xfs: introduce xfs_sb.c for sharing with libxfs

xfs_mount.c is shared with userspace, but the only functions that
are shared are to do with physical superblock manipulations. This
means that less than 25% of the xfs_mount.c code is actually shared
with userspace. Move all the superblock functions to xfs_sb.c and
share that instead with libxfs.

Note that this will leave all the in-core transaction related
superblock counter modifications in xfs_mount.c as none of that is
shared with userspace. With a few more small changes, xfs_mount.h
won't need to be shared with userspace anymore, either.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

5 files changed, 863 insertions, 797 deletions

diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index 20b1d949b090..fb14461d414e 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -47,6 +47,7 @@ xfs-y				+= xfs_aops.o \
 				   xfs_iops.o \
 				   xfs_itable.o \
 				   xfs_message.o \
+				   xfs_mount.o \
 				   xfs_mru_cache.o \
 				   xfs_rename.o \
 				   xfs_super.o \
@@ -81,7 +82,7 @@ xfs-y				+= xfs_alloc.o \
 				   xfs_inode_fork.o \
 				   xfs_inode_buf.o \
 				   xfs_log_recover.o \
-				   xfs_mount.o \
+				   xfs_sb.o \
 				   xfs_symlink_remote.o \
 				   xfs_trans_resv.o
 
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index b07ca4be3941..3b6fe4ffd724 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -61,69 +61,6 @@ STATIC void	xfs_icsb_disable_counter(xfs_mount_t *, xfs_sb_field_t);
 #define xfs_icsb_balance_counter_locked(mp, a, b)	do { } while (0)
 #endif
 
-static const struct {
-	short offset;
-	short type;	/* 0 = integer
-			 * 1 = binary / string (no translation)
-			 */
-} xfs_sb_info[] = {
-    { offsetof(xfs_sb_t, sb_magicnum),   0 },
-    { offsetof(xfs_sb_t, sb_blocksize),  0 },
-    { offsetof(xfs_sb_t, sb_dblocks),    0 },
-    { offsetof(xfs_sb_t, sb_rblocks),    0 },
-    { offsetof(xfs_sb_t, sb_rextents),   0 },
-    { offsetof(xfs_sb_t, sb_uuid),       1 },
-    { offsetof(xfs_sb_t, sb_logstart),   0 },
-    { offsetof(xfs_sb_t, sb_rootino),    0 },
-    { offsetof(xfs_sb_t, sb_rbmino),     0 },
-    { offsetof(xfs_sb_t, sb_rsumino),    0 },
-    { offsetof(xfs_sb_t, sb_rextsize),   0 },
-    { offsetof(xfs_sb_t, sb_agblocks),   0 },
-    { offsetof(xfs_sb_t, sb_agcount),    0 },
-    { offsetof(xfs_sb_t, sb_rbmblocks),  0 },
-    { offsetof(xfs_sb_t, sb_logblocks),  0 },
-    { offsetof(xfs_sb_t, sb_versionnum), 0 },
-    { offsetof(xfs_sb_t, sb_sectsize),   0 },
-    { offsetof(xfs_sb_t, sb_inodesize),  0 },
-    { offsetof(xfs_sb_t, sb_inopblock),  0 },
-    { offsetof(xfs_sb_t, sb_fname[0]),   1 },
-    { offsetof(xfs_sb_t, sb_blocklog),   0 },
-    { offsetof(xfs_sb_t, sb_sectlog),    0 },
-    { offsetof(xfs_sb_t, sb_inodelog),   0 },
-    { offsetof(xfs_sb_t, sb_inopblog),   0 },
-    { offsetof(xfs_sb_t, sb_agblklog),   0 },
-    { offsetof(xfs_sb_t, sb_rextslog),   0 },
-    { offsetof(xfs_sb_t, sb_inprogress), 0 },
-    { offsetof(xfs_sb_t, sb_imax_pct),   0 },
-    { offsetof(xfs_sb_t, sb_icount),     0 },
-    { offsetof(xfs_sb_t, sb_ifree),      0 },
-    { offsetof(xfs_sb_t, sb_fdblocks),   0 },
-    { offsetof(xfs_sb_t, sb_frextents),  0 },
-    { offsetof(xfs_sb_t, sb_uquotino),   0 },
-    { offsetof(xfs_sb_t, sb_gquotino),   0 },
-    { offsetof(xfs_sb_t, sb_qflags),     0 },
-    { offsetof(xfs_sb_t, sb_flags),      0 },
-    { offsetof(xfs_sb_t, sb_shared_vn),  0 },
-    { offsetof(xfs_sb_t, sb_inoalignmt), 0 },
-    { offsetof(xfs_sb_t, sb_unit),	 0 },
-    { offsetof(xfs_sb_t, sb_width),	 0 },
-    { offsetof(xfs_sb_t, sb_dirblklog),	 0 },
-    { offsetof(xfs_sb_t, sb_logsectlog), 0 },
-    { offsetof(xfs_sb_t, sb_logsectsize),0 },
-    { offsetof(xfs_sb_t, sb_logsunit),	 0 },
-    { offsetof(xfs_sb_t, sb_features2),	 0 },
-    { offsetof(xfs_sb_t, sb_bad_features2), 0 },
-    { offsetof(xfs_sb_t, sb_features_compat), 0 },
-    { offsetof(xfs_sb_t, sb_features_ro_compat), 0 },
-    { offsetof(xfs_sb_t, sb_features_incompat), 0 },
-    { offsetof(xfs_sb_t, sb_features_log_incompat), 0 },
-    { offsetof(xfs_sb_t, sb_crc),	 0 },
-    { offsetof(xfs_sb_t, sb_pad),	 0 },
-    { offsetof(xfs_sb_t, sb_pquotino),	 0 },
-    { offsetof(xfs_sb_t, sb_lsn),	 0 },
-    { sizeof(xfs_sb_t),			 0 }
-};
-
 static DEFINE_MUTEX(xfs_uuid_table_mutex);
 static int xfs_uuid_table_size;
 static uuid_t *xfs_uuid_table;
@@ -199,64 +136,6 @@ xfs_uuid_unmount(
 }
 
 
-/*
- * Reference counting access wrappers to the perag structures.
- * Because we never free per-ag structures, the only thing we
- * have to protect against changes is the tree structure itself.
- */
-struct xfs_perag *
-xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
-{
-	struct xfs_perag	*pag;
-	int			ref = 0;
-
-	rcu_read_lock();
-	pag = radix_tree_lookup(&mp->m_perag_tree, agno);
-	if (pag) {
-		ASSERT(atomic_read(&pag->pag_ref) >= 0);
-		ref = atomic_inc_return(&pag->pag_ref);
-	}
-	rcu_read_unlock();
-	trace_xfs_perag_get(mp, agno, ref, _RET_IP_);
-	return pag;
-}
-
-/*
- * search from @first to find the next perag with the given tag set.
- */
-struct xfs_perag *
-xfs_perag_get_tag(
-	struct xfs_mount	*mp,
-	xfs_agnumber_t		first,
-	int			tag)
-{
-	struct xfs_perag	*pag;
-	int			found;
-	int			ref;
-
-	rcu_read_lock();
-	found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
-					(void **)&pag, first, 1, tag);
-	if (found <= 0) {
-		rcu_read_unlock();
-		return NULL;
-	}
-	ref = atomic_inc_return(&pag->pag_ref);
-	rcu_read_unlock();
-	trace_xfs_perag_get_tag(mp, pag->pag_agno, ref, _RET_IP_);
-	return pag;
-}
-
-void
-xfs_perag_put(struct xfs_perag *pag)
-{
-	int	ref;
-
-	ASSERT(atomic_read(&pag->pag_ref) > 0);
-	ref = atomic_dec_return(&pag->pag_ref);
-	trace_xfs_perag_put(pag->pag_mount, pag->pag_agno, ref, _RET_IP_);
-}
-
 STATIC void
 __xfs_free_perag(
 	struct rcu_head	*head)
@@ -309,189 +188,6 @@ xfs_sb_validate_fsb_count(
 	return 0;
 }
 
