On 13.11.2017 07:44, Anand Jain wrote:
> Support for a new command is being added here:
> btrfs dev ignore <dev>
> Which shall undo the effects of the command
> btrfs dev scan <dev>
>
> This cli/ioctl is needed as there is no way to continue to mount in
> degraded mode if the device is already scanned, which is required to
> recover from the split brain raid conditions.
>
> This patch proposes to use ioctl #5 as it was empty.
> IOW(BTRFS_IOCTL_MAGIC, 5, ..)
> If #5 is reserved for some other purpose, I think I should change this.
>
> Signed-off-by: Anand Jain <anand.j...@oracle.com>
> ---
> fs/btrfs/super.c | 4 +++
> fs/btrfs/volumes.c | 70
> ++++++++++++++++++++++++++++++++++++++++++++++
> fs/btrfs/volumes.h | 2 ++
> include/uapi/linux/btrfs.h | 2 ++
> 4 files changed, 78 insertions(+)
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index fa7bad8b22da..64f4beb1526d 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -2183,6 +2183,10 @@ static long btrfs_control_ioctl(struct file *file,
> unsigned int cmd,
> ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> &btrfs_fs_type, &fs_devices);
> break;
> + case BTRFS_IOC_IGNORE_DEV:
> + ret = btrfs_ignore_one_device(vol->name, FMODE_READ,
> + &btrfs_fs_type, &fs_devices);
> + break;
> case BTRFS_IOC_DEVICES_READY:
> ret = btrfs_scan_one_device(vol->name, FMODE_READ,
> &btrfs_fs_type, &fs_devices);
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 8ead85dba6f5..1a06a17e111e 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1181,6 +1181,76 @@ int btrfs_read_disk_super(struct block_device *bdev,
> u64 bytenr,
> return 0;
> }
>
> +static int device_list_remove(struct btrfs_super_block *disk_super, u64
> devid)
> +{
> + int ret = 0;
> + struct btrfs_fs_devices *fs_devices;
> + struct btrfs_device *device;
> +
> + fs_devices = find_fsid(disk_super->fsid);
> + if (!fs_devices)
> + return -ENOENT;
> +
> + if (fs_devices->opened)
> + return -EPERM;
Isn't -EBUSY more appropriate?
> +
> + mutex_lock(&uuid_mutex);
> + mutex_lock(&fs_devices->device_list_mutex);
> + device = find_device(fs_devices, devid, disk_super->dev_item.uuid);
> + if (!device) {
> + ret = -ENOENT;
> + goto error;
> + }
> +
> + delete_device_from_list(device);
> +
> +error:
> + mutex_unlock(&fs_devices->device_list_mutex);
> + mutex_unlock(&uuid_mutex);
> +
> + return ret;
> +}
> +
> +int btrfs_ignore_one_device(const char *path, fmode_t flags, void *holder,
> + struct btrfs_fs_devices **fs_devices_ret)
> +{
> + struct btrfs_super_block *disk_super;
> + struct block_device *bdev;
> + struct page *page;
> + int ret = -EINVAL;
> + u64 devid;
> + u64 bytenr;
> +
> + bytenr = btrfs_sb_offset(0);
> + flags |= FMODE_EXCL;
> +
> + bdev = blkdev_get_by_path(path, flags, holder);
> + if (IS_ERR(bdev)) {
> + ret = PTR_ERR(bdev);
> + goto error;
> + }
> +
> + if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super))
> + goto error_bdev_put;
> +
> + devid = btrfs_stack_device_id(&disk_super->dev_item);
> +
> + ret = device_list_remove(disk_super, devid);
> + if (ret)
> + pr_err("BTRFS: %pU: device %s uuid %pU devid %llu failed to unscan: %d",
> + disk_super->fsid, path, disk_super->dev_item.uuid, devid, ret);
> + else
> + pr_info("BTRFS: %pU: device %s uuid %pU devid %llu ran undo scan",
> + disk_super->fsid, path, disk_super->dev_item.uuid, devid);
> +
> + btrfs_release_disk_super(page);
> +
> +error_bdev_put:
> + blkdev_put(bdev, flags);
> +error:
> + return ret;
> +}
> +
> /*
> * 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 6108fdfec67f..340e40acdab5 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -421,6 +421,8 @@ 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_ignore_one_device(const char *path, fmode_t flags, void *holder,
> + struct btrfs_fs_devices **fs_devices_ret);
> 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 378230c163d5..928485c31aa4 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -739,6 +739,8 @@ 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_IGNORE_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
>
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