lkml.org 
[lkml]   [2020]   [Mar]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] f2fs: fix long latency due to discard during umount
Date
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@codeaurora.org>
---
v2:
- Handle the case where a dc can have multiple bios associated with it

fs/f2fs/f2fs.h | 1 +
fs/f2fs/segment.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++-------
2 files changed, 74 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 12a197e..67b8dcc 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -340,6 +340,7 @@ struct discard_cmd_control {
struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
struct list_head wait_list; /* store on-flushing entries */
struct list_head fstrim_list; /* in-flight discard from fstrim */
+ struct list_head retry_list; /* list of cmds to retry */
wait_queue_head_t discard_wait_queue; /* waiting queue for wake-up */
unsigned int discard_wake; /* to wake up discard thread */
struct mutex cmd_lock;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fb3e531..4162c76 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;
- block_t lstart, start, len, total_len;
+ int flag;
+ block_t lstart, start, len, total_len, orig_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;

@@ -1139,7 +1145,7 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
lstart = dc->lstart;
start = dc->start;
len = dc->len;
- total_len = len;
+ orig_len = total_len = len;

dc->len = 0;

@@ -1203,6 +1209,14 @@ 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) {
+ dc->len = orig_len;
+ list_move(&dc->list, &dcc->retry_list);
+ err = dc->error;
+ break;
+ }
+ }

atomic_inc(&dcc->issued_discard);

@@ -1463,6 +1477,40 @@ static unsigned int __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi,
return issued;
}

+static bool __should_discard_retry(struct f2fs_sb_info *sbi,
+ struct discard_policy *dpolicy)
+{
+ struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+ struct discard_cmd *dc, *tmp;
+ bool retry = false;
+ unsigned long flags;
+
+ if (dpolicy->type != DPOLICY_UMOUNT)
+ f2fs_bug_on(sbi, 1);
+
+ mutex_lock(&dcc->cmd_lock);
+ list_for_each_entry_safe(dc, tmp, &(dcc->retry_list), list) {
+ if (dpolicy->timeout != 0 &&
+ f2fs_time_over(sbi, dpolicy->timeout)) {
+ retry = false;
+ break;
+ }
+
+ spin_lock_irqsave(&dc->lock, flags);
+ if (!dc->bio_ref) {
+ dc->state = D_PREP;
+ dc->error = 0;
+ reinit_completion(&dc->wait);
+ __relocate_discard_cmd(dcc, dc);
+ retry = true;
+ }
+ spin_unlock_irqrestore(&dc->lock, flags);
+ }
+ mutex_unlock(&dcc->cmd_lock);
+
+ return retry;
+}
+
static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
struct discard_policy *dpolicy)
{
@@ -1470,12 +1518,13 @@ 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;

if (dpolicy->timeout != 0)
f2fs_update_time(sbi, dpolicy->timeout);

+retry:
for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
if (dpolicy->timeout != 0 &&
f2fs_time_over(sbi, dpolicy->timeout))
@@ -1509,7 +1558,10 @@ 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);

if (issued >= dpolicy->max_requests)
break;
@@ -1522,6 +1574,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
break;
}

+ if (!list_empty(&dcc->retry_list) &&
+ __should_discard_retry(sbi, dpolicy))
+ goto retry;
+
if (!issued && io_interrupted)
issued = -1;

@@ -1613,6 +1669,12 @@ static unsigned int __wait_discard_cmd_range(struct f2fs_sb_info *sbi,
goto next;
}

+ if (dpolicy->type == DPOLICY_UMOUNT &&
+ !list_empty(&dcc->retry_list)) {
+ wait_list = &dcc->retry_list;
+ goto next;
+ }
+
return trimmed;
}

@@ -2051,6 +2113,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
for (i = 0; i < MAX_PLIST_NUM; i++)
INIT_LIST_HEAD(&dcc->pend_list[i]);
INIT_LIST_HEAD(&dcc->wait_list);
+ INIT_LIST_HEAD(&dcc->retry_list);
INIT_LIST_HEAD(&dcc->fstrim_list);
mutex_init(&dcc->cmd_lock);
atomic_set(&dcc->issued_discard, 0);
--
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.
\
 
 \ /
  Last update: 2020-03-18 05:45    [W:0.090 / U:38.632 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site