Messages in this thread Patch in this message | | | Date | Wed, 1 Apr 2020 14:52:01 +0530 | From | Sahitya Tummala <> | Subject | Re: [PATCH v3] f2fs: fix long latency due to discard during umount |
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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; 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@codeaurora.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.
-- -- Sent by a consultant of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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