref)
- continue;
+ if (!wait_cond || (dc->state == D_DONE && !dc->ref)) {
wait_for_completion_io(&dc->wait);
__remove_discard_cmd(sbi, dc);
+ } else {
+ dc->ref++;
+ need_wait = true;
+ break;
}
}
mutex_unlock(&dcc->cmd_lock);
+
+ if (need_wait) {
+ wait_for_completion_io(&dc->wait);
+ mutex_lock(&dcc->cmd_lock);
+ f2fs_bug_on(sbi, dc->state != D_DONE);
+ dc->ref--;
+ if (!dc->ref)
+ __remove_discard_cmd(sbi, dc);
+ mutex_unlock(&dcc->cmd_lock);
+ goto next;
+ }
}

/* This should be covered by global mutex, &sit_i->sentry_lock */
--
2.12.2.575.gb14f27f
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