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Message-Id: <1585550730-1858-1-git-send-email-stummala@codeaurora.org>
Date: Mon, 30 Mar 2020 12:15:30 +0530
From: Sahitya Tummala <stummala@...eaurora.org>
To: Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <yuchao0@...wei.com>,
linux-f2fs-devel@...ts.sourceforge.net
Cc: Sahitya Tummala <stummala@...eaurora.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH v3] f2fs: fix long latency due to discard during umount
F2FS already has a default timeout of 5 secs for discards that
can be issued during umount, but it can take more than the 5 sec
timeout if the underlying UFS device queue is already full and there
are no more available free tags to be used. In that case, submit_bio()
will wait for the already queued discard requests to complete to get
a free tag, which can potentially take way more than 5 sec.
Fix this by submitting the discard requests with REQ_NOWAIT
flags during umount. This will return -EAGAIN for UFS queue/tag full
scenario without waiting in the context of submit_bio(). The FS can
then handle these requests by retrying again within the stipulated
discard timeout period to avoid long latencies.
Signed-off-by: Sahitya Tummala <stummala@...eaurora.org>
---
v3:
-Handle the regression reported by Chao with v2.
-simplify the logic to split the dc with multiple bios incase any bio returns
EAGAIN and retry those new dc within 5 sec timeout.
fs/f2fs/segment.c | 65 +++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 51 insertions(+), 14 deletions(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fb3e531..55d18c7 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1029,13 +1029,16 @@ static void f2fs_submit_discard_endio(struct bio *bio)
struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
unsigned long flags;
- dc->error = blk_status_to_errno(bio->bi_status);
-
spin_lock_irqsave(&dc->lock, flags);
+ if (!dc->error)
+ dc->error = blk_status_to_errno(bio->bi_status);
+
dc->bio_ref--;
- if (!dc->bio_ref && dc->state == D_SUBMIT) {
- dc->state = D_DONE;
- complete_all(&dc->wait);
+ if (!dc->bio_ref) {
+ if (dc->error || dc->state == D_SUBMIT) {
+ dc->state = D_DONE;
+ complete_all(&dc->wait);
+ }
}
spin_unlock_irqrestore(&dc->lock, flags);
bio_put(bio);
@@ -1124,10 +1127,13 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
struct list_head *wait_list = (dpolicy->type == DPOLICY_FSTRIM) ?
&(dcc->fstrim_list) : &(dcc->wait_list);
- int flag = dpolicy->sync ? REQ_SYNC : 0;
+ int flag;
block_t lstart, start, len, total_len;
int err = 0;
+ flag = dpolicy->sync ? REQ_SYNC : 0;
+ flag |= dpolicy->type == DPOLICY_UMOUNT ? REQ_NOWAIT : 0;
+
if (dc->state != D_PREP)
return 0;
@@ -1192,10 +1198,6 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
dc->bio_ref++;
spin_unlock_irqrestore(&dc->lock, flags);
- atomic_inc(&dcc->queued_discard);
- dc->queued++;
- list_move_tail(&dc->list, wait_list);
-
/* sanity check on discard range */
__check_sit_bitmap(sbi, lstart, lstart + len);
@@ -1203,6 +1205,29 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
bio->bi_end_io = f2fs_submit_discard_endio;
bio->bi_opf |= flag;
submit_bio(bio);
+ if (flag & REQ_NOWAIT) {
+ if (dc->error == -EAGAIN) {
+ spin_lock_irqsave(&dc->lock, flags);
+ dc->len -= len;
+ if (!dc->len) {
+ dc->len = total_len;
+ dc->state = D_PREP;
+ reinit_completion(&dc->wait);
+ } else {
+ dcc->undiscard_blks -= total_len;
+ if (dc->state == D_PARTIAL)
+ dc->state = D_SUBMIT;
+ }
+ err = dc->error;
+ dc->error = 0;
+ spin_unlock_irqrestore(&dc->lock, flags);
+ break;
+ }
+ }
+
+ atomic_inc(&dcc->queued_discard);
+ dc->queued++;
+ list_move_tail(&dc->list, wait_list);
atomic_inc(&dcc->issued_discard);
@@ -1214,8 +1239,9 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
len = total_len;
}
- if (!err && len)
- __update_discard_tree_range(sbi, bdev, lstart, start, len);
+ if ((!err || err == -EAGAIN) && total_len && dc->start != start)
+ __update_discard_tree_range(sbi, bdev, lstart, start,
+ total_len);
return err;
}
@@ -1470,12 +1496,15 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
struct list_head *pend_list;
struct discard_cmd *dc, *tmp;
struct blk_plug plug;
- int i, issued = 0;
+ int i, err, issued = 0;
bool io_interrupted = false;
+ bool retry;
if (dpolicy->timeout != 0)
f2fs_update_time(sbi, dpolicy->timeout);
+retry:
+ retry = false;
for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
if (dpolicy->timeout != 0 &&
f2fs_time_over(sbi, dpolicy->timeout))
@@ -1509,7 +1538,12 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
break;
}
- __submit_discard_cmd(sbi, dpolicy, dc, &issued);
+ err = __submit_discard_cmd(sbi, dpolicy, dc, &issued);
+ if (err == -EAGAIN) {
+ congestion_wait(BLK_RW_ASYNC,
+ DEFAULT_IO_TIMEOUT);
+ retry = true;
+ }
if (issued >= dpolicy->max_requests)
break;
@@ -1522,6 +1556,9 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
break;
}
+ if (retry)
+ goto retry;
+
if (!issued && io_interrupted)
issued = -1;
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
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