From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:55402 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753707AbeAJClO (ORCPT ); Tue, 9 Jan 2018 21:41:14 -0500 Date: Wed, 10 Jan 2018 10:40:53 +0800 From: Ming Lei To: Dmitry Osipenko 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 Subject: Re: [PATCH V4 13/45] block: blk-merge: try to make front segments in full size Message-ID: <20180110024046.GA18922@ming.t460p> References: <20171218122247.3488-1-ming.lei@redhat.com> <20171218122247.3488-14-ming.lei@redhat.com> <20180109023432.GB31067@ming.t460p> <20180109143339.GC4356@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org 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. Thanks, Ming From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 10 Jan 2018 10:40:53 +0800 From: Ming Lei To: Dmitry Osipenko 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 Subject: Re: [PATCH V4 13/45] block: blk-merge: try to make front segments in full size Message-ID: <20180110024046.GA18922@ming.t460p> References: <20171218122247.3488-1-ming.lei@redhat.com> <20171218122247.3488-14-ming.lei@redhat.com> <20180109023432.GB31067@ming.t460p> <20180109143339.GC4356@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: 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. Thanks, Ming -- 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