On Mon, 12 Jul 2010 10:23:21 +0200, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Mon, 12 Jul 2010, Aneesh Kumar K.V wrote:
> > The patch update may_open to allow handle based open on symlinks.
> > The file handle based API use file descritor returned from open_by_handle_at
> > to do different file system operations. To find the link target name we
> > need to get a file descriptor on symlinks.
> >
> > We should be able to read the link target using file handle. The exact
> > usecase is with respect to implementing READLINK operation on a
> > userspace NFS server. The request contain the file handle and the
> > response include target name.
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> > ---
> > fs/namei.c | 10 +++++++++-
> > fs/open.c | 9 ++++++++-
> > include/linux/fs.h | 1 +
> > 3 files changed, 18 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/namei.c b/fs/namei.c
> > index 4d590a3..a6a8093 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -1456,7 +1456,15 @@ int may_open(struct path *path, int acc_mode, int flag)
> >
> > switch (inode->i_mode & S_IFMT) {
> > case S_IFLNK:
> > - return -ELOOP;
> > + /*
> > + * Allow only if acc_mode contain
> > + * open link request and read request.
> > + */
> > + if (acc_mode != (MAY_OPEN_LINK | MAY_READ))
>
> Why require MAY_READ?
a value of 0x0 for flag in open(2) implies a read ?
>
> Actually, open_by_handle() should be a good place to start supporting
> O_NOACCESS from the start. I.e. neigher read, nor write access is
> permitted on the file.
Yes that would be ideal. But that will include much larger change. I was
hoping we could get something in this merge window with the change
suggested above ?
>
>
> > + return -ELOOP;
> > + if (flag != O_RDONLY)
> > + return -ELOOP;
> > + break;
> > case S_IFDIR:
> > if (acc_mode & MAY_WRITE)
> > return -EISDIR;
-aneesh
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