From: Erez Zadok <ezk@cs.sunysb.edu>
To: jjohansen@suse.de
Cc: linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
Andreas Gruenbacher <agruen@suse.de>
Subject: Re: [RFD 1/4] Pass no useless nameidata to the create, lookup, and permission IOPs
Date: Tue, 26 Jun 2007 20:11:41 -0400 [thread overview]
Message-ID: <200706270011.l5R0BfPO011424@agora.fsl.cs.sunysb.edu> (raw)
In-Reply-To: Your message of "Tue, 26 Jun 2007 16:15:11 PDT." <20070626231541.697783295@suse.de>
In message <20070626231541.697783295@suse.de>, jjohansen@suse.de writes:
> The create, lookup, and permission inode operations are all passed a
> full nameidata. This is unfortunate because in nfsd and the mqueue
> filesystem, we must instantiate a struct nameidata but cannot provide
> all of the same information that a regular lookup would provide. The
> unused fields take up space on the stack, but more importantly, it is
> not obvious which fields have meaningful values and which don't, and so
> things might easily break.
>
> This patch introduces struct nameidata2 with only the fields that make
> sense independent of an actual lookup, and uses that struct in those
> places where a full nameidat is not needed.
I agree w/ Trond that a better name is needed other than 'nameidata2',
esp. for something that's a sub-structure (perhaps start it with a '__'?)
These changes would probably help stackable file systems (e.g., eCryptfs and
esp. Unionfs) a lot, b/c stackable f/s often call the lower f/s to lookup
files and such; and in most cases, we just need to pass the intent down, not
the full VFS-level state info.
> +/**
> + * Fields shared between nameidata and nameidata2 -- nameidata2 could
> + * simply be embedded in nameidata, but then the vfs code would become
> + * cluttered with dereferences.
> + */
> +#define __NAMEIDATA2 \
> + struct dentry *dentry; \
> + struct vfsmount *mnt; \
> + unsigned int flags; \
> + \
> + union { \
> + struct open_intent open; \
> + } intent;
Perhaps it is also time to put the dentry + mnt into a single struct path?
It's a small change, but it emphasizes that the two items here, dentry+mnt,
really define a single path to be passed around:
#define __NAMEIDATA \
struct path path; \
unsigned int flags; \
...
Of course, you'll have to change instances of nd->dentry to nd->path.dentry
and so on.
Erez.
next prev parent reply other threads:[~2007-06-27 0:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-26 23:15 [RFD 0/4] AppArmor - Don't pass NULL nameidata to vfs_create/lookup/permission IOPs jjohansen
2007-06-26 23:15 ` [RFD 1/4] Pass no useless nameidata to the create, lookup, and permission IOPs jjohansen
2007-06-27 0:11 ` Erez Zadok [this message]
2007-06-30 9:14 ` Christoph Hellwig
2007-06-30 9:13 ` Christoph Hellwig
2007-06-30 16:13 ` Andreas Gruenbacher
2007-06-26 23:15 ` [RFD 2/4] Never pass a NULL nameidata to vfs_create() jjohansen
2007-06-26 23:15 ` [RFD 3/4] Dont use a NULL nameidata in xattr_permission() jjohansen
2007-06-26 23:15 ` [RFD 4/4] Pass nameidata2 to permission() from nfsd_permission() jjohansen
2007-06-26 23:46 ` [RFD 0/4] AppArmor - Don't pass NULL nameidata to vfs_create/lookup/permission IOPs Trond Myklebust
2007-06-27 20:42 ` Andreas Gruenbacher
2007-06-30 9:15 ` Christoph Hellwig
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