NFS: Don't invalidate a submounted dentry in nfs_prime_dcache()

If we're traversing a directory which contains a submounted filesystem,
or one that has a referral, the NFS server that is processing the READDIR
request will often return information for the underlying (mounted-on)
directory. It may, or may not, also return filehandle information.

If this happens, and the lookup in nfs_prime_dcache() returns the
dentry for the submounted directory, the filehandle comparison will
fail, and we call d_invalidate(). Post-commit 8ed936b5671bf
("vfs: Lazily remove mounts on unlinked files and directories."), this
means the entire subtree is unmounted.

The following minimal patch addresses this problem by punting on
the invalidation if there is a submount.

Kudos to Neil Brown <[email protected]> for having tracked down this
issue (see link).

Reported-by: Nix <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Cc: [email protected] # 3.18+
Signed-off-by: Trond Myklebust <[email protected]>

0 files changed, 0 insertions, 0 deletions