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Fri, 13 Mar 2020 05:12:53 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id AD944C432C2; Fri, 13 Mar 2020 05:12:52 +0000 (UTC) Received: from codeaurora.org (blr-c-bdr-fw-01_GlobalNAT_AllZones-Outside.qualcomm.com [103.229.19.19]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) (Authenticated sender: stummala) by smtp.codeaurora.org (Postfix) with ESMTPSA id EFD02C433D2; Fri, 13 Mar 2020 05:12:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org EFD02C433D2 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=stummala@codeaurora.org Date: Fri, 13 Mar 2020 10:42:46 +0530 From: Sahitya Tummala To: Jaegeuk Kim Message-ID: <20200313051245.GK20234@codeaurora.org> References: <1584011671-20939-1-git-send-email-stummala@codeaurora.org> <20200312170242.GA185506@google.com> <20200313012604.GI20234@codeaurora.org> <20200313014535.GA72547@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200313014535.GA72547@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Headers-End: 1jCcdC-006HxG-Tl Subject: Re: [f2fs-dev] [PATCH] 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 Thu, Mar 12, 2020 at 06:45:35PM -0700, Jaegeuk Kim wrote: > On 03/13, Sahitya Tummala wrote: > > On Thu, Mar 12, 2020 at 10:02:42AM -0700, Jaegeuk Kim wrote: > > > On 03/12, 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. > > > > > > > > Signed-off-by: Sahitya Tummala > > > > --- > > > > 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); > > > > > > --> need to be DEFAULT_IO_TIMEOUT > > > > Yes, i will update it. > > > > > > > > > + __relocate_discard_cmd(dcc, dc); > > > > > > It seems we need to submit bio first, and then move dc to wait_list, if there's > > > no error, in __submit_discard_cmd(). > > > > Yes, that is not changed and it still happens for the failed request > > that is re-queued here too when it gets submitted again later. > > > > I am requeuing the discard request failed with -EAGAIN error back to > > dcc->pend_list[] from wait_list. It will call submit_bio() for this request > > and also move to wait_list when it calls __submit_discard_cmd() again next > > time. Please let me know if I am missing anything? > > This patch has no problem, but I'm thinking that __submit_discard_cmd() needs > to return with any values by assumption where the waiting list should have > submitted commands. I think dc->queued will indicated that dc is moved to wait_list. This can be used along with return value to take right action. Can you check if this works? diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index a06bbac..91df060 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -1478,7 +1478,7 @@ 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; if (dpolicy->timeout != 0) @@ -1517,8 +1517,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, break; } - __submit_discard_cmd(sbi, dpolicy, dc, &issued); - if (dc->error == -EAGAIN) { + err = __submit_discard_cmd(sbi, dpolicy, dc, &issued); + if (err && err != -EAGAIN) { + __remove_discard_cmd(sbi, dc); + } else if (err == -EAGAIN && dc->queued) { congestion_wait(BLK_RW_ASYNC, HZ/50); __relocate_discard_cmd(dcc, dc); } thanks, > > > > > Thanks, > > > > > > > > > + } > > > > > > > > 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. > > > > -- > > -- > > Sent by a consultant of the Qualcomm Innovation Center, Inc. > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- -- Sent by a consultant of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel