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Subject[PATCH v2 4/6] f2fs: reduce cmd_lock coverage in __issue_discard_cmd
Date
From: Chao Yu <yuchao0@huawei.com>

__submit_discard_cmd may lead long latency due to exhaustion of I/O
request resource in block layer, so issuing all discard under cmd_lock
may lead to hangtask, in order to avoid that, let's reduce it's coverage.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
v2:
- rebase on last codes of Jaegeuk's dev-test branch.
fs/f2fs/segment.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e8fcc1eb4e0a..ba433828c170 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1158,14 +1158,14 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
int i, iter = 0, issued = 0;
bool io_interrupted = false;

- mutex_lock(&dcc->cmd_lock);
- f2fs_bug_on(sbi,
- !__check_rb_tree_consistence(sbi, &dcc->root));
- blk_start_plug(&plug);
for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
if (i + 1 < dpolicy->granularity)
break;
pend_list = &dcc->pend_list[i];
+
+ mutex_lock(&dcc->cmd_lock);
+ f2fs_bug_on(sbi, !__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);

@@ -1179,12 +1179,14 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
issued++;
skip:
if (++iter >= dpolicy->max_requests)
- goto out;
+ break;
}
+ blk_finish_plug(&plug);
+ mutex_unlock(&dcc->cmd_lock);
+
+ if (iter >= dpolicy->max_requests)
+ break;
}
-out:
- blk_finish_plug(&plug);
- mutex_unlock(&dcc->cmd_lock);

if (!issued && io_interrupted)
issued = -1;
--
2.14.1.145.gb3622a4ee
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