On Thu, Jan 11, 2018 at 09:25:50AM +0800, Anand Jain wrote:
> Support for a new command 'btrfs dev forget [dev]' is proposed here,
> to undo the effects of 'btrfs dev scan [dev]'. For this purpose,
> this patch proposes to use ioctl #5 as it was empty.
> IOW(BTRFS_IOCTL_MAGIC, 5, ..)
> This patch adds new ioctl BTRFS_IOC_FORGET_DEV which can be sent from
> the /dev/btrfs-control to forget one or all devices, (devices which are
> not mounted) from the btrfs kernel.
>
To me this seems to offer a debugging ability, could you please
elaborate the use case where we need to forget a particular device
instead of just wiping the uuid?
Thanks,
-liubo
> The argument it takes is struct btrfs_ioctl_vol_args_v2, and ::name can be
> set to specify the device path. And all unmounted devices can be removed
> from the kernel using the BTRFS_DEVICE_SPEC_ALL_DEV flag. Remove all
> devices functionality would override remove one device when both are
> specified in an IOCTL call.
> Again, the devices are removed only if the relevant fsid aren't mounted.
>
> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
> ---
> fs/btrfs/super.c | 27 +++++++++++++++++++++++----
> fs/btrfs/volumes.c | 9 +++++++++
> fs/btrfs/volumes.h | 1 +
> include/uapi/linux/btrfs.h | 6 +++++-
> 4 files changed, 38 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 559fc53ff59e..6a9a5ce8af3b 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -2219,21 +2219,37 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
> unsigned long arg)
> {
> struct btrfs_ioctl_vol_args *vol;
> + struct btrfs_ioctl_vol_args_v2 *vol2;
> struct btrfs_fs_devices *fs_devices;
> int ret = -ENOTTY;
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - vol = memdup_user((void __user *)arg, sizeof(*vol));
> - if (IS_ERR(vol))
> - return PTR_ERR(vol);
> + if (cmd == BTRFS_IOC_FORGET_DEV) {
> + vol2 = memdup_user((void __user *)arg, sizeof(*vol2));
> + if (IS_ERR(vol2))
> + return PTR_ERR(vol2);
> +
> + if (vol2->flags & ~BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED)
> + return -EOPNOTSUPP;
> + } else {
> + vol = memdup_user((void __user *)arg, sizeof(*vol));
> + if (IS_ERR(vol))
> + return PTR_ERR(vol);
> + }
>
> switch (cmd) {
> case BTRFS_IOC_SCAN_DEV:
> ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> &btrfs_fs_type, &fs_devices);
> break;
> + case BTRFS_IOC_FORGET_DEV:
> + if (vol2->flags & BTRFS_DEVICE_SPEC_ALL_DEV)
> + ret = btrfs_forget_devices(NULL);
> + else
> + ret = btrfs_forget_devices(vol2->name);
> + break;
> case BTRFS_IOC_DEVICES_READY:
> ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> &btrfs_fs_type, &fs_devices);
> @@ -2246,7 +2262,10 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
> break;
> }
>
> - kfree(vol);
> + if (cmd == BTRFS_IOC_FORGET_DEV)
> + kfree(vol2);
> + else
> + kfree(vol);
> return ret;
> }
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index e947e47f8fff..b0c9948baf9a 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1171,6 +1171,15 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
> return 0;
> }
>
> +int btrfs_forget_devices(const char *path)
> +{
> + mutex_lock(&uuid_mutex);
> + btrfs_free_stale_devices(path, NULL);
> + mutex_unlock(&uuid_mutex);
> +
> + return 0;
> +}
> +
> /*
> * Look for a btrfs signature on a device. This may be called out of the mount path
> * and we are not allowed to call set_blocksize during the scan. The superblock
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 15216fed918b..b954ca3b79a9 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -422,6 +422,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
> fmode_t flags, void *holder);
> int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
> struct btrfs_fs_devices **fs_devices_ret);
> +int btrfs_forget_devices(const char *path);
> int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
> void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices, int step);
> void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> index c8d99b9ca550..4e8ec1391872 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -41,12 +41,14 @@ struct btrfs_ioctl_vol_args {
> #define BTRFS_SUBVOL_QGROUP_INHERIT (1ULL << 2)
>
> #define BTRFS_DEVICE_SPEC_BY_ID (1ULL << 3)
> +#define BTRFS_DEVICE_SPEC_ALL_DEV (1ULL << 4)
>
> #define BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED \
> (BTRFS_SUBVOL_CREATE_ASYNC | \
> BTRFS_SUBVOL_RDONLY | \
> BTRFS_SUBVOL_QGROUP_INHERIT | \
> - BTRFS_DEVICE_SPEC_BY_ID)
> + BTRFS_DEVICE_SPEC_BY_ID | \
> + BTRFS_DEVICE_SPEC_ALL_DEV)
>
> #define BTRFS_FSID_SIZE 16
> #define BTRFS_UUID_SIZE 16
> @@ -745,6 +747,8 @@ enum btrfs_err_code {
> struct btrfs_ioctl_vol_args)
> #define BTRFS_IOC_SCAN_DEV _IOW(BTRFS_IOCTL_MAGIC, 4, \
> struct btrfs_ioctl_vol_args)
> +#define BTRFS_IOC_FORGET_DEV _IOW(BTRFS_IOCTL_MAGIC, 5, \
> + struct btrfs_ioctl_vol_args)
> /* trans start and trans end are dangerous, and only for
> * use by applications that know how to avoid the
> * resulting deadlocks
> --
> 2.7.0
>
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