Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1442 insertions, 0 deletions

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
new file mode 100644
index 000000000..02d15098d
--- /dev/null
+++ b/fs/xfs/xfs_mount.c
@@ -0,0 +1,1442 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2000-2005 Silicon Graphics, Inc.
+ * All Rights Reserved.
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_log_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_bit.h"
+#include "xfs_sb.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_da_format.h"
+#include "xfs_da_btree.h"
+#include "xfs_inode.h"
+#include "xfs_dir2.h"
+#include "xfs_ialloc.h"
+#include "xfs_alloc.h"
+#include "xfs_rtalloc.h"
+#include "xfs_bmap.h"
+#include "xfs_trans.h"
+#include "xfs_trans_priv.h"
+#include "xfs_log.h"
+#include "xfs_error.h"
+#include "xfs_quota.h"
+#include "xfs_fsops.h"
+#include "xfs_trace.h"
+#include "xfs_icache.h"
+#include "xfs_sysfs.h"
+#include "xfs_rmap_btree.h"
+#include "xfs_refcount_btree.h"
+#include "xfs_reflink.h"
+#include "xfs_extent_busy.h"
+
+
+static DEFINE_MUTEX(xfs_uuid_table_mutex);
+static int xfs_uuid_table_size;
+static uuid_t *xfs_uuid_table;
+
+void
+xfs_uuid_table_free(void)
+{
+	if (xfs_uuid_table_size == 0)
+		return;
+	kmem_free(xfs_uuid_table);
+	xfs_uuid_table = NULL;
+	xfs_uuid_table_size = 0;
+}
+
+/*
+ * See if the UUID is unique among mounted XFS filesystems.
+ * Mount fails if UUID is nil or a FS with the same UUID is already mounted.
+ */
+STATIC int
+xfs_uuid_mount(
+	struct xfs_mount	*mp)
+{
+	uuid_t			*uuid = &mp->m_sb.sb_uuid;
+	int			hole, i;
+
+	/* Publish UUID in struct super_block */
+	uuid_copy(&mp->m_super->s_uuid, uuid);
+
+	if (mp->m_flags & XFS_MOUNT_NOUUID)
+		return 0;
+
+	if