majianpeng
2012-Jul-30 07:13 UTC
[Ocfs2-devel] [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.
When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page, it will use bi_rw. Fox example, in functiion __bio_add_page,it will call merge_bvec_fn(). The merge_bvec_fn of raid456 will use the bi_rw to judge the merge.>> if ((bvm->bi_rw & 1) == WRITE) >> return biovec->bv_len; /* always allow writes to be mergeable */Jianpeng Ma (8): Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). Evalue bio->bi_rw after calling bio_alloc() and before calling bio_add_page(). block/blk-lib.c | 1 + drivers/block/xen-blkback/blkback.c | 1 + fs/btrfs/check-integrity.c | 1 + fs/direct-io.c | 1 + fs/ext4/page-io.c | 1 + fs/jfs/jfs_metapage.c | 1 + fs/ocfs2/cluster/heartbeat.c | 8 +++++--- fs/xfs/xfs_aops.c | 2 ++ fs/xfs/xfs_buf.c | 1 + 9 files changed, 14 insertions(+), 3 deletions(-) -- 1.7.9.5
Konrad Rzeszutek Wilk
2012-Jul-30 15:48 UTC
[Ocfs2-devel] [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.
On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote:> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page,What about submit_bio? That sets the bi_rw as well?> it will use bi_rw. > Fox example, in functiion __bio_add_page,it will call merge_bvec_fn().function.> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. > >> if ((bvm->bi_rw & 1) == WRITE) > >> return biovec->bv_len; /* always allow writes to be mergeable */So what does that mean? Without this patch what happens?> > > Jianpeng Ma (8):Can you collapse all of this in just one patch?> Evalue bio->bi_rw after calling bio_alloc() and before callingIt is 'evaluate'> bio_add_page(). > Evalue bio->bi_rw after calling bio_alloc() and before calling > bio_add_page(). > Evalue bio->bi_rw after calling bio_alloc() and before calling > bio_add_page(). > Evalue bio->bi_rw after calling bio_alloc() and before calling > bio_add_page(). > Evalue bio->bi_rw after calling bio_alloc() and before calling > bio_add_page(). > Evalue bio->bi_rw after calling bio_alloc() and before calling > bio_add_page(). > Evalue bio->bi_rw after calling bio_alloc() and before calling > bio_add_page(). > Evalue bio->bi_rw after calling bio_alloc() and before calling > bio_add_page(). > > block/blk-lib.c | 1 + > drivers/block/xen-blkback/blkback.c | 1 +I am not really sure if that is correct. Does 'submit_bio' not do the job properly?> fs/btrfs/check-integrity.c | 1 + > fs/direct-io.c | 1 + > fs/ext4/page-io.c | 1 + > fs/jfs/jfs_metapage.c | 1 + > fs/ocfs2/cluster/heartbeat.c | 8 +++++--- > fs/xfs/xfs_aops.c | 2 ++ > fs/xfs/xfs_buf.c | 1 + > 9 files changed, 14 insertions(+), 3 deletions(-) > > -- > 1.7.9.5
Dave Chinner
2012-Jul-30 21:42 UTC
[Ocfs2-devel] [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.
On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote:> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page, > it will use bi_rw. > Fox example, in functiion __bio_add_page,it will call merge_bvec_fn(). > The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. > >> if ((bvm->bi_rw & 1) == WRITE) > >> return biovec->bv_len; /* always allow writes to be mergeable */So if bio_add_page() requires bi_rw to be set, then shouldn't it be set up for every caller? I noticed there are about 50 call sites for bio_add_page(), and you've only touched about 10 of them. Indeed, I notice that the RAID0/1 code uses bio_add_page, and as that can be stacked on top of RAID456, it also needs to set bi_rw correctly. As a result, your patch set is nowhere near complete, not does it document that bio_add_page requires that bi_rw be set before calling (which is the new API requirement, AFAICT). So, my question is whether the RAID456 code is doing something valid. That write optimisation is clearly not enabled for a significant amount of code and filesystems, so the first thing to do is quantify the benefit of the optimisation. I can't evalute the merit of this change without data telling me it is worthwhile, and it's a lot of code to churn for no benefit.... Cheers, Dave. -- Dave Chinner david at fromorbit.com
majianpeng
2012-Jul-31 00:55 UTC
Re: [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.
