On Wed, 2008-04-02 at 23:36 +0100, Al Viro wrote:
> On Wed, Apr 02, 2008 at 06:21:30PM -0400, Trond Myklebust wrote:
> > On Wed, 2008-04-02 at 22:48 +0100, Al Viro wrote:
> > > I disagree. First of all, clear separation between operations on
> > > _filesystem_, which should all be namespace-agnostic and things
> > > that depend on vfsmount is a Good Thing(tm). Think of that as
> > > of separation between server (superblock and everything related
> > > to it, starting with dentry tree) and clients; mixing those is a
> > > bloody bad idea.
> >
> > Speaking of which: is there any reason why we can't get rid of the
> > vfsmount reference in struct file?
> >
> > Most file operations, don't involve namespace traversal at all: aside
> > from fchdir(), and the *at() functions (all of which take file
> > descriptors, not pointers to struct file) the only function of that
> > vfsmount reference appears to be to prevent the superblock from going
> > away.
>
> Huh? Are you proposing to move that to descriptor table, of all things?
> Not to mention SCM_RIGHTS datagrams and hell knows what else...
I'm just suggesting splitting out the namespace-specific part of struct
file into a separate structure that would be private to the VFS.
Something like
struct file_descriptor {
struct file *file;
struct vfsmount *mnt;
atomic_t refcount;
};
and then having the 'struct file' hold a reference to the superblock
instead of holding a reference to the vfsmount.
Why would that be problematic for SCM_RIGHTS? We don't allow people to
send arbitrary references to 'struct file' using SCM_RIGHTS now; they
have to send descriptors.
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