btrfs: implement shutdown ioctl

The shutdown ioctl should follow the XFS one, which use magic number 'X',
and ioctl number 125, with a uint32 as flags.

For now btrfs don't distinguish DEFAULT and LOGFLUSH flags (just like
f2fs), both will freeze the fs first (implies committing the current
transaction), setting the SHUTDOWN flag and finally thaw the fs.

For NOLOGFLUSH flag, the freeze/thaw part is skipped thus the current
transaction is aborted.

The new shutdown ioctl is hidden behind experimental features for more
testing.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Tested-by: Anand Jain <asj@kernel.org>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 803556ec0e183965f9b601eed673c86ae88c2431..127b5d8303a8c8457370721b298ffeaf4f0de538 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -5223,6 +5223,43 @@ static int btrfs_ioctl_subvol_sync(struct btrfs_fs_info *fs_info, void __user *a
        return 0;
 }
 
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+static int btrfs_ioctl_shutdown(struct btrfs_fs_info *fs_info, unsigned long arg)
+{
+       int ret = 0;
+       u32 flags;
+
+       if (!capable(CAP_SYS_ADMIN))
+               return -EPERM;
+
+       if (get_user(flags, (u32 __user *)arg))
+               return -EFAULT;
+
+       if (flags >= BTRFS_SHUTDOWN_FLAGS_LAST)
+               return -EINVAL;
+
+       if (btrfs_is_shutdown(fs_info))
+               return 0;
+
+       switch (flags) {
+       case BTRFS_SHUTDOWN_FLAGS_LOGFLUSH:
+       case BTRFS_SHUTDOWN_FLAGS_DEFAULT:
+               ret = freeze_super(fs_info->sb, FREEZE_HOLDER_KERNEL, NULL);
+               if (ret)
+                       return ret;
+               btrfs_force_shutdown(fs_info);
+               ret = thaw_super(fs_info->sb, FREEZE_HOLDER_KERNEL, NULL);
+               if (ret)
+                       return ret;
+               break;
+       case BTRFS_SHUTDOWN_FLAGS_NOLOGFLUSH:
+               btrfs_force_shutdown(fs_info);
+               break;
+       }
+       return ret;
+}
+#endif
+
 long btrfs_ioctl(struct file *file, unsigned int
                cmd, unsigned long arg)
 {
@@ -5378,6 +5415,10 @@ long btrfs_ioctl(struct file *file, unsigned int
 #endif
        case BTRFS_IOC_SUBVOL_SYNC_WAIT:
                return btrfs_ioctl_subvol_sync(fs_info, argp);
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+       case BTRFS_IOC_SHUTDOWN:
+               return btrfs_ioctl_shutdown(fs_info, arg);
+#endif
        }
 
        return -ENOTTY;

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 8e710bbb688e042479eaa5fdc2811be7e1468c63..e8fd92789423e12c17366b5b204bde71ca928ba6 100644 (file)
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -1099,6 +1099,12 @@ enum btrfs_err_code {
        BTRFS_ERROR_DEV_RAID1C4_MIN_NOT_MET,
 };
 
+/* Flags for IOC_SHUTDOWN, must match XFS_FSOP_GOING_FLAGS_* flags. */
+#define BTRFS_SHUTDOWN_FLAGS_DEFAULT                   0x0
+#define BTRFS_SHUTDOWN_FLAGS_LOGFLUSH                  0x1
+#define BTRFS_SHUTDOWN_FLAGS_NOLOGFLUSH                        0x2
+#define BTRFS_SHUTDOWN_FLAGS_LAST                      0x3
+
 #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
                                   struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
@@ -1220,6 +1226,9 @@ enum btrfs_err_code {
 #define BTRFS_IOC_SUBVOL_SYNC_WAIT _IOW(BTRFS_IOCTL_MAGIC, 65, \
                                        struct btrfs_ioctl_subvol_wait)
 
+/* Shutdown ioctl should follow XFS's interfaces, thus not using btrfs magic. */
+#define BTRFS_IOC_SHUTDOWN     _IOR('X', 125, __u32)
+
 #ifdef __cplusplus
 }
 #endif