On 2012-07-31 05:42 Dave Chinner <david@fromorbit.com> Wrote:>On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote: >> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page, >> it will use bi_rw. >> Fox example, in functiion __bio_add_page,it will call merge_bvec_fn(). >> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. >> >> if ((bvm->bi_rw & 1) == WRITE) >> >> return biovec->bv_len; /* always allow writes to be mergeable */ > >So if bio_add_page() requires bi_rw to be set, then shouldn''t it be >set up for every caller? I noticed there are about 50 call sites for >bio_add_page(), and you''ve only touched about 10 of them. Indeed, I >notice that the RAID0/1 code uses bio_add_page, and as that can be >stacked on top of RAID456, it also needs to set bi_rw correctly. >As a result, your patch set is nowhere near complete, not does it >document that bio_add_page requires that bi_rw be set before calling >(which is the new API requirement, AFAICT).There are many place call bio_add_page and I send some of those. Because my abilty, so I only send some patchs which i understand clearly. In __bio_add_page:>>if (q->merge_bvec_fn) { >> struct bvec_merge_data bvm = { >> /* prev_bvec is already charged in >> bi_size, discharge it in order to >> simulate merging updated prev_bvec >> as new bvec. */ >> .bi_bdev = bio->bi_bdev, >> .bi_sector = bio->bi_sector, >> .bi_size = bio->bi_size - prev_bv_len, >> .bi_rw = bio->bi_rw, >> };it used bio->bi_rw. Before raid5_mergeable_bvec appearing, in kernel ''merge_bvec_fn'' did not use bio->bi_rw. But i think we shold not suppose bi_rw not meanless. And I think we not need an new API to do. Most used bio_alloc and bio_add_page, like this:>> bio = bio_alloc(gfp_mask, 1); >> if (!bio) >> ret = -ENOMEM;>> bio->bi_sector = sector; >> bio->bi_end_io = bio_batch_end_io; >> bio->bi_bdev = bdev; >> bio->bi_private = &bb;We only add bio->bi_rw = value; But we shold modify Document for this.> >So, my question is whether the RAID456 code is doing something >valid. That write optimisation is clearly not enabled for a >significant amount of code and filesystems, so the first thing to do >is quantify the benefit of the optimisation. I can''t evalute the >merit of this change without data telling me it is worthwhile, and >it''s a lot of code to churn for no benefit.... >Sorry, we do not think the ''merge_bvec_fn'' did not use bi_rw.>Cheers, > >Dave. >-- >Dave Chinner >david@fromorbit.com------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today''s security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
Dave Chinner
2012-Jul-31 01:14 UTC
Re: Re: [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.
