From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f67.google.com ([209.85.215.67]:42040 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932348AbeAJPlU (ORCPT ); Wed, 10 Jan 2018 10:41:20 -0500 Subject: Re: [PATCH V4 13/45] block: blk-merge: try to make front segments in full size To: Ming Lei Cc: Jens Axboe , Christoph Hellwig , Alexander Viro , Kent Overstreet , Huang Ying , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o , "Darrick J . Wong" , Coly Li , Filipe Manana , Ulf Hansson , linux-mmc@vger.kernel.org References: <20171218122247.3488-1-ming.lei@redhat.com> <20171218122247.3488-14-ming.lei@redhat.com> <20180109023432.GB31067@ming.t460p> <20180109143339.GC4356@ming.t460p> <20180110024046.GA18922@ming.t460p> From: Dmitry Osipenko Message-ID: Date: Wed, 10 Jan 2018 18:41:14 +0300 MIME-Version: 1.0 In-Reply-To: <20180110024046.GA18922@ming.t460p> Content-Type: text/plain; charset=utf-8 Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On 10.01.2018 05:40, Ming Lei wrote: > On Tue, Jan 09, 2018 at 08:02:53PM +0300, Dmitry Osipenko wrote: >> On 09.01.2018 17:33, Ming Lei wrote: >>> On Tue, Jan 09, 2018 at 04:18:39PM +0300, Dmitry Osipenko wrote: >>>> On 09.01.2018 05:34, Ming Lei wrote: >>>>> On Tue, Jan 09, 2018 at 12:09:27AM +0300, Dmitry Osipenko wrote: >>>>>> On 18.12.2017 15:22, Ming Lei wrote: >>>>>>> When merging one bvec into segment, if the bvec is too big >>>>>>> to merge, current policy is to move the whole bvec into another >>>>>>> new segment. >>>>>>> >>>>>>> This patchset changes the policy into trying to maximize size of >>>>>>> front segments, that means in above situation, part of bvec >>>>>>> is merged into current segment, and the remainder is put >>>>>>> into next segment. >>>>>>> >>>>>>> This patch prepares for support multipage bvec because >>>>>>> it can be quite common to see this case and we should try >>>>>>> to make front segments in full size. >>>>>>> >>>>>>> Signed-off-by: Ming Lei >>>>>>> --- >>>>>>> block/blk-merge.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++----- >>>>>>> 1 file changed, 49 insertions(+), 5 deletions(-) >>>>>>> >>>>>>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>>>>>> index a476337a8ff4..42ceb89bc566 100644 >>>>>>> --- a/block/blk-merge.c >>>>>>> +++ b/block/blk-merge.c >>>>>>> @@ -109,6 +109,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>>>>>> bool do_split = true; >>>>>>> struct bio *new = NULL; >>>>>>> const unsigned max_sectors = get_max_io_size(q, bio); >>>>>>> + unsigned advance = 0; >>>>>>> >>>>>>> bio_for_each_segment(bv, bio, iter) { >>>>>>> /* >>>>>>> @@ -134,12 +135,32 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>>>>>> } >>>>>>> >>>>>>> if (bvprvp && blk_queue_cluster(q)) { >>>>>>> - if (seg_size + bv.bv_len > queue_max_segment_size(q)) >>>>>>> - goto new_segment; >>>>>>> if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) >>>>>>> goto new_segment; >>>>>>> if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) >>>>>>> goto new_segment; >>>>>>> + if (seg_size + bv.bv_len > queue_max_segment_size(q)) { >>>>>>> + /* >>>>>>> + * On assumption is that initial value of >>>>>>> + * @seg_size(equals to bv.bv_len) won't be >>>>>>> + * bigger than max segment size, but will >>>>>>> + * becomes false after multipage bvec comes. >>>>>>> + */ >>>>>>> + advance = queue_max_segment_size(q) - seg_size; >>>>>>> + >>>>>>> + if (advance > 0) { >>>>>>> + seg_size += advance; >>>>>>> + sectors += advance >> 9; >>>>>>> + bv.bv_len -= advance; >>>>>>> + bv.bv_offset += advance; >>>>>>> + } >>>>>>> + >>>>>>> + /* >>>>>>> + * Still need to put remainder of current >>>>>>> + * bvec into a new segment. >>>>>>> + */ >>>>>>> + goto new_segment; >>>>>>> + } >>>>>>> >>>>>>> seg_size += bv.bv_len; >>>>>>> bvprv = bv; >>>>>>> @@ -161,6 +182,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>>>>>> seg_size = bv.bv_len; >>>>>>> sectors += bv.bv_len >> 9; >>>>>>> >>>>>>> + /* restore the bvec for iterator */ >>>>>>> + if (advance) { >>>>>>> + bv.bv_len += advance; >>>>>>> + bv.bv_offset -= advance; >>>>>>> + advance = 0; >>>>>>> + } >>>>>>> } >>>>>>> >>>>>>> do_split = false; >>>>>>> @@ -361,16 +388,29 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>>>>>> { >>>>>>> >>>>>>> int nbytes = bvec->bv_len; >>>>>>> + unsigned advance = 0; >>>>>>> >>>>>>> if (*sg && *cluster) { >>>>>>> - if ((*sg)->length + nbytes > queue_max_segment_size(q)) >>>>>>> - goto new_segment; >>>>>>> - >>>>>>> if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) >>>>>>> goto new_segment; >>>>>>> if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) >>>>>>> goto new_segment; >>>>>>> >>>>>>> + /* >>>>>>> + * try best to merge part of the bvec into previous >>>>>>> + * segment and follow same policy with >>>>>>> + * blk_bio_segment_split() >>>>>>> + */ >>>>>>> + if ((*sg)->length + nbytes > queue_max_segment_size(q)) { >>>>>>> + advance = queue_max_segment_size(q) - (*sg)->length; >>>>>>> + if (advance) { >>>>>>> + (*sg)->length += advance; >>>>>>> + bvec->bv_offset += advance; >>>>>>> + bvec->bv_len -= advance; >>>>>>> + } >>>>>>> + goto new_segment; >>>>>>> + } >>>>>>> + >>>>>>> (*sg)->length += nbytes; >>>>>>> } else { >>>>>>> new_segment: >>>>>>> @@ -393,6 +433,10 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>>>>>> >>>>>>> sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); >>>>>>> (*nsegs)++; >>>>>>> + >>>>>>> + /* for making iterator happy */ >>>>>>> + bvec->bv_offset -= advance; >>>>>>> + bvec->bv_len += advance; >>>>>>> } >>>>>>> *bvprv = *bvec; >>>>>>> } >>>>>>> >>>>>> >>>>>> Hello, >>>>>> >>>>>> This patch breaks MMC on next-20180108, in particular MMC doesn't work anymore >>>>>> with this patch on NVIDIA Tegra20: >>>>>> >>>>>> <3>[ 36.622253] print_req_error: I/O error, dev mmcblk1, sector 512 >>>>>> <3>[ 36.671233] print_req_error: I/O error, dev mmcblk2, sector 128 >>>>>> <3>[ 36.711308] print_req_error: I/O error, dev mmcblk1, sector 31325304 >>>>>> <3>[ 36.749232] print_req_error: I/O error, dev mmcblk2, sector 512 >>>>>> <3>[ 36.761235] print_req_error: I/O error, dev mmcblk1, sector 31325816 >>>>>> <3>[ 36.832039] print_req_error: I/O error, dev mmcblk2, sector 31259768 >>>>>> <3>[ 99.793248] print_req_error: I/O error, dev mmcblk1, sector 31323136 >>>>>> <3>[ 99.982043] print_req_error: I/O error, dev mmcblk1, sector 929792 >>>>>> <3>[ 99.986301] print_req_error: I/O error, dev mmcblk1, sector 930816 >>>>>> <3>[ 100.293624] print_req_error: I/O error, dev mmcblk1, sector 932864 >>>>>> <3>[ 100.466839] print_req_error: I/O error, dev mmcblk1, sector 947200 >>>>>> <3>[ 100.642955] print_req_error: I/O error, dev mmcblk1, sector 949248 >>>>>> <3>[ 100.818838] print_req_error: I/O error, dev mmcblk1, sector 230400 >>>>>> >>>>>> Any attempt of mounting MMC block dev ends with a kernel crash. Reverting this >>>>>> patch fixes the issue. >>>>> >>>>> Hi Dmitry, >>>>> >>>>> Thanks for your report! >>>>> >>>>> Could you share us what the segment limits are on your MMC? >>>>> >>>>> cat /sys/block/mmcN/queue/max_segment_size >>>>> cat /sys/block/mmcN/queue/max_segments >>>>> >>>>> Please test the following patch to see if your issue can be fixed? >>>>> >>>>> --- >>>>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>>>> index 446f63e076aa..cfab36c26608 100644 >>>>> --- a/block/blk-merge.c >>>>> +++ b/block/blk-merge.c >>>>> @@ -431,12 +431,14 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>>>> >>>>> sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); >>>>> (*nsegs)++; >>>>> + } >>>>> >>>>> + *bvprv = *bvec; >>>>> + if (advance) { >>>>> /* for making iterator happy */ >>>>> bvec->bv_offset -= advance; >>>>> bvec->bv_len += advance; >>>>> } >>>>> - *bvprv = *bvec; >>>>> } >>>>> >>>>> static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, >>>> >>>> Hi Ming, >>>> >>>> I've tried your patch and unfortunately it doesn't help with the issue. >>>> >>>> Here are the segment limits: >>>> >>>> # cat /sys/block/mmc*/queue/max_segment_size >>>> 65535 >>> >>> Hi Dmitry, >>> >>> The 'max_segment_size' of 65535 should be the reason, could you test the >>> following patch? >>> >>> --- >>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>> index 446f63e076aa..38a66e3e678e 100644 >>> --- a/block/blk-merge.c >>> +++ b/block/blk-merge.c >>> @@ -12,6 +12,8 @@ >>> >>> #include "blk.h" >>> >>> +#define sector_align(x) ALIGN_DOWN(x, 512) >>> + >>> static struct bio *blk_bio_discard_split(struct request_queue *q, >>> struct bio *bio, >>> struct bio_set *bs, >>> @@ -109,7 +111,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>> bool do_split = true; >>> struct bio *new = NULL; >>> const unsigned max_sectors = get_max_io_size(q, bio); >>> - unsigned advance = 0; >>> + int advance = 0; >>> >>> bio_for_each_segment(bv, bio, iter) { >>> /* >>> @@ -144,8 +146,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>> * bigger than max segment size, but this >>> * becomes false after multipage bvecs. >>> */ >>> - advance = queue_max_segment_size(q) - seg_size; >>> - >>> + advance = sector_align( >>> + queue_max_segment_size(q) - >>> + seg_size); >>> if (advance > 0) { >>> seg_size += advance; >>> sectors += advance >> 9; >>> @@ -386,7 +389,7 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>> { >>> >>> int nbytes = bvec->bv_len; >>> - unsigned advance = 0; >>> + int advance = 0; >>> >>> if (*sg && *cluster) { >>> if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) >>> @@ -400,8 +403,9 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>> * blk_bio_segment_split() >>> */ >>> if ((*sg)->length + nbytes > queue_max_segment_size(q)) { >>> - advance = queue_max_segment_size(q) - (*sg)->length; >>> - if (advance) { >>> + advance = sector_align(queue_max_segment_size(q) - >>> + (*sg)->length); >>> + if (advance > 0) { >>> (*sg)->length += advance; >>> bvec->bv_offset += advance; >>> bvec->bv_len -= advance; >>> @@ -431,12 +435,14 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>> >>> sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); >>> (*nsegs)++; >>> + } >>> >>> + *bvprv = *bvec; >>> + if (advance > 0) { >>> /* for making iterator happy */ >>> bvec->bv_offset -= advance; >>> bvec->bv_len += advance; >>> } >>> - *bvprv = *bvec; >>> } >>> >>> static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, >> >> This patch doesn't help either. > > OK, I will send a revert later. > > Thinking of the patch further, we don't need this kind of logic for > multipage bvec at all since almost all bvecs won't be contiguous if > bio_add_page() is used after multipage bvec is enabled. Revert works for me, thanks. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH V4 13/45] block: blk-merge: try to make front segments in full size To: Ming Lei Cc: Jens Axboe , Christoph Hellwig , Alexander Viro , Kent Overstreet , Huang Ying , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o , "Darrick J . Wong" , Coly Li , Filipe Manana , Ulf Hansson , linux-mmc@vger.kernel.org References: <20171218122247.3488-1-ming.lei@redhat.com> <20171218122247.3488-14-ming.lei@redhat.com> <20180109023432.GB31067@ming.t460p> <20180109143339.GC4356@ming.t460p> <20180110024046.GA18922@ming.t460p> From: Dmitry Osipenko Message-ID: Date: Wed, 10 Jan 2018 18:41:14 +0300 MIME-Version: 1.0 In-Reply-To: <20180110024046.GA18922@ming.t460p> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: On 10.01.2018 05:40, Ming Lei wrote: > On Tue, Jan 09, 2018 at 08:02:53PM +0300, Dmitry Osipenko wrote: >> On 09.01.2018 17:33, Ming Lei wrote: >>> On Tue, Jan 09, 2018 at 04:18:39PM +0300, Dmitry Osipenko wrote: >>>> On 09.01.2018 05:34, Ming Lei wrote: >>>>> On Tue, Jan 09, 2018 at 12:09:27AM +0300, Dmitry Osipenko wrote: >>>>>> On 18.12.2017 15:22, Ming Lei wrote: >>>>>>> When merging one bvec into segment, if the bvec is too big >>>>>>> to merge, current policy is to move the whole bvec into another >>>>>>> new segment. >>>>>>> >>>>>>> This patchset changes the policy into trying to maximize size of >>>>>>> front segments, that means in above situation, part of bvec >>>>>>> is merged into current segment, and the remainder is put >>>>>>> into next segment. >>>>>>> >>>>>>> This patch prepares for support multipage bvec because >>>>>>> it can be quite common to see this case and we should try >>>>>>> to make front segments in full size. >>>>>>> >>>>>>> Signed-off-by: Ming Lei >>>>>>> --- >>>>>>> block/blk-merge.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++----- >>>>>>> 1 file changed, 49 insertions(+), 5 deletions(-) >>>>>>> >>>>>>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>>>>>> index a476337a8ff4..42ceb89bc566 100644 >>>>>>> --- a/block/blk-merge.c >>>>>>> +++ b/block/blk-merge.c >>>>>>> @@ -109,6 +109,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>>>>>> bool do_split = true; >>>>>>> struct bio *new = NULL; >>>>>>> const unsigned max_sectors = get_max_io_size(q, bio); >>>>>>> + unsigned advance = 0; >>>>>>> >>>>>>> bio_for_each_segment(bv, bio, iter) { >>>>>>> /* >>>>>>> @@ -134,12 +135,32 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>>>>>> } >>>>>>> >>>>>>> if (bvprvp && blk_queue_cluster(q)) { >>>>>>> - if (seg_size + bv.bv_len > queue_max_segment_size(q)) >>>>>>> - goto new_segment; >>>>>>> if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) >>>>>>> goto new_segment; >>>>>>> if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) >>>>>>> goto new_segment; >>>>>>> + if (seg_size + bv.bv_len > queue_max_segment_size(q)) { >>>>>>> + /* >>>>>>> + * On assumption is that initial value of >>>>>>> + * @seg_size(equals to bv.bv_len) won't be >>>>>>> + * bigger than max segment size, but will >>>>>>> + * becomes false after multipage bvec comes. >>>>>>> + */ >>>>>>> + advance = queue_max_segment_size(q) - seg_size; >>>>>>> + >>>>>>> + if (advance > 0) { >>>>>>> + seg_size += advance; >>>>>>> + sectors += advance >> 9; >>>>>>> + bv.bv_len -= advance; >>>>>>> + bv.bv_offset += advance; >>>>>>> + } >>>>>>> + >>>>>>> + /* >>>>>>> + * Still need to put remainder of current >>>>>>> + * bvec