On 06/21/2018 01:51 AM, David Sterba wrote:
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. Signed-off-by: David Sterba <dste...@suse.com>
Reviewed-by: Anand Jain <anand.j...@oracle.com> Thanks, Anand
--- fs/btrfs/super.c | 12 +++++++++++- fs/btrfs/volumes.c | 4 ++-- 2 files changed, 13 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 81107ad49f3a..735402ed3154 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -917,8 +917,10 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags, 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(struct file_system_type *fs_type, 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;@@ -2234,15 +2238,21 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd, 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); diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 02246f9af0a3..958bfe1a725c 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1226,6 +1226,8 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, 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. @@ -1244,13 +1246,11 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, goto error_bdev_put; }- mutex_lock(&uuid_mutex);device = device_list_add(path, disk_super); if (IS_ERR(device)) ret = PTR_ERR(device); else *fs_devices_ret = device->fs_devices; - mutex_unlock(&uuid_mutex);btrfs_release_disk_super(page);
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