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>

4 files changed, 25 insertions, 27 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 4de4984fa99b..677e9d9e1527 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -257,7 +257,7 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 		return -EINVAL;
 	}
 
-	bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
+	bdev = blkdev_get_by_path(device_path, FMODE_WRITE,
 				  fs_info->bdev_holder, NULL);
 	if (IS_ERR(bdev)) {
 		btrfs_err(fs_info, "target device %s is invalid!", device_path);
@@ -315,7 +315,7 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	device->bdev = bdev;
 	set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 	set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
-	device->mode = FMODE_EXCL;
+	device->holder = fs_info->bdev_holder;
 	device->dev_stats_valid = 1;
 	set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 	device->fs_devices = fs_devices;
@@ -334,7 +334,7 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	return 0;
 
 error:
-	blkdev_put(bdev, FMODE_EXCL);
+	blkdev_put(bdev, fs_info->bdev_holder);
 	return ret;
 }
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 2fa36f694daa..d99376a79ef4 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2672,7 +2672,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_ioctl_vol_args_v2 *vol_args;
 	struct block_device *bdev = NULL;
-	fmode_t mode;
+	void *holder;
 	int ret;
 	bool cancel = false;
 
@@ -2709,7 +2709,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
 		goto err_drop;
 
 	/* Exclusive operation is now claimed */
-	ret = btrfs_rm_device(fs_info, &args, &bdev, &mode);
+	ret = btrfs_rm_device(fs_info, &args, &bdev, &holder);
 
 	btrfs_exclop_finish(fs_info);
 
@@ -2724,7 +2724,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
 err_drop:
 	mnt_drop_write_file(file);
 	if (bdev)
-		blkdev_put(bdev, mode);
+		blkdev_put(bdev, holder);
 out:
 	btrfs_put_dev_args_from_path(&args);
 	kfree(vol_args);
@@ -2738,7 +2738,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_ioctl_vol_args *vol_args;
 	struct block_device *bdev = NULL;
-	fmode_t mode;
+	void *holder;
 	int ret;
 	bool cancel = false;
 
@@ -2765,7 +2765,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 	ret = exclop_start_or_cancel_reloc(fs_info, BTRFS_EXCLOP_DEV_REMOVE,
 					   cancel);
 	if (ret == 0) {
-		ret = btrfs_rm_device(fs_info, &args, &bdev, &mode);
+		ret = btrfs_rm_device(fs_info, &args, &bdev, &holder);
 		if (!ret)
 			btrfs_info(fs_info, "disk deleted %s", vol_args->name);
 		btrfs_exclop_finish(fs_info);
@@ -2773,7 +2773,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 
 	mnt_drop_write_file(file);
 	if (bdev)
-		blkdev_put(bdev, mode);
+		blkdev_put(bdev, holder);
 out:
 	btrfs_put_dev_args_from_path(&args);
 	kfree(vol_args);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 035868cee3dd..7b12e05cdbf0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -507,14 +507,14 @@ btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder,
 		sync_blockdev(*bdev);
 	ret = set_blocksize(*bdev, BTRFS_BDEV_BLOCKSIZE);
 	if (ret) {
-		blkdev_put(*bdev, flags);
+		blkdev_put(*bdev, holder);
 		goto error;
 	}
 	invalidate_bdev(*bdev);
 	*disk_super = btrfs_read_dev_super(*bdev);
 	if (IS_ERR(*disk_super)) {
 		ret = PTR_ERR(*disk_super);
-		blkdev_put(*bdev, flags);
+		blkdev_put(*bdev, holder);
 		goto error;
 	}
 
@@ -642,7 +642,7 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
 
 	device->bdev = bdev;
 	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
-	device->mode = flags;
+	device->holder = holder;
 
 	fs_devices->open_devices++;
 	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
@@ -656,7 +656,7 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
 
 error_free_page:
 	btrfs_release_disk_super(disk_super);
-	blkdev_put(bdev, flags);
+	blkdev_put(bdev, holder);
 
 	return -EINVAL;
 }
@@ -1057,7 +1057,7 @@ static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices,
 			continue;
 
 		if (device->bdev) {
-			blkdev_put(device->bdev, device->mode);
+			blkdev_put(device->bdev, device->holder);
 			device->bdev = NULL;
 			fs_devices->open_devices--;
 		}
@@ -1103,7 +1103,7 @@ static void btrfs_close_bdev(struct btrfs_device *device)
 		invalidate_bdev(device->bdev);
 	}
 
