From: "Mika Penttilä" <mika.penttila@kolumbus.fi>
To: Mike Waychison <michael.waychison@sun.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
raven@themaw.net
Subject: Re: [PATCH 13/28] VFS: Introduce soft reference counts
Date: Mon, 25 Oct 2004 20:20:48 +0300 [thread overview]
Message-ID: <417D35F0.1070501@kolumbus.fi> (raw)
In-Reply-To: <10987155032816@sun.com>
Mike Waychison wrote:
>This patch introduces the concept of a 'soft' reference count for a vfsmount.
>This type of reference count allows for references to be held on mountpoints
>that do not affect their busy states for userland unmounting. Some might
>argue that this is wrong because 'when I unmount a filesystem, I want the
>resources associated with it to go away too', but this way of thinking was
>deprecated with the addition of namespaces and --bind back in the 2.4 series.
>
>A future addition may see a callback mechanism so that in kernel users can
>use a given mountpoint and have it deregistered some way (quota and
>accounting come to mind).
>
>These soft reference counts are used by a later patch that adds an interface
>for holding and manipulating mountpoints using filedescriptors.
>
>Signed-off-by: Mike Waychison <michael.waychison@sun.com>
>
>+static inline struct vfsmount *mntsoftget(struct vfsmount *mnt)
>+{
>+ if (mnt) {
>+ read_lock(&vfsmountref_lock);
>+ atomic_inc(&mnt->mnt_softcount);
>+ mntgroupget(mnt);
>+ read_unlock(&vfsmountref_lock);
>+ }
>+ return mnt;
>+}
>+
>+static inline void mntsoftput(struct vfsmount *mnt)
>+{
>+ struct vfsmount *cleanup;
>+ might_sleep();
>+ if (mnt) {
>+ if (atomic_dec_and_test(&mnt->mnt_count))
>+ __mntput(mnt);
>+ read_lock(&vfsmountref_lock);
>+ cleanup = mntgroupput(mnt);
>+ atomic_dec(&mnt->mnt_softcount);
>+ read_unlock(&vfsmountref_lock);
>+ if (cleanup)
>+ __mntgroupput(cleanup);
>+ }
>+}
>+
> extern void free_vfsmnt(struct vfsmount *mnt);
>
>
What is this against? What are mntgroupput and mntgroupget? Why does
soft put decrement mnt_count which isn't increment by soft get? How do
soft references allow userland umount? I don't see soft references used
anywhere...
--Mika
next prev parent reply other threads:[~2004-10-25 17:16 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-25 14:38 [PATCH 0/28] Autofs NG Patchset 0.2 Mike Waychison
2004-10-25 14:39 ` [PATCH 1/28] VFS: Unexport umount_tree Mike Waychison
2004-10-25 14:39 ` [PATCH 2/28] VFS: mnt_fslink -> mnt_expire Mike Waychison
2004-10-25 14:40 ` [PATCH 3/28] VFS: Move expiry into vfs Mike Waychison
2004-10-25 14:40 ` [PATCH 4/28] VFS: Stat shouldn't stop expire Mike Waychison
2004-10-25 14:41 ` [PATCH 5/28] VFS: Make expiry timeout configurable Mike Waychison
2004-10-25 14:41 ` [PATCH 6/28] VFS: Make expiry recursive Mike Waychison
2004-10-25 14:42 ` [PATCH 7/28] AFS: Update AFS to use new expiry interface Mike Waychison
2004-10-25 14:42 ` [PATCH 8/28] VFS: Remove MNT_EXPIRE support Mike Waychison
2004-10-25 14:43 ` [PATCH 9/28] VFS: Give sane expiry semantics Mike Waychison
2004-10-25 14:43 ` [PATCH 10/28] VFS: Move next_mnt() Mike Waychison
2004-10-25 14:44 ` [PATCH 11/28] VFS: Allow for detachable subtrees Mike Waychison
2004-10-25 14:44 ` [PATCH 12/28] VFS: Remove (now bogus) check_mnt Mike Waychison
2004-10-25 14:45 ` [PATCH 13/28] VFS: Introduce soft reference counts Mike Waychison
2004-10-25 15:25 ` Christoph Hellwig
2004-10-25 15:35 ` [PATCH 14/28] VFS: Introduce Mountpoint file descriptors (resend) Mike Waychison
2004-10-25 17:20 ` Mika Penttilä [this message]
2004-10-25 17:25 ` [PATCH 13/28] VFS: Introduce soft reference counts Mike Waychison
2004-10-25 17:52 ` Mika Penttilä
2004-10-25 17:56 ` [PATCH 11/28] VFS: Allow for detachable subtrees (resend) Mike Waychison
2004-10-25 15:09 ` [PATCH 12/28] VFS: Remove (now bogus) check_mnt Christoph Hellwig
2004-10-25 15:15 ` Mike Waychison
2004-10-25 15:04 ` [PATCH 8/28] VFS: Remove MNT_EXPIRE support Christoph Hellwig
2004-10-25 15:12 ` Mike Waychison
2004-10-25 15:16 ` Christoph Hellwig
2004-10-25 15:30 ` Mike Waychison
2004-10-25 17:16 ` Mike Waychison
2004-10-25 17:29 ` Mike Waychison
2004-10-25 15:04 ` [PATCH 6/28] VFS: Make expiry recursive Christoph Hellwig
2004-10-26 10:27 ` [PATCH 4/28] VFS: Stat shouldn't stop expire Christoph Hellwig
2004-10-27 18:36 ` Mike Waychison
2004-10-25 14:59 ` [PATCH 3/28] VFS: Move expiry into vfs Christoph Hellwig
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