Subject: [PATCH] docuement filesystem helpers for custom 'struct file's
From: Dave Hansen <haveblue@us.ibm.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org
In-Reply-To: <20070919172611.GA20917@infradead.org>
References: <20070917182718.70494C9B@kernel>
	 <20070917182718.A6B9F7FD@kernel>  <20070919172611.GA20917@infradead.org>
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Date: Wed, 19 Sep 2007 10:47:23 -0700
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On Wed, 2007-09-19 at 18:26 +0100, Christoph Hellwig wrote:
> On Mon, Sep 17, 2007 at 11:27:18AM -0700, Dave Hansen wrote:
> > 
> > Christoph H. says this stands on its own and can go in before the
> > rest of the r/o bind mount set.  
> > 
> > ---
> > 
> > Some filesystems forego the vfs and may_open() and create their
> > own 'struct file's.
> > 
> > This patch creates a couple of helper functions which can be
> > used by these filesystems, and will provide a unified place
> > which the r/o bind mount code may patch.
> > 
> > Also, rename an existing, static-scope init_file() to a less
> > generic name.
> 
> Looks good.  But please provide a patch ontop of your patchkit to
> add kernel-doc comments for the two new exported functions.

Appended.  I started to write the comments to describe the function
arguments, but they all looked pretty retarded.  

> Are there any direct caller of get_empty_filp left after this patch?
> We really should get rid of that export to stop people from shooting
> themselves in the foot.

Yeah, there are a few left.  But, they're in the middle of what is
sometimes tricky error handling, so I think we should trickle those in
later. 


-- Dave

 lxc-dave/fs/file_table.c |   22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff -puN fs/file_table.c~document fs/file_table.c
--- lxc/fs/file_table.c~document	2007-09-19 10:31:13.000000000 -0700
+++ lxc-dave/fs/file_table.c	2007-09-19 10:39:34.000000000 -0700
@@ -137,6 +137,18 @@ fail:
 
 EXPORT_SYMBOL(get_empty_filp);
 
+/**
+ * alloc_file - allocate and initialize a 'struct file' with
+ * the given arguments
+ *
+ * Use this instead of get_empty_filp() to get a new
+ * 'struct file'.  Do so because of the same initialization
+ * pitfalls reasons listed for init_file().  This is a
+ * preferred interface to using init_file().
+ *
+ * If all the callers of init_file() are eliminated, its
+ * code should be moved into this function.
+ */
 struct file *alloc_file(struct vfsmount *mnt, struct dentry *dentry,
 		mode_t mode, const struct file_operations *fop)
 {
@@ -152,7 +164,15 @@ struct file *alloc_file(struct vfsmount 
 }
 EXPORT_SYMBOL(alloc_file);
 
-/*
+/**
+ * init_file - initialize a 'struct file'
+ * @file: the already allocated 'struct file' to initialized
+ * @mnt: the vfsmount on which the file resides
+ *
+ * Use this instead of setting the members directly.  Doing so
+ * avoids making mistakes like forgetting the mntget() or
+ * forgetting to take a write on the mnt.
+ *
  * Note: This is a crappy interface.  It is here to make
  * merging with the existing users of get_empty_filp()
  * who have complex failure logic easier.  All users
_


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