into a new segment. >>>>>>> + */ >>>>>>> + goto new_segment; >>>>>>> + } >>>>>>> >>>>>>> seg_size += bv.bv_len; >>>>>>> bvprv = bv; >>>>>>> @@ -161,6 +182,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>>>>>> seg_size = bv.bv_len; >>>>>>> sectors += bv.bv_len >> 9; >>>>>>> >>>>>>> + /* restore the bvec for iterator */ >>>>>>> + if (advance) { >>>>>>> + bv.bv_len += advance; >>>>>>> + bv.bv_offset -= advance; >>>>>>> + advance = 0; >>>>>>> + } >>>>>>> } >>>>>>> >>>>>>> do_split = false; >>>>>>> @@ -361,16 +388,29 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>>>>>> { >>>>>>> >>>>>>> int nbytes = bvec->bv_len; >>>>>>> + unsigned advance = 0; >>>>>>> >>>>>>> if (*sg && *cluster) { >>>>>>> - if ((*sg)->length + nbytes > queue_max_segment_size(q)) >>>>>>> - goto new_segment; >>>>>>> - >>>>>>> if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) >>>>>>> goto new_segment; >>>>>>> if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) >>>>>>> goto new_segment; >>>>>>> >>>>>>> + /* >>>>>>> + * try best to merge part of the bvec into previous >>>>>>> + * segment and follow same policy with >>>>>>> + * blk_bio_segment_split() >>>>>>> + */ >>>>>>> + if ((*sg)->length + nbytes > queue_max_segment_size(q)) { >>>>>>> + advance = queue_max_segment_size(q) - (*sg)->length; >>>>>>> + if (advance) { >>>>>>> + (*sg)->length += advance; >>>>>>> + bvec->bv_offset += advance; >>>>>>> + bvec->bv_len -= advance; >>>>>>> + } >>>>>>> + goto new_segment; >>>>>>> + } >>>>>>> + >>>>>>> (*sg)->length += nbytes; >>>>>>> } else { >>>>>>> new_segment: >>>>>>> @@ -393,6 +433,10 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>>>>>> >>>>>>> sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); >>>>>>> (*nsegs)++; >>>>>>> + >>>>>>> + /* for making iterator happy */ >>>>>>> + bvec->bv_offset -= advance; >>>>>>> + bvec->bv_len += advance; >>>>>>> } >>>>>>> *bvprv = *bvec; >>>>>>> } >>>>>>> >>>>>> >>>>>> Hello, >>>>>> >>>>>> This patch breaks MMC on next-20180108, in particular MMC doesn't work anymore >>>>>> with this patch on NVIDIA Tegra20: >>>>>> >>>>>> <3>[ 36.622253] print_req_error: I/O error, dev mmcblk1, sector 512 >>>>>> <3>[ 36.671233] print_req_error: I/O error, dev mmcblk2, sector 128 >>>>>> <3>[ 36.711308] print_req_error: I/O error, dev mmcblk1, sector 31325304 >>>>>> <3>[ 36.749232] print_req_error: I/O error, dev mmcblk2, sector 512 >>>>>> <3>[ 36.761235] print_req_error: I/O error, dev mmcblk1, sector 31325816 >>>>>> <3>[ 36.832039] print_req_error: I/O error, dev mmcblk2, sector 31259768 >>>>>> <3>[ 99.793248] print_req_error: I/O error, dev mmcblk1, sector 31323136 >>>>>> <3>[ 99.982043] print_req_error: I/O error, dev mmcblk1, sector 929792 >>>>>> <3>[ 99.986301] print_req_error: I/O error, dev mmcblk1, sector 930816 >>>>>> <3>[ 100.293624] print_req_error: I/O error, dev mmcblk1, sector 932864 >>>>>> <3>[ 100.466839] print_req_error: I/O error, dev mmcblk1, sector 947200 >>>>>> <3>[ 100.642955] print_req_error: I/O error, dev mmcblk1, sector 949248 >>>>>> <3>[ 100.818838] print_req_error: I/O error, dev mmcblk1, sector 230400 >>>>>> >>>>>> Any attempt of mounting MMC block dev ends with a kernel crash. Reverting this >>>>>> patch fixes the issue. >>>>> >>>>> Hi Dmitry, >>>>> >>>>> Thanks for your report! >>>>> >>>>> Could you share us what the segment limits are on your MMC? >>>>> >>>>> cat /sys/block/mmcN/queue/max_segment_size >>>>> cat /sys/block/mmcN/queue/max_segments >>>>> >>>>> Please test the following patch to see if