On Tue, Jul 31, 2012 at 08:55:59AM +0800, majianpeng wrote:> On 2012-07-31 05:42 Dave Chinner <david@fromorbit.com> Wrote: > >On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote: > >> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page, > >> it will use bi_rw. > >> Fox example, in functiion __bio_add_page,it will call merge_bvec_fn(). > >> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. > >> >> if ((bvm->bi_rw & 1) == WRITE) > >> >> return biovec->bv_len; /* always allow writes to be mergeable */ > > > >So if bio_add_page() requires bi_rw to be set, then shouldn''t it be > >set up for every caller? I noticed there are about 50 call sites for > >bio_add_page(), and you''ve only touched about 10 of them. Indeed, I > >notice that the RAID0/1 code uses bio_add_page, and as that can be > >stacked on top of RAID456, it also needs to set bi_rw correctly. > >As a result, your patch set is nowhere near complete, not does it > >document that bio_add_page requires that bi_rw be set before calling > >(which is the new API requirement, AFAICT). > There are many place call bio_add_page and I send some of those. Because my abilty, so I only send > some patchs which i understand clearly.Sure, but my point is that there is no point changing only a few and ignoring the great majority of callers. Either fix them all, fix it some other way (e.g. API change), or remove the code from the RAID5 function that requires it.> In __bio_add_page: > >>if (q->merge_bvec_fn) { > >> struct bvec_merge_data bvm = { > >> /* prev_bvec is already charged in > >> bi_size, discharge it in order to > >> simulate merging updated prev_bvec > >> as new bvec. */ > >> .bi_bdev = bio->bi_bdev, > >> .bi_sector = bio->bi_sector, > >> .bi_size = bio->bi_size - prev_bv_len, > >> .bi_rw = bio->bi_rw, > >> }; > it used bio->bi_rw. > Before raid5_mergeable_bvec appearing, in kernel ''merge_bvec_fn'' did not use bio->bi_rw.Right, but as things stand right now, the RAID5 code is a no-op because nobody is setting bio->bi_rw correctly. it is effectively dead code.> But i think we shold not suppose bi_rw not meanless.To decide whether we should take it to have meaning, data is required to show that the RAID5 optimisation it enables is worthwhile. If the optimisation is not worthwhile, then the correct thing to do is remove the optimisation in the RAID5 code and remove the bi_rw field from the struct bvec_merge_data.> >So, my question is whether the RAID456 code is doing something > >valid. That write optimisation is clearly not enabled for a > >significant amount of code and filesystems, so the first thing to do > >is quantify the benefit of the optimisation. I can''t evalute the > >merit of this change without data telling me it is worthwhile, and > >it''s a lot of code to churn for no benefit.... > > > Sorry, we do not think the ''merge_bvec_fn'' did not use bi_rw.It''s entirely possible that when bi_rw was added to struct bvec_merge_data, the person who added it was mistaken that bi_rw was set at this point in time when in fact it never has been. Hence it''s presence and reliance on it would be a bug. That''s what I''m asking - is this actually beneificial, or should it simply be removed from struct bvec_merge_data? Data is needed to answer that question.... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Muthu Kumar
2012-Aug-10 15:23 UTC
Re: [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.
Hi, On Mon, Jul 30, 2012 at 6:14 PM, Dave Chinner <david@fromorbit.com> wrote:> On Tue, Jul 31, 2012 at 08:55:59AM +0800, majianpeng wrote: >> On 2012-07-31 05:42 Dave Chinner <david@fromorbit.com> Wrote: >> >On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote: >> >> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page, >> >> it will use bi_rw. >> >> Fox example, in functiion __bio_add_page,it will call merge_bvec_fn(). >> >> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. >> >> >> if ((bvm->bi_rw & 1) == WRITE) >> >> >> return biovec->bv_len; /* always allow writes to be mergeable */ >> > >> >So if bio_add_page() requires bi_rw to be set, then shouldn''t it be >> >set up for every caller? I noticed there are about 50 call sites for >> >bio_add_page(), and you''ve only touched about 10 of them. Indeed, I >> >notice that the RAID0/1 code uses bio_add_page, and as that can be >> >stacked on top of RAID456, it also needs to set bi_rw correctly. >> >As a result, your patch set is nowhere near complete, not does it >> >document that bio_add_page requires that bi_rw be set before calling >> >(which is the new API requirement, AFAICT). >> There are many place call bio_add_page and I send some of those. Becausemy abilty, so I only send>> some patchs which i understand clearly. > > Sure, but my point is that there is no point changing only a few and > ignoring the great majority of callers. Either fix them all, fix it > some other way (e.g. API change), or remove the code from the RAID5 > function that requires it. >A while back, we tried to address this by changing the alloc functions to take rw argument and set it (as per Jens suggestion). I guess the patch did not make it in. Please check: https://lkml.org/lkml/2011/7/11/275 And the follow ups. If needed, I can dust up that patch and resend it.