From: Al Viro <viro@zeniv.linux.org.uk>
To: Rik van Riel <riel@surriel.com>
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
linux-fsdevel@vger.kernel.org, paulmck@kernel.org,
gscrivan@redhat.com, Eric Biederman <ebiederm@xmission.com>,
Chris Mason <clm@fb.com>
Subject: Re: [PATCH 1/2] vfs: free vfsmount through rcu work from kern_unmount
Date: Fri, 18 Feb 2022 19:26:34 +0000 [thread overview]
Message-ID: <Yg/y6qv6dZ2fc5z1@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <20220218183114.2867528-2-riel@surriel.com>
On Fri, Feb 18, 2022 at 01:31:13PM -0500, Rik van Riel wrote:
> After kern_unmount returns, callers can no longer access the
> vfsmount structure. However, the vfsmount structure does need
> to be kept around until the end of the RCU grace period, to
> make sure other accesses have all gone away too.
>
> This can be accomplished by either gating each kern_unmount
> on synchronize_rcu (the comment in the code says it all), or
> by deferring the freeing until the next grace period, where
> it needs to be handled in a workqueue due to the locking in
> mntput_no_expire().
NAK. There's code that relies upon kern_unmount() being
synchronous. That's precisely the reason why MNT_INTERNAL
is treated that way in mntput_no_expire().
next prev parent reply other threads:[~2022-02-18 19:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-18 18:31 [PATCH 0/2] fix rate limited ipc_namespace freeing Rik van Riel
2022-02-18 18:31 ` [PATCH 1/2] vfs: free vfsmount through rcu work from kern_unmount Rik van Riel
2022-02-18 19:26 ` Al Viro [this message]
2022-02-18 19:33 ` Rik van Riel
2022-02-18 19:43 ` Al Viro
2022-02-18 20:24 ` Al Viro
2022-02-18 21:06 ` Al Viro
2022-02-19 5:50 ` Al Viro
2022-02-19 5:53 ` Al Viro
2022-02-19 5:58 ` Al Viro
2022-02-19 6:07 ` Al Viro
2022-02-18 18:31 ` [PATCH 2/2] ipc: get rid of free_ipc_work workqueue Rik van Riel
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