xfs: push corruption -> ESTALE conversion to xfs_nfs_get_inode()

In xfs_imap_to_bp(), we convert a -EFSCORRUPTED error to -EINVAL if
we are doing an untrusted lookup. This is done because we need
failed filehandle lookups to report -ESTALE to the caller, and it
does this by converting -EINVAL and -ENOENT errors to -ESTALE.

The squashing of EFSCORRUPTED in imap_to_bp makes it impossible for
for xfs_iget(UNTRUSTED) callers to determine the difference between
"inode does not exist" and "corruption detected during lookup". We
realy need that distinction in places calling xfS_iget(UNTRUSTED),
so move the filehandle error case handling all the way out to
xfs_nfs_get_inode() where it is needed.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_inode_buf.c

@@ -201,11 +201,6 @@ xfs_imap_to_bp(
 			ASSERT(buf_flags & XBF_TRYLOCK);
 			return error;
 		}
-
-		if (error == -EFSCORRUPTED &&
-		    (iget_flags & XFS_IGET_UNTRUSTED))
-			return -EINVAL;
-
 		xfs_warn(mp, "%s: xfs_trans_read_buf() returned error %d.",
 			__func__, error);
 		return error;

fs/xfs/xfs_export.c

@@ -140,15 +140,24 @@ xfs_nfs_get_inode(
 	 */
 	error = xfs_iget(mp, NULL, ino, XFS_IGET_UNTRUSTED, 0, &ip);
 	if (error) {
+
 		/*
 		 * EINVAL means the inode cluster doesn't exist anymore.
-		 * This implies the filehandle is stale, so we should
-		 * translate it here.
+		 * EFSCORRUPTED means the metadata pointing to the inode cluster
+		 * or the inode cluster itself is corrupt.  This implies the
+		 * filehandle is stale, so we should translate it here.
 		 * We don't use ESTALE directly down the chain to not
 		 * confuse applications using bulkstat that expect EINVAL.
 		 */
-		if (error == -EINVAL || error == -ENOENT)
+		switch (error) {
+		case -EINVAL:
+		case -ENOENT:
+		case -EFSCORRUPTED:
 			error = -ESTALE;
+			break;
+		default:
+			break;
+		}
 		return ERR_PTR(error);
 	}