nilfs2: get rid of sget use for checking if current mount is present

This stops using sget() for checking if an r/w-mount or an r/o-mount exists on the device. This elimination uses a back pointer to the current mount added to nilfs object. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

nilfs2: get rid of sget use for checking if current mount is present
This stops using sget() for checking if an r/w-mount or an r/o-mount exists on the device. This elimination uses a back pointer to the current mount added to nilfs object. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Ryusuke Konishi · Al Viro
1 parent 33c8e57c86
Showing 2 changed files with 35 additions and 60 deletions Side-by-side Diff
fs/nilfs2/super.c
fs/nilfs2/the_nilfs.h
@@ -67,8 +67,6 @@
  
 static void nilfs_write_super(struct super_block *sb);
 static int nilfs_remount(struct super_block *sb, int *flags, char *data);
-static int test_exclusive_mount(struct file_system_type *fs_type,
-				struct block_device *bdev, int flags);
  
 /**
  * nilfs_error() - report failure condition on a filesystem
@@ -329,6 +327,10 @@
 		nilfs_commit_super(sbi, 1);
 		up_write(&nilfs->ns_sem);
 	}
+	down_write(&nilfs->ns_sem);
+	if (nilfs->ns_current == sbi)
+		nilfs->ns_current = NULL;
+	up_write(&nilfs->ns_sem);
  
 	nilfs_detach_checkpoint(sbi);
 	put_nilfs(sbi->s_nilfs);
@@ -880,6 +882,11 @@
 		goto failed_root;
 	}
  
+	down_write(&nilfs->ns_sem);
+	if (!nilfs_test_opt(sbi, SNAPSHOT))
+		nilfs->ns_current = sbi;
+	up_write(&nilfs->ns_sem);
+
 	return 0;
  
  failed_root:
  
  
  
@@ -958,14 +965,16 @@
 		 * by fsck since we originally mounted the partition.)
 		 */
 		down(&sb->s_bdev->bd_mount_sem);
-		/* Check existing RW-mount */
-		if (test_exclusive_mount(sb->s_type, sb->s_bdev, 0)) {
+		down_read(&nilfs->ns_sem);
+		if (nilfs->ns_current && nilfs->ns_current != sbi) {
 			printk(KERN_WARNING "NILFS (device %s): couldn't "
-			       "remount because a RW-mount exists.\n",
+			       "remount because an RW-mount exists.\n",
 			       sb->s_id);
+			up_read(&nilfs->ns_sem);
 			err = -EBUSY;
 			goto rw_remount_failed;
 		}
+		up_read(&nilfs->ns_sem);
 		if (sbi->s_snapshot_cno != nilfs_last_cno(nilfs)) {
 			printk(KERN_WARNING "NILFS (device %s): couldn't "
 			       "remount because the current RO-mount is not "
@@ -984,6 +993,7 @@
  
 		down_write(&nilfs->ns_sem);
 		nilfs_setup_super(sbi);
+		nilfs->ns_current = sbi;
 		up_write(&nilfs->ns_sem);
  
 		up(&sb->s_bdev->bd_mount_sem);
@@ -1118,10 +1128,23 @@
 	}
  
 	down(&sd.bdev->bd_mount_sem);
-	if (!sd.cno &&
-	    (err = test_exclusive_mount(fs_type, sd.bdev, flags ^ MS_RDONLY))) {
-		err = (err < 0) ? : -EBUSY;
-		goto failed_unlock;
+
+	if (!sd.cno) {
+		/*
+		 * Check if an exclusive mount exists or not.
+		 * Snapshot mounts coexist with a current mount
+		 * (i.e. rw-mount or ro-mount), whereas rw-mount and
+		 * ro-mount are mutually exclusive.
+		 */
+		down_read(&nilfs->ns_sem);
+		if (nilfs->ns_current &&
+		    ((nilfs->ns_current->s_super->s_flags ^ flags)
+		     & MS_RDONLY)) {
+			up_read(&nilfs->ns_sem);
+			err = -EBUSY;
+			goto failed_unlock;
+		}
+		up_read(&nilfs->ns_sem);
 	}
  
