| Message ID | 1477728600-12938-29-git-send-email-tom.leiming@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, Oct 29, 2016 at 04:08:27PM +0800, Ming Lei wrote: > Some drivers(such as dm) should be capable of dealing with multipage > bvec, but the incoming bio may be too big, such as, a new singlepage bvec > bio can't be cloned from the bio, or can't be allocated to singlepage > bvec with same size. > > At least crypt dm, log writes and bcache have this kind of issue. We already have the segment_size limitation for request based drivers. I'd rather extent it to bio drivers if really needed. But then again we should look into not having this limitation. E.g. for bcache I'd be really surprised if it's that limited, given that Kent came up with this whole multipage bvec scheme. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Oct 31, 2016 at 11:39 PM, Christoph Hellwig <hch@infradead.org> wrote: > On Sat, Oct 29, 2016 at 04:08:27PM +0800, Ming Lei wrote: >> Some drivers(such as dm) should be capable of dealing with multipage >> bvec, but the incoming bio may be too big, such as, a new singlepage bvec >> bio can't be cloned from the bio, or can't be allocated to singlepage >> bvec with same size. >> >> At least crypt dm, log writes and bcache have this kind of issue. > > We already have the segment_size limitation for request based drivers. > I'd rather extent it to bio drivers if really needed. Yeah, just found dm actually don't need the flag, and it has its own way for limitting bio size. For bcache, there is only place which need the flag, so we can use max sectors limit to address it or use multiple bio to read & check ony by one. > > But then again we should look into not having this limitation. E.g. > for bcache I'd be really surprised if it's that limited, given that > Kent came up with this whole multipage bvec scheme. As far as I find, the only one which need the flag is bch_data_verify(). Thanks, Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Oct 31, 2016 at 08:39:15AM -0700, Christoph Hellwig wrote: > On Sat, Oct 29, 2016 at 04:08:27PM +0800, Ming Lei wrote: > > Some drivers(such as dm) should be capable of dealing with multipage > > bvec, but the incoming bio may be too big, such as, a new singlepage bvec > > bio can't be cloned from the bio, or can't be allocated to singlepage > > bvec with same size. > > > > At least crypt dm, log writes and bcache have this kind of issue. > > We already have the segment_size limitation for request based drivers. > I'd rather extent it to bio drivers if really needed. > > But then again we should look into not having this limitation. E.g. > for bcache I'd be really surprised if it's that limited, given that > Kent came up with this whole multipage bvec scheme. AFAIK the only issue is with drivers that may have to bounce bios - pages that were contiguous in the original bio won't necessarily be contiguous in the bounced bio, thus bouncing might require more than BIO_MAX_SEGMENTS bvecs. I don't know what Ming's referring to by "singlepage bvec bios". Anyways, bouncing comes up in multiple places so we probably need to come up with a generic solution for that. Other than that, there shouldn't be any issues or limitations - if you're not bouncing, there's no need to clone the bvecs. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Nov 2, 2016 at 11:08 AM, Kent Overstreet <kent.overstreet@gmail.com> wrote: > On Mon, Oct 31, 2016 at 08:39:15AM -0700, Christoph Hellwig wrote: >> On Sat, Oct 29, 2016 at 04:08:27PM +0800, Ming Lei wrote: >> > Some drivers(such as dm) should be capable of dealing with multipage >> > bvec, but the incoming bio may be too big, such as, a new singlepage bvec >> > bio can't be cloned from the bio, or can't be allocated to singlepage >> > bvec with same size. >> > >> > At least crypt dm, log writes and bcache have this kind of issue. >> >> We already have the segment_size limitation for request based drivers. >> I'd rather extent it to bio drivers if really needed. >> >> But then again we should look into not having this limitation. E.g. >> for bcache I'd be really surprised if it's that limited, given that >> Kent came up with this whole multipage bvec scheme. > > AFAIK the only issue is with drivers that may have to bounce bios - pages that > were contiguous in the original bio won't necessarily be contiguous in the > bounced bio, thus bouncing might require more than BIO_MAX_SEGMENTS bvecs. > > I don't know what Ming's referring to by "singlepage bvec bios". > > Anyways, bouncing comes up in multiple places so we probably need to come up > with a generic solution for that. Other than that, there shouldn't be any issues > or