From: Jan Kara <jack@suse.cz>
To: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
Christoph Hellwig <hch@lst.de>, Ilya Dryomov <idryomov@gmail.com>,
Johannes Thumshirn <johannes.thumshirn@wdc.com>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: always respect QUEUE_FLAG_STABLE_WRITES on the block device
Date: Fri, 5 May 2023 12:49:04 +0200 [thread overview]
Message-ID: <20230505104904.2zr4escdxvoekr2k@quack3> (raw)
In-Reply-To: <20230504230736.GA2651828@dread.disaster.area>
On Fri 05-05-23 09:07:36, Dave Chinner wrote:
> On Thu, May 04, 2023 at 05:16:48PM +0100, Matthew Wilcox wrote:
> > On Thu, May 04, 2023 at 05:55:56PM +0200, Jan Kara wrote:
> > > For bdev address_space that's easy but what Ilya also mentioned is a
> > > problem when 'stable_write' flag gets toggled on the device and in that
> > > case having to propagate the flag update to all the address_space
> > > structures is a nightmare...
> >
> > We have a number of flags which don't take effect when modified on a
> > block device with a mounted filesystem on it. For example, modifying
> > the readahead settings do not change existing files, only new ones.
> > Since this flag is only modifiable for debugging purposes, I think I'm
> > OK with it not affecting already-mounted filesystems. It feels like a
> > decision that reasonable people could disagree on, though.
>
> I think an address space flag makes sense, because then we don't
> even have to care about the special bdev sb/inode thing -
> folio->mapping will already point at the bdev mapping and so do the
> right thing.
>
> That is, if the bdev changes stable_write state, it can toggle the
> AS_STABLE_WRITE flag on it's inode->i_mapping straight away and all
> the folios and files pointing to the bdev mapping will change
> behaviour immediately. Everything else retains the same behaviour
> we have now - the stable_write state is persistent on the superblock
> until the filesystem mount is cycled.
Yeah, I'm fine with this behavior. I just wasn't sure whether Ilya didn't
need the sysfs change to be visible in the filesystem so that was why I
pointed that out. But apparently he doesn't need it.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2023-05-05 10:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-04 10:56 Ilya Dryomov
2023-05-04 13:55 ` Christoph Hellwig
2023-05-04 14:16 ` Matthew Wilcox
2023-05-04 15:07 ` Ilya Dryomov
2023-05-04 15:37 ` Matthew Wilcox
2023-05-04 15:55 ` Jan Kara
2023-05-04 16:16 ` Matthew Wilcox
2023-05-04 23:07 ` Dave Chinner
2023-05-05 10:49 ` Jan Kara [this message]
2023-05-04 15:03 ` Ilya Dryomov
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