xfs: implement online get/set fs label
The GET ioctl is trivial, just return the current label.
The SET ioctl is more involved:
It transactionally modifies the superblock to write a new filesystem
label to the primary super.
A new variant of xfs_sync_sb then writes the superblock buffer
immediately to disk so that the change is visible from userspace.
It then invalidates any page cache that userspace might have previously
read on the block device so that i.e. blkid can see the change
immediately, and updates all secondary superblocks as userspace relable
does.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
[darrick: use dchinner's new xfs_update_secondary_sbs function]
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 42956d8..c1cb29a 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -98,6 +98,9 @@ struct xfs_ifork;
XFS_SB_VERSION2_PROJID32BIT | \
XFS_SB_VERSION2_FTYPE)
+/* Maximum size of the xfs filesystem label, no terminating NULL */
+#define XFSLABEL_MAX 12
+
/*
* Superblock - in core version. Must match the ondisk version below.
* Must be padded to 64 bit alignment.
@@ -122,7 +125,7 @@ typedef struct xfs_sb {
uint16_t sb_sectsize; /* volume sector size, bytes */
uint16_t sb_inodesize; /* inode size, bytes */
uint16_t sb_inopblock; /* inodes per block */
- char sb_fname[12]; /* file system name */
+ char sb_fname[XFSLABEL_MAX]; /* file system name */
uint8_t sb_blocklog; /* log2 of sb_blocksize */
uint8_t sb_sectlog; /* log2 of sb_sectsize */
uint8_t sb_inodelog; /* log2 of sb_inodesize */
@@ -213,7 +216,7 @@ typedef struct xfs_dsb {
__be16 sb_sectsize; /* volume sector size, bytes */
__be16 sb_inodesize; /* inode size, bytes */
__be16 sb_inopblock; /* inodes per block */
- char sb_fname[12]; /* file system name */
+ char sb_fname[XFSLABEL_MAX]; /* file system name */
__u8 sb_blocklog; /* log2 of sb_blocksize */
__u8 sb_sectlog; /* log2 of sb_sectsize */
__u8 sb_inodelog; /* log2 of sb_inodesize */