btrfs: introduce device delete by devid

This introduces new ioctl BTRFS_IOC_RM_DEV_V2, which uses enhanced struct
btrfs_ioctl_vol_args_v2 to carry devid as an user argument.

The patch won't delete the old ioctl interface and so kernel remains
backward compatible with user land progs.

Test case/script:
echo "0 $(blockdev --getsz /dev/sdf) linear /dev/sdf 0" | dmsetup create bad_disk
mkfs.btrfs -f -d raid1 -m raid1 /dev/sdd /dev/sde /dev/mapper/bad_disk
mount /dev/sdd /btrfs
dmsetup suspend bad_disk
echo "0 $(blockdev --getsz /dev/sdf) error /dev/sdf 0" | dmsetup load bad_disk
dmsetup resume bad_disk
echo "bad disk failed. now deleting/replacing"
btrfs dev del  3  /btrfs
echo $?
btrfs fi show /btrfs
umount /btrfs
btrfs-show-super /dev/sdd | egrep num_device
dmsetup remove bad_disk
wipefs -a /dev/sdf

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reported-by: Martin <m_btrfs@ml1.co.uk>
[ adjust messages, s/disk/device/ ]
Signed-off-by: David Sterba <dsterba@suse.com>

4 files changed, 73 insertions, 5 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 5a23806ae418..7cf0f6328d99 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2667,6 +2667,60 @@ out:
         return ret;
 }
 
+static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
+{
+        struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
+        struct btrfs_ioctl_vol_args_v2 *vol_args;
+        int ret;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        ret = mnt_want_write_file(file);
+        if (ret)
+                return ret;
+
+        vol_args = memdup_user(arg, sizeof(*vol_args));
+        if (IS_ERR(vol_args)) {
+                ret = PTR_ERR(vol_args);
+                goto err_drop;
+        }
+
+        /* Check for compatibility reject unknown flags */
+        if (vol_args->flags & ~BTRFS_VOL_ARG_V2_FLAGS)
+                return -ENOTTY;
+
+        if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
+                        1)) {
+                ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
+                goto out;
+        }
+
+        mutex_lock(&root->fs_info->volume_mutex);
+        if (vol_args->flags & BTRFS_DEVICE_BY_ID) {
+                ret = btrfs_rm_device(root, NULL, vol_args->devid);
+        } else {
+                vol_args->name[BTRFS_SUBVOL_NAME_MAX] = '\0';
+                ret = btrfs_rm_device(root, vol_args->name, 0);
+        }
+        mutex_unlock(&root->fs_info->volume_mutex);
+        atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
+
+        if (!ret) {
+                if (vol_args->flags & BTRFS_DEVICE_BY_ID)
+                        btrfs_info(root->fs_info, "device deleted: id %llu",
+                                        vol_args->devid);
+                else
+                        btrfs_info(root->fs_info, "device deleted: %s",
+                                        vol_args->name);
+        }
+out:
+        kfree(vol_args);
+err_drop:
+        mnt_drop_write_file(file);
+        return ret;
+}
+
 static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 {
         struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
@@ -2695,7 +2749,7 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
         }
 
         mutex_lock(&root->fs_info->volume_mutex);
-        ret = btrfs_rm_device(root, vol_args->name);
+        ret = btrfs_rm_device(root, vol_args->name, 0);
         mutex_unlock(&root->fs_info->volume_mutex);
         atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
 
@@ -5459,6 +5513,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_add_dev(root, argp);
         case BTRFS_IOC_RM_DEV:
                 return btrfs_ioctl_rm_dev(file, argp);
+        case BTRFS_IOC_RM_DEV_V2:
+                return btrfs_ioctl_rm_dev_v2(file, argp);
         case BTRFS_IOC_FS_INFO:
                 return btrfs_ioctl_fs_info(root, argp);
         case BTRFS_IOC_DEV_INFO:
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 8264b06756e6..1421d711629f 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1748,7 +1748,7 @@ static int __check_raid_min_devices(struct btrfs_fs_info *fs_info)
         return 0;
 }
 
-int btrfs_rm_device(struct btrfs_root *root, char *device_path)
+int btrfs_rm_device(struct btrfs_root *root, char *device_path, u64 devid)
 {
         struct btrfs_device *device;
         struct btrfs_device *next_device;
@@ -1764,7 +1764,7 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
         if (ret)
                 goto out;
 
-        ret = btrfs_find_device_by_user_input(root, 0, device_path,
+        ret = btrfs_find_device_by_user_input(root, devid, device_path,
                                 &device);
         if (ret)
                 goto out;
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 508739314e43..c73d027e2f8b 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -454,7 +454,7 @@ int btrfs_find_device_by_user_input(struct btrfs_root *root, u64 srcdevid,
 struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,
                                         const u64 *devid,
                                         const u8 *uuid);
-int btrfs_rm_device(struct btrfs_root *root, char *device_path);
+int btrfs_rm_device(struct btrfs_root *root, char *device_path, u64 devid);
 void btrfs_cleanup_fs_uuids(void);
 int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len);
 int btrfs_grow_device(struct btrfs_trans_handle *trans,
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index dea893199257..396a4efca775 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -36,6 +36,13 @@ struct btrfs_ioctl_vol_args {
 #define BTRFS_SUBVOL_CREATE_ASYNC       (1ULL << 0)
 #define BTRFS_SUBVOL_RDONLY             (1ULL << 1)
 #define BTRFS_SUBVOL_QGROUP_INHERIT     (1ULL << 2)
+#define BTRFS_DEVICE_BY_ID              (1ULL << 3)
+#define BTRFS_VOL_ARG_V2_FLAGS                          \
+                        (BTRFS_SUBVOL_CREATE_ASYNC |    \
+                        BTRFS_SUBVOL_RDONLY |           \
+                        BTRFS_SUBVOL_QGROUP_INHERIT |   \
+                        BTRFS_DEVICE_BY_ID)
+
 #define BTRFS_FSID_SIZE 16
 #define BTRFS_UUID_SIZE 16
 #define BTRFS_UUID_UNPARSED_SIZE        37
@@ -76,7 +83,10 @@ struct btrfs_ioctl_vol_args_v2 {
                 };
                 __u64 unused[4];
         };
-        char name[BTRFS_SUBVOL_NAME_MAX + 1];
+        union {
+                char name[BTRFS_SUBVOL_NAME_MAX + 1];
+                u64 devid;
+        };
 };
 
 /*
@@ -659,5 +669,7 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
                                    struct btrfs_ioctl_feature_flags[2])
 #define BTRFS_IOC_GET_SUPPORTED_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 57, \
                                    struct btrfs_ioctl_feature_flags[3])
+#define BTRFS_IOC_RM_DEV_V2 _IOW(BTRFS_IOCTL_MAGIC, 58, \
+                                   struct btrfs_ioctl_vol_args_v2)
 
 #endif /* _UAPI_LINUX_BTRFS_H */