limitations - if you're not bouncing, there's no need to clone the bvecs. AFAIK, the only special case is bch_data_verify(): drivers/md/bcache/debug.c, for other bio_clone(), no direct access to io vec table, so default multipage bvec copy is fine. I will remove the flag and try to fix bch_data_verify() by using multiple bio, and I remembered I cooked patch to do that long time ago, :-) Thanks, Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Nov 03, 2016 at 06:38:57PM +0800, Ming Lei wrote: > On Wed, Nov 2, 2016 at 11:08 AM, Kent Overstreet > <kent.overstreet@gmail.com> wrote: > > On Mon, Oct 31, 2016 at 08:39:15AM -0700, Christoph Hellwig wrote: > >> On Sat, Oct 29, 2016 at 04:08:27PM +0800, Ming Lei wrote: > >> > Some drivers(such as dm) should be capable of dealing with multipage > >> > bvec, but the incoming bio may be too big, such as, a new singlepage bvec > >> > bio can't be cloned from the bio, or can't be allocated to singlepage > >> > bvec with same size. > >> > > >> > At least crypt dm, log writes and bcache have this kind of issue. > >> > >> We already have the segment_size limitation for request based drivers. > >> I'd rather extent it to bio drivers if really needed. > >> > >> But then again we should look into not having this limitation. E.g. > >> for bcache I'd be really surprised if it's that limited, given that > >> Kent came up with this whole multipage bvec scheme. > > > > AFAIK the only issue is with drivers that may have to bounce bios - pages that > > were contiguous in the original bio won't necessarily be contiguous in the > > bounced bio, thus bouncing might require more than BIO_MAX_SEGMENTS bvecs. > > > > I don't know what Ming's referring to by "singlepage bvec bios". > > > > Anyways, bouncing comes up in multiple places so we probably need to come up > > with a generic solution for that. Other than that, there shouldn't be any issues > > or limitations - if you're not bouncing, there's no need to clone the bvecs. > > AFAIK, the only special case is bch_data_verify(): drivers/md/bcache/debug.c, > for other bio_clone(), no direct access to io vec table, so default > multipage bvec > copy is fine. > > I will remove the flag and try to fix bch_data_verify() by using multiple bio, > and I remembered I cooked patch to do that long time ago, :-) You can #ifdef out the bch_data_verify() code, it's debug code that hasn't been used in ages. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Nov 3, 2016 at 7:20 PM, Kent Overstreet <kent.overstreet@gmail.com> wrote: > On Thu, Nov 03, 2016 at 06:38:57PM +0800, Ming Lei wrote: >> On Wed, Nov 2, 2016 at 11:08 AM, Kent Overstreet >> <kent.overstreet@gmail.com> wrote: >> > On Mon, Oct 31, 2016 at 08:39:15AM -0700, Christoph Hellwig wrote: >> >> On Sat, Oct 29, 2016 at 04:08:27PM +0800, Ming Lei wrote: >> >> > Some drivers(such as dm) should be capable of dealing with multipage >> >> > bvec, but the incoming bio may be too big, such as, a new singlepage bvec >> >> > bio can't be cloned from the bio, or can't be allocated to singlepage >> >> > bvec with same size. >> >> > >> >> > At least crypt dm, log writes and bcache have this kind of issue. >> >> >> >> We already have the segment_size limitation for request based drivers. >> >> I'd rather extent it to bio drivers if really needed. >> >> >> >> But then again we should look into not having this limitation. E.g. >> >> for bcache I'd be really surprised if it's that limited, given that >> >> Kent came up with this whole multipage bvec scheme. >> > >> > AFAIK the only issue is with drivers that may have to bounce bios - pages that >> > were contiguous in the original bio won't necessarily be contiguous in the >> > bounced bio, thus bouncing might require more than BIO_MAX_SEGMENTS bvecs. >> > >> > I don't know what Ming's referring to by "singlepage bvec bios". >> > >> > Anyways, bouncing comes up in multiple places so we probably need to come up >> > with a generic solution for that. Other than that, there shouldn't be any issues >> > or limitations - if you're not bouncing, there's no need to clone the bvecs. >> >> AFAIK, the only special case is bch_data_verify(): drivers/md/bcache/debug.c, >> for other bio_clone(), no direct access to io vec table, so default >> multipage bvec >> copy is fine. >> >> I will remove the flag and try to fix bch_data_verify() by using multiple bio, >> and I remembered I cooked patch to do that long time ago, :-) > > You can #ifdef out the bch_data_verify() code, it's debug code that hasn't been > used in ages. Though you didn't test it ages, it is sitll working in my last test, :-) But someone can enable that for debug too, I don't want to make him/her sad.