-/*
- * Check the validity of the SB found.
- */
-STATIC int
-xfs_mount_validate_sb(
-	xfs_mount_t	*mp,
-	xfs_sb_t	*sbp,
-	bool		check_inprogress,
-	bool		check_version)
-{
-
-	/*
-	 * If the log device and data device have the
-	 * same device number, the log is internal.
-	 * Consequently, the sb_logstart should be non-zero.  If
-	 * we have a zero sb_logstart in this case, we may be trying to mount
-	 * a volume filesystem in a non-volume manner.
-	 */
-	if (sbp->sb_magicnum != XFS_SB_MAGIC) {
-		xfs_warn(mp, "bad magic number");
-		return XFS_ERROR(EWRONGFS);
-	}
-
-
-	if (!xfs_sb_good_version(sbp)) {
-		xfs_warn(mp, "bad version");
-		return XFS_ERROR(EWRONGFS);
-	}
-
-	/*
-	 * Version 5 superblock feature mask validation. Reject combinations the
-	 * kernel cannot support up front before checking anything else. For
-	 * write validation, we don't need to check feature masks.
-	 */
-	if (check_version && XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) {
-		xfs_alert(mp,
-"Version 5 superblock detected. This kernel has EXPERIMENTAL support enabled!\n"
-"Use of these features in this kernel is at your own risk!");
-
-		if (xfs_sb_has_compat_feature(sbp,
-					XFS_SB_FEAT_COMPAT_UNKNOWN)) {
-			xfs_warn(mp,
-"Superblock has unknown compatible features (0x%x) enabled.\n"
-"Using a more recent kernel is recommended.",
-				(sbp->sb_features_compat &
-						XFS_SB_FEAT_COMPAT_UNKNOWN));
-		}
-
-		if (xfs_sb_has_ro_compat_feature(sbp,
-					XFS_SB_FEAT_RO_COMPAT_UNKNOWN)) {
-			xfs_alert(mp,
-"Superblock has unknown read-only compatible features (0x%x) enabled.",
-				(sbp->sb_features_ro_compat &
-						XFS_SB_FEAT_RO_COMPAT_UNKNOWN));
-			if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
-				xfs_warn(mp,
-"Attempted to mount read-only compatible filesystem read-write.\n"
-"Filesystem can only be safely mounted read only.");
-				return XFS_ERROR(EINVAL);
-			}
-		}
-		if (xfs_sb_has_incompat_feature(sbp,
-					XFS_SB_FEAT_INCOMPAT_UNKNOWN)) {
-			xfs_warn(mp,
-"Superblock has unknown incompatible features (0x%x) enabled.\n"
-"Filesystem can not be safely mounted by this kernel.",
-				(sbp->sb_features_incompat &
-						XFS_SB_FEAT_INCOMPAT_UNKNOWN));
-			return XFS_ERROR(EINVAL);
-		}
-	}
-
-	if (xfs_sb_version_has_pquotino(sbp)) {
-		if (sbp->sb_qflags & (XFS_OQUOTA_ENFD | XFS_OQUOTA_CHKD)) {
-			xfs_notice(mp,
-			   "Version 5 of Super block has XFS_OQUOTA bits.\n");
-			return XFS_ERROR(EFSCORRUPTED);
-		}
-	} else if (sbp->sb_qflags & (XFS_PQUOTA_ENFD | XFS_GQUOTA_ENFD |
-				XFS_PQUOTA_CHKD | XFS_GQUOTA_CHKD)) {
-			xfs_notice(mp,
-"Superblock earlier than Version 5 has XFS_[PQ]UOTA_{ENFD|CHKD} bits.\n");
-			return XFS_ERROR(EFSCORRUPTED);
-	}
-
-	if (unlikely(
-	    sbp->sb_logstart == 0 && mp->m_logdev_targp == mp->m_ddev_targp)) {
-		xfs_warn(mp,
-		"filesystem is marked as having an external log; "
-		"specify logdev on the mount command line.");
-		return XFS_ERROR(EINVAL);
-	}
-
-	if (unlikely(
-	    sbp->sb_logstart != 0 && mp->m_logdev_targp != mp->m_ddev_targp)) {
-		xfs_warn(mp,
-		"filesystem is marked as having an internal log; "
-		"do not specify logdev on the mount command line.");
-		return XFS_ERROR(EINVAL);
-	}
-
-	/*
-	 * More sanity checking.  Most of these were stolen directly from
-	 * xfs_repair.
-	 */
-	if (unlikely(
-	    sbp->sb_agcount <= 0					||
-	    sbp->sb_sectsize < XFS_MIN_SECTORSIZE			||
-	    sbp->sb_sectsize > XFS_MAX_SECTORSIZE			||
-	    sbp->sb_sectlog < XFS_MIN_SECTORSIZE_LOG			||
-	    sbp->sb_sectlog > XFS_MAX_SECTORSIZE_LOG			||
-	    sbp->sb_sectsize != (1 << sbp->sb_sectlog)			||
-	    sbp->sb_blocksize < XFS_MIN_BLOCKSIZE			||
-	    sbp->sb_blocksize > XFS_MAX_BLOCKSIZE			||
-	    sbp->sb_blocklog < XFS_MIN_BLOCKSIZE_LOG			||
-	    sbp->sb_blocklog > XFS_MAX_BLOCKSIZE_LOG			||
-	    sbp->sb_blocksize != (1 << sbp->sb_blocklog)		||
-	    sbp->sb_inodesize < XFS_DINODE_MIN_SIZE			||
-	    sbp->sb_inodesize > XFS_DINODE_MAX_SIZE			||
-	    sbp->sb_inodelog < XFS_DINODE_MIN_LOG			||
-	    sbp->sb_inodelog > XFS_DINODE_MAX_LOG			||
-	    sbp->sb_inodesize != (1 << sbp->sb_inodelog)		||
-	    (sbp->sb_blocklog - sbp->sb_inodelog != sbp->sb_inopblog)	||
-	    (sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE)	||
-	    (sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE)	||
-	    (sbp->sb_imax_pct > 100 /* zero sb_imax_pct is valid */)	||
-	    sbp->sb_dblocks == 0					||
-	    sbp->sb_dblocks > XFS_MAX_DBLOCKS(sbp)			||
-	    sbp->sb_dblocks < XFS_MIN_DBLOCKS(sbp))) {
-		XFS_CORRUPTION_ERROR("SB sanity check failed",
-				XFS_ERRLEVEL_LOW, mp, sbp);
-		return XFS_ERROR(EFSCORRUPTED);
-	}
-
-	/*
-	 * Until this is fixed only page-sized or smaller data blocks work.
-	 */
-	if (unlikely(sbp->sb_blocksize > PAGE_SIZE)) {
-		xfs_warn(mp,
-		"File system with blocksize %d bytes. "
-		"Only pagesize (%ld) or less will currently work.",
-				sbp->sb_blocksize, PAGE_SIZE);
-		return XFS_ERROR(ENOSYS);
-	}
-
-	/*
-	 * Currently only very few inode sizes are supported.
-	 */
-	switch (sbp->sb_inodesize) {
-	case 256:
-	case 512:
-	case 1024:
-	case 2048:
-		break;
-	default:
-		xfs_warn(mp, "inode size of %d bytes not supported",
-				sbp->sb_inodesize);
-		return XFS_ERROR(ENOSYS);
-	}
-
-	if (xfs_sb_validate_fsb_count(sbp, sbp->sb_dblocks) ||
-	    xfs_sb_validate_fsb_count(sbp, sbp->sb_rblocks)) {
-		xfs_warn(mp,
-		"file system too large to be mounted on this system.");
-		return XFS_ERROR(EFBIG);
-	}
-
-	if (check_inprogress && sbp->sb_inprogress) {
-		xfs_warn(mp, "Offline file system operation in progress!");
-		return XFS_ERROR(EFSCORRUPTED);
-	}
-
-	/*
-	 * Version 1 directory format has never worked on Linux.
-	 */
-	if (unlikely(!xfs_sb_version_hasdirv2(sbp))) {
-		xfs_warn(mp, "file system using version 1 directory format");
-		return XFS_ERROR(ENOSYS);
-	}
-
-	return 0;
-}
-
 int
 xfs_initialize_perag(
 	xfs_mount_t	*mp,
@@ -576,342 +272,15 @@ out_unwind:
 	return error;
 }
 
-static void
-xfs_sb_quota_from_disk(struct xfs_sb *sbp)
-{
-	/*
-	 * older mkfs doesn't initialize quota inodes to NULLFSINO. This
-	 * leads to in-core values having two different values for a quota
-	 * inode to be invalid: 0 and NULLFSINO. Change it to a single value
-	 * NULLFSINO.
-	 *
-	 * Note that this change affect only the in-core values. These
-	 * values are not written back to disk unless any quota information
-	 * is written to the disk. Even in that case, sb_pquotino field is
-	 * not written to disk unless the superblock supports pquotino.
-	 */
-	if (sbp->sb_uquotino == 0)
-		sbp->sb_uquotino = NULLFSINO;
-	if (sbp->sb_gquotino == 0)
-		sbp->sb_gquotino = NULLFSINO;
-	if (sbp->sb_pquotino == 0)
-		sbp->sb_pquotino = NULLFSINO;
-
-	/*
-	 * We need to do these manipilations only if we are working
-	 * with an older version of on-disk superblock.
-	 */
-	if (xfs_sb_version_has_pquotino(sbp))
-		return;
-
-	if (sbp->sb_qflags & XFS_OQUOTA_ENFD)
-		sbp->sb_qflags |= (sbp->sb_qflags & XFS_PQUOTA_ACCT) ?
-					XFS_PQUOTA_ENFD : XFS_GQUOTA_ENFD;
-	if (sbp->sb_qflags & XFS_OQUOTA_CHKD)
-		sbp->sb_qflags |= (sbp->sb_qflags & XFS_PQUOTA_ACCT) ?
-					XFS_PQUOTA_CHKD : XFS_GQUOTA_CHKD;
-	sbp->sb_qflags &= ~(XFS_OQUOTA_ENFD | XFS_OQUOTA_CHKD);
-
-	if (sbp->sb_qflags & XFS_PQUOTA_ACCT)  {
-		/*
-		 * In older version of superblock, on-disk superblock only
-		 * has sb_gquotino, and in-core superblock has both sb_gquotino
-		 * and sb_pquotino. But, only one of them is supported at any
-		 * point of time. So, if PQUOTA is set in disk superblock,
-		 * copy over sb_gquotino to sb_pquotino.
-		 */
-		sbp->sb_pquotino = sbp->sb_gquotino;
-		sbp->sb_gquotino = NULLFSINO;
-	}
-}
-
-void
-xfs_sb_from_disk(
-	struct xfs_sb	*to,
-	xfs_dsb_t	*from)
-{
-	to->sb_magicnum = be32_to_cpu(from->sb_magicnum);
-	to->sb_blocksize = be32_to_cpu(from->sb_blocksize);
-	to->sb_dblocks = be64_to_cpu(from->sb_dblocks);
-	to->sb_rblocks = be64_to_cpu(from->sb_rblocks);
-	to->sb_rextents = be64_to_cpu(from->sb_rextents);
-	memcpy(&to->sb_uuid, &from->sb_uuid, sizeof(to->sb_uuid));
-	to->sb_logstart = be64_to_cpu(from->sb_logstart);
-	to->sb_rootino = be64_to_cpu(from->sb_rootino);
-	to->sb_rbmino = be64_to_cpu(from->sb_rbmino);
-	to->sb_rsumino = be64_to_cpu(from->sb_rsumino);
-	to->sb_rextsize = be32_to_cpu(from->sb_rextsize);
-	to->sb_agblocks = be32_to_cpu(from->sb_agblocks);
-	to->sb_agcount = be32_to_cpu(from->sb_agcount);
-	to->sb_rbmblocks = be32_to_cpu(from->sb_rbmblocks);
-	to->sb_logblocks = be32_to_cpu(from->sb_logblocks);
-	to->sb_versionnum = be16_to_cpu(from->sb_versionnum);
-	to->sb_sectsize = be16_to_cpu(from->sb_sectsize);
-	to->sb_inodesize = be16_to_cpu(from->sb_inodesize);
-	to->sb_inopblock = be16_to_cpu(from->sb_inopblock);
-	memcpy(&to->sb_fname, &from->sb_fname, sizeof(to->sb_fname));
-	to->sb_blocklog = from->sb_blocklog;
-	to->sb_sectlog = from->sb_sectlog;
-	to->sb_inodelog = from->sb_inodelog;
-	to->sb_inopblog = from->sb_inopblog;
-	to->sb_agblklog = from->sb_agblklog;
-	to->sb_rextslog = from->sb_rextslog;
-	to->sb_inprogress = from->sb_inprogress;
-	to->sb_imax_pct = from->sb_imax_pct;
-	to->sb_icount = be64_to_cpu(from->sb_icount);
-	to->sb_ifree = be64_to_cpu(from->sb_ifree);
-	to->sb_fdblocks = be64_to_cpu(from->sb_fdblocks);
-	to->sb_frextents = be64_to_cpu(from->sb_frextents);
-	to->sb_uquotino = be64_to_cpu(from->sb_uquotino);
-	to->sb_gquotino = be64_to_cpu(from->sb_gquotino);
-	to->sb_qflags = be16_to_cpu(from->sb_qflags);
-	to->sb_flags = from->sb_flags;
-	to->sb_shared_vn = from->sb_shared_vn;
-	to->sb_inoalignmt = be32_to_cpu(from->sb_inoalignmt);
-	to->sb_unit = be32_to_cpu(from->sb_unit);
-	to->sb_width = be32_to_cpu(from->sb_width);
-	to->sb_dirblklog = from->sb_dirblklog;
-	to->sb_logsectlog = from->sb_logsectlog;
-	to->sb_logsectsize = be16_to_cpu(from->sb_logsectsize);
-	to->sb_logsunit = be32_to_cpu(from->sb_logsunit);
-	to->sb_features2 = be32_to_cpu(from->sb_features2);
-	to->sb_bad_features2 = be32_to_cpu(from->sb_bad_features2);
-	to->sb_features_compat = be32_to_cpu(from->sb_features_compat);
-	to->sb_features_ro_compat = be32_to_cpu(from->sb_features_ro_compat);
-	to->sb_features_incompat = be32_to_cpu(from->sb_features_incompat);
-	to->sb_features_log_incompat =
-				be32_to_cpu(from->sb_features_log_incompat);
-	to->sb_pad = 0;
-	to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
-	to->sb_lsn = be64_to_cpu(from->sb_lsn);
-}
-
-static inline void
-xfs_sb_quota_to_disk(
-	xfs_dsb_t	*to,
-	xfs_sb_t	*from,
-	__int64_t	*fields)
-{
-	__uint16_t	qflags = from->sb_qflags;
-
-	/*
-	 * We need to do these manipilations only if we are working
-	 * with an older version of on-disk superblock.
-	 */
-	if (xfs_sb_version_has_pquotino(from))
-		return;
-
-	if (*fields & XFS_SB_QFLAGS) {
-		/*
-		 * The in-core version of sb_qflags do not have
-		 * XFS_OQUOTA_* flags, whereas the on-disk version
-		 * does.  So, convert incore XFS_{PG}QUOTA_* flags
-		 * to on-disk XFS_OQUOTA_* flags.
-		 */
-		qflags &= ~(XFS_PQUOTA_ENFD | XFS_PQUOTA_CHKD |
-				XFS_GQUOTA_ENFD | XFS_GQUOTA_CHKD);
-
-		if (from->sb_qflags &
-				(XFS_PQUOTA_ENFD | XFS_GQUOTA_ENFD))
-			qflags |= XFS_OQUOTA_ENFD;
-		if (from->sb_qflags &
-				(XFS_PQUOTA_CHKD | XFS_GQUOTA_CHKD))
-			qflags |= XFS_OQUOTA_CHKD;
-		to->sb_qflags = cpu_to_be16(qflags);
-		*fields &= ~XFS_SB_QFLAGS;
-	}
-
-	/*
-	 * GQUOTINO and PQUOTINO cannot be used together in versions
-	 * of superblock that do not have pquotino. from->sb_flags
-	 * tells us which quota is active and should be copied to
-	 * disk.
-	 */
-	if ((*fields & XFS_SB_GQUOTINO) &&
-				(from->sb_qflags & XFS_GQUOTA_ACCT))
-		to->sb_gquotino = cpu_to_be64(from->sb_gquotino);
-	else if ((*fields & XFS_SB_PQUOTINO) &&
-				(from->sb_qflags & XFS_PQUOTA_ACCT))
-		to->sb_gquotino = cpu_to_be64(from->sb_pquotino);
-
-	*fields &= ~(XFS_SB_PQUOTINO | XFS_SB_GQUOTINO);
-}
-
-/*
- * Copy in core superblock to ondisk one.
- *
- * The fields argument is mask of superblock fields to copy.
- */
-void
-xfs_sb_to_disk(
-	xfs_dsb_t	*to,
-	xfs_sb_t	*from,
-	__int64_t	fields)
-{
-	xfs_caddr_t	to_ptr = (xfs_caddr_t)to;
-	xfs_caddr_t	from_ptr = (xfs_caddr_t)from;
-	xfs_sb_field_t	f;
-	int		first;
-	int		size;
-
-	ASSERT(fields);
-	if (!fields)
-		return;
-
-	xfs_sb_quota_to_disk(to, from, &fields);
-	while (fields) {
-		f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
-		first = xfs_sb_info[f].offset;
-		size = xfs_sb_info[f + 1].offset - first;
-
-		ASSERT(xfs_sb_info[f].type == 0 || xfs_sb_info[f].type == 1);
-
-		if (size == 1 || xfs_sb_info[f].type == 1) {
-			memcpy(to_ptr + first, from_ptr + first, size);
-		} else {
-			switch (size) {
-			case 2:
-				*(__be16 *)(to_ptr + first) =
-					cpu_to_be16(*(__u16 *)(from_ptr + first));
-				break;
-			case 4:
-				*(__be32 *)(to_ptr + first) =
-					cpu_to_be32(*(__u32 *)(from_ptr + first));
-				break;
-			case 8:
-				*(__be64 *)(to_ptr + first) =
-					cpu_to_be64(*(__u64 *)(from_ptr + first));
-				break;
-			default:
-				ASSERT(0);
-			}
-		}
-
-		fields &= ~(1LL << f);
-	}
-}
-
-static int
-xfs_sb_verify(
-	struct xfs_buf	*bp,
-	bool		check_version)
-{
-	struct xfs_mount *mp = bp->b_target->bt_mount;
-	struct xfs_sb	sb;
-
-	xfs_sb_from_disk(&sb, XFS_BUF_TO_SBP(bp));
-
-	/*
-	 * Only check the in progress field for the primary superblock as
-	 * mkfs.xfs doesn't clear it from secondary superblocks.
-	 */
-	return xfs_mount_validate_sb(mp, &sb, bp->b_bn == XFS_SB_DADDR,
-				     check_version);
-}
-
-/*
- * If the superblock has the CRC feature bit set or the CRC field is non-null,
- * check that the CRC is valid.  We check the CRC field is non-null because a
- * single bit error could clear the feature bit and unused parts of the
- * superblock are supposed to be zero. Hence a non-null crc field indicates that
- * we've potentially lost a feature bit and we should check it anyway.
- */
-static void
-xfs_sb_read_verify(
-	struct xfs_buf	*bp)
-{
-	struct xfs_mount *mp = bp->b_target->bt_mount;
-	struct xfs_dsb	*dsb = XFS_BUF_TO_SBP(bp);
-	int		error;
-
-	/*
-	 * open code the version check to avoid needing to convert the entire
-	 * superblock from disk order just to check the version number
-	 */
-	if (dsb->sb_magicnum == cpu_to_be32(XFS_SB_MAGIC) &&
-	    (((be16_to_cpu(dsb->sb_versionnum) & XFS_SB_VERSION_NUMBITS) ==
-						XFS_SB_VERSION_5) ||
-	     dsb->sb_crc != 0)) {
-
-		if (!xfs_verify_cksum(bp->b_addr, be16_to_cpu(dsb->sb_sectsize),
-				      offsetof(struct xfs_sb, sb_crc))) {
-			error = EFSCORRUPTED;
-			goto out_error;
-		}
-	}
-	error = xfs_sb_verify(bp, true);
-
-out_error:
-	if (error) {
-		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
-		xfs_buf_ioerror(bp, error);
-	}
-}
-
-/*
- * We may be probed for a filesystem match, so we may not want to emit
- * messages when the superblock buffer is not actually an XFS superblock.
- * If we find an XFS superblock, the run a normal, noisy mount because we are
- * really going to mount it and want to know about errors.
- */
-static void
-xfs_sb_quiet_read_verify(
-	struct xfs_buf	*bp)
-{
-	struct xfs_dsb	*dsb = XFS_BUF_TO_SBP(bp);
-
-
-	if (dsb->sb_magicnum == cpu_to_be32(XFS_SB_MAGIC)) {
-		/* XFS filesystem, verify noisily! */
-		xfs_sb_read_verify(bp);
-		return;
-	}
-	/* quietly fail */
-	xfs_buf_ioerror(bp, EWRONGFS);
-}
-
-static void
-xfs_sb_write_verify(
-	struct xfs_buf		*bp)
-{
-	struct xfs_mount	*mp = bp->b_target->bt_mount;
-	struct xfs_buf_log_item	*bip = bp->b_fspriv;
-	int			error;
-
-	error = xfs_sb_verify(bp, false);
-	if (error) {
-		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
-		xfs_buf_ioerror(bp, error);
-		return;
-	}
-
-	if (!xfs_sb_version_hascrc(&mp->m_sb))
-		return;
-
-	if (bip)
-		XFS_BUF_TO_SBP(bp)->sb_lsn = cpu_to_be64(bip->bli_item.li_lsn);
-
-	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
-			 offsetof(struct xfs_sb, sb_crc));
-}
-
-const struct xfs_buf_ops xfs_sb_buf_ops = {
-	.verify_read = xfs_sb_read_verify,
-	.verify_write = xfs_sb_write_verify,
-};
-
-static const struct xfs_buf_ops xfs_sb_quiet_buf_ops = {
-	.verify_read = xfs_sb_quiet_read_verify,
-	.verify_write = xfs_sb_write_verify,
-};
-
 /*
  * xfs_readsb
  *
  * Does the initial read of the superblock.
  */
 int
-xfs_readsb(xfs_mount_t *mp, int flags)
+xfs_readsb(
+	struct xfs_mount *mp,
+	int		flags)
 {
 	unsigned int	sector_size;
 	struct xfs_buf	*bp;
@@ -950,8 +319,8 @@ reread:
 	 * Initialize the mount structure from the superblock.
 	 */
 	xfs_sb_from_disk(&mp->m_sb, XFS_BUF_TO_SBP(bp));
-
 	xfs_sb_quota_from_disk(&mp->m_sb);
+
 	/*
 	 * We must be able to do sector-sized and sector-aligned IO.
 	 */
@@ -988,107 +357,6 @@ release_buf:
 	return error;
 }
 
