4.18-stable review patch. If anyone has any objections, please let me know.
------------------ From: David Sterba <[email protected]> [ Upstream commit 899f9307c33ce4758c30a076b10ed54d5c91c6e7 ] Prepartory work to fix race between mount and device scan. The callers will have to manage the critical section, eg. mount wants to scan and then call btrfs_open_devices without the ioctl scan walking in and modifying the fs devices in the meantime. Reviewed-by: Anand Jain <[email protected]> Signed-off-by: David Sterba <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/btrfs/super.c | 12 +++++++++++- fs/btrfs/volumes.c | 4 ++-- 2 files changed, 13 insertions(+), 3 deletions(-) --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -917,8 +917,10 @@ static int btrfs_parse_early_options(con error = -ENOMEM; goto out; } + mutex_lock(&uuid_mutex); error = btrfs_scan_one_device(device_name, flags, holder, fs_devices); + mutex_unlock(&uuid_mutex); kfree(device_name); if (error) goto out; @@ -1539,7 +1541,9 @@ static struct dentry *btrfs_mount_root(s return ERR_PTR(error); } + mutex_lock(&uuid_mutex); error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices); + mutex_unlock(&uuid_mutex); if (error) goto error_sec_opts; @@ -2236,15 +2240,21 @@ static long btrfs_control_ioctl(struct f switch (cmd) { case BTRFS_IOC_SCAN_DEV: + mutex_lock(&uuid_mutex); ret = btrfs_scan_one_device(vol->name, FMODE_READ, &btrfs_root_fs_type, &fs_devices); + mutex_unlock(&uuid_mutex); break; case BTRFS_IOC_DEVICES_READY: + mutex_lock(&uuid_mutex); ret = btrfs_scan_one_device(vol->name, FMODE_READ, &btrfs_root_fs_type, &fs_devices); - if (ret) + if (ret) { + mutex_unlock(&uuid_mutex); break; + } ret = !(fs_devices->num_devices == fs_devices->total_devices); + mutex_unlock(&uuid_mutex); break; case BTRFS_IOC_GET_SUPPORTED_FEATURES: ret = btrfs_ioctl_get_supported_features((void __user*)arg); --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1241,6 +1241,8 @@ int btrfs_scan_one_device(const char *pa int ret = 0; u64 bytenr; + lockdep_assert_held(&uuid_mutex); + /* * we would like to check all the supers, but that would make * a btrfs mount succeed after a mkfs from a different FS. @@ -1259,7 +1261,6 @@ int btrfs_scan_one_device(const char *pa goto error_bdev_put; } - mutex_lock(&uuid_mutex); device = device_list_add(path, disk_super, &new_device_added); if (IS_ERR(device)) { ret = PTR_ERR(device); @@ -1268,7 +1269,6 @@ int btrfs_scan_one_device(const char *pa if (new_device_added) btrfs_free_stale_devices(path, device); } - mutex_unlock(&uuid_mutex); btrfs_release_disk_super(page);
