[PATCH] nfsd4: return better error on io incompatible with open mode

from RFC 3530:
"Share reservations are established by OPEN operations and by their
nature are mandatory in that when the OPEN denies READ or WRITE
operations, that denial results in such operations being rejected
with error NFS4ERR_LOCKED."

(Note that share_denied is really only a legal error for OPEN.)
Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/nfs4state.c

@@ -1295,7 +1295,7 @@ nfs4_share_conflict(struct svc_fh *current_fh, unsigned int deny_type)
 	fp = find_file(ino);
 	if (!fp)
 		return nfs_ok;
-	ret = nfserr_share_denied;
+	ret = nfserr_locked;
 	/* Search for conflicting share reservations */
 	list_for_each_entry(stp, &fp->fi_stateids, st_perfile) {
 		if (test_bit(deny_type, &stp->st_deny_bmap) ||

include/linux/nfsd/nfsd.h

@@ -231,6 +231,7 @@ void		nfsd_lockd_shutdown(void);
 #define	nfserr_reclaim_bad	__constant_htonl(NFSERR_RECLAIM_BAD)
 #define	nfserr_badname		__constant_htonl(NFSERR_BADNAME)
 #define	nfserr_cb_path_down	__constant_htonl(NFSERR_CB_PATH_DOWN)
+#define	nfserr_locked		__constant_htonl(NFSERR_LOCKED)
 
 /* error codes for internal use */
 /* if a request fails due to kmalloc failure, it gets dropped.