From: Al Viro <viro@ZenIV.linux.org.uk>
To: Eric Paris <eparis@redhat.com>
Cc: linux-kernel@vger.kernel.org, hch@infradead.org,
alan@lxorguk.ukuu.org.uk, sfr@canb.auug.org.au,
john@johnmccutchan.com, rlove@rlove.org,
akpm@linux-foundation.org
Subject: Re: [PATCH 04/13] fsnotify: add in inode fsnotify markings
Date: Mon, 23 Mar 2009 09:28:30 +0000 [thread overview]
Message-ID: <20090323092830.GN28946@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20090319180514.17449.34794.stgit@paris.rdu.redhat.com>
On Thu, Mar 19, 2009 at 02:05:14PM -0400, Eric Paris wrote:
> This patch creates in inode fsnotify markings. dnotify will make use of in
> inode markings to mark which inodes it wishes to send events for. fanotify
> will use this to mark which inodes it does not wish to send events for.
Hrm... What happens if fsnotify_clear_marks_by_inode() is called, gets
the only mark we had for a group, removes it from all lists, drops all
locks and races with the final fsnotify_put_group()? Said put_group
sees nothing whatsoever on the per-group mark list (the only mark we
used to have there is already evicted) and the group is cheerfully
freed. Then fsnotify_destroy_mark_by_entry() calls
group->ops->freeing_mark(entry, group)
with group already freed... Gets really interesting in case of inotify -
there ->freeing_mark() leads to blocking allocations and really touches
group in non-trivial ways.
Note that for inotify ->freeing_mark() will happily add notification to
group's queue and that's another race of the same nature - even if
group itself isn't yet freed, that final put_group() might bloody well
get past flushing the queue.
I really don't like the idea of having marks contributing to group refcount -
that would have solved this one, but we'd get potential leaks from hell ;-/
Maybe a separate counter controlling only actual freeing of group?
next prev parent reply other threads:[~2009-03-23 9:28 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-19 18:04 [PATCH 01/13] mutex: add atomic_dec_and_mutex_lock Eric Paris
2009-03-19 18:05 ` [PATCH 02/13] fsnotify: unified filesystem notification backend Eric Paris
2009-04-07 23:45 ` Paul E. McKenney
2009-03-19 18:05 ` [PATCH 03/13] fsnotify: add group priorities Eric Paris
2009-03-19 18:05 ` [PATCH 04/13] fsnotify: add in inode fsnotify markings Eric Paris
2009-03-23 9:28 ` Al Viro [this message]
2009-03-23 9:53 ` Al Viro
2009-03-19 18:05 ` [PATCH 05/13] fsnotify: parent event notification Eric Paris
2009-03-19 18:05 ` [PATCH 06/13] dnotify: reimplement dnotify using fsnotify Eric Paris
2009-03-19 18:05 ` [PATCH 07/13] fsnotify: generic notification queue and waitq Eric Paris
2009-03-19 18:05 ` [PATCH 08/13] fsnotify: include pathnames with entries when possible Eric Paris
2009-03-19 18:05 ` [PATCH 09/13] fsnotify: add correlations between events Eric Paris
2009-03-19 18:05 ` [PATCH 10/13] fsnotify: allow groups to add private data to events Eric Paris
2009-03-23 11:04 ` Al Viro
2009-03-19 18:05 ` [PATCH 11/13] fsnotify: fsnotify marks on inodes pin them in core Eric Paris
2009-03-19 18:05 ` [PATCH 12/13] fsnotify: handle filesystem unmounts with fsnotify marks Eric Paris
2009-03-19 18:06 ` [PATCH 13/13] inotify: reimplement inotify using fsnotify Eric Paris
2009-03-23 10:29 ` Al Viro
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