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Subject[PATCH] docuement filesystem helpers for custom 'struct file's
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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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