Messages in this thread Patch in this message | | | From | Sahitya Tummala <> | Subject | [PATCH] f2fs: fix long latency due to discard during umount | Date | Thu, 12 Mar 2020 16:44:31 +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> --- fs/f2fs/segment.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index fb3e531..a06bbac 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -1124,10 +1124,13 @@ 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; @@ -1203,6 +1206,11 @@ 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) && (dc->error == -EAGAIN)) { + dc->state = D_PREP; + err = dc->error; + break; + } atomic_inc(&dcc->issued_discard); @@ -1510,6 +1518,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, } __submit_discard_cmd(sbi, dpolicy, dc, &issued); + if (dc->error == -EAGAIN) { + congestion_wait(BLK_RW_ASYNC, HZ/50); + __relocate_discard_cmd(dcc, dc); + } if (issued >= dpolicy->max_requests) break; -- 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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