From: Al Viro <viro@ZenIV.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: dave@linux.vnet.ibm.com, akpm@linux-foundation.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/9 updated] vfs: protect remounting superblock read-only
Date: Sat, 23 Oct 2010 22:42:35 +0100 [thread overview]
Message-ID: <20101023214235.GT19804@ZenIV.linux.org.uk> (raw)
In-Reply-To: <E1P9js4-0007cE-9G@pomaz-ex.szeredi.hu>
On Sat, Oct 23, 2010 at 09:35:16PM +0200, Miklos Szeredi wrote:
> > Another thing:
> > "If clone_mnt() happens while mnt_make_readonly() is running, the
> > cloned mount might have MNT_WRITE_HOLD flag set, which results in
> > mnt_want_write() spinning forever on this mount."
> > actually means
> > "neither clone_mnt() nor remounts should ever be done without
> > namespace_sem held exclusive; if that ever happens, we have a serious
> > bug that can lead to any number of bad things happening".
> >
> > Do you actually see such places? If so, that's what needs fixing.
>
> do_remount() takes s_umount, but not namespace_sem.
Duh... Right, ignore that part; we really don't want to do anything
blocking beyond simple allocations under namespace_sem (e.g. everything
that gets unmounted is collected to be dropped after namespace_sem
is released).
Applied.
next prev parent reply other threads:[~2010-10-23 21:42 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-05 10:31 [PATCH 0/9] read-only remount fixes Miklos Szeredi
2010-10-05 10:31 ` [PATCH 1/9] vfs: fix infinite loop caused by clone_mnt race Miklos Szeredi
2010-10-05 10:49 ` Miklos Szeredi
2010-10-05 10:31 ` [PATCH 2/9] vfs: ignore error on forced remount Miklos Szeredi
2010-10-05 10:31 ` [PATCH 3/9] vfs: fix per mount read-write Miklos Szeredi
2010-10-05 10:31 ` [PATCH 4/9] vfs: add sb_force_remount_readonly() helper Miklos Szeredi
2010-10-05 10:31 ` [PATCH 5/9] vfs: allow mnt_want_write() to sleep Miklos Szeredi
2010-10-05 10:31 ` [PATCH 6/9] vfs: keep list of mounts for each superblock Miklos Szeredi
2010-10-05 10:31 ` [PATCH 7/9] vfs: protect remounting superblock read-only Miklos Szeredi
2010-10-22 6:46 ` Al Viro
2010-10-22 12:25 ` Miklos Szeredi
2010-10-22 16:10 ` Miklos Szeredi
2010-10-22 16:14 ` [PATCH 7/9 updated] " Miklos Szeredi
2010-10-23 16:19 ` Al Viro
2010-10-23 19:35 ` Miklos Szeredi
2010-10-23 21:42 ` Al Viro [this message]
2010-10-25 12:36 ` Miklos Szeredi
2010-10-05 10:31 ` [PATCH 8/9] vfs: fs_may_remount_ro: turn unnecessary check into a WARN_ON Miklos Szeredi
2010-10-05 10:31 ` [PATCH 9/9] vfs: mark mounts read-only on forced remount Miklos Szeredi
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