-
-/*
- * xfs_mount_common
- *
- * Mount initialization code establishing various mount
- * fields from the superblock associated with the given
- * mount structure
- */
-STATIC void
-xfs_mount_common(xfs_mount_t *mp, xfs_sb_t *sbp)
-{
-	mp->m_agfrotor = mp->m_agirotor = 0;
-	spin_lock_init(&mp->m_agirotor_lock);
-	mp->m_maxagi = mp->m_sb.sb_agcount;
-	mp->m_blkbit_log = sbp->sb_blocklog + XFS_NBBYLOG;
-	mp->m_blkbb_log = sbp->sb_blocklog - BBSHIFT;
-	mp->m_sectbb_log = sbp->sb_sectlog - BBSHIFT;
-	mp->m_agno_log = xfs_highbit32(sbp->sb_agcount - 1) + 1;
-	mp->m_agino_log = sbp->sb_inopblog + sbp->sb_agblklog;
-	mp->m_blockmask = sbp->sb_blocksize - 1;
-	mp->m_blockwsize = sbp->sb_blocksize >> XFS_WORDLOG;
-	mp->m_blockwmask = mp->m_blockwsize - 1;
-
-	mp->m_alloc_mxr[0] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 1);
-	mp->m_alloc_mxr[1] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 0);
-	mp->m_alloc_mnr[0] = mp->m_alloc_mxr[0] / 2;
-	mp->m_alloc_mnr[1] = mp->m_alloc_mxr[1] / 2;
-
-	mp->m_inobt_mxr[0] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 1);
-	mp->m_inobt_mxr[1] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 0);
-	mp->m_inobt_mnr[0] = mp->m_inobt_mxr[0] / 2;
-	mp->m_inobt_mnr[1] = mp->m_inobt_mxr[1] / 2;
-
-	mp->m_bmap_dmxr[0] = xfs_bmbt_maxrecs(mp, sbp->sb_blocksize, 1);
-	mp->m_bmap_dmxr[1] = xfs_bmbt_maxrecs(mp, sbp->sb_blocksize, 0);
-	mp->m_bmap_dmnr[0] = mp->m_bmap_dmxr[0] / 2;
-	mp->m_bmap_dmnr[1] = mp->m_bmap_dmxr[1] / 2;
-
-	mp->m_bsize = XFS_FSB_TO_BB(mp, 1);
-	mp->m_ialloc_inos = (int)MAX((__uint16_t)XFS_INODES_PER_CHUNK,
-					sbp->sb_inopblock);
-	mp->m_ialloc_blks = mp->m_ialloc_inos >> sbp->sb_inopblog;
-}
-
-/*
- * xfs_initialize_perag_data
- *
- * Read in each per-ag structure so we can count up the number of
- * allocated inodes, free inodes and used filesystem blocks as this
- * information is no longer persistent in the superblock. Once we have
- * this information, write it into the in-core superblock structure.
- */
-STATIC int
-xfs_initialize_perag_data(xfs_mount_t *mp, xfs_agnumber_t agcount)
-{
-	xfs_agnumber_t	index;
-	xfs_perag_t	*pag;
-	xfs_sb_t	*sbp = &mp->m_sb;
-	uint64_t	ifree = 0;
-	uint64_t	ialloc = 0;
-	uint64_t	bfree = 0;
-	uint64_t	bfreelst = 0;
-	uint64_t	btree = 0;
-	int		error;
-
-	for (index = 0; index < agcount; index++) {
-		/*
-		 * read the agf, then the agi. This gets us
-		 * all the information we need and populates the
-		 * per-ag structures for us.
-		 */
-		error = xfs_alloc_pagf_init(mp, NULL, index, 0);
-		if (error)
-			return error;
-
-		error = xfs_ialloc_pagi_init(mp, NULL, index);
-		if (error)
-			return error;
-		pag = xfs_perag_get(mp, index);
-		ifree += pag->pagi_freecount;
-		ialloc += pag->pagi_count;
-		bfree += pag->pagf_freeblks;
-		bfreelst += pag->pagf_flcount;
-		btree += pag->pagf_btreeblks;
-		xfs_perag_put(pag);
-	}
-	/*
-	 * Overwrite incore superblock counters with just-read data
-	 */
-	spin_lock(&mp->m_sb_lock);
-	sbp->sb_ifree = ifree;
-	sbp->sb_icount = ialloc;
-	sbp->sb_fdblocks = bfree + bfreelst + btree;
-	spin_unlock(&mp->m_sb_lock);
-
-	/* Fixup the per-cpu counters as well. */
-	xfs_icsb_reinit_counters(mp);
-
-	return 0;
-}
-
 /*
  * Update alignment values based on mount options and sb values
  */
@@ -1381,7 +649,7 @@ xfs_mountfs(
 	uint		quotaflags = 0;
 	int		error = 0;
 
-	xfs_mount_common(mp, sbp);
+	xfs_sb_mount_common(mp, sbp);
 
 	/*
 	 * Check for a mismatched features2 values.  Older kernels
@@ -1818,48 +1086,6 @@ xfs_log_sbcount(xfs_mount_t *mp)
 }
 
 /*
- * xfs_mod_sb() can be used to copy arbitrary changes to the
- * in-core superblock into the superblock buffer to be logged.
- * It does not provide the higher level of locking that is
- * needed to protect the in-core superblock from concurrent
- * access.
- */
-void
-xfs_mod_sb(xfs_trans_t *tp, __int64_t fields)
-{
-	xfs_buf_t	*bp;
-	int		first;
-	int		last;
-	xfs_mount_t	*mp;
-	xfs_sb_field_t	f;
-
-	ASSERT(fields);
-	if (!fields)
-		return;
-	mp = tp->t_mountp;
-	bp = xfs_trans_getsb(tp, mp, 0);
-	first = sizeof(xfs_sb_t);
-	last = 0;
-
-	/* translate/copy */
-
-	xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, fields);
-
-	/* find modified range */
-	f = (xfs_sb_field_t)xfs_highbit64((__uint64_t)fields);
-	ASSERT((1LL << f) & XFS_SB_MOD_BITS);
-	last = xfs_sb_info[f + 1].offset - 1;
-
-	f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
-	ASSERT((1LL << f) & XFS_SB_MOD_BITS);
-	first = xfs_sb_info[f].offset;
-
-	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
-	xfs_trans_log_buf(tp, bp, first, last);
-}
-
-
-/*
  * xfs_mod_incore_sb_unlocked() is a utility routine common used to apply
  * a delta to a specified field in the in-core superblock.  Simply
  * switch on the field indicated and apply the delta to that field.
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 27d0d5c72f4f..5488df18c200 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -292,14 +292,6 @@ xfs_daddr_to_agbno(struct xfs_mount *mp, xfs_daddr_t d)
 }
 
 /*
- * perag get/put wrappers for ref counting
- */
-struct xfs_perag *xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno);
-struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *mp, xfs_agnumber_t agno,
-					int tag);
-void	xfs_perag_put(struct xfs_perag *pag);
-
-/*
  * Per-cpu superblock locking functions
  */
 #ifdef HAVE_PERCPU_SB
@@ -331,6 +323,8 @@ typedef struct xfs_mod_sb {
 extern int	xfs_log_sbcount(xfs_mount_t *);
 extern __uint64_t xfs_default_resblks(xfs_mount_t *mp);
 extern int	xfs_mountfs(xfs_mount_t *mp);
+extern int	xfs_initialize_perag(xfs_mount_t *mp, xfs_agnumber_t agcount,
+				     xfs_agnumber_t *maxagi);
 
 extern void	xfs_unmountfs(xfs_mount_t *);
 extern int	xfs_mod_incore_sb(xfs_mount_t *, xfs_sb_field_t, int64_t, int);
@@ -349,13 +343,4 @@ extern void	xfs_set_low_space_thresholds(struct xfs_mount *);
 
