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    vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op · ecf3d1f1
    Jeff Layton 提交于
    The following set of operations on a NFS client and server will cause
    
        server# mkdir a
        client# cd a
        server# mv a a.bak
        client# sleep 30  # (or whatever the dir attrcache timeout is)
        client# stat .
        stat: cannot stat `.': Stale NFS file handle
    
    Obviously, we should not be getting an ESTALE error back there since the
    inode still exists on the server. The problem is that the lookup code
    will call d_revalidate on the dentry that "." refers to, because NFS has
    FS_REVAL_DOT set.
    
    nfs_lookup_revalidate will see that the parent directory has changed and
    will try to reverify the dentry by redoing a LOOKUP. That of course
    fails, so the lookup code returns ESTALE.
    
    The problem here is that d_revalidate is really a bad fit for this case.
    What we really want to know at this point is whether the inode is still
    good or not, but we don't really care what name it goes by or whether
    the dcache is still valid.
    
    Add a new d_op->d_weak_revalidate operation and have complete_walk call
    that instead of d_revalidate. The intent there is to allow for a
    "weaker" d_revalidate that just checks to see whether the inode is still
    good. This is also gives us an opportunity to kill off the FS_REVAL_DOT
    special casing.
    
    [AV: changed method name, added note in porting, fixed confusion re
    having it possibly called from RCU mode (it won't be)]
    
    Cc: NeilBrown <neilb@suse.de>
    Signed-off-by: NJeff Layton <jlayton@redhat.com>
    Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
    ecf3d1f1
super.c 70.7 KB