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bh=X2IjdLbfEZCadHZ8GMsouTlS6EmyNqi92pBzT66NYpY=; b=dm11fYxIbvYCZWVF2etQ/gBPw7 agpmJ5rD7VVcv8u0HrZI5Il546NMfCMCY+7cpBeaDDdJjKwqcjWLHrGUmVmwqkuJgX91fDuY3drTI MsYeKygCmHC3cbvoCf2nKh6I+vq3R5PFITY6SZsVoLmHpJV1WE8iDZgqCokCq8L2MXTI=; Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-3.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.2) id 1jJLuj-00H4EO-Q9 for linux-f2fs-devel@lists.sourceforge.net; Tue, 31 Mar 2020 18:47:10 +0000 Received: from localhost (unknown [104.132.1.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0F894207FF; Tue, 31 Mar 2020 18:46:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585680416; bh=YpdsDoiVHzsdfsRG8KkgIZ0+9jhzFhX4NZGYfworz/s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jTmueXNPeYP3+RbCPpfmqtZg8VIynDk2iSoPacbf8L7eEtVJtf9rOT2i3Nsy+Dtv+ SKoe/ro1QnZEHE/uoqDT7vwXbnoLv9zmIQ2CT0sweiLJEOOg1LZcjemYYMAuGhuS4f wit+aWnqbnS0BcanGg3WD43qlWRVuZhhTXoKGdiA= Date: Tue, 31 Mar 2020 11:46:55 -0700 From: Jaegeuk Kim To: Sahitya Tummala Message-ID: <20200331184655.GB198665@google.com> References: <1585550730-1858-1-git-send-email-stummala@codeaurora.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1585550730-1858-1-git-send-email-stummala@codeaurora.org> X-Headers-End: 1jJLuj-00H4EO-Q9 Subject: Re: [f2fs-dev] [PATCH v3] f2fs: fix long latency due to discard during umount X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net 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()? > > Signed-off-by: Sahitya Tummala > --- > 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. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel