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From: Vivek Goyal <vgoyal@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-unionfs@vger.kernel.org, jlayton@kernel.org,
	amir73il@gmail.com, sargun@sargun.me, miklos@szeredi.hu,
	jack@suse.cz, neilb@suse.com, viro@zeniv.linux.org.uk,
	hch@lst.de
Subject: Re: [PATCH 3/3] overlayfs: Report writeback errors on upper
Date: Tue, 22 Dec 2020 11:29:25 -0500	[thread overview]
Message-ID: <20201222162925.GC3248@redhat.com> (raw)
In-Reply-To: <20201222162027.GJ874@casper.infradead.org>

On Tue, Dec 22, 2020 at 04:20:27PM +0000, Matthew Wilcox wrote:
> On Mon, Dec 21, 2020 at 02:50:55PM -0500, Vivek Goyal wrote:
> > +static int ovl_errseq_check_advance(struct super_block *sb, struct file *file)
> > +{
> > +	struct ovl_fs *ofs = sb->s_fs_info;
> > +	struct super_block *upper_sb;
> > +	int ret;
> > +
> > +	if (!ovl_upper_mnt(ofs))
> > +		return 0;
> > +
> > +	upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
> > +
> > +	if (!errseq_check(&upper_sb->s_wb_err, file->f_sb_err))
> > +		return 0;
> > +
> > +	/* Something changed, must use slow path */
> > +	spin_lock(&file->f_lock);
> > +	ret = errseq_check_and_advance(&upper_sb->s_wb_err, &file->f_sb_err);
> > +	spin_unlock(&file->f_lock);
> 
> Why are you microoptimising syncfs()?  Are there really applications which
> call syncfs() in a massively parallel manner on the same file descriptor?

This is atleast theoritical race. I am not aware which application can
trigger this race. So to me it makes sense to fix the race.

Jeff Layton also posted a fix for syncfs().

https://lore.kernel.org/linux-fsdevel/20201219134804.20034-1-jlayton@kernel.org/

To me it makes sense to fix the race irrespective of the fact if somebody
hit it or not. People end up copying code in other parts of kernel and
and they will atleast copy race free code.

Vivek


  reply	other threads:[~2020-12-22 16:30 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-21 19:50 [RFC PATCH 0/3][v3] vfs, overlayfs: Fix syncfs() to return correct errors Vivek Goyal
2020-12-21 19:50 ` [PATCH 1/3] vfs: Do not ignore return code from s_op->sync_fs Vivek Goyal
2020-12-22  1:23   ` NeilBrown
2020-12-22 15:17     ` Vivek Goyal
2020-12-21 19:50 ` [PATCH 2/3] vfs: Add a super block operation to check for writeback errors Vivek Goyal
2020-12-22 16:19   ` Matthew Wilcox
2020-12-22 16:25     ` Vivek Goyal
2020-12-23 12:44       ` Jeff Layton
2020-12-23 12:48   ` Jeff Layton
2021-01-04 19:41     ` Vivek Goyal
2020-12-21 19:50 ` [PATCH 3/3] overlayfs: Report writeback errors on upper Vivek Goyal
2020-12-22 16:20   ` Matthew Wilcox
2020-12-22 16:29     ` Vivek Goyal [this message]
2020-12-22 17:46       ` Matthew Wilcox
2020-12-22 17:55         ` Vivek Goyal
2020-12-23 12:53           ` Jeff Layton
2020-12-23 18:20   ` Sargun Dhillon
2020-12-23 18:50     ` Matthew Wilcox
2020-12-23 19:29       ` Sargun Dhillon
2020-12-23 20:07         ` Matthew Wilcox
2020-12-23 20:21           ` Sargun Dhillon
2020-12-23 20:44             ` Matthew Wilcox
2020-12-24  9:32               ` Amir Goldstein
2020-12-24 10:12                 ` Sargun Dhillon
2020-12-24 12:13                 ` Matthew Wilcox
2020-12-25  6:50                   ` Amir Goldstein
2020-12-28 13:25                     ` Jeff Layton
2020-12-28 15:51                       ` Amir Goldstein
2021-01-04 15:51                         ` Vivek Goyal
2020-12-28 15:56                       ` Matthew Wilcox
2020-12-28 17:26                         ` Jeff Layton
2020-12-28 19:25                           ` Sargun Dhillon
2020-12-28 19:37                           ` Amir Goldstein
2020-12-28 20:48                             ` Matthew Wilcox
2021-01-02 13:25                               ` Jeff Layton
2021-01-04 16:59                         ` Vivek Goyal
2021-01-04 15:14                 ` Vivek Goyal
2021-01-04 15:22                   ` Amir Goldstein
2021-01-04 15:40                     ` Vivek Goyal
2021-01-04 21:42                       ` Amir Goldstein
2021-01-04 22:44                         ` Vivek Goyal
2021-01-05  7:11                           ` Amir Goldstein
2021-01-05 16:26                             ` Vivek Goyal
2021-01-05 16:57                               ` Amir Goldstein
2020-12-23 19:00     ` Jeff Layton
2021-01-04 20:00     ` Vivek Goyal

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