-	blkdev_put(device->bdev, device->mode);
+	blkdev_put(device->bdev, device->holder);
 }
 
 static void btrfs_close_one_device(struct btrfs_device *device)
@@ -1213,8 +1213,6 @@ static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 	struct btrfs_device *latest_dev = NULL;
 	struct btrfs_device *tmp_device;
 
-	flags |= FMODE_EXCL;
-
 	list_for_each_entry_safe(device, tmp_device, &fs_devices->devices,
 				 dev_list) {
 		int ret;
@@ -1400,7 +1398,7 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags)
 	btrfs_release_disk_super(disk_super);
 
 error_bdev_put:
-	blkdev_put(bdev, flags);
+	blkdev_put(bdev, NULL);
 
 	return device;
 }
@@ -2087,7 +2085,7 @@ void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
 
 int btrfs_rm_device(struct btrfs_fs_info *fs_info,
 		    struct btrfs_dev_lookup_args *args,
-		    struct block_device **bdev, fmode_t *mode)
+		    struct block_device **bdev, void **holder)
 {
 	struct btrfs_trans_handle *trans;
 	struct btrfs_device *device;
@@ -2226,7 +2224,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info,
 	}
 
 	*bdev = device->bdev;
-	*mode = device->mode;
+	*holder = device->holder;
 	synchronize_rcu();
 	btrfs_free_device(device);
 
@@ -2394,7 +2392,7 @@ int btrfs_get_dev_args_from_path(struct btrfs_fs_info *fs_info,
 	else
 		memcpy(args->fsid, disk_super->fsid, BTRFS_FSID_SIZE);
 	btrfs_release_disk_super(disk_super);
-	blkdev_put(bdev, FMODE_READ);
+	blkdev_put(bdev, NULL);
 	return 0;
 }
 
@@ -2627,7 +2625,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	if (sb_rdonly(sb) && !fs_devices->seeding)
 		return -EROFS;
 
-	bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
+	bdev = blkdev_get_by_path(device_path, FMODE_WRITE,
 				  fs_info->bdev_holder, NULL);
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
@@ -2690,7 +2688,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	device->commit_total_bytes = device->total_bytes;
 	set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 	clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
-	device->mode = FMODE_EXCL;
+	device->holder = fs_info->bdev_holder;
 	device->dev_stats_valid = 1;
 	set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 
@@ -2848,7 +2846,7 @@ error_free_zone:
 error_free_device:
 	btrfs_free_device(device);
 error:
-	blkdev_put(bdev, FMODE_EXCL);
+	blkdev_put(bdev, fs_info->bdev_holder);
 	if (locked) {
 		mutex_unlock(&uuid_mutex);
 		up_write(&sb->s_umount);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index eb97a397b3c3..840a8df39907 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -94,8 +94,8 @@ struct btrfs_device {
 
 	struct btrfs_zoned_device_info *zone_info;
 
-	/* the mode sent to blkdev_get */
-	fmode_t mode;
+	/* block device holder for blkdev_get/put */
+	void *holder;
 
 	/*
 	 * Device's major-minor number. Must be set even if the device is not
@@ -619,7 +619,7 @@ void btrfs_put_dev_args_from_path(struct btrfs_dev_lookup_args *args);
 void btrfs_free_device(struct btrfs_device *device);
 int btrfs_rm_device(struct btrfs_fs_info *fs_info,
 		    struct btrfs_dev_lookup_args *args,
-		    struct block_device **bdev, fmode_t *mode);
+		    struct block_device **bdev, void **holder);
 void __exit btrfs_cleanup_fs_uuids(void);
 int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len);
 int btrfs_grow_device(struct btrfs_trans_handle *trans,