Messages in this thread | | | Subject | Re: [patch 01/10] vfs: add path_create() and path_mknod() | From | Trond Myklebust <> | Date | Wed, 02 Apr 2008 19:19:58 -0400 |
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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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