On Thu, Nov 03, 2016 at 07:26:52PM +0800, Ming Lei wrote: > On Thu, Nov 3, 2016 at 7:20 PM, Kent Overstreet > <kent.overstreet@gmail.com> wrote: > > On Thu, Nov 03, 2016 at 06:38:57PM +0800, Ming Lei wrote: > >> On Wed, Nov 2, 2016 at 11:08 AM, Kent Overstreet > >> <kent.overstreet@gmail.com> wrote: > >> > On Mon, Oct 31, 2016 at 08:39:15AM -0700, Christoph Hellwig wrote: > >> >> On Sat, Oct 29, 2016 at 04:08:27PM +0800, Ming Lei wrote: > >> >> > Some drivers(such as dm) should be capable of dealing with multipage > >> >> > bvec, but the incoming bio may be too big, such as, a new singlepage bvec > >> >> > bio can't be cloned from the bio, or can't be allocated to singlepage > >> >> > bvec with same size. > >> >> > > >> >> > At least crypt dm, log writes and bcache have this kind of issue. > >> >> > >> >> We already have the segment_size limitation for request based drivers. > >> >> I'd rather extent it to bio drivers if really needed. > >> >> > >> >> But then again we should look into not having this limitation. E.g. > >> >> for bcache I'd be really surprised if it's that limited, given that > >> >> Kent came up with this whole multipage bvec scheme. > >> > > >> > AFAIK the only issue is with drivers that may have to bounce bios - pages that > >> > were contiguous in the original bio won't necessarily be contiguous in the > >> > bounced bio, thus bouncing might require more than BIO_MAX_SEGMENTS bvecs. > >> > > >> > I don't know what Ming's referring to by "singlepage bvec bios". > >> > > >> > Anyways, bouncing comes up in multiple places so we probably need to come up > >> > with a generic solution for that. Other than that, there shouldn't be any issues > >> > or limitations - if you're not bouncing, there's no need to clone the bvecs. > >> > >> AFAIK, the only special case is bch_data_verify(): drivers/md/bcache/debug.c, > >> for other bio_clone(), no direct access to io vec table, so default > >> multipage bvec > >> copy is fine. > >> > >> I will remove the flag and try to fix bch_data_verify() by using multiple bio, > >> and I remembered I cooked patch to do that long time ago, :-) > > > > You can #ifdef out the bch_data_verify() code, it's debug code that hasn't been > > used in ages. > > Though you didn't test it ages, it is sitll working in my last test, :-) > > But someone can enable that for debug too, I don't want to make him/her sad. Up to you :) It's not useful for anything but debugging though, so I wouldn't worry about impacting end users. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/block/blk-merge.c b/block/blk-merge.c index 2642e5fc8b69..266c94d1d82f 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -79,6 +79,10 @@ static inline unsigned get_max_io_size(struct request_queue *q, /* aligned to logical block size */ sectors &= ~(mask >> 9); + /* some queues can't handle bigger bio even it is ready for mp bvecs */ + if (blk_queue_split_mp(q) && sectors > BIO_SP_MAX_SECTORS) + sectors = BIO_SP_MAX_SECTORS; + return sectors; } diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index e4dd25361bd6..7cee0179c9e6 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -506,6 +506,7 @@ struct request_queue { #define QUEUE_FLAG_FLUSH_NQ 25 /* flush not queueuable */ #define QUEUE_FLAG_DAX 26 /* device supports DAX */ #define QUEUE_FLAG_NO_MP 27 /* multipage bvecs isn't ready */ +#define QUEUE_FLAG_SPLIT_MP 28 /* split MP bvecs if too bigger */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ @@ -597,6 +598,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q) (test_bit(QUEUE_FLAG_SECERASE, &(q)->queue_flags)) #define blk_queue_dax(q) test_bit(QUEUE_FLAG_DAX, &(q)->queue_flags) #define blk_queue_no_mp(q) test_bit(QUEUE_FLAG_NO_MP, &(q)->queue_flags) +#define blk_queue_split_mp(q) test_bit(QUEUE_FLAG_SPLIT_MP, &(q)->queue_flags) #define blk_noretry_request(rq) \ ((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \
Some drivers(such as dm) should be capable of dealing with multipage bvec, but the incoming bio may be too big, such as, a new singlepage bvec bio can't be cloned from the bio, or can't be allocated to singlepage bvec with same size. At least crypt dm, log writes and bcache have this kind of issue. Signed-off-by: Ming Lei <tom.leiming@gmail.com> --- block/blk-merge.c | 4 ++++ include/linux/blkdev.h | 2 ++ 2 files changed, 6 insertions(+)