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From:   Christoph Hellwig <hch@lst.de>
To:     Al Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>
Cc:     Jan Kara <jack@suse.cz>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <chao@kernel.org>,
        Ryusuke Konishi <konishi.ryusuke@gmail.com>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Jens Axboe <axboe@kernel.dk>, linux-btrfs@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net,
        linux-nilfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-xfs@vger.kernel.org, linux-block@vger.kernel.org
Subject: [PATCH 03/12] btrfs: always open the device read-only in btrfs_scan_one_device
Date:   Wed,  2 Aug 2023 17:41:22 +0200
Message-Id: <20230802154131.2221419-4-hch@lst.de>
In-Reply-To: <20230802154131.2221419-1-hch@lst.de>
References: <20230802154131.2221419-1-hch@lst.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

btrfs_scan_one_device opens the block device only to read the super
block.  Instead of passing a blk_mode_t argument to sometimes open
it for writing, just hard code BLK_OPEN_READ as it will never write
to the device or hand the block_device out to someone else.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/super.c   | 15 +++++++--------
 fs/btrfs/volumes.c |  4 ++--
 fs/btrfs/volumes.h |  2 +-
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f1dd172d8d5bd7..b318bddefd5236 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -849,7 +849,7 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
  * All other options will be parsed on much later in the mount process and
  * only when we need to allocate a new super block.
  */
-static int btrfs_parse_device_options(const char *options, blk_mode_t flags)
+static int btrfs_parse_device_options(const char *options)
 {
 	substring_t args[MAX_OPT_ARGS];
 	char *device_name, *opts, *orig, *p;
@@ -883,7 +883,7 @@ static int btrfs_parse_device_options(const char *options, blk_mode_t flags)
 				error = -ENOMEM;
 				goto out;
 			}
-			device = btrfs_scan_one_device(device_name, flags);
+			device = btrfs_scan_one_device(device_name);
 			kfree(device_name);
 			if (IS_ERR(device)) {
 				error = PTR_ERR(device);
@@ -1440,7 +1440,6 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 	struct btrfs_fs_devices *fs_devices = NULL;
 	struct btrfs_fs_info *fs_info = NULL;
 	void *new_sec_opts = NULL;
-	blk_mode_t mode = sb_open_mode(flags);
 	int error = 0;
 
 	if (data) {
@@ -1472,13 +1471,13 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 	}
 
 	mutex_lock(&uuid_mutex);
-	error = btrfs_parse_device_options(data, mode);
+	error = btrfs_parse_device_options(data);
 	if (error) {
 		mutex_unlock(&uuid_mutex);
 		goto error_fs_info;
 	}
 
-	device = btrfs_scan_one_device(device_name, mode);
+	device = btrfs_scan_one_device(device_name);
 	if (IS_ERR(device)) {
 		mutex_unlock(&uuid_mutex);
 		error = PTR_ERR(device);
@@ -1488,7 +1487,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 	fs_devices = device->fs_devices;
 	fs_info->fs_devices = fs_devices;
 
-	error = btrfs_open_devices(fs_devices, mode, fs_type);
+	error = btrfs_open_devices(fs_devices, sb_open_mode(flags), fs_type);
 	mutex_unlock(&uuid_mutex);
 	if (error)
 		goto error_fs_info;
@@ -2190,7 +2189,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 	switch (cmd) {
 	case BTRFS_IOC_SCAN_DEV:
 		mutex_lock(&uuid_mutex);
-		device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ);
+		device = btrfs_scan_one_device(vol->name);
 		ret = PTR_ERR_OR_ZERO(device);
 		mutex_unlock(&uuid_mutex);
 		break;
@@ -2204,7 +2203,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 		break;
 	case BTRFS_IOC_DEVICES_READY:
 		mutex_lock(&uuid_mutex);
-		device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ);
+		device = btrfs_scan_one_device(vol->name);
 		if (IS_ERR(device)) {
 			mutex_unlock(&uuid_mutex);
 			ret = PTR_ERR(device);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 73f9ea7672dbda..8246578c70f55b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1356,7 +1356,7 @@ int btrfs_forget_devices(dev_t devt)
  * and we are not allowed to call set_blocksize during the scan. The superblock
  * is read via pagecache
  */
-struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags)
+struct btrfs_device *btrfs_scan_one_device(const char *path)
 {
 	struct btrfs_super_block *disk_super;
 	bool new_device_added = false;
@@ -1384,7 +1384,7 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags)
 	 * values temporarily, as the device paths of the fsid are the only
 	 * required information for assembling the volume.
 	 */
-	bdev = blkdev_get_by_path(path, flags, NULL, NULL);
+	bdev = blkdev_get_by_path(path, BLK_OPEN_READ, NULL, NULL);
 	if (IS_ERR(bdev))
 		return ERR_CAST(bdev);
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index b8c51f16ba867f..824161c6dd063e 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -611,7 +611,7 @@ struct btrfs_block_group *btrfs_create_chunk(struct btrfs_trans_handle *trans,
 void btrfs_mapping_tree_free(struct extent_map_tree *tree);
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       blk_mode_t flags, void *holder);
-struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags);
+struct btrfs_device *btrfs_scan_one_device(const char *path);
 int btrfs_forget_devices(dev_t devt);
 void btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
 void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices);
-- 
2.39.2