block: clean up blkdev_get() wrappers and their users

After recent blkdev_get() modifications, open_by_devnum() and
open_bdev_exclusive() are simple wrappers around blkdev_get().
Replace them with blkdev_get_by_dev() and blkdev_get_by_path().

blkdev_get_by_dev() is identical to open_by_devnum().
blkdev_get_by_path() is slightly different in that it doesn't
automatically add %FMODE_EXCL to @mode.

All users are converted.  Most conversions are mechanical and don't
introduce any behavior difference.  There are several exceptions.

* btrfs now sets FMODE_EXCL in btrfs_device->mode, so there's no
  reason to OR it explicitly on blkdev_put().

* gfs2, nilfs2 and the generic mount_bdev() now set FMODE_EXCL in
  sb->s_mode.

* With the above changes, sb->s_mode now always should contain
  FMODE_EXCL.  WARN_ON_ONCE() added to kill_block_super() to detect
  errors.

The new blkdev_get_*() functions are with proper docbook comments.
While at it, add function description to blkdev_get() too.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Joern Engel <joern@lazybastard.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp>
Cc: reiserfs-devel@vger.kernel.org
Cc: xfs-masters@oss.sgi.com
Cc: Alexander Viro <viro@zeniv.linux.org.uk>

12 files changed, 132 insertions, 78 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 606a5259f87..c1c1b8c3fb9 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -854,24 +854,6 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev)
 { }
 #endif
 
-/*
- * Tries to open block device by device number.  Use it ONLY if you
- * really do not have anything better - i.e. when you are behind a
- * truly sucky interface and all you are given is a device number.  _Never_
- * to be used for internal purposes.  If you ever need it - reconsider
- * your API.
- */
-struct block_device *open_by_devnum(dev_t dev, fmode_t mode, void *holder)
-{
-	struct block_device *bdev = bdget(dev);
-	int err = -ENOMEM;
-	if (bdev)
-		err = blkdev_get(bdev, mode, holder);
-	return err ? ERR_PTR(err) : bdev;
-}
-
-EXPORT_SYMBOL(open_by_devnum);
-
 /**
  * flush_disk - invalidates all buffer-cache entries on a disk
  *
@@ -1132,6 +1114,25 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 	return ret;
 }
 
+/**
+ * blkdev_get - open a block device
+ * @bdev: block_device to open
+ * @mode: FMODE_* mask
+ * @holder: exclusive holder identifier
+ *
+ * Open @bdev with @mode.  If @mode includes %FMODE_EXCL, @bdev is
+ * open with exclusive access.  Specifying %FMODE_EXCL with %NULL
+ * @holder is invalid.  Exclusive opens may nest for the same @holder.
+ *
+ * On success, the reference count of @bdev is unchanged.  On failure,
+ * @bdev is put.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
 int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)
 {
 	struct block_device *whole = NULL;
@@ -1186,6 +1187,80 @@ int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)
 }
 EXPORT_SYMBOL(blkdev_get);
 
+/**
+ * blkdev_get_by_path - open a block device by name
+ * @path: path to the block device to open
+ * @mode: FMODE_* mask
+ * @holder: exclusive holder identifier
+ *
+ * Open the blockdevice described by the device file at @path.  @mode
+ * and @holder are identical to blkdev_get().
+ *
+ * On success, the returned block_device has reference count of one.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * Pointer to block_device on success, ERR_PTR(-errno) on failure.
+ */
+struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
+					void *holder)
+{
+	struct block_device *bdev;
+	int err;
+
+	bdev = lookup_bdev(path);
+	if (IS_ERR(bdev))
+		return bdev;
+
+	err = blkdev_get(bdev, mode, holder);
+	if (err)
+		return ERR_PTR(err);
+
+	return bdev;
+}
+EXPORT_SYMBOL(blkdev_get_by_path);
+
+/**
+ * blkdev_get_by_dev - open a block device by device number
+ * @dev: device number of block device to open
+ * @mode: FMODE_* mask
+ * @holder: exclusive holder identifier
+ *
+ * Open the blockdevice described by device number @dev.  @mode and
+ * @holder are identical to blkdev_get().
+ *
+ * Use it ONLY if you really do not have anything better - i.e. when
+ * you are behind a truly sucky interface and all you are given is a
+ * device number.  _Never_ to be used for internal purposes.  If you
+ * ever need it - reconsider your API.
+ *
+ * On success, the returned block_device has reference count of one.
+ *
+ * CONTEXT:
+ * Might sleep.
+ *
+ * RETURNS:
+ * Pointer to block_device on success, ERR_PTR(-errno) on failure.
+ */
+struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder)
+{
+	struct block_device *bdev;
+	int err;
+
+	bdev = bdget(dev);
+	if (!bdev)
+		return ERR_PTR(-ENOMEM);
+
+	err = blkdev_get(bdev, mode, holder);
+	if (err)
+		return ERR_PTR(err);
+
+	return bdev;
+}
+EXPORT_SYMBOL(blkdev_get_by_dev);
+
 static int blkdev_open(struct inode * inode, struct file * filp)
 {
 	struct block_device *bdev;
@@ -1436,34 +1511,6 @@ fail:
 }
 EXPORT_SYMBOL(lookup_bdev);
 