your issue can be fixed? >>>>> >>>>> --- >>>>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>>>> index 446f63e076aa..cfab36c26608 100644 >>>>> --- a/block/blk-merge.c >>>>> +++ b/block/blk-merge.c >>>>> @@ -431,12 +431,14 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>>>> >>>>> sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); >>>>> (*nsegs)++; >>>>> + } >>>>> >>>>> + *bvprv = *bvec; >>>>> + if (advance) { >>>>> /* for making iterator happy */ >>>>> bvec->bv_offset -= advance; >>>>> bvec->bv_len += advance; >>>>> } >>>>> - *bvprv = *bvec; >>>>> } >>>>> >>>>> static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, >>>> >>>> Hi Ming, >>>> >>>> I've tried your patch and unfortunately it doesn't help with the issue. >>>> >>>> Here are the segment limits: >>>> >>>> # cat /sys/block/mmc*/queue/max_segment_size >>>> 65535 >>> >>> Hi Dmitry, >>> >>> The 'max_segment_size' of 65535 should be the reason, could you test the >>> following patch? >>> >>> --- >>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>> index 446f63e076aa..38a66e3e678e 100644 >>> --- a/block/blk-merge.c >>> +++ b/block/blk-merge.c >>> @@ -12,6 +12,8 @@ >>> >>> #include "blk.h" >>> >>> +#define sector_align(x) ALIGN_DOWN(x, 512) >>> + >>> static struct bio *blk_bio_discard_split(struct request_queue *q, >>> struct bio *bio, >>> struct bio_set *bs, >>> @@ -109,7 +111,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>> bool do_split = true; >>> struct bio *new = NULL; >>> const unsigned max_sectors = get_max_io_size(q, bio); >>> - unsigned advance = 0; >>> + int advance = 0; >>> >>> bio_for_each_segment(bv, bio, iter) { >>> /* >>> @@ -144,8 +146,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, >>> * bigger than max segment size, but this >>> * becomes false after multipage bvecs. >>> */ >>> - advance = queue_max_segment_size(q) - seg_size; >>> - >>> + advance = sector_align( >>> + queue_max_segment_size(q) - >>> + seg_size); >>> if (advance > 0) { >>> seg_size += advance; >>> sectors += advance >> 9; >>> @@ -386,7 +389,7 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>> { >>> >>> int nbytes = bvec->bv_len; >>> - unsigned advance = 0; >>> + int advance = 0; >>> >>> if (*sg && *cluster) { >>> if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) >>> @@ -400,8 +403,9 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>> * blk_bio_segment_split() >>> */ >>> if ((*sg)->length + nbytes > queue_max_segment_size(q)) { >>> - advance = queue_max_segment_size(q) - (*sg)->length; >>> - if (advance) { >>> + advance = sector_align(queue_max_segment_size(q) - >>> + (*sg)->length); >>> + if (advance > 0) { >>> (*sg)->length += advance; >>> bvec->bv_offset += advance; >>> bvec->bv_len -= advance; >>> @@ -431,12 +435,14 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, >>> >>> sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); >>> (*nsegs)++; >>> + } >>> >>> + *bvprv = *bvec; >>> + if (advance > 0) { >>> /* for making iterator happy */ >>> bvec->bv_offset -= advance; >>> bvec->bv_len += advance; >>> } >>> - *bvprv = *bvec; >>> } >>> >>> static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv, >> >> This patch doesn't help either. > > OK, I will send a revert later. > > Thinking of the patch further, we don't need this kind of logic for > multipage bvec at all since almost all bvecs won't be contiguous if > bio_add_page() is used after multipage bvec is enabled. Revert works for me, thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org