On Tue, 2016-03-08 at 10:17 +0100, Mateusz Guzik wrote:
> On Thu, Feb 25, 2016 at 11:36:48AM -0800, James Bottomley wrote:
> > I need an API that allows me to obtain a clone of the current file
> > pointer to pass in to an exec handler. I've labelled this as an
> > internal API because I can't see how it would be useful outside of
> > the
> > fs subsystem. The use case will be a persistent binfmt_misc
> > handler.
> >
> > Signed-off-by: James Bottomley <
> > James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> > ---
> > fs/internal.h | 1 +
> > fs/open.c | 20 ++++++++++++++++++++
> > 2 files changed, 21 insertions(+)
> >
> > diff --git a/fs/internal.h b/fs/internal.h
> > index b71deee..c8ca0c9 100644
> > --- a/fs/internal.h
> > +++ b/fs/internal.h
> > @@ -108,6 +108,7 @@ extern long do_handle_open(int mountdirfd,
> > struct file_handle __user *ufh, int
> > open_flag);
> > extern int open_check_o_direct(struct file *f);
> > extern int vfs_open(const struct path *, struct file *, const
> > struct cred *);
> > +extern struct file *filp_clone_open(struct file *);
> >
> > /*
> > * inode.c
> > diff --git a/fs/open.c b/fs/open.c
> > index 55bdc75..bb7ffd6 100644
> > --- a/fs/open.c
> > +++ b/fs/open.c
> > @@ -1004,6 +1004,26 @@ struct file *file_open_root(struct dentry
> > *dentry, struct vfsmount *mnt,
> > }
> > EXPORT_SYMBOL(file_open_root);
> >
> > +struct file *filp_clone_open(struct file *oldfile)
> > +{
> > + struct file *file;
> > + int retval;
> > +
> > + file = get_empty_filp();
> > + if (IS_ERR(file))
> > + return file;
> > +
> > + file->f_flags = oldfile->f_flags;
> > + retval = vfs_open(&oldfile->f_path, file, oldfile
> > ->f_cred);
> > + if (retval) {
> > + fput(file);
>
> You likely want put_file instead, although if I read it right this is
> only cosmetics for consistency with dentry_open.
get_empty_filp() is always paired with fput(). There isn't a
put_file(); there's a put_files_struct() but that's for something
different.
> Also vast majority of the file uses 'error' instead of 'retval'. Any
> reason to deviate here?
it mirrors the close routines which also use retval.
James
> > + return ERR_PTR(retval);
> > + }
> > +
> > + return file;
> > +}
> > +EXPORT_SYMBOL(filp_clone_open);
> > +
> > long do_sys_open(int dfd, const char __user *filename, int flags,
> > umode_t mode)
> > {
> > struct open_flags op;
> > --
> > 2.6.2
> >
>
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