>> In __bio_add_page: >> >>if (q->merge_bvec_fn) { >> >> struct bvec_merge_data bvm = { >> >> /* prev_bvec is already charged in >> >> bi_size, discharge it in orderto>> >> simulate merging updatedprev_bvec>> >> as new bvec. */ >> >> .bi_bdev = bio->bi_bdev, >> >> .bi_sector = bio->bi_sector, >> >> .bi_size = bio->bi_size -prev_bv_len,>> >> .bi_rw = bio->bi_rw, >> >> }; >> it used bio->bi_rw. >> Before raid5_mergeable_bvec appearing, in kernel ''merge_bvec_fn'' did notuse bio->bi_rw.><snip>> It''s entirely possible that when bi_rw was added to struct > bvec_merge_data, the person who added it was mistaken that bi_rw was > set at this point in time when in fact it never has been. Hence it''s > presence and reliance on it would be a bug. > > That''s what I''m asking - is this actually beneificial, or should it > simply be removed from struct bvec_merge_data? Data is needed to > answer that question....There are cases where we found it really beneficial to know the rw field to decide if the can be really merged or not. Regards, Muthu> > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today''s security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Jfs-discussion mailing list Jfs-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jfs-discussion
Muthu Kumar
2012-Aug-10 15:29 UTC
Re: Re: [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.
[ Resending in plain text... sorry for the duplicate ] Hi, On Mon, Jul 30, 2012 at 6:14 PM, Dave Chinner <david@fromorbit.com> wrote:> > On Tue, Jul 31, 2012 at 08:55:59AM +0800, majianpeng wrote: > > On 2012-07-31 05:42 Dave Chinner <david@fromorbit.com> Wrote: > > >On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote: > > >> When exec bio_alloc, the bi_rw is zero.But after calling > > >> bio_add_page, > > >> it will use bi_rw. > > >> Fox example, in functiion __bio_add_page,it will call > > >> merge_bvec_fn(). > > >> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. > > >> >> if ((bvm->bi_rw & 1) == WRITE) > > >> >> return biovec->bv_len; /* always allow writes to be mergeable */ > > > > > >So if bio_add_page() requires bi_rw to be set, then shouldn''t it be > > >set up for every caller? I noticed there are about 50 call sites for > > >bio_add_page(), and you''ve only touched about 10 of them. Indeed, I > > >notice that the RAID0/1 code uses bio_add_page, and as that can be > > >stacked on top of RAID456, it also needs to set bi_rw correctly. > > >As a result, your patch set is nowhere near complete, not does it > > >document that bio_add_page requires that bi_rw be set before calling > > >(which is the new API requirement, AFAICT). > > There are many place call bio_add_page and I send some of those. Because > > my abilty, so I only send > > some patchs which i understand clearly. > > Sure, but my point is that there is no point changing only a few and > ignoring the great majority of callers. Either fix them all, fix it > some other way (e.g. API change), or remove the code from the RAID5 > function that requires it.A while back, we tried to address this by changing the alloc functions to take rw argument and set it (as per Jens suggestion). I guess the patch did not make it in. Please check: https://lkml.org/lkml/2011/7/11/275 and the follow ups. If needed, I can dust up that patch and resend it.><snip>> > It''s entirely possible that when bi_rw was added to struct > bvec_merge_data, the person who added it was mistaken that bi_rw was > set at this point in time when in fact it never has been. Hence it''s > presence and reliance on it would be a bug. > > That''s what I''m asking - is this actually beneificial, or should it > simply be removed from struct bvec_merge_data? Data is needed to > answer that question....There are cases where we found it really beneficial to know the rw field to decide if the can be really merged or not. Regards, Muthu> > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/-- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html