 	/*
@@ -1180,57 +1203,6 @@
 	 * put_nilfs() and unlocking bd_mount_sem need the block device.
 	 */
 	return err;
-}
-
-static int nilfs_test_bdev_super3(struct super_block *s, void *data)
-{
-	struct nilfs_super_data *sd = data;
-	int ret;
-
-	if (s->s_bdev != sd->bdev)
-		return 0;
-	if (down_read_trylock(&s->s_umount)) {
-		ret = (s->s_flags & MS_RDONLY) && s->s_root &&
-			nilfs_test_opt(NILFS_SB(s), SNAPSHOT);
-		up_read(&s->s_umount);
-		if (ret)
-			return 0; /* ignore snapshot mounts */
-	}
-	return !((sd->flags ^ s->s_flags) & MS_RDONLY);
-}
-
-static int __false_bdev_super(struct super_block *s, void *data)
-{
-#if 0 /* XXX: workaround for lock debug. This is not good idea */
-	up_write(&s->s_umount);
-#endif
-	return -EFAULT;
-}
-
-/**
- * test_exclusive_mount - check whether an exclusive RW/RO mount exists or not.
- * fs_type: filesystem type
- * bdev: block device
- * flag: 0 (check rw-mount) or MS_RDONLY (check ro-mount)
- * res: pointer to an integer to store result
- *
- * This function must be called within a section protected by bd_mount_mutex.
- */
-static int test_exclusive_mount(struct file_system_type *fs_type,
-				struct block_device *bdev, int flags)
-{
-	struct super_block *s;
-	struct nilfs_super_data sd = { .flags = flags, .bdev = bdev };
-
-	s = sget(fs_type, nilfs_test_bdev_super3, __false_bdev_super, &sd);
-	if (IS_ERR(s)) {
-		if (PTR_ERR(s) != -EFAULT)
-			return PTR_ERR(s);
-		return 0;  /* Not found */
-	}
-	up_write(&s->s_umount);
-	deactivate_super(s);
-	return 1;  /* Found */
 }
  
 struct file_system_type nilfs_fs_type = {
@@ -50,6 +50,7 @@
  * @ns_sem: semaphore for shared states
  * @ns_writer_mutex: mutex protecting ns_writer attach/detach
  * @ns_writer_refcount: number of referrers on ns_writer
+ * @ns_current: back pointer to current mount
  * @ns_sbh: buffer heads of on-disk super blocks
  * @ns_sbp: pointers to super block data
  * @ns_sbwtime: previous write time of super blocks
@@ -97,6 +98,8 @@
 	struct rw_semaphore	ns_sem;
 	struct mutex		ns_writer_mutex;
 	atomic_t		ns_writer_refcount;
+
+	struct nilfs_sb_info   *ns_current;
  
