| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <417fffb8-0638-e674-cf39-e54665080c36@huawei.com>
Date: Thu, 2 Apr 2020 17:32:13 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Sahitya Tummala <stummala@...eaurora.org>,
Jaegeuk Kim <jaegeuk@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] f2fs: fix long latency due to discard during umount
On 2020/4/1 17:22, Sahitya Tummala wrote:
> Hi Jaegeuk,
>
> On Tue, Mar 31, 2020 at 11:46:55AM -0700, Jaegeuk Kim wrote:
>> On 03/30, Sahitya Tummala wrote:
>>> 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.
>>
>> Sorry, Sahitya, but, do we really need to do like this? How about just
>> controlling # of outstanding discarding bios in __issue_discard_cmd()?
>
> Do you mean something like this?
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 1a62b27..860dd43 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1099,7 +1099,7 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
> } else if (discard_type == DPOLICY_FSTRIM) {
> dpolicy->io_aware = false;
> } else if (discard_type == DPOLICY_UMOUNT) {
> - dpolicy->max_requests = UINT_MAX;
> + dpolicy->max_requests = 30;
8 or 16?
It looks more simple than previous implementation.
Thanks,
> dpolicy->io_aware = false;
> /* we need to issue all to keep CP_TRIMMED_FLAG */
> dpolicy->granularity = 1;
> @@ -1470,12 +1470,14 @@ 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, issued;
> bool io_interrupted = false;
>
> if (dpolicy->timeout != 0)
> f2fs_update_time(sbi, dpolicy->timeout);
>
> +retry:
> + issued = 0;
> for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
> if (dpolicy->timeout != 0 &&
> f2fs_time_over(sbi, dpolicy->timeout))
> @@ -1522,6 +1524,11 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
> break;
> }
>
> + if (dpolicy->type == DPOLICY_UMOUNT && issued) {
> + __wait_all_discard_cmd(sbi, dpolicy);
> + goto retry;
> + }
> +
> if (!issued && io_interrupted)
> issued = -1;
>
> Thanks,
>
>>
>>>
>>> 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.
>
Powered by blists - more mailing lists