Merge tag 'afs-fixes-20231124' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull AFS fixes from David Howells:

 - Fix the afs_server_list struct to be cleaned up with RCU

 - Fix afs to translate a no-data result from a DNS lookup into ENOENT,
   not EDESTADDRREQ for consistency with OpenAFS

 - Fix afs to translate a negative DNS lookup result into ENOENT rather
   than EDESTADDRREQ

 - Fix file locking on R/O volumes to operate in local mode as the
   server doesn't handle exclusive locks on such files

 - Set SB_RDONLY on superblocks for RO and Backup volumes so that the
   VFS can see that they're read only

* tag 'afs-fixes-20231124' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  afs: Mark a superblock for an R/O or Backup volume as SB_RDONLY
  afs: Fix file locking on R/O volumes to operate in local mode
  afs: Return ENOENT if no cell DNS record can be found
  afs: Make error on cell lookup failure consistent with OpenAFS
  afs: Fix afs_server_list to be cleaned up with RCU

fs/afs/dynroot.c

@@ -132,8 +132,8 @@ static int afs_probe_cell_name(struct dentry *dentry)
 
 	ret = dns_query(net->net, "afsdb", name, len, "srv=1",
 			NULL, NULL, false);
-	if (ret == -ENODATA)
-		ret = -EDESTADDRREQ;
+	if (ret == -ENODATA || ret == -ENOKEY)
+		ret = -ENOENT;
 	return ret;
 }
 

fs/afs/internal.h

@@ -553,6 +553,7 @@ struct afs_server_entry {
 };
 
 struct afs_server_list {
+	struct rcu_head		rcu;
 	afs_volid_t		vids[AFS_MAXTYPES]; /* Volume IDs */
 	refcount_t		usage;
 	unsigned char		nr_servers;

fs/afs/server_list.c

@@ -17,7 +17,7 @@ void afs_put_serverlist(struct afs_net *net, struct afs_server_list *slist)
 		for (i = 0; i < slist->nr_servers; i++)
 			afs_unuse_server(net, slist->servers[i].server,
 					 afs_server_trace_put_slist);
-		kfree(slist);
+		kfree_rcu(slist, rcu);
 	}
 }
 

fs/afs/super.c

@@ -407,6 +407,10 @@ static int afs_validate_fc(struct fs_context *fc)
 			return PTR_ERR(volume);
 
 		ctx->volume = volume;
+		if (volume->type != AFSVL_RWVOL) {
+			ctx->flock_mode = afs_flock_mode_local;
+			fc->sb_flags |= SB_RDONLY;
+		}
 	}
 
 	return 0;

fs/afs/vl_rotate.c

@@ -58,6 +58,12 @@ static bool afs_start_vl_iteration(struct afs_vl_cursor *vc)
 		}
 
 		/* Status load is ordered after lookup counter load */
+		if (cell->dns_status == DNS_LOOKUP_GOT_NOT_FOUND) {
+			pr_warn("No record of cell %s\n", cell->name);
+			vc->error = -ENOENT;
+			return false;
+		}
+
 		if (cell->dns_source == DNS_RECORD_UNAVAILABLE) {
 			vc->error = -EDESTADDRREQ;
 			return false;
@@ -285,6 +291,7 @@ failed:
  */
 static void afs_vl_dump_edestaddrreq(const struct afs_vl_cursor *vc)
 {
+	struct afs_cell *cell = vc->cell;
 	static int count;
 	int i;
 
@@ -294,6 +301,9 @@ static void afs_vl_dump_edestaddrreq(const struct afs_vl_cursor *vc)
 
 	rcu_read_lock();
 	pr_notice("EDESTADDR occurred\n");
+	pr_notice("CELL: %s err=%d\n", cell->name, cell->error);
+	pr_notice("DNS: src=%u st=%u lc=%x\n",
+		  cell->dns_source, cell->dns_status, cell->dns_lookup_count);
 	pr_notice("VC: ut=%lx ix=%u ni=%hu fl=%hx err=%hd\n",
 		  vc->untried, vc->index, vc->nr_iterations, vc->flags, vc->error);