 #endif	/* __KERNEL__ */
 
-extern void	xfs_sb_calc_crc(struct xfs_buf	*);
-extern void	xfs_mod_sb(struct xfs_trans *, __int64_t);
-extern int	xfs_initialize_perag(struct xfs_mount *, xfs_agnumber_t,
-					xfs_agnumber_t *);
-extern void	xfs_sb_from_disk(struct xfs_sb *, struct xfs_dsb *);
-extern void	xfs_sb_to_disk(struct xfs_dsb *, struct xfs_sb *, __int64_t);
-
-extern const struct xfs_buf_ops xfs_sb_buf_ops;
-
 #endif	/* __XFS_MOUNT_H__ */
diff --git a/fs/xfs/xfs_sb.c b/fs/xfs/xfs_sb.c
new file mode 100644
index 000000000000..98d896f94280
--- /dev/null
+++ b/fs/xfs/xfs_sb.c
@@ -0,0 +1,834 @@
+/*
+ * Copyright (c) 2000-2005 Silicon Graphics, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_format.h"
+#include "xfs_bit.h"
+#include "xfs_log.h"
+#include "xfs_inum.h"
+#include "xfs_trans.h"
+#include "xfs_trans_priv.h"
+#include "xfs_sb.h"
+#include "xfs_ag.h"
+#include "xfs_mount.h"
+#include "xfs_da_btree.h"
+#include "xfs_dir2_format.h"
+#include "xfs_dir2.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_dinode.h"
+#include "xfs_inode.h"
+#include "xfs_btree.h"
+#include "xfs_ialloc.h"
+#include "xfs_alloc.h"
+#include "xfs_rtalloc.h"
+#include "xfs_bmap.h"
+#include "xfs_error.h"
+#include "xfs_quota.h"
+#include "xfs_fsops.h"
+#include "xfs_trace.h"
+#include "xfs_cksum.h"
+#include "xfs_buf_item.h"
+
+/*
+ * Physical superblock buffer manipulations. Shared with libxfs in userspace.
+ */
+
+static const struct {
+	short offset;
+	short type;	/* 0 = integer
+			 * 1 = binary / string (no translation)
+			 */
+} xfs_sb_info[] = {
+	{ offsetof(xfs_sb_t, sb_magicnum),	0 },
+	{ offsetof(xfs_sb_t, sb_blocksize),	0 },
+	{ offsetof(xfs_sb_t, sb_dblocks),	0 },
+	{ offsetof(xfs_sb_t, sb_rblocks),	0 },
+	{ offsetof(xfs_sb_t, sb_rextents),	0 },
+	{ offsetof(xfs_sb_t, sb_uuid),		1 },
+	{ offsetof(xfs_sb_t, sb_logstart),	0 },
+	{ offsetof(xfs_sb_t, sb_rootino),	0 },
+	{ offsetof(xfs_sb_t, sb_rbmino),	0 },
+	{ offsetof(xfs_sb_t, sb_rsumino),	0 },
+	{ offsetof(xfs_sb_t, sb_rextsize),	0 },
+	{ offsetof(xfs_sb_t, sb_agblocks),	0 },
+	{ offsetof(xfs_sb_t, sb_agcount),	0 },
+	{ offsetof(xfs_sb_t, sb_rbmblocks),	0 },
+	{ offsetof(xfs_sb_t, sb_logblocks),	0 },
+	{ offsetof(xfs_sb_t, sb_versionnum),	0 },
+	{ offsetof(xfs_sb_t, sb_sectsize),	0 },
+	{ offsetof(xfs_sb_t, sb_inodesize),	0 },
+	{ offsetof(xfs_sb_t, sb_inopblock),	0 },
+	{ offsetof(xfs_sb_t, sb_fname[0]),	1 },
+	{ offsetof(xfs_sb_t, sb_blocklog),	0 },
+	{ offsetof(xfs_sb_t, sb_sectlog),	0 },
+	{ offsetof(xfs_sb_t, sb_inodelog),	0 },
+	{ offsetof(xfs_sb_t, sb_inopblog),	0 },
+	{ offsetof(xfs_sb_t, sb_agblklog),	0 },
+	{ offsetof(xfs_sb_t, sb_rextslog),	0 },
+	{ offsetof(xfs_sb_t, sb_inprogress),	0 },
+	{ offsetof(xfs_sb_t, sb_imax_pct),	0 },
+	{ offsetof(xfs_sb_t, sb_icount),	0 },
+	{ offsetof(xfs_sb_t, sb_ifree),		0 },
+	{ offsetof(xfs_sb_t, sb_fdblocks),	0 },
+	{ offsetof(xfs_sb_t, sb_frextents),	0 },
+	{ offsetof(xfs_sb_t, sb_uquotino),	0 },
+	{ offsetof(xfs_sb_t, sb_gquotino),	0 },
+	{ offsetof(xfs_sb_t, sb_qflags),	0 },
+	{ offsetof(xfs_sb_t, sb_flags),		0 },
+	{ offsetof(xfs_sb_t, sb_shared_vn),	0 },
+	{ offsetof(xfs_sb_t, sb_inoalignmt),	0 },
+	{ offsetof(xfs_sb_t, sb_unit),		0 },
+	{ offsetof(xfs_sb_t, sb_width),		0 },
+	{ offsetof(xfs_sb_t, sb_dirblklog),	0 },
+	{ offsetof(xfs_sb_t, sb_logsectlog),	0 },
+	{ offsetof(xfs_sb_t, sb_logsectsize),	0 },
+	{ offsetof(xfs_sb_t, sb_logsunit),	0 },
+	{ offsetof(xfs_sb_t, sb_features2),	0 },
+	{ offsetof(xfs_sb_t, sb_bad_features2),	0 },
+	{ offsetof(xfs_sb_t, sb_features_compat),	0 },
+	{ offsetof(xfs_sb_t, sb_features_ro_compat),	0 },
+	{ offsetof(xfs_sb_t, sb_features_incompat),	0 },
+	{ offsetof(xfs_sb_t, sb_features_log_incompat),	0 },
+	{ offsetof(xfs_sb_t, sb_crc),		0 },
+	{ offsetof(xfs_sb_t, sb_pad),		0 },
+	{ offsetof(xfs_sb_t, sb_pquotino),	0 },
+	{ offsetof(xfs_sb_t, sb_lsn),		0 },
+	{ sizeof(xfs_sb_t),			0 }
+};
+
+/*
+ * Reference counting access wrappers to the perag structures.
+ * Because we never free per-ag structures, the only thing we
+ * have to protect against changes is the tree structure itself.
+ */
+struct xfs_perag *
+xfs_perag_get(
+	struct xfs_mount	*mp,
+	xfs_agnumber_t		agno)
+{
+	struct xfs_perag	*pag;
+	int			ref = 0;
+
+	rcu_read_lock();
+	pag = radix_tree_lookup(&mp->m_perag_tree, agno);
+	if (pag) {
+		ASSERT(atomic_read(&pag->pag_ref) >= 0);
+		ref = atomic_inc_return(&pag->pag_ref);
+	}
+	rcu_read_unlock();
+	trace_xfs_perag_get(mp, agno, ref, _RET_IP_);
+	return pag;
+}
+
+/*
+ * search from @first to find the next perag with the given tag set.
+ */
+struct xfs_perag *
+xfs_perag_get_tag(
+	struct xfs_mount	*mp,
+	xfs_agnumber_t		first,
+	int			tag)
+{
+	struct xfs_perag	*pag;
+	int			found;
+	int			ref;
+
+	rcu_read_lock();
+	found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
+					(void **)&pag, first, 1, tag);
+	if (found <= 0) {
+		rcu_read_unlock();
+		return NULL;
+	}
+	ref = atomic_inc_return(&pag->pag_ref);
+	rcu_read_unlock();
+	trace_xfs_perag_get_tag(mp, pag->pag_agno, ref, _RET_IP_);
+	return pag;
+}
+
+void
+xfs_perag_put(
+	struct xfs_perag	*pag)
+{
+	int	ref;
+
+	ASSERT(atomic_read(&pag->pag_ref) > 0);
+	ref = atomic_dec_return(&pag->pag_ref);
+	trace_xfs_perag_put(pag->pag_mount, pag->pag_agno, ref, _RET_IP_);
+}
+
+/*
+ * Check the validity of the SB found.
+ */
+STATIC int
+xfs_mount_validate_sb(
+	xfs_mount_t	*mp,
+	xfs_sb_t	*sbp,
+	bool		check_inprogress,
+	bool		check_version)
+{
+
+	/*
+	 * If the log device and data device have the
+	 * same device number, the log is internal.
+	 * Consequently, the sb_logstart should be non-zero.  If
+	 * we have a zero sb_logstart in this case, we may be trying to mount
+	 * a volume filesystem in a non-volume manner.
+	 */
+	if (sbp->sb_magicnum != XFS_SB_MAGIC) {
+		xfs_warn(mp, "bad magic number");
+		return XFS_ERROR(EWRONGFS);
+	}
+
+
+	if (!xfs_sb_good_version(sbp)) {
+		xfs_warn(mp, "bad version");
+		return XFS_ERROR(EWRONGFS);
+	}
+
+	/*
+	 * Version 5 superblock feature mask validation. Reject combinations the
+	 * kernel cannot support up front before checking anything else. For
+	 * write validation, we don't need to check feature masks.
+	 */
+	if (check_version && XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) {
+		xfs_alert(mp,
+"Version 5 superblock detected. This kernel has EXPERIMENTAL support enabled!\n"
+"Use of these features in this kernel is at your own risk!");
+
+		if (xfs_sb_has_compat_feature(sbp,
+					XFS_SB_FEAT_COMPAT_UNKNOWN)) {
+			xfs_warn(mp,
+"Superblock has unknown compatible features (0x%x) enabled.\n"
+"Using a more recent kernel is recommended.",
+				(sbp->sb_features_compat &
+						XFS_SB_FEAT_COMPAT_UNKNOWN));
+		}
+
+		if (xfs_sb_has_ro_compat_feature(sbp,
+					XFS_SB_FEAT_RO_COMPAT_UNKNOWN)) {
+			xfs_alert(mp,
+"Superblock has unknown read-only compatible features (0x%x) enabled.",
+				(sbp->sb_features_ro_compat &
+						XFS_SB_FEAT_RO_COMPAT_UNKNOWN));
+			if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
+				xfs_warn(mp,
+"Attempted to mount read-only compatible filesystem read-write.\n"
+"Filesystem can only be safely mounted read only.");
+				return XFS_ERROR(EINVAL);
+			}
+		}
+		if (xfs_sb_has_incompat_feature(sbp,
+					XFS_SB_FEAT_INCOMPAT_UNKNOWN)) {
+			xfs_warn(mp,
+"Superblock has unknown incompatible features (0x%x) enabled.\n"
+"Filesystem can not be safely mounted by this kernel.",
+				(sbp->sb_features_incompat &
+						XFS_SB_FEAT_INCOMPAT_UNKNOWN));
+			return XFS_ERROR(EINVAL);
+		}
+	}
+
+	if (xfs_sb_version_has_pquotino(sbp)) {
+		if (sbp->sb_qflags & (XFS_OQUOTA_ENFD | XFS_OQUOTA_CHKD)) {
+			xfs_notice(mp,
+			   "Version 5 of Super block has XFS_OQUOTA bits.\n");
+			return XFS_ERROR(EFSCORRUPTED);
+		}
+	} else if (sbp->sb_qflags & (XFS_PQUOTA_ENFD | XFS_GQUOTA_ENFD |
+				XFS_PQUOTA_CHKD | XFS_GQUOTA_CHKD)) {
+			xfs_notice(mp,
+"Superblock earlier than Version 5 has XFS_[PQ]UOTA_{ENFD|CHKD} bits.\n");
+			return XFS_ERROR(EFSCORRUPTED);
+	}
+
+	if (unlikely(
+	    sbp->sb_logstart == 0 && mp->m_logdev_targp == mp->m_ddev_targp)) {
+		xfs_warn(mp,
+		"filesystem is marked as having an external log; "
+		"specify logdev on the mount command line.");
+		return XFS_ERROR(EINVAL);
+	}
+
+	if (unlikely(
+	    sbp->sb_logstart != 0 && mp->m_logdev_targp != mp->m_ddev_targp)) {
+		xfs_warn(mp,
+		"filesystem is marked as having an internal log; "
+		"do not specify logdev on the mount command line.");
+		return XFS_ERROR(EINVAL);
+	}
+
+	/*
+	 * More sanity checking.  Most of these were stolen directly from
+	 * xfs_repair.
+	 */
+	if (unlikely(
