fuse: nfs export special lookups

Implement the get_parent export operation by sending a LOOKUP request with
".." as the name.

Implement looking up an inode by node ID after it has been evicted from
the cache.  This is done by seding a LOOKUP request with "." as the name
(for all file types, not just directories).

The filesystem can set the FUSE_EXPORT_SUPPORT flag in the INIT reply, to
indicate that it supports these special lookups.

Thanks to John Muir for the original implementation of this feature.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: David Teigland <teigland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index d48282197696..265635dc9908 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -104,11 +104,14 @@ struct fuse_file_lock {
 
 /**
  * INIT request/reply flags
+ *
+ * FUSE_EXPORT_SUPPORT: filesystem handles lookups of "." and ".."
  */
 #define FUSE_ASYNC_READ         (1 << 0)
 #define FUSE_POSIX_LOCKS        (1 << 1)
 #define FUSE_FILE_OPS           (1 << 2)
 #define FUSE_ATOMIC_O_TRUNC     (1 << 3)
+#define FUSE_EXPORT_SUPPORT     (1 << 4)
 #define FUSE_BIG_WRITES         (1 << 5)
 
 /**