From: "Darrick J. Wong" <djwong@kernel.org>
To: Christian Brauner <brauner@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Next Mailing List <linux-next@vger.kernel.org>
Subject: Re: linux-next: manual merge of the vfs-brauner tree with the djw-vfs tree
Date: Tue, 22 Aug 2023 14:14:56 -0700 [thread overview]
Message-ID: <20230822211456.GC11286@frogsfrogsfrogs> (raw)
In-Reply-To: <20230822-mitbringen-unwillig-176fd9e8873b@brauner>
On Tue, Aug 22, 2023 at 10:19:00PM +0200, Christian Brauner wrote:
> > > my preferred solution. How do you feel about that?
> >
> > I'm happy to have you pull my xfs-linux tags into your vfs tree. :)
>
> Ah, sweet. I apppreciate that. I'll mention in the pr to Linus that if
> he wants to reject other parts of the super work that he should then
> still simply pull the freeze stuff from you without the rest.
>
> >
> > Here's a tag with just the two vfs patches:
> > https://git.kernel.org/pub/scm/fs/xfs/xfs-linux.git/tag/?h=vfs-6.6-merge-2
> >
> > This second tag builds on that, by adding the first actual user of
> > FREEZE_HOLDER_KERNEL:
> > https://git.kernel.org/pub/scm/fs/xfs/xfs-linux.git/tag/?h=vfs-6.6-merge-3
>
> Assuming I understood correctly I did just pull both tags and pushed
> them out. Would you please take a look at
> https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/log/?h=vfs.super
> and let me know if everything looks as expected? I'll be going afk in a
> bit just waiting for the kernel build to finish to kick of some
> xfstests. If you find anything I'll fix up any issues up tomorrow
> morning.
Hmm. Looking at the {up,down}_write -> super_{un,}lock_excl conversion,
I think you missed wait_for_partially_frozen:
static int wait_for_partially_frozen(struct super_block *sb)
{
int ret = 0;
do {
unsigned short old = sb->s_writers.frozen;
up_write(&sb->s_umount);
ret = wait_var_event_killable(&sb->s_writers.frozen,
sb->s_writers.frozen != old);
down_write(&sb->s_umount);
} while (ret == 0 &&
sb->s_writers.frozen != SB_UNFROZEN &&
sb->s_writers.frozen != SB_FREEZE_COMPLETE);
return ret;
}
That said, freeze_super() took an s_active refcount at the top, called
super_lock_excl (which means the sb isn't DYING and has been BORN) and
doesn't release it before calling wait_for_partially_frozen.
AFAICT, the subsequent down_write -> super_lock_excl conversions in
freeze_super do not gain us much since I don't think the sb can get to
SB_DYING state without s_active reaching zero, right? According to
"super: use higher-level helper for {freeze,thaw}", it sounds like the
subsequent down_write calls in freeze_super were replaced for
consistency, even though it "...isn't possible to observe a dying
superblock".
The missing conversion isn't strictly necessary, but it probably makese
sense to do it anyway.
(Aside from that, the conversion looks correct to me.)
> >
> > There will be more for 6.7(+?) if Luis manages to get back to his
> > auto-fsfreeze during suspend, or if Shiyang finishes the series to
> > handle pmem media error reporting in xfs.
>
> Ok, sounds good let me know/Cc me when ready/needed.
Will do!
--D
>
> Thanks for all the help!
next prev parent reply other threads:[~2023-08-22 21:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-22 1:05 linux-next: manual merge of the vfs-brauner tree with the djw-vfs tree Stephen Rothwell
2023-08-22 2:51 ` Darrick J. Wong
2023-08-22 9:46 ` Christian Brauner
2023-08-22 18:26 ` Darrick J. Wong
2023-08-22 20:19 ` Christian Brauner
2023-08-22 21:14 ` Darrick J. Wong [this message]
2023-08-23 7:44 ` Christian Brauner
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