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From: Al Viro <viro@ZenIV.linux.org.uk>
To: NeilBrown <neilb@suse.de>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 06/13] VFS/namei: new flag to support RCU symlinks: LOOKUP_LINK_RCU.
Date: Mon, 16 Mar 2015 22:33:45 +0000	[thread overview]
Message-ID: <20150316223345.GD29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20150316044320.23648.45500.stgit@notabene.brown>

On Mon, Mar 16, 2015 at 03:43:20PM +1100, NeilBrown wrote:
> When we support ->follow_link in RCU-walk we will not want to
> take a reference to the 'struct path *link' passed to follow_link,
> and correspondingly will not want to drop that reference.
> 
> As link_path_walk will complete_walk() in the case of an error,
> and as complete_walk() will clear LOOKUP_RCU, we cannot test
> LOOKUP_RCU to determine if the path should be 'put'.
> 
> So introduce a new flag: LOOKUP_LINK_RCU.  This is set on
> entry to follow_link() if appropriate and put_link() will
> only call path_put() if it is clear.

Umm...  How is it different from nd->depth > 0 && nd->flags & LOOKUP_RCU?
IOW, could we bump nd->depth before that (conditional) mntget()?

  reply	other threads:[~2015-03-16 22:33 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-16  4:43 [PATCH 00/13] Support follow_link in RCU-walk. - V2 NeilBrown
2015-03-16  4:43 ` [PATCH 01/13] VFS: replace {, total_}link_count in task_struct with pointer to nameidata NeilBrown
2015-03-16 19:46   ` Al Viro
2015-03-16  4:43 ` [PATCH 02/13] VFS: make all ->follow_link handlers aware for LOOKUP_RCU NeilBrown
2015-03-16  4:43 ` [PATCH 04/13] security/selinux: check for LOOKUP_RCU in _follow_link NeilBrown
2015-03-16 21:00   ` Al Viro
2015-03-20  4:39     ` NeilBrown
2015-03-20  5:12       ` Al Viro
2015-03-16  4:43 ` [PATCH 03/13] VFS: remove nameidata args from ->follow_link and ->put_link NeilBrown
2015-03-16 20:47   ` Al Viro
2015-03-16  4:43 ` [PATCH 05/13] VFS/namei: use terminate_walk when symlink lookup fails NeilBrown
2015-03-16  4:43 ` [PATCH 12/13] XFS: allow follow_link to often succeed in RCU-walk NeilBrown
2015-03-16 22:37   ` Al Viro
2015-03-16  4:43 ` [PATCH 10/13] VFS/namei: handle LOOKUP_RCU in page_follow_link_light NeilBrown
2015-03-16 22:50   ` Al Viro
2015-03-19 22:38     ` NeilBrown
2015-03-19 23:46       ` Al Viro
2015-03-16  4:43 ` [PATCH 11/13] xfs: use RCU to free 'struct xfs_mount' NeilBrown
2015-03-16  4:43 ` [PATCH 13/13] NFS: support LOOKUP_RCU in nfs_follow_link NeilBrown
2015-03-16  4:43 ` [PATCH 06/13] VFS/namei: new flag to support RCU symlinks: LOOKUP_LINK_RCU NeilBrown
2015-03-16 22:33   ` Al Viro [this message]
2015-03-17  0:59     ` Al Viro
2015-03-16  4:43 ` [PATCH 07/13] VFS/namei: abort RCU-walk on symlink if atime needs updating NeilBrown
2015-03-16  4:43 ` [PATCH 09/13] VFS/namei: enable RCU-walk when following symlinks NeilBrown
2015-03-16 22:44   ` Al Viro
2015-03-16  4:43 ` [PATCH 08/13] VFS/namei: enhance follow_link to support RCU-walk NeilBrown
2015-03-16 19:14 ` [PATCH 00/13] Support follow_link in RCU-walk. - V2 Al Viro

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