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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 03/13] VFS: remove nameidata args from ->follow_link and ->put_link
Date: Mon, 16 Mar 2015 20:47:32 +0000	[thread overview]
Message-ID: <20150316204732.GB29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20150316044319.23648.2840.stgit@notabene.brown>

On Mon, Mar 16, 2015 at 03:43:19PM +1100, NeilBrown wrote:
> Now that current->nameidata is available, nd_set_link() and
> nd_get_link() can use that directly, so 'nd' doesn't need to
> be passed through ->follow_link and  ->put_link.

FWIW, I would rather pass nd_get_link(nd) to ->put_link() instead of nd.
Note that that's the only thing instances were ever using nd for; what's more,
that's the only thing nd_get_link() is ever used for outside of fs/namei.c,
so with that change it could become static in fs/namei.c.  After such change
we would have it used in
	* follow_link().  We have nd right there.
	* put_link().  Ditto.
	* generic_readlink().  Again, nd is right there (and we obviously
only need to call nd_get_link() once).
Hell, it can even become static inline...

>  	nd->last_type = LAST_BIND;
> -	*p = dentry->d_inode->i_op->follow_link(dentry, nd);
> +	*p = dentry->d_inode->i_op->follow_link(dentry, nd->flags);

I'm not sure if it's a good idea to expose all flags here - it's really
asking for somebody trying to be "smart" and acting differently depending
on what we are doing pathname resolution for/where in lookup we are/etc.
nd->flags & LOOKUP_RCU might be less tempting.

> @@ -4458,13 +4464,13 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
>  	int res;
>  
>  	nd.depth = 0;
> -	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
> +	cookie = dentry->d_inode->i_op->follow_link(dentry, nd.flags);

...(dentry, 0);  nd.flags is uninitialized, for pity sake...

  reply	other threads:[~2015-03-16 20:47 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 [this message]
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
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 08/13] VFS/namei: enhance follow_link to support RCU-walk 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 19:14 ` [PATCH 00/13] Support follow_link in RCU-walk. - V2 Al Viro

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