+	    sbp->sb_agcount <= 0					||
+	    sbp->sb_sectsize < XFS_MIN_SECTORSIZE			||
+	    sbp->sb_sectsize > XFS_MAX_SECTORSIZE			||
+	    sbp->sb_sectlog < XFS_MIN_SECTORSIZE_LOG			||
+	    sbp->sb_sectlog > XFS_MAX_SECTORSIZE_LOG			||
+	    sbp->sb_sectsize != (1 << sbp->sb_sectlog)			||
+	    sbp->sb_blocksize < XFS_MIN_BLOCKSIZE			||
+	    sbp->sb_blocksize > XFS_MAX_BLOCKSIZE			||
+	    sbp->sb_blocklog < XFS_MIN_BLOCKSIZE_LOG			||
+	    sbp->sb_blocklog > XFS_MAX_BLOCKSIZE_LOG			||
+	    sbp->sb_blocksize != (1 << sbp->sb_blocklog)		||
+	    sbp->sb_inodesize < XFS_DINODE_MIN_SIZE			||
+	    sbp->sb_inodesize > XFS_DINODE_MAX_SIZE			||
+	    sbp->sb_inodelog < XFS_DINODE_MIN_LOG			||
+	    sbp->sb_inodelog > XFS_DINODE_MAX_LOG			||
+	    sbp->sb_inodesize != (1 << sbp->sb_inodelog)		||
+	    (sbp->sb_blocklog - sbp->sb_inodelog != sbp->sb_inopblog)	||
+	    (sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE)	||
+	    (sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE)	||
+	    (sbp->sb_imax_pct > 100 /* zero sb_imax_pct is valid */)	||
+	    sbp->sb_dblocks == 0					||
+	    sbp->sb_dblocks > XFS_MAX_DBLOCKS(sbp)			||
+	    sbp->sb_dblocks < XFS_MIN_DBLOCKS(sbp))) {
+		XFS_CORRUPTION_ERROR("SB sanity check failed",
+				XFS_ERRLEVEL_LOW, mp, sbp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+
+	/*
+	 * Until this is fixed only page-sized or smaller data blocks work.
+	 */
+	if (unlikely(sbp->sb_blocksize > PAGE_SIZE)) {
+		xfs_warn(mp,
+		"File system with blocksize %d bytes. "
+		"Only pagesize (%ld) or less will currently work.",
+				sbp->sb_blocksize, PAGE_SIZE);
+		return XFS_ERROR(ENOSYS);
+	}
+
+	/*
+	 * Currently only very few inode sizes are supported.
+	 */
+	switch (sbp->sb_inodesize) {
+	case 256:
+	case 512:
+	case 1024:
+	case 2048:
+		break;
+	default:
+		xfs_warn(mp, "inode size of %d bytes not supported",
+				sbp->sb_inodesize);
+		return XFS_ERROR(ENOSYS);
+	}
+
+	if (xfs_sb_validate_fsb_count(sbp, sbp->sb_dblocks) ||
+	    xfs_sb_validate_fsb_count(sbp, sbp->sb_rblocks)) {
+		xfs_warn(mp,
+		"file system too large to be mounted on this system.");
+		return XFS_ERROR(EFBIG);
+	}
+
+	if (check_inprogress && sbp->sb_inprogress) {
+		xfs_warn(mp, "Offline file system operation in progress!");
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+
+	/*
+	 * Version 1 directory format has never worked on Linux.
+	 */
+	if (unlikely(!xfs_sb_version_hasdirv2(sbp))) {
+		xfs_warn(mp, "file system using version 1 directory format");
+		return XFS_ERROR(ENOSYS);
+	}
+
+	return 0;
+}
+
+void
+xfs_sb_quota_from_disk(struct xfs_sb *sbp)
+{
+	/*
+	 * older mkfs doesn't initialize quota inodes to NULLFSINO. This
+	 * leads to in-core values having two different values for a quota
+	 * inode to be invalid: 0 and NULLFSINO. Change it to a single value
+	 * NULLFSINO.
+	 *
+	 * Note that this change affect only the in-core values. These
+	 * values are not written back to disk unless any quota information
+	 * is written to the disk. Even in that case, sb_pquotino field is
+	 * not written to disk unless the superblock supports pquotino.
+	 */
+	if (sbp->sb_uquotino == 0)
+		sbp->sb_uquotino = NULLFSINO;
+	if (sbp->sb_gquotino == 0)
+		sbp->sb_gquotino = NULLFSINO;
+	if (sbp->sb_pquotino == 0)
+		sbp->sb_pquotino = NULLFSINO;
+
+	/*
+	 * We need to do these manipilations only if we are working
+	 * with an older version of on-disk superblock.
+	 */
+	if (xfs_sb_version_has_pquotino(sbp))
+		return;
+
+	if (sbp->sb_qflags & XFS_OQUOTA_ENFD)
+		sbp->sb_qflags |= (sbp->sb_qflags & XFS_PQUOTA_ACCT) ?
+					XFS_PQUOTA_ENFD : XFS_GQUOTA_ENFD;
+	if (sbp->sb_qflags & XFS_OQUOTA_CHKD)
+		sbp->sb_qflags |= (sbp->sb_qflags & XFS_PQUOTA_ACCT) ?
+					XFS_PQUOTA_CHKD : XFS_GQUOTA_CHKD;
+	sbp->sb_qflags &= ~(XFS_OQUOTA_ENFD | XFS_OQUOTA_CHKD);
+
+	if (sbp->sb_qflags & XFS_PQUOTA_ACCT)  {
+		/*
+		 * In older version of superblock, on-disk superblock only
+		 * has sb_gquotino, and in-core superblock has both sb_gquotino
+		 * and sb_pquotino. But, only one of them is supported at any
+		 * point of time. So, if PQUOTA is set in disk superblock,
+		 * copy over sb_gquotino to sb_pquotino.
+		 */
+		sbp->sb_pquotino = sbp->sb_gquotino;
+		sbp->sb_gquotino = NULLFSINO;
+	}
+}
+
+void
+xfs_sb_from_disk(
+	struct xfs_sb	*to,
+	xfs_dsb_t	*from)
+{
+	to->sb_magicnum = be32_to_cpu(from->sb_magicnum);
+	to->sb_blocksize = be32_to_cpu(from->sb_blocksize);
+	to->sb_dblocks = be64_to_cpu(from->sb_dblocks);
+	to->sb_rblocks = be64_to_cpu(from->sb_rblocks);
+	to->sb_rextents = be64_to_cpu(from->sb_rextents);
+	memcpy(&to->sb_uuid, &from->sb_uuid, sizeof(to->sb_uuid));
+	to->sb_logstart = be64_to_cpu(from->sb_logstart);
+	to->sb_rootino = be64_to_cpu(from->sb_rootino);
+	to->sb_rbmino = be64_to_cpu(from->sb_rbmino);
+	to->sb_rsumino = be64_to_cpu(from->sb_rsumino);
+	to->sb_rextsize = be32_to_cpu(from->sb_rextsize);
+	to->sb_agblocks = be32_to_cpu(from->sb_agblocks);
+	to->sb_agcount = be32_to_cpu(from->sb_agcount);
+	to->sb_rbmblocks = be32_to_cpu(from->sb_rbmblocks);
+	to->sb_logblocks = be32_to_cpu(from->sb_logblocks);
+	to->sb_versionnum = be16_to_cpu(from->sb_versionnum);
+	to->sb_sectsize = be16_to_cpu(from->sb_sectsize);
+	to->sb_inodesize = be16_to_cpu(from->sb_inodesize);
+	to->sb_inopblock = be16_to_cpu(from->sb_inopblock);
+	memcpy(&to->sb_fname, &from->sb_fname, sizeof(to->sb_fname));
+	to->sb_blocklog = from->sb_blocklog;
+	to->sb_sectlog = from->sb_sectlog;
+	to->sb_inodelog = from->sb_inodelog;
+	to->sb_inopblog = from->sb_inopblog;
+	to->sb_agblklog = from->sb_agblklog;
+	to->sb_rextslog = from->sb_rextslog;
+	to->sb_inprogress = from->sb_inprogress;
+	to->sb_imax_pct = from->sb_imax_pct;
+	to->sb_icount = be64_to_cpu(from->sb_icount);
+	to->sb_ifree = be64_to_cpu(from->sb_ifree);
+	to->sb_fdblocks = be64_to_cpu(from->sb_fdblocks);
+	to->sb_frextents = be64_to_cpu(from->sb_frextents);
+	to->sb_uquotino = be64_to_cpu(from->sb_uquotino);
+	to->sb_gquotino = be64_to_cpu(from->sb_gquotino);
+	to->sb_qflags = be16_to_cpu(from->sb_qflags);
+	to->sb_flags = from->sb_flags;
+	to->sb_shared_vn = from->sb_shared_vn;
+	to->sb_inoalignmt = be32_to_cpu(from->sb_inoalignmt);
+	to->sb_unit = be32_to_cpu(from->sb_unit);
+	to->sb_width = be32_to_cpu(from->sb_width);
+	to->sb_dirblklog = from->sb_dirblklog;
+	to->sb_logsectlog = from->sb_logsectlog;
+	to->sb_logsectsize = be16_to_cpu(from->sb_logsectsize);
+	to->sb_logsunit = be32_to_cpu(from->sb_logsunit);
+	to->sb_features2 = be32_to_cpu(from->sb_features2);
+	to->sb_bad_features2 = be32_to_cpu(from->sb_bad_features2);
+	to->sb_features_compat = be32_to_cpu(from->sb_features_compat);
+	to->sb_features_ro_compat = be32_to_cpu(from->sb_features_ro_compat);
+	to->sb_features_incompat = be32_to_cpu(from->sb_features_incompat);
+	to->sb_features_log_incompat =
+				be32_to_cpu(from->sb_features_log_incompat);
+	to->sb_pad = 0;
+	to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
+	to->sb_lsn = be64_to_cpu(from->sb_lsn);
+}
+
+static inline void
+xfs_sb_quota_to_disk(
+	xfs_dsb_t	*to,
+	xfs_sb_t	*from,
+	__int64_t	*fields)
+{
+	__uint16_t	qflags = from->sb_qflags;
+
+	/*
+	 * We need to do these manipilations only if we are working
+	 * with an older version of on-disk superblock.
+	 */
+	if (xfs_sb_version_has_pquotino(from))
+		return;
+
+	if (*fields & XFS_SB_QFLAGS) {
+		/*
+		 * The in-core version of sb_qflags do not have
+		 * XFS_OQUOTA_* flags, whereas the on-disk version
+		 * does.  So, convert incore XFS_{PG}QUOTA_* flags
+		 * to on-disk XFS_OQUOTA_* flags.
+		 */
+		qflags &= ~(XFS_PQUOTA_ENFD | XFS_PQUOTA_CHKD |
+				XFS_GQUOTA_ENFD | XFS_GQUOTA_CHKD);
+
+		if (from->sb_qflags &
+				(XFS_PQUOTA_ENFD | XFS_GQUOTA_ENFD))
+			qflags |= XFS_OQUOTA_ENFD;
+		if (from->sb_qflags &
+				(XFS_PQUOTA_CHKD | XFS_GQUOTA_CHKD))
+			qflags |= XFS_OQUOTA_CHKD;
+		to->sb_qflags = cpu_to_be16(qflags);
+		*fields &= ~XFS_SB_QFLAGS;
+	}
+
+	/*
+	 * GQUOTINO and PQUOTINO cannot be used together in versions
+	 * of superblock that do not have pquotino. from->sb_flags
+	 * tells us which quota is active and should be copied to
+	 * disk.
+	 */
+	if ((*fields & XFS_SB_GQUOTINO) &&
+				(from->sb_qflags & XFS_GQUOTA_ACCT))
+		to->sb_gquotino = cpu_to_be64(from->sb_gquotino);
+	else if ((*fields & XFS_SB_PQUOTINO) &&
+				(from->sb_qflags & XFS_PQUOTA_ACCT))
+		to->sb_gquotino = cpu_to_be64(from->sb_pquotino);
+
+	*fields &= ~(XFS_SB_PQUOTINO | XFS_SB_GQUOTINO);
+}
+
+/*
+ * Copy in core superblock to ondisk one.
+ *
+ * The fields argument is mask of superblock fields to copy.
+ */
+void
+xfs_sb_to_disk(
