[PATCH 03/12] btrfs: always open the device read-only in btrfs_scan_one_device

Christoph Hellwig
2023-08-02T15:42:08Z

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