Messages in this thread Patch in this message | | | From | Sahitya Tummala <> | Subject | [PATCH v3] f2fs: fix long latency due to discard during umount | Date | Mon, 30 Mar 2020 12:15:30 +0530 |
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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> --- 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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