From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] fs: don't scan the inode cache before SB_ACTIVE is set
Date: Mon, 26 Mar 2018 06:31:51 +0100 [thread overview]
Message-ID: <20180326053151.GO30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180326043503.17828-1-david@fromorbit.com>
On Mon, Mar 26, 2018 at 03:35:03PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> We recently had an oops reported on a 4.14 kernel in
> xfs_reclaim_inodes_count() where sb->s_fs_info pointed to garbage
> and so the m_perag_tree lookup walked into lala land.
>
> We found a mount in a failed state, blocked on teh shrinker rwsem
> here:
>
> mount_bdev()
> deactivate_locked_super()
> unregister_shrinker()
>
> Essentially, the machine was under memory pressure when the mount
> was being run, xfs_fs_fill_super() failed after allocating the
> xfs_mount and attaching it to sb->s_fs_info. It then cleaned up and
> freed the xfs_mount, but the sb->s_fs_info field still pointed to
> the freed memory. Hence when the superblock shrinker then ran
> it fell off the bad pointer.
>
> This is reproduced by using the mount_delay sysfs control as added
> in teh previous patch. It produces an oops down this path during the
> stalled mount:
> The problem is that the superblock shrinker is running before the
> filesystem structures it depends on have been fully set up. i.e.
> the shrinker is registered in sget(), before ->fill_super() has been
> called, and the shrinker can call into the filesystem before
> fill_super() does it's setup work.
Wait a sec... How the hell does it get through trylock_super() before
->s_root is set and ->s_umount is unlocked?
next prev parent reply other threads:[~2018-03-26 5:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-26 4:35 [PATCH] fs: don't scan the inode cache before SB_ACTIVE is set Dave Chinner
2018-03-26 5:31 ` Al Viro [this message]
2018-03-26 5:51 ` Al Viro
2018-03-26 6:33 ` Dave Chinner
2018-03-26 6:55 ` Al Viro
2018-03-26 7:21 ` Dave Chinner
2018-03-27 6:57 ` [PATCH V2] fs: don't scan the inode cache before SB_BORN " Dave Chinner
2018-03-27 7:24 ` Al Viro
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180326053151.GO30522@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=david@fromorbit.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-xfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.