[PATCH 3/4] xfs: implement online get/set fs label

[Eric Sandeen]

Wire up label ioctls for XFS.

Signed-off-by: Eric Sandeen <sandeen at redhat.com>
---

This is where the implementation questions come in;
is using growlock an abomination?  How can I make the
primary super change immediately visible?

 fs/xfs/xfs_ioctl.c |   62 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 62 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index dbca737..ab59213 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -41,6 +41,8 @@
 #include "xfs_trans.h"
 #include "xfs_pnfs.h"
 #include "xfs_acl.h"
+#include "xfs_log.h"
+#include "xfs_sb.h"
 
 #include <linux/capability.h>
 #include <linux/dcache.h>
@@ -1603,6 +1605,62 @@ xfs_ioc_swapext(
 	return error;
 }
 
+static int
+xfs_ioc_getlabel(
+	struct xfs_mount	*mp,
+	char			__user *label)
+{
+	int			error = 0;
+	struct xfs_sb		*sbp = &mp->m_sb;
+
+	if (!mutex_trylock(&mp->m_growlock))
+		return -EWOULDBLOCK;
+	if (copy_to_user(label, sbp->sb_fname, sizeof(sbp->sb_fname)))
+		error = -EFAULT;
+	mutex_unlock(&mp->m_growlock);
+	return error;
+}
+
+static int
+xfs_ioc_setlabel(
+	struct file		*filp,
+	struct xfs_mount	*mp,
+	char			__user *newlabel)
+{
+	int			error;
+	struct xfs_sb		*sbp = &mp->m_sb;
+	char			sb_fname[12];
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (copy_from_user(sb_fname, newlabel, sizeof(sb_fname)))
+		return -EFAULT;
+
+	error = mnt_want_write_file(filp);
+	if (error)
+		return error;
+
+	/* growfs & label both muck w/ the super directly... */
+	if (!mutex_trylock(&mp->m_growlock))
+		return -EWOULDBLOCK;
+	memset(sbp->sb_fname, 0, sizeof(sbp->sb_fname));
+	strncpy(sbp->sb_fname, sb_fname, sizeof(sbp->sb_fname));
+
+	error = xfs_sync_sb(mp, true);
+	if (error)
+		goto out;
+	/*
+	 * Most kernelspace superblock updates only update sb 0.
+	 * Userspace relabel has always updated all, though, so:
+	 */
+	error = xfs_update_secondary_supers(mp, sbp->sb_agcount, 0);
+out:
+	mutex_unlock(&mp->m_growlock);
+	mnt_drop_write_file(filp);
+	return error;
+}
+
 /*
  * Note: some of the ioctl's return positive numbers as a
  * byte count indicating success, such as readlink_by_handle.
@@ -1630,6 +1688,10 @@ xfs_file_ioctl(
 	switch (cmd) {
 	case FITRIM:
 		return xfs_ioc_trim(mp, arg);
+	case FS_IOC_GET_FSLABEL:
+		return xfs_ioc_getlabel(mp, arg);
+	case FS_IOC_SET_FSLABEL:
+		return xfs_ioc_setlabel(filp, mp, arg);
 	case XFS_IOC_ALLOCSP:
 	case XFS_IOC_FREESP:
 	case XFS_IOC_RESVSP:
-- 
1.7.1