 	/*
 	 * used for
...	...	@@ -67,8 +67,6 @@
67	67
68	68	static void nilfs_write_super(struct super_block *sb);
69	69	static int nilfs_remount(struct super_block sb, int flags, char *data);
70		-static int test_exclusive_mount(struct file_system_type *fs_type,
71		- struct block_device *bdev, int flags);
72	70
73	71	/**
74	72	* nilfs_error() - report failure condition on a filesystem
...	...	@@ -329,6 +327,10 @@
329	327	nilfs_commit_super(sbi, 1);
330	328	up_write(&nilfs->ns_sem);
331	329	}
	330	+ down_write(&nilfs->ns_sem);
	331	+ if (nilfs->ns_current == sbi)
	332	+ nilfs->ns_current = NULL;
	333	+ up_write(&nilfs->ns_sem);
332	334
333	335	nilfs_detach_checkpoint(sbi);
334	336	put_nilfs(sbi->s_nilfs);
...	...	@@ -880,6 +882,11 @@
880	882	goto failed_root;
881	883	}
882	884
	885	+ down_write(&nilfs->ns_sem);
	886	+ if (!nilfs_test_opt(sbi, SNAPSHOT))
	887	+ nilfs->ns_current = sbi;
	888	+ up_write(&nilfs->ns_sem);
	889	+
883	890	return 0;
884	891
885	892	failed_root:
886	893
887	894
888	895
...	...	@@ -958,14 +965,16 @@
958	965	* by fsck since we originally mounted the partition.)
959	966	*/
960	967	down(&sb->s_bdev->bd_mount_sem);
961		- /* Check existing RW-mount */
962		- if (test_exclusive_mount(sb->s_type, sb->s_bdev, 0)) {
	968	+ down_read(&nilfs->ns_sem);
	969	+ if (nilfs->ns_current && nilfs->ns_current != sbi) {
963	970	printk(KERN_WARNING "NILFS (device %s): couldn't "
964		- "remount because a RW-mount exists.\n",
	971	+ "remount because an RW-mount exists.\n",
965	972	sb->s_id);
	973	+ up_read(&nilfs->ns_sem);
966	974	err = -EBUSY;
967	975	goto rw_remount_failed;
968	976	}
	977	+ up_read(&nilfs->ns_sem);
969	978	if (sbi->s_snapshot_cno != nilfs_last_cno(nilfs)) {
970	979	printk(KERN_WARNING "NILFS (device %s): couldn't "
971	980	"remount because the current RO-mount is not "
...	...	@@ -984,6 +993,7 @@
984	993
985	994	down_write(&nilfs->ns_sem);
986	995	nilfs_setup_super(sbi);
	996	+ nilfs->ns_current = sbi;
987	997	up_write(&nilfs->ns_sem);
988	998
989	999	up(&sb->s_bdev->bd_mount_sem);
...	...	@@ -1118,10 +1128,23 @@
1118	1128	}
1119	1129
1120	1130	down(&sd.bdev->bd_mount_sem);
1121		- if (!sd.cno &&
1122		- (err = test_exclusive_mount(fs_type, sd.bdev, flags ^ MS_RDONLY))) {
1123		- err = (err < 0) ? : -EBUSY;
1124		- goto failed_unlock;
	1131	+
	1132	+ if (!sd.cno) {
	1133	+ /*
	1134	+ * Check if an exclusive mount exists or not.
	1135	+ * Snapshot mounts coexist with a current mount
	1136	+ * (i.e. rw-mount or ro-mount), whereas rw-mount and
	1137	+ * ro-mount are mutually exclusive.
	1138	+ */
	1139	+ down_read(&nilfs->ns_sem);
	1140	+ if (nilfs->ns_current &&
	1141	+ ((nilfs->ns_current->s_super->s_flags ^ flags)
	1142	+ & MS_RDONLY)) {
	1143	+ up_read(&nilfs->ns_sem);
	1144	+ err = -EBUSY;
	1145	+ goto failed_unlock;
	1146	+ }
	1147	+ up_read(&nilfs->ns_sem);
1125	1148	}
1126	1149
1127	1150	/*
...	...	@@ -1180,57 +1203,6 @@
1180	1203	* put_nilfs() and unlocking bd_mount_sem need the block device.
1181	1204	*/
1182	1205	return err;
1183		-}
1184		-
1185		-static int nilfs_test_bdev_super3(struct super_block s, void data)
1186		-{
1187		- struct nilfs_super_data *sd = data;
1188		- int ret;
1189		-
1190		- if (s->s_bdev != sd->bdev)
1191		- return 0;
1192		- if (down_read_trylock(&s->s_umount)) {
1193		- ret = (s->s_flags & MS_RDONLY) && s->s_root &&
1194		- nilfs_test_opt(NILFS_SB(s), SNAPSHOT);
1195		- up_read(&s->s_umount);
1196		- if (ret)
1197		- return 0; /* ignore snapshot mounts */
1198		- }
1199		- return !((sd->flags ^ s->s_flags) & MS_RDONLY);
1200		-}
1201		-
1202		-static int __false_bdev_super(struct super_block s, void data)
1203		-{
1204		-#if 0 /* XXX: workaround for lock debug. This is not good idea */
1205		- up_write(&s->s_umount);
1206		-#endif
1207		- return -EFAULT;
1208		-}
1209		-
1210		-/**
1211		- * test_exclusive_mount - check whether an exclusive RW/RO mount exists or not.
1212		- * fs_type: filesystem type
1213		- * bdev: block device
1214		- * flag: 0 (check rw-mount) or MS_RDONLY (check ro-mount)
1215		- * res: pointer to an integer to store result
1216		- *
1217		- * This function must be called within a section protected by bd_mount_mutex.
1218		- */
1219		-static int test_exclusive_mount(struct file_system_type *fs_type,
1220		- struct block_device *bdev, int flags)
1221		-{
1222		- struct super_block *s;
1223		- struct nilfs_super_data sd = { .flags = flags, .bdev = bdev };
1224		-
1225		- s = sget(fs_type, nilfs_test_bdev_super3, __false_bdev_super, &sd);
1226		- if (IS_ERR(s)) {
1227		- if (PTR_ERR(s) != -EFAULT)
1228		- return PTR_ERR(s);
1229		- return 0; /* Not found */
1230		- }
1231		- up_write(&s->s_umount);
1232		- deactivate_super(s);
1233		- return 1; /* Found */
1234	1206	}
1235	1207
1236	1208	struct file_system_type nilfs_fs_type = {
...	...	@@ -50,6 +50,7 @@
50	50	* @ns_sem: semaphore for shared states
51	51	* @ns_writer_mutex: mutex protecting ns_writer attach/detach
52	52	* @ns_writer_refcount: number of referrers on ns_writer
	53	+ * @ns_current: back pointer to current mount
53	54	* @ns_sbh: buffer heads of on-disk super blocks
54	55	* @ns_sbp: pointers to super block data
55	56	* @ns_sbwtime: previous write time of super blocks
...	...	@@ -97,6 +98,8 @@
97	98	struct rw_semaphore ns_sem;
98	99	struct mutex ns_writer_mutex;
99	100	atomic_t ns_writer_refcount;
	101	+
	102	+ struct nilfs_sb_info *ns_current;
100	103
101	104	/*
102	105	* used for