+	xfs_dsb_t	*to,
+	xfs_sb_t	*from,
+	__int64_t	fields)
+{
+	xfs_caddr_t	to_ptr = (xfs_caddr_t)to;
+	xfs_caddr_t	from_ptr = (xfs_caddr_t)from;
+	xfs_sb_field_t	f;
+	int		first;
+	int		size;
+
+	ASSERT(fields);
+	if (!fields)
+		return;
+
+	xfs_sb_quota_to_disk(to, from, &fields);
+	while (fields) {
+		f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
+		first = xfs_sb_info[f].offset;
+		size = xfs_sb_info[f + 1].offset - first;
+
+		ASSERT(xfs_sb_info[f].type == 0 || xfs_sb_info[f].type == 1);
+
+		if (size == 1 || xfs_sb_info[f].type == 1) {
+			memcpy(to_ptr + first, from_ptr + first, size);
+		} else {
+			switch (size) {
+			case 2:
+				*(__be16 *)(to_ptr + first) =
+				      cpu_to_be16(*(__u16 *)(from_ptr + first));
+				break;
+			case 4:
+				*(__be32 *)(to_ptr + first) =
+				      cpu_to_be32(*(__u32 *)(from_ptr + first));
+				break;
+			case 8:
+				*(__be64 *)(to_ptr + first) =
+				      cpu_to_be64(*(__u64 *)(from_ptr + first));
+				break;
+			default:
+				ASSERT(0);
+			}
+		}
+
+		fields &= ~(1LL << f);
+	}
+}
+
+static int
+xfs_sb_verify(
+	struct xfs_buf	*bp,
+	bool		check_version)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	struct xfs_sb	sb;
+
+	xfs_sb_from_disk(&sb, XFS_BUF_TO_SBP(bp));
+
+	/*
+	 * Only check the in progress field for the primary superblock as
+	 * mkfs.xfs doesn't clear it from secondary superblocks.
+	 */
+	return xfs_mount_validate_sb(mp, &sb, bp->b_bn == XFS_SB_DADDR,
+				     check_version);
+}
+
+/*
+ * If the superblock has the CRC feature bit set or the CRC field is non-null,
+ * check that the CRC is valid.  We check the CRC field is non-null because a
+ * single bit error could clear the feature bit and unused parts of the
+ * superblock are supposed to be zero. Hence a non-null crc field indicates that
+ * we've potentially lost a feature bit and we should check it anyway.
+ */
+static void
+xfs_sb_read_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	struct xfs_dsb	*dsb = XFS_BUF_TO_SBP(bp);
+	int		error;
+
+	/*
+	 * open code the version check to avoid needing to convert the entire
+	 * superblock from disk order just to check the version number
+	 */
+	if (dsb->sb_magicnum == cpu_to_be32(XFS_SB_MAGIC) &&
+	    (((be16_to_cpu(dsb->sb_versionnum) & XFS_SB_VERSION_NUMBITS) ==
+						XFS_SB_VERSION_5) ||
+	     dsb->sb_crc != 0)) {
+
+		if (!xfs_verify_cksum(bp->b_addr, be16_to_cpu(dsb->sb_sectsize),
+				      offsetof(struct xfs_sb, sb_crc))) {
+			error = EFSCORRUPTED;
+			goto out_error;
+		}
+	}
+	error = xfs_sb_verify(bp, true);
+
+out_error:
+	if (error) {
+		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW,
+				     mp, bp->b_addr);
+		xfs_buf_ioerror(bp, error);
+	}
+}
+
+/*
+ * We may be probed for a filesystem match, so we may not want to emit
+ * messages when the superblock buffer is not actually an XFS superblock.
+ * If we find an XFS superblock, the run a normal, noisy mount because we are
+ * really going to mount it and want to know about errors.
+ */
+static void
+xfs_sb_quiet_read_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_dsb	*dsb = XFS_BUF_TO_SBP(bp);
+
+
+	if (dsb->sb_magicnum == cpu_to_be32(XFS_SB_MAGIC)) {
+		/* XFS filesystem, verify noisily! */
+		xfs_sb_read_verify(bp);
+		return;
+	}
+	/* quietly fail */
+	xfs_buf_ioerror(bp, EWRONGFS);
+}
+
+static void
+xfs_sb_write_verify(
+	struct xfs_buf		*bp)
+{
+	struct xfs_mount	*mp = bp->b_target->bt_mount;
+	struct xfs_buf_log_item	*bip = bp->b_fspriv;
+	int			error;
+
+	error = xfs_sb_verify(bp, false);
+	if (error) {
+		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW,
+				     mp, bp->b_addr);
+		xfs_buf_ioerror(bp, error);
+		return;
+	}
+
+	if (!xfs_sb_version_hascrc(&mp->m_sb))
+		return;
+
+	if (bip)
+		XFS_BUF_TO_SBP(bp)->sb_lsn = cpu_to_be64(bip->bli_item.li_lsn);
+
+	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
+			 offsetof(struct xfs_sb, sb_crc));
+}
+
+const struct xfs_buf_ops xfs_sb_buf_ops = {
+	.verify_read = xfs_sb_read_verify,
+	.verify_write = xfs_sb_write_verify,
+};
+
+const struct xfs_buf_ops xfs_sb_quiet_buf_ops = {
+	.verify_read = xfs_sb_quiet_read_verify,
+	.verify_write = xfs_sb_write_verify,
+};
+
+/*
+ * xfs_mount_common
+ *
+ * Mount initialization code establishing various mount
+ * fields from the superblock associated with the given
+ * mount structure
+ */
+void
+xfs_sb_mount_common(
+	struct xfs_mount *mp,
+	struct xfs_sb	*sbp)
+{
+	mp->m_agfrotor = mp->m_agirotor = 0;
+	spin_lock_init(&mp->m_agirotor_lock);
+	mp->m_maxagi = mp->m_sb.sb_agcount;
+	mp->m_blkbit_log = sbp->sb_blocklog + XFS_NBBYLOG;
+	mp->m_blkbb_log = sbp->sb_blocklog - BBSHIFT;
+	mp->m_sectbb_log = sbp->sb_sectlog - BBSHIFT;
+	mp->m_agno_log = xfs_highbit32(sbp->sb_agcount - 1) + 1;
+	mp->m_agino_log = sbp->sb_inopblog + sbp->sb_agblklog;
+	mp->m_blockmask = sbp->sb_blocksize - 1;
+	mp->m_blockwsize = sbp->sb_blocksize >> XFS_WORDLOG;
+	mp->m_blockwmask = mp->m_blockwsize - 1;
+
+	mp->m_alloc_mxr[0] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 1);
+	mp->m_alloc_mxr[1] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 0);
+	mp->m_alloc_mnr[0] = mp->m_alloc_mxr[0] / 2;
+	mp->m_alloc_mnr[1] = mp->m_alloc_mxr[1] / 2;
+
+	mp->m_inobt_mxr[0] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 1);
+	mp->m_inobt_mxr[1] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 0);
+	mp->m_inobt_mnr[0] = mp->m_inobt_mxr[0] / 2;
+	mp->m_inobt_mnr[1] = mp->m_inobt_mxr[1] / 2;
+
+	mp->m_bmap_dmxr[0] = xfs_bmbt_maxrecs(mp, sbp->sb_blocksize, 1);
+	mp->m_bmap_dmxr[1] = xfs_bmbt_maxrecs(mp, sbp->sb_blocksize, 0);
+	mp->m_bmap_dmnr[0] = mp->m_bmap_dmxr[0] / 2;
+	mp->m_bmap_dmnr[1] = mp->m_bmap_dmxr[1] / 2;
+
+	mp->m_bsize = XFS_FSB_TO_BB(mp, 1);
+	mp->m_ialloc_inos = (int)MAX((__uint16_t)XFS_INODES_PER_CHUNK,
+					sbp->sb_inopblock);
+	mp->m_ialloc_blks = mp->m_ialloc_inos >> sbp->sb_inopblog;
+}
+
+/*
+ * xfs_initialize_perag_data
+ *
+ * Read in each per-ag structure so we can count up the number of
+ * allocated inodes, free inodes and used filesystem blocks as this
+ * information is no longer persistent in the superblock. Once we have
+ * this information, write it into the in-core superblock structure.
+ */
+int
+xfs_initialize_perag_data(
+	struct xfs_mount *mp,
+	xfs_agnumber_t	agcount)
+{
+	xfs_agnumber_t	index;
+	xfs_perag_t	*pag;
+	xfs_sb_t	*sbp = &mp->m_sb;
+	uint64_t	ifree = 0;
+	uint64_t	ialloc = 0;
+	uint64_t	bfree = 0;
+	uint64_t	bfreelst = 0;
+	uint64_t	btree = 0;
+	int		error;
+
+	for (index = 0; index < agcount; index++) {
+		/*
+		 * read the agf, then the agi. This gets us
+		 * all the information we need and populates the
+		 * per-ag structures for us.
+		 */
+		error = xfs_alloc_pagf_init(mp, NULL, index, 0);
+		if (error)
+			return error;
+
+		error = xfs_ialloc_pagi_init(mp, NULL, index);
+		if (error)
+			return error;
+		pag = xfs_perag_get(mp, index);
+		ifree += pag->pagi_freecount;
+		ialloc += pag->pagi_count;
+		bfree += pag->pagf_freeblks;
+		bfreelst += pag->pagf_flcount;
+		btree += pag->pagf_btreeblks;
+		xfs_perag_put(pag);
+	}
+	/*
+	 * Overwrite incore superblock counters with just-read data
+	 */
+	spin_lock(&mp->m_sb_lock);
+	sbp->sb_ifree = ifree;
+	sbp->sb_icount = ialloc;
+	sbp->sb_fdblocks = bfree + bfreelst + btree;
+	spin_unlock(&mp->m_sb_lock);
+
+	/* Fixup the per-cpu counters as well. */
+	xfs_icsb_reinit_counters(mp);
+
+	return 0;
+}
+
+/*
+ * xfs_mod_sb() can be used to copy arbitrary changes to the
+ * in-core superblock into the superblock buffer to be logged.
+ * It does not provide the higher level of locking that is
+ * needed to protect the in-core superblock from concurrent
+ * access.
+ */
+void
+xfs_mod_sb(xfs_trans_t *tp, __int64_t fields)
+{
+	xfs_buf_t	*bp;
+	int		first;
+	int		last;
+	xfs_mount_t	*mp;
+	xfs_sb_field_t	f;
+
+	ASSERT(fields);
+	if (!fields)
+		return;
+	mp = tp->t_mountp;
+	bp = xfs_trans_getsb(tp, mp, 0);
+	first = sizeof(xfs_sb_t);
+	last = 0;
+
+	/* translate/copy */
+
+	xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, fields);
+
+	/* find modified range */
+	f = (xfs_sb_field_t)xfs_highbit64((__uint64_t)fields);
+	ASSERT((1LL << f) & XFS_SB_MOD_BITS);
+	last = xfs_sb_info[f + 1].offset - 1;
+
+	f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
+	ASSERT((1LL << f) & XFS_SB_MOD_BITS);
+	first = xfs_sb_info[f].offset;
+
+	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
+	xfs_trans_log_buf(tp, bp, first, last);
+}
diff --git a/fs/xfs/xfs_sb.h b/fs/xfs/xfs_sb.h
index 40b003e47845..91e163a3794d 100644
--- a/fs/xfs/xfs_sb.h
+++ b/fs/xfs/xfs_sb.h
@@ -26,6 +26,7 @@
 
