From: Sergei Shtepa <sergei.shtepa@veeam.com> To: Hannes Reinecke <hare@suse.de> Cc: "hch@infradead.org" <hch@infradead.org>, Mike Snitzer <snitzer@redhat.com>, "Darrick J. Wong" <darrick.wong@oracle.com>, "Damien Le Moal" <Damien.LeMoal@wdc.com>, "axboe@kernel.dk" <axboe@kernel.dk>, "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>, "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, "rjw@rjwysocki.net" <rjw@rjwysocki.net>, "len.brown@intel.com" <len.brown@intel.com>, "pavel@ucw.cz" <pavel@ucw.cz>, "akpm@linux-foundation.org" <akpm@linux-foundation.org>, Johannes Thumshirn <Johannes.Thumshirn@wdc.com>, "ming.lei@redhat.com" <ming.lei@redhat.com>, "jack@suse.cz" <jack@suse.cz>, "tj@kernel.org" <tj@kernel.org>, "gustavo@embeddedor.com" <gustavo@embeddedor.com>, "bvanassche@acm.org" <bvanassche@acm.org>, "osandov@fb.com" <osandov@fb.com>, "koct9i@gmail.com" <koct9i@gmail.com>, "steve@sk2.org" <steve@sk2.org>, "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, device-mapper development <dm-devel@redhat.com>, Alasdair G Kergon <agk@redhat.com> Subject: Re: [PATCH 0/2] block layer filter and block device snapshot module Date: Fri, 23 Oct 2020 14:04:07 +0300 [thread overview] Message-ID: <20201023110407.GA23020@veeam.com> (raw) In-Reply-To: <d50062cd-929d-c8ff-5851-4e1d517dc4cb@suse.de> The 10/23/2020 13:31, Hannes Reinecke wrote: > On 10/23/20 11:13 AM, hch@infradead.org wrote: > > On Thu, Oct 22, 2020 at 01:54:16PM -0400, Mike Snitzer wrote: > >> On Thu, Oct 22, 2020 at 11:14 AM Darrick J. Wong > >>> Stupid question: Why don't you change the block layer to make it > >>> possible to insert device mapper devices after the blockdev has been set > >>> up? > >> > >> Not a stupid question. Definitely something that us DM developers > >> have wanted to do for a while. Devil is in the details but it is the > >> right way forward. > >> > > > > Yes, I think that is the right thing to do. And I don't think it should > > be all that hard. All we'd need in the I/O path is something like the > > pseudo-patch below, which will allow the interposer driver to resubmit > > bios using submit_bio_noacct as long as the driver sets BIO_INTERPOSED. > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > index ac00d2fa4eb48d..3f6f1eb565e0a8 100644 > > --- a/block/blk-core.c > > +++ b/block/blk-core.c > > @@ -1051,6 +1051,9 @@ blk_qc_t submit_bio_noacct(struct bio *bio) > > return BLK_QC_T_NONE; > > } > > > > + if (blk_has_interposer(bio->bi_disk) && > > + !(bio->bi_flags & BIO_INTERPOSED)) > > + return __submit_bio_interposed(bio); > > if (!bio->bi_disk->fops->submit_bio) > > return __submit_bio_noacct_mq(bio); > > return __submit_bio_noacct(bio); > > It`s will be great! Approximately this interception capability is not enough now. > My thoughts went more into the direction of hooking into ->submit_bio, > seeing that it's a NULL pointer for most (all?) block drivers. > > But sure, I'll check how the interposer approach would turn out. If anyone will do the patch blk-interposer, please add me to CC. I will try to offer my module that will use blk-interposer. -- Sergei Shtepa Veeam Software developer.
