block: use the holder as indication for exclusive opens

The current interface for exclusive opens is rather confusing as it
requires both the FMODE_EXCL flag and a holder.  Remove the need to pass
FMODE_EXCL and just key off the exclusive open off a non-NULL holder.

For blkdev_put this requires adding the holder argument, which provides
better debug checking that only the holder actually releases the hold,
but at the same time allows removing the now superfluous mode argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Christian Brauner <brauner@kernel.org>
Acked-by: David Sterba <dsterba@suse.com>		[btrfs]
Acked-by: Jack Wang <jinpu.wang@ionos.com>		[rnbd]
Link: https://lore.kernel.org/r/20230608110258.189493-16-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 9 insertions, 11 deletions

diff --git a/fs/super.c b/fs/super.c
index f127589700ab..8563794a8bc4 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1255,7 +1255,7 @@ int get_tree_bdev(struct fs_context *fc,
 {
 	struct block_device *bdev;
 	struct super_block *s;
-	fmode_t mode = FMODE_READ | FMODE_EXCL;
+	fmode_t mode = FMODE_READ;
 	int error = 0;
 
 	if (!(fc->sb_flags & SB_RDONLY))
@@ -1279,7 +1279,7 @@ int get_tree_bdev(struct fs_context *fc,
 	if (bdev->bd_fsfreeze_count > 0) {
 		mutex_unlock(&bdev->bd_fsfreeze_mutex);
 		warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
-		blkdev_put(bdev, mode);
+		blkdev_put(bdev, fc->fs_type);
 		return -EBUSY;
 	}
 
@@ -1288,7 +1288,7 @@ int get_tree_bdev(struct fs_context *fc,
 	s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
 	mutex_unlock(&bdev->bd_fsfreeze_mutex);
 	if (IS_ERR(s)) {
-		blkdev_put(bdev, mode);
+		blkdev_put(bdev, fc->fs_type);
 		return PTR_ERR(s);
 	}
 
@@ -1297,7 +1297,7 @@ int get_tree_bdev(struct fs_context *fc,
 		if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
 			warnf(fc, "%pg: Can't mount, would change RO state", bdev);
 			deactivate_locked_super(s);
-			blkdev_put(bdev, mode);
+			blkdev_put(bdev, fc->fs_type);
 			return -EBUSY;
 		}
 
@@ -1309,7 +1309,7 @@ int get_tree_bdev(struct fs_context *fc,
 		 * holding an active reference.
 		 */
 		up_write(&s->s_umount);
-		blkdev_put(bdev, mode);
+		blkdev_put(bdev, fc->fs_type);
 		down_write(&s->s_umount);
 	} else {
 		s->s_mode = mode;
@@ -1344,7 +1344,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 {
 	struct block_device *bdev;
 	struct super_block *s;
-	fmode_t mode = FMODE_READ | FMODE_EXCL;
+	fmode_t mode = FMODE_READ;
 	int error = 0;
 
 	if (!(flags & SB_RDONLY))
@@ -1386,7 +1386,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 		 * holding an active reference.
 		 */
 		up_write(&s->s_umount);
-		blkdev_put(bdev, mode);
+		blkdev_put(bdev, fs_type);
 		down_write(&s->s_umount);
 	} else {
 		s->s_mode = mode;
@@ -1409,7 +1409,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 error_s:
 	error = PTR_ERR(s);
 error_bdev:
-	blkdev_put(bdev, mode);
+	blkdev_put(bdev, fs_type);
 error:
 	return ERR_PTR(error);
 }
@@ -1418,13 +1418,11 @@ EXPORT_SYMBOL(mount_bdev);
 void kill_block_super(struct super_block *sb)
 {
 	struct block_device *bdev = sb->s_bdev;
-	fmode_t mode = sb->s_mode;
 
 	bdev->bd_super = NULL;
 	generic_shutdown_super(sb);
 	sync_blockdev(bdev);
-	WARN_ON_ONCE(!(mode & FMODE_EXCL));
-	blkdev_put(bdev, mode | FMODE_EXCL);
+	blkdev_put(bdev, sb->s_type);
 }
 
 EXPORT_SYMBOL(kill_block_super);