From: Jan Kara <jack@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>, Jan Kara <jack@suse.cz>,
Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
Josef Bacik <josef@toxicpanda.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Coly Li <colyli@suse.de>, Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, Richard Weinberger <richard@nod.at>,
Jan Kara <jack@suse.com>,
linux-block@vger.kernel.org, xen-devel@lists.xenproject.org,
linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 14/20] block: remove the nr_sects field in struct hd_struct
Date: Fri, 20 Nov 2020 21:05:48 +0100 [thread overview]
Message-ID: <20201120200548.GA27360@quack2.suse.cz> (raw)
In-Reply-To: <20201120155956.GB4327@casper.infradead.org>
On Fri 20-11-20 15:59:56, Matthew Wilcox wrote:
> On Fri, Nov 20, 2020 at 04:32:53PM +0100, Christoph Hellwig wrote:
> > On Fri, Nov 20, 2020 at 12:21:21PM +0100, Jan Kara wrote:
> > > > > AFAICT bd_size_lock is pointless after these changes so we can just remove
> > > > > it?
> > > >
> > > > I don't think it is, as reuqiring bd_mutex for size updates leads to
> > > > rather awkward lock ordering problems.
> > >
> > > OK, let me ask differently: What is bd_size_lock protecting now? Ah, I see,
> > > on 32-bit it is needed to prevent torn writes to i_size, right?
> >
> > Exactly. In theory we could skip it for 64-bit, but as updating the
> > size isn't a fast path, and struct block_device isn't super size critical
> > I'd rather keep the same code for 32 vs 64-bit builds.
>
> Is it better to switch to i_size_write() / i_size_read()?
The code is already switched to it AFAICT (the lock is really only used in
the two places that write i_size). But the problem is that in theory two
i_size_write() calls can race in a way that the resulting stored i_size is a
mix of two stored sizes. Now I have hard time imagining how this could
happen for a block device and if two reconfigurations of a block device
could race like that we'd have a large problems anyway...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, Jan Kara <jack@suse.cz>,
Mike Snitzer <snitzer@redhat.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Richard Weinberger <richard@nod.at>,
Josef Bacik <josef@toxicpanda.com>, Coly Li <colyli@suse.de>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
dm-devel@redhat.com, linux-mtd@lists.infradead.org,
linux-mm@kvack.org, Jan Kara <jack@suse.com>,
Tejun Heo <tj@kernel.org>,
xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 14/20] block: remove the nr_sects field in struct hd_struct
Date: Fri, 20 Nov 2020 21:05:48 +0100 [thread overview]
Message-ID: <20201120200548.GA27360@quack2.suse.cz> (raw)
In-Reply-To: <20201120155956.GB4327@casper.infradead.org>
On Fri 20-11-20 15:59:56, Matthew Wilcox wrote:
> On Fri, Nov 20, 2020 at 04:32:53PM +0100, Christoph Hellwig wrote:
> > On Fri, Nov 20, 2020 at 12:21:21PM +0100, Jan Kara wrote:
> > > > > AFAICT bd_size_lock is pointless after these changes so we can just remove
> > > > > it?
> > > >
> > > > I don't think it is, as reuqiring bd_mutex for size updates leads to
> > > > rather awkward lock ordering problems.
> > >
> > > OK, let me ask differently: What is bd_size_lock protecting now? Ah, I see,
> > > on 32-bit it is needed to prevent torn writes to i_size, right?
> >
> > Exactly. In theory we could skip it for 64-bit, but as updating the
> > size isn't a fast path, and struct block_device isn't super size critical
> > I'd rather keep the same code for 32 vs 64-bit builds.
>
> Is it better to switch to i_size_write() / i_size_read()?
The code is already switched to it AFAICT (the lock is really only used in
the two places that write i_size). But the problem is that in theory two
i_size_write() calls can race in a way that the resulting stored i_size is a
mix of two stored sizes. Now I have hard time imagining how this could
happen for a block device and if two reconfigurations of a block device
could race like that we'd have a large problems anyway...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/
WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, Jan Kara <jack@suse.cz>,
Mike Snitzer <snitzer@redhat.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Richard Weinberger <richard@nod.at>,
Josef Bacik <josef@toxicpanda.com>, Coly Li <colyli@suse.de>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
dm-devel@redhat.com, linux-mtd@lists.infradead.org,
linux-mm@kvack.org, Jan Kara <jack@suse.com>,
Tejun Heo <tj@kernel.org>,
xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org,
Christoph Hellwig <hch@lst.de>
Subject: Re: [dm-devel] [PATCH 14/20] block: remove the nr_sects field in struct hd_struct
Date: Fri, 20 Nov 2020 21:05:48 +0100 [thread overview]
Message-ID: <20201120200548.GA27360@quack2.suse.cz> (raw)
In-Reply-To: <20201120155956.GB4327@casper.infradead.org>
On Fri 20-11-20 15:59:56, Matthew Wilcox wrote:
> On Fri, Nov 20, 2020 at 04:32:53PM +0100, Christoph Hellwig wrote:
> > On Fri, Nov 20, 2020 at 12:21:21PM +0100, Jan Kara wrote:
> > > > > AFAICT bd_size_lock is pointless after these changes so we can just remove
> > > > > it?
> > > >
> > > > I don't think it is, as reuqiring bd_mutex for size updates leads to
> > > > rather awkward lock ordering problems.
> > >
> > > OK, let me ask differently: What is bd_size_lock protecting now? Ah, I see,
> > > on 32-bit it is needed to prevent torn writes to i_size, right?
> >
> > Exactly. In theory we could skip it for 64-bit, but as updating the
> > size isn't a fast path, and struct block_device isn't super size critical
> > I'd rather keep the same code for 32 vs 64-bit builds.
>
> Is it better to switch to i_size_write() / i_size_read()?
The code is already switched to it AFAICT (the lock is really only used in
the two places that write i_size). But the problem is that in theory two
i_size_write() calls can race in a way that the resulting stored i_size is a
mix of two stored sizes. Now I have hard time imagining how this could
happen for a block device and if two reconfigurations of a block device
could race like that we'd have a large problems anyway...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
next prev parent reply other threads:[~2020-11-20 20:06 UTC|newest]
Thread overview: 237+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-18 8:47 merge struct block_device and struct hd_struct Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 8:47 ` [PATCH 01/20] blk-cgroup: fix a hd_struct leak in blkcg_fill_root_iostats Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:09 ` Jan Kara
2020-11-18 14:09 ` [dm-devel] " Jan Kara
2020-11-18 14:09 ` Jan Kara
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-19 8:37 ` [dm-devel] " Johannes Thumshirn
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-24 12:26 ` Tejun Heo
2020-11-24 12:26 ` [dm-devel] " Tejun Heo
2020-11-24 12:26 ` Tejun Heo
2020-11-18 8:47 ` [PATCH 02/20] block: remove a duplicate __disk_get_part prototype Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:10 ` Jan Kara
2020-11-18 14:10 ` [dm-devel] " Jan Kara
2020-11-18 14:10 ` Jan Kara
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-19 8:37 ` [dm-devel] " Johannes Thumshirn
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-18 8:47 ` [PATCH 03/20] block: add a bdev_kobj helper Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:18 ` Jan Kara
2020-11-18 14:18 ` [dm-devel] " Jan Kara
2020-11-18 14:18 ` Jan Kara
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-19 8:37 ` [dm-devel] " Johannes Thumshirn
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-18 8:47 ` [PATCH 04/20] block: use disk_part_iter_exit in disk_part_iter_next Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:19 ` Jan Kara
2020-11-18 14:19 ` [dm-devel] " Jan Kara
2020-11-18 14:19 ` Jan Kara
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-19 8:37 ` [dm-devel] " Johannes Thumshirn
2020-11-19 8:37 ` Johannes Thumshirn
2020-11-18 8:47 ` [PATCH 05/20] block: use put_device in put_disk Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:20 ` Jan Kara
2020-11-18 14:20 ` [dm-devel] " Jan Kara
2020-11-18 14:20 ` Jan Kara
2020-11-19 8:38 ` Johannes Thumshirn
2020-11-19 8:38 ` [dm-devel] " Johannes Thumshirn
2020-11-19 8:38 ` Johannes Thumshirn
2020-11-18 8:47 ` [PATCH 06/20] block: change the hash used for looking up block devices Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:22 ` Jan Kara
2020-11-18 14:22 ` [dm-devel] " Jan Kara
2020-11-18 14:22 ` Jan Kara
2020-11-18 8:47 ` [PATCH 07/20] init: refactor name_to_dev_t Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:37 ` Jan Kara
2020-11-18 14:37 ` [dm-devel] " Jan Kara
2020-11-18 14:37 ` Jan Kara
2020-11-19 7:52 ` Christoph Hellwig
2020-11-19 7:52 ` [dm-devel] " Christoph Hellwig
2020-11-19 7:52 ` Christoph Hellwig
2020-11-19 8:25 ` Jan Kara
2020-11-19 8:25 ` [dm-devel] " Jan Kara
2020-11-19 8:25 ` Jan Kara
2020-11-20 8:49 ` Christoph Hellwig
2020-11-20 8:49 ` [dm-devel] " Christoph Hellwig
2020-11-20 8:49 ` Christoph Hellwig
2020-11-19 8:38 ` Johannes Thumshirn
2020-11-19 8:38 ` [dm-devel] " Johannes Thumshirn
2020-11-19 8:38 ` Johannes Thumshirn
2020-11-18 8:47 ` [PATCH 08/20] init: refactor devt_from_partuuid Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:41 ` Jan Kara
2020-11-18 14:41 ` [dm-devel] " Jan Kara
2020-11-18 14:41 ` Jan Kara
2020-11-18 8:47 ` [PATCH 09/20] init: cleanup match_dev_by_uuid and match_dev_by_label Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:42 ` Jan Kara
2020-11-18 14:42 ` [dm-devel] " Jan Kara
2020-11-18 14:42 ` Jan Kara
2020-11-19 8:38 ` Johannes Thumshirn
2020-11-19 8:38 ` [dm-devel] " Johannes Thumshirn
2020-11-19 8:38 ` Johannes Thumshirn
2020-11-18 8:47 ` [PATCH 10/20] block: refactor __blkdev_put Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 14:46 ` Jan Kara
2020-11-18 14:46 ` [dm-devel] " Jan Kara
2020-11-18 14:46 ` Jan Kara
2020-11-18 8:47 ` [PATCH 11/20] block: reference struct block_device from struct hd_struct Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 9:41 ` Jan Kara
2020-11-19 9:41 ` [dm-devel] " Jan Kara
2020-11-19 9:41 ` Jan Kara
2020-11-20 8:56 ` Christoph Hellwig
2020-11-20 8:56 ` [dm-devel] " Christoph Hellwig
2020-11-20 8:56 ` Christoph Hellwig
2020-11-24 16:59 ` Tejun Heo
2020-11-24 16:59 ` [dm-devel] " Tejun Heo
2020-11-24 16:59 ` Tejun Heo
2020-11-25 11:40 ` Jan Kara
2020-11-25 11:40 ` [dm-devel] " Jan Kara
2020-11-25 11:40 ` Jan Kara
2020-11-25 12:09 ` Tejun Heo
2020-11-25 12:09 ` [dm-devel] " Tejun Heo
2020-11-25 12:09 ` Tejun Heo
2020-11-18 8:47 ` [PATCH 12/20] block: simplify the block device claiming interface Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 10:07 ` Jan Kara
2020-11-19 10:07 ` [dm-devel] " Jan Kara
2020-11-19 10:07 ` Jan Kara
2020-11-18 8:47 ` [PATCH 13/20] block: remove ->bd_contains Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 10:32 ` Jan Kara
2020-11-19 10:32 ` [dm-devel] " Jan Kara
2020-11-19 10:32 ` Jan Kara
2020-11-20 9:01 ` Christoph Hellwig
2020-11-20 9:01 ` [dm-devel] " Christoph Hellwig
2020-11-20 9:01 ` Christoph Hellwig
2020-11-18 8:47 ` [PATCH 14/20] block: remove the nr_sects field in struct hd_struct Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 12:05 ` Jan Kara
2020-11-19 12:05 ` [dm-devel] " Jan Kara
2020-11-19 12:05 ` Jan Kara
2020-11-20 9:08 ` Christoph Hellwig
2020-11-20 9:08 ` [dm-devel] " Christoph Hellwig
2020-11-20 9:08 ` Christoph Hellwig
2020-11-20 11:21 ` Jan Kara
2020-11-20 11:21 ` [dm-devel] " Jan Kara
2020-11-20 11:21 ` Jan Kara
2020-11-20 15:32 ` Christoph Hellwig
2020-11-20 15:32 ` [dm-devel] " Christoph Hellwig
2020-11-20 15:32 ` Christoph Hellwig
2020-11-20 15:59 ` Matthew Wilcox
2020-11-20 15:59 ` [dm-devel] " Matthew Wilcox
2020-11-20 15:59 ` Matthew Wilcox
2020-11-20 16:01 ` Christoph Hellwig
2020-11-20 16:01 ` [dm-devel] " Christoph Hellwig
2020-11-20 16:01 ` Christoph Hellwig
2020-11-20 20:05 ` Jan Kara [this message]
2020-11-20 20:05 ` [dm-devel] " Jan Kara
2020-11-20 20:05 ` Jan Kara
2020-11-21 16:24 ` Christoph Hellwig
2020-11-21 16:24 ` [dm-devel] " Christoph Hellwig
2020-11-21 16:24 ` Christoph Hellwig
2020-11-18 8:47 ` [PATCH 15/20] block: merge struct block_device and " Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 14:39 ` Jan Kara
2020-11-19 14:39 ` [dm-devel] " Jan Kara
2020-11-19 14:39 ` Jan Kara
2020-11-20 9:15 ` Christoph Hellwig
2020-11-20 9:15 ` [dm-devel] " Christoph Hellwig
2020-11-20 9:15 ` Christoph Hellwig
2020-11-20 10:53 ` Jan Kara
2020-11-20 10:53 ` [dm-devel] " Jan Kara
2020-11-20 10:53 ` Jan Kara
2020-11-18 8:47 ` [PATCH 16/20] block: stop using bdget_disk for partition 0 Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 14:43 ` Jan Kara
2020-11-19 14:43 ` [dm-devel] " Jan Kara
2020-11-19 14:43 ` Jan Kara
2020-11-18 8:47 ` [PATCH 17/20] filemap: consistently use ->f_mapping over ->i_mapping Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 14:53 ` Jan Kara
2020-11-19 14:53 ` [dm-devel] " Jan Kara
2020-11-19 14:53 ` Jan Kara
2020-11-19 15:13 ` Matthew Wilcox
2020-11-19 15:13 ` [dm-devel] " Matthew Wilcox
2020-11-19 15:13 ` Matthew Wilcox
2020-11-20 9:17 ` Christoph Hellwig
2020-11-20 9:17 ` [dm-devel] " Christoph Hellwig
2020-11-20 9:17 ` Christoph Hellwig
2020-11-18 8:47 ` [PATCH 18/20] fs: remove get_super_thawed and get_super_exclusive_thawed Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-19 14:59 ` Jan Kara
2020-11-19 14:59 ` [dm-devel] " Jan Kara
2020-11-19 14:59 ` Jan Kara
2020-11-18 8:47 ` [PATCH 19/20] bcache: remove a superflous lookup_bdev all Christoph Hellwig
2020-11-18 8:47 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:47 ` Christoph Hellwig
2020-11-18 8:54 ` Coly Li
2020-11-18 8:54 ` [dm-devel] " Coly Li
2020-11-18 8:54 ` Coly Li
2020-11-18 9:10 ` Greg KH
2020-11-18 9:10 ` [dm-devel] " Greg KH
2020-11-18 9:10 ` Greg KH
2020-11-18 9:55 ` Coly Li
2020-11-18 9:55 ` [dm-devel] " Coly Li
2020-11-18 9:55 ` Coly Li
2020-11-18 16:24 ` Christoph Hellwig
2020-11-18 16:24 ` [dm-devel] " Christoph Hellwig
2020-11-18 16:24 ` Christoph Hellwig
2020-11-18 8:48 ` [PATCH 20/20] block: remove i_bdev Christoph Hellwig
2020-11-18 8:48 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:48 ` Christoph Hellwig
2020-11-18 8:56 ` merge struct block_device and struct hd_struct Jan Beulich
2020-11-18 8:56 ` [dm-devel] " Jan Beulich
2020-11-18 8:56 ` Jan Beulich
2020-11-18 8:58 ` Christoph Hellwig
2020-11-18 8:58 ` [dm-devel] " Christoph Hellwig
2020-11-18 8:58 ` Christoph Hellwig
2020-11-18 9:04 ` Jan Beulich
2020-11-18 9:04 ` [dm-devel] " Jan Beulich
2020-11-18 9:04 ` Jan Beulich
2020-11-18 9:08 ` Christoph Hellwig
2020-11-18 9:08 ` [dm-devel] " Christoph Hellwig
2020-11-18 9:08 ` Christoph Hellwig
2020-11-18 9:09 ` Greg KH
2020-11-18 9:09 ` [dm-devel] " Greg KH
2020-11-18 9:09 ` Greg KH
2020-11-18 9:23 ` Jan Beulich
2020-11-18 9:23 ` [dm-devel] " Jan Beulich
2020-11-18 9:23 ` Jan Beulich
2020-11-18 9:32 ` Greg KH
2020-11-18 9:32 ` [dm-devel] " Greg KH
2020-11-18 9:32 ` Greg KH
2020-11-18 12:50 ` Matthew Wilcox
2020-11-18 12:50 ` [dm-devel] " Matthew Wilcox
2020-11-18 12:50 ` Matthew Wilcox
2020-11-18 9:13 ` Greg KH
2020-11-18 9:13 ` [dm-devel] " Greg KH
2020-11-18 9:13 ` Greg KH
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