 struct xfs_buf;
 struct xfs_mount;
+struct xfs_trans;
 
 #define	XFS_SB_MAGIC		0x58465342	/* 'XFSB' */
 #define	XFS_SB_VERSION_1	1		/* 5.3, 6.0.1, 6.1 */
@@ -674,4 +675,23 @@ xfs_is_quota_inode(struct xfs_sb *sbp, xfs_ino_t ino)
 #define XFS_B_TO_FSBT(mp,b)	(((__uint64_t)(b)) >> (mp)->m_sb.sb_blocklog)
 #define XFS_B_FSB_OFFSET(mp,b)	((b) & (mp)->m_blockmask)
 
+/*
+ * perag get/put wrappers for ref counting
+ */
+extern struct xfs_perag *xfs_perag_get(struct xfs_mount *, xfs_agnumber_t);
+extern struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *, xfs_agnumber_t,
+					   int tag);
+extern void	xfs_perag_put(struct xfs_perag *pag);
+extern int	xfs_initialize_perag_data(struct xfs_mount *, xfs_agnumber_t);
+
+extern void	xfs_sb_calc_crc(struct xfs_buf	*);
+extern void	xfs_mod_sb(struct xfs_trans *, __int64_t);
+extern void	xfs_sb_mount_common(struct xfs_mount *, struct xfs_sb *);
+extern void	xfs_sb_from_disk(struct xfs_sb *, struct xfs_dsb *);
+extern void	xfs_sb_to_disk(struct xfs_dsb *, struct xfs_sb *, __int64_t);
+extern void	xfs_sb_quota_from_disk(struct xfs_sb *sbp);
+
+extern const struct xfs_buf_ops xfs_sb_buf_ops;
+extern const struct xfs_buf_ops xfs_sb_quiet_buf_ops;
+
 #endif	/* __XFS_SB_H__ */