WARNING: multiple messages have this Message-ID (diff)
From: Sergei Shtepa <sergei.shtepa@veeam.com> To: Hannes Reinecke <hare@suse.de> Cc: "jack@suse.cz" <jack@suse.cz>, Mike Snitzer <snitzer@redhat.com>, "gustavo@embeddedor.com" <gustavo@embeddedor.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, device-mapper development <dm-devel@redhat.com>, "pavel@ucw.cz" <pavel@ucw.cz>, "steve@sk2.org" <steve@sk2.org>, "osandov@fb.com" <osandov@fb.com>, Alasdair G Kergon <agk@redhat.com>, "bvanassche@acm.org" <bvanassche@acm.org>, "Darrick J. Wong" <darrick.wong@oracle.com>, "hch@infradead.org" <hch@infradead.org>, "len.brown@intel.com" <len.brown@intel.com>, "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>, "ming.lei@redhat.com" <ming.lei@redhat.com>, "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>, "koct9i@gmail.com" <koct9i@gmail.com>, "axboe@kernel.dk" <axboe@kernel.dk>, Damien Le Moal <Damien.LeMoal@wdc.com>, Johannes Thumshirn <Johannes.Thumshirn@wdc.com>, "rjw@rjwysocki.net" <rjw@rjwysocki.net>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>, "tj@kernel.org" <tj@kernel.org>, "akpm@linux-foundation.org" <akpm@linux-foundation.org> Subject: Re: [dm-devel] [PATCH 0/2] block layer filter and block device snapshot module Date: Fri, 23 Oct 2020 14:04:07 +0300 [thread overview] Message-ID: <20201023110407.GA23020@veeam.com> (raw) In-Reply-To: <d50062cd-929d-c8ff-5851-4e1d517dc4cb@suse.de> The 10/23/2020 13:31, Hannes Reinecke wrote: > On 10/23/20 11:13 AM, hch@infradead.org wrote: > > On Thu, Oct 22, 2020 at 01:54:16PM -0400, Mike Snitzer wrote: > >> On Thu, Oct 22, 2020 at 11:14 AM Darrick J. Wong > >>> Stupid question: Why don't you change the block layer to make it > >>> possible to insert device mapper devices after the blockdev has been set > >>> up? > >> > >> Not a stupid question. Definitely something that us DM developers > >> have wanted to do for a while. Devil is in the details but it is the > >> right way forward. > >> > > > > Yes, I think that is the right thing to do. And I don't think it should > > be all that hard. All we'd need in the I/O path is something like the > > pseudo-patch below, which will allow the interposer driver to resubmit > > bios using submit_bio_noacct as long as the driver sets BIO_INTERPOSED. > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > index ac00d2fa4eb48d..3f6f1eb565e0a8 100644 > > --- a/block/blk-core.c > > +++ b/block/blk-core.c > > @@ -1051,6 +1051,9 @@ blk_qc_t submit_bio_noacct(struct bio *bio) > > return BLK_QC_T_NONE; > > } > > > > + if (blk_has_interposer(bio->bi_disk) && > > + !(bio->bi_flags & BIO_INTERPOSED)) > > + return __submit_bio_interposed(bio); > > if (!bio->bi_disk->fops->submit_bio) > > return __submit_bio_noacct_mq(bio); > > return __submit_bio_noacct(bio); > > It`s will be great! Approximately this interception capability is not enough now. > My thoughts went more into the direction of hooking into ->submit_bio, > seeing that it's a NULL pointer for most (all?) block drivers. > > But sure, I'll check how the interposer approach would turn out. If anyone will do the patch blk-interposer, please add me to CC. I will try to offer my module that will use blk-interposer. -- Sergei Shtepa Veeam Software developer. -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
next prev parent reply other threads:[~2020-10-23 11:03 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-21 9:04 [PATCH 0/2] block layer filter and block device snapshot module Sergei Shtepa 2020-10-21 9:04 ` [PATCH 1/2] Block layer filter - second version Sergei Shtepa 2020-10-21 9:14 ` Johannes Thumshirn 2020-10-21 10:01 ` Sergei Shtepa 2020-10-21 9:21 ` Damien Le Moal 2020-10-21 10:27 ` Sergei Shtepa 2020-10-21 11:44 ` Matthew Wilcox 2020-10-21 12:55 ` Sergei Shtepa 2020-10-21 13:07 ` Matthew Wilcox 2020-10-21 14:35 ` Sergei Shtepa 2020-10-21 15:09 ` Randy Dunlap 2020-10-24 14:53 ` Greg KH 2020-10-21 9:04 ` [PATCH 2/2] blk-snap - snapshots and change-tracking for block devices Sergei Shtepa 2020-10-21 9:08 ` Pavel Machek 2020-10-21 9:37 ` Sergei Shtepa 2020-10-21 9:23 ` Damien Le Moal 2020-10-21 11:15 ` Sergei Shtepa 2020-10-21 10:48 ` kernel test robot 2020-10-21 10:48 ` kernel test robot 2020-10-21 15:11 ` Randy Dunlap 2020-10-21 13:31 ` [PATCH 0/2] block layer filter and block device snapshot module Hannes Reinecke 2020-10-21 14:10 ` Sergei Shtepa 2020-10-22 5:58 ` Hannes Reinecke 2020-10-22 9:44 ` Sergei Shtepa 2020-10-22 10:28 ` Damien Le Moal 2020-10-22 13:52 ` Sergei Shtepa 2020-10-22 15:14 ` Darrick J. Wong 2020-10-22 17:54 ` Mike Snitzer 2020-10-22 17:54 ` [dm-devel] " Mike Snitzer 2020-10-22 17:54 ` Mike Snitzer 2020-10-23 9:13 ` hch 2020-10-23 9:13 ` [dm-devel] " hch 2020-10-23 10:31 ` Hannes Reinecke 2020-10-23 10:31 ` [dm-devel] " Hannes Reinecke 2020-10-23 11:04 ` Sergei Shtepa [this message] 2020-10-23 11:04 ` Sergei Shtepa 2020-10-23 11:12 ` hch 2020-10-23 11:12 ` hch 2020-10-22 18:35 ` Mike Snitzer 2020-10-22 18:35 ` [dm-devel] " Mike Snitzer 2020-10-22 18:35 ` Mike Snitzer
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