-/**
- * open_bdev_exclusive  -  open a block device by name and set it up for use
- *
- * @path:	special file representing the block device
- * @mode:	FMODE_... combination to pass be used
- * @holder:	owner for exclusion
- *
- * Open the blockdevice described by the special file at @path, claim it
- * for the @holder.
- */
-struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *holder)
-{
-	struct block_device *bdev;
-	int error;
-
-	bdev = lookup_bdev(path);
-	if (IS_ERR(bdev))
-		return bdev;
-
-	error = blkdev_get(bdev, mode | FMODE_EXCL, holder);
-	if (error)
-		return ERR_PTR(error);
-
-	return bdev;
-}
-
-EXPORT_SYMBOL(open_bdev_exclusive);
-
 int __invalidate_device(struct block_device *bdev)
 {
 	struct super_block *sb = get_super(bdev);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f1b729d3b88..95324e9f928 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -489,7 +489,7 @@ again:
 			continue;
 
 		if (device->bdev) {
-			blkdev_put(device->bdev, device->mode | FMODE_EXCL);
+			blkdev_put(device->bdev, device->mode);
 			device->bdev = NULL;
 			fs_devices->open_devices--;
 		}
@@ -523,7 +523,7 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 
 	list_for_each_entry(device, &fs_devices->devices, dev_list) {
 		if (device->bdev) {
-			blkdev_put(device->bdev, device->mode | FMODE_EXCL);
+			blkdev_put(device->bdev, device->mode);
 			fs_devices->open_devices--;
 		}
 		if (device->writeable) {
@@ -580,13 +580,15 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 	int seeding = 1;
 	int ret = 0;
 
+	flags |= FMODE_EXCL;
+
 	list_for_each_entry(device, head, dev_list) {
 		if (device->bdev)
 			continue;
 		if (!device->name)
 			continue;
 
-		bdev = open_bdev_exclusive(device->name, flags, holder);
+		bdev = blkdev_get_by_path(device->name, flags, holder);
 		if (IS_ERR(bdev)) {
 			printk(KERN_INFO "open %s failed\n", device->name);
 			goto error;
@@ -638,7 +640,7 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 error_brelse:
 		brelse(bh);
 error_close:
-		blkdev_put(bdev, flags | FMODE_EXCL);
+		blkdev_put(bdev, flags);
 error:
 		continue;
 	}
@@ -684,7 +686,8 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 
 	mutex_lock(&uuid_mutex);
 
-	bdev = open_bdev_exclusive(path, flags, holder);
+	flags |= FMODE_EXCL;
+	bdev = blkdev_get_by_path(path, flags, holder);
 
 	if (IS_ERR(bdev)) {
 		ret = PTR_ERR(bdev);
@@ -716,7 +719,7 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 
 	brelse(bh);
 error_close:
-	blkdev_put(bdev, flags | FMODE_EXCL);
+	blkdev_put(bdev, flags);
 error:
 	mutex_unlock(&uuid_mutex);
 	return ret;
@@ -1179,8 +1182,8 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 			goto out;
 		}
 	} else {
-		bdev = open_bdev_exclusive(device_path, FMODE_READ,
-				      root->fs_info->bdev_holder);
+		bdev = blkdev_get_by_path(device_path, FMODE_READ | FMODE_EXCL,
+					  root->fs_info->bdev_holder);
 		if (IS_ERR(bdev)) {
 			ret = PTR_ERR(bdev);
 			goto out;
@@ -1244,7 +1247,7 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 		root->fs_info->fs_devices->latest_bdev = next_device->bdev;
 
 	if (device->bdev) {
-		blkdev_put(device->bdev, device->mode | FMODE_EXCL);
+		blkdev_put(device->bdev, device->mode);
 		device->bdev = NULL;
 		device->fs_devices->open_devices--;
 	}
@@ -1439,7 +1442,8 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 	if ((sb->s_flags & MS_RDONLY) && !root->fs_info->fs_devices->seeding)
 		return -EINVAL;
 
-	bdev = open_bdev_exclusive(device_path, 0, root->fs_info->bdev_holder);
+	bdev = blkdev_get_by_path(device_path, FMODE_EXCL,
+				  root->fs_info->bdev_holder);
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 2b638b6e4ee..856e7577030 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -49,7 +49,7 @@ struct btrfs_device {
 
 	struct block_device *bdev;
 
-	/* the mode sent to open_bdev_exclusive */
+	/* the mode sent to blkdev_get */
 	fmode_t mode;
 
 	char *name;
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 23e7513dba9..123720ba786 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -347,7 +347,7 @@ static struct block_device *ext3_blkdev_get(dev_t dev, struct super_block *sb)
 	struct block_device *bdev;
 	char b[BDEVNAME_SIZE];
 
-	bdev = open_by_devnum(dev, FMODE_READ|FMODE_WRITE|FMODE_EXCL, sb);
+	bdev = blkdev_get_by_dev(dev, FMODE_READ|FMODE_WRITE|FMODE_EXCL, sb);
 	if (IS_ERR(bdev))
 		goto fail;
 	return bdev;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 5dd0b3e76fa..bd63e692721 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -647,7 +647,7 @@ static struct block_device *ext4_blkdev_get(dev_t dev, struct super_block *sb)
 	struct block_device *bdev;
 	char b[BDEVNAME_SIZE];
 
-	bdev = open_by_devnum(dev, FMODE_READ|FMODE_WRITE|FMODE_EXCL, sb);
+	bdev = blkdev_get_by_dev(dev, FMODE_READ|FMODE_WRITE|FMODE_EXCL, sb);
 	if (IS_ERR(bdev))
 		goto fail;
 	return bdev;
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index c1f0763a022..bc56ccf98ff 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1268,7 +1268,7 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags,
 {
 	struct block_device *bdev;
 	struct super_block *s;
-	fmode_t mode = FMODE_READ;
+	fmode_t mode = FMODE_READ | FMODE_EXCL;
 	int error;
 	struct gfs2_args args;
 	struct gfs2_sbd *sdp;
@@ -1276,7 +1276,7 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags,
 	if (!(flags & MS_RDONLY))
 		mode |= FMODE_WRITE;
 
-	bdev = open_bdev_exclusive(dev_name, mode, fs_type);
+	bdev = blkdev_get_by_path(dev_name, mode, fs_type);
 	if (IS_ERR(bdev))
 		return ERR_CAST(bdev);
 
@@ -1298,7 +1298,7 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags,
 		goto error_bdev;
 
 	if (s->s_root)
-		blkdev_put(bdev, mode | FMODE_EXCL);
+		blkdev_put(bdev, mode);
 
 	memset(&args, 0, sizeof(args));
 	args.ar_quota = GFS2_QUOTA_DEFAULT;
@@ -1342,7 +1342,7 @@ error_super:
 	deactivate_locked_super(s);
 	return ERR_PTR(error);
 error_bdev:
-	blkdev_put(bdev, mode | FMODE_EXCL);
+	blkdev_put(bdev, mode);
 	return ERR_PTR(error);
 }
 
diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 5a290f22dcc..278e3fb40b7 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1120,8 +1120,8 @@ int lmLogOpen(struct super_block *sb)
 	 * file systems to log may have n-to-1 relationship;
 	 */
 
-	bdev = open_by_devnum(sbi->logdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
-			      log);
+	bdev = blkdev_get_by_dev(sbi->logdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
+				 log);
 	if (IS_ERR(bdev)) {
 		rc = -PTR_ERR(bdev);
 		goto free;
diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index 734b9025858..723bc5bca09 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -325,7 +325,8 @@ int logfs_get_sb_bdev(struct logfs_super *p, struct file_system_type *type,
 {
 	struct block_device *bdev;
 
-	bdev = open_bdev_exclusive(devname, FMODE_READ|FMODE_WRITE, type);
+	bdev = blkdev_get_by_path(devname, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
+				  type);
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
 
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 756a6798d7c..0030640e2d7 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -1147,14 +1147,14 @@ nilfs_mount(struct file_system_type *fs_type, int flags,
 {
 	struct nilfs_super_data sd;
 	struct super_block *s;
-	fmode_t mode = FMODE_READ;
+	fmode_t mode = FMODE_READ | FMODE_EXCL;
 	struct dentry *root_dentry;
 	int err, s_new = false;
 
 	if (!(flags & MS_RDONLY))
 		mode |= FMODE_WRITE;
 
-	sd.bdev = open_bdev_exclusive(dev_name, mode, fs_type);
+	sd.bdev = blkdev_get_by_path(dev_name, mode, fs_type);
 	if (IS_ERR(sd.bdev))
 		return ERR_CAST(sd.bdev);
 
@@ -1233,7 +1233,7 @@ nilfs_mount(struct file_system_type *fs_type, int flags,
 	}
 
 	if (!s_new)
-		blkdev_put(sd.bdev, mode | FMODE_EXCL);
+		blkdev_put(sd.bdev, mode);
 
 	return root_dentry;
 
@@ -1242,7 +1242,7 @@ nilfs_mount(struct file_system_type *fs_type, int flags,
 
  failed:
 	if (!s_new)
-		blkdev_put(sd.bdev, mode | FMODE_EXCL);
+		blkdev_put(sd.bdev, mode);
 	return ERR_PTR(err);
 }
 
diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
index b488136f5ac..e2fce519c0f 100644
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -2585,7 +2585,8 @@ static int journal_init_dev(struct super_block *super,
 	if ((!jdev_name || !jdev_name[0])) {
 		if (jdev == super->s_dev)
 			blkdev_mode &= ~FMODE_EXCL;
-		journal->j_dev_bd = open_by_devnum(jdev, blkdev_mode, journal);
+		journal->j_dev_bd = blkdev_get_by_dev(jdev, blkdev_mode,
+						      journal);
 		journal->j_dev_mode = blkdev_mode;
 		if (IS_ERR(journal->j_dev_bd)) {
 			result = PTR_ERR(journal->j_dev_bd);
@@ -2601,8 +2602,7 @@ static int journal_init_dev(struct super_block *super,
 	}
 
 	journal->j_dev_mode = blkdev_mode;
-	journal->j_dev_bd = open_bdev_exclusive(jdev_name,
-						blkdev_mode, journal);
+	journal->j_dev_bd = blkdev_get_by_path(jdev_name, blkdev_mode, journal);
 	if (IS_ERR(journal->j_dev_bd)) {
 		result = PTR_ERR(journal->j_dev_bd);
 		journal->j_dev_bd = NULL;
diff --git a/fs/super.c b/fs/super.c
index 22374bf0ba8..5d9a4497849 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -766,13 +766,13 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 {
 	struct block_device *bdev;
 	struct super_block *s;
-	fmode_t mode = FMODE_READ;
+	fmode_t mode = FMODE_READ | FMODE_EXCL;
 	int error = 0;
 
 	if (!(flags & MS_RDONLY))
 		mode |= FMODE_WRITE;
 
-	bdev = open_bdev_exclusive(dev_name, mode, fs_type);
+	bdev = blkdev_get_by_path(dev_name, mode, fs_type);
 	if (IS_ERR(bdev))
 		return ERR_CAST(bdev);
 
@@ -807,7 +807,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 		 * holding an active reference.
 		 */
 		up_write(&s->s_umount);
-		blkdev_put(bdev, mode | FMODE_EXCL);
+		blkdev_put(bdev, mode);
 		down_write(&s->s_umount);
 	} else {
 		char b[BDEVNAME_SIZE];
@@ -831,7 +831,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 error_s:
 	error = PTR_ERR(s);
 error_bdev:
-	blkdev_put(bdev, mode | FMODE_EXCL);
+	blkdev_put(bdev, mode);
 error:
 	return ERR_PTR(error);
 }
@@ -862,6 +862,7 @@ void kill_block_super(struct super_block *sb)
 	bdev->bd_super = NULL;
 	generic_shutdown_super(sb);
 	sync_blockdev(bdev);
+	WARN_ON_ONCE(!(mode & FMODE_EXCL));
 	blkdev_put(bdev, mode | FMODE_EXCL);
 }
 
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index a1a6e5ceea6..9209cd199c4 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -609,7 +609,8 @@ xfs_blkdev_get(
 {
 	int			error = 0;
 
-	*bdevp = open_bdev_exclusive(name, FMODE_READ|FMODE_WRITE, mp);
+	*bdevp = blkdev_get_by_path(name, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
+				    mp);
 	if (IS_ERR(*bdevp)) {
 		error = PTR_ERR(*bdevp);
 		printk("XFS: Invalid device [%s], error=%d\n", name, error);