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>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/super.c b/fs/super.c
index 22374bf0ba87..5d9a4497849a 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);
 }