9p locks: add mount option for lock retry interval

The default P9_LOCK_TIMEOUT can be too long for some users exporting
a local file system to a guest VM (30s), make this configurable at
mount time.

Link: http://lkml.kernel.org/r/1536295827-3181-1-git-send-email-asmadeus@codewreck.org
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=195727
Signed-off-by: Dinu-Razvan Chis-Serban <justcsdr@gmail.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

fs/9p/v9fs.c

@@ -61,6 +61,8 @@ enum {
 	Opt_cache_loose, Opt_fscache, Opt_mmap,
 	/* Access options */
 	Opt_access, Opt_posixacl,
+	/* Lock timeout option */
+	Opt_locktimeout,
 	/* Error token */
 	Opt_err
 };
@@ -80,6 +82,7 @@ static const match_table_t tokens = {
 	{Opt_cachetag, "cachetag=%s"},
 	{Opt_access, "access=%s"},
 	{Opt_posixacl, "posixacl"},
+	{Opt_locktimeout, "locktimeout=%u"},
 	{Opt_err, NULL}
 };
 
@@ -187,6 +190,7 @@ static int v9fs_parse_options(struct v9fs_session_info *v9ses, char *opts)
 #ifdef CONFIG_9P_FSCACHE
 	v9ses->cachetag = NULL;
 #endif
+	v9ses->session_lock_timeout = P9_LOCK_TIMEOUT;
 
 	if (!opts)
 		return 0;
@@ -359,6 +363,23 @@ static int v9fs_parse_options(struct v9fs_session_info *v9ses, char *opts)
 #endif
 			break;
 
+		case Opt_locktimeout:
+			r = match_int(&args[0], &option);
+			if (r < 0) {
+				p9_debug(P9_DEBUG_ERROR,
+					 "integer field, but no integer?\n");
+				ret = r;
+				continue;
+			}
+			if (option < 1) {
+				p9_debug(P9_DEBUG_ERROR,
+					 "locktimeout must be a greater than zero integer.\n");
+				ret = -EINVAL;
+				continue;
+			}
+			v9ses->session_lock_timeout = (long)option * HZ;
+			break;
+
 		default:
 			continue;
 		}

fs/9p/v9fs.h

@@ -116,6 +116,7 @@ struct v9fs_session_info {
 	struct p9_client *clnt;	/* 9p client */
 	struct list_head slist; /* list of sessions registered with v9fs */
 	struct rw_semaphore rename_sem;
+	long session_lock_timeout; /* retry interval for blocking locks */
 };
 
 /* cache_validity flags */

fs/9p/vfs_file.c

@@ -154,6 +154,7 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
 	uint8_t status = P9_LOCK_ERROR;
 	int res = 0;
 	unsigned char fl_type;
+	struct v9fs_session_info *v9ses;
 
 	fid = filp->private_data;
 	BUG_ON(fid == NULL);
@@ -189,6 +190,8 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
 	if (IS_SETLKW(cmd))
 		flock.flags = P9_LOCK_FLAGS_BLOCK;
 
+	v9ses = v9fs_inode2v9ses(file_inode(filp));
+
 	/*
 	 * if its a blocked request and we get P9_LOCK_BLOCKED as the status
 	 * for lock request, keep on trying
@@ -202,7 +205,8 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
 			break;
 		if (status == P9_LOCK_BLOCKED && !IS_SETLKW(cmd))
 			break;
-		if (schedule_timeout_interruptible(P9_LOCK_TIMEOUT) != 0)
+		if (schedule_timeout_interruptible(v9ses->session_lock_timeout)
+				!= 0)
 			break;
 	}