btrfs: lift uuid_mutex to callers of btrfs_scan_one_device

[ 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 <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index fdda3cd..b00e88f 100644 (file)
--- 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;
 
@@ -2236,15 +2240,21 @@ 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 6e6b4f2..5304b8d 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1241,6 +1241,8 @@ 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.
@@ -1259,7 +1261,6 @@ 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, &new_device_added);
        if (IS_ERR(device)) {
                ret = PTR_ERR(device);
@@ -1268,7 +1269,6 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
                if (new_device_added)
                        btrfs_free_stale_devices(path, device);
        }
-       mutex_unlock(&uuid_mutex);
 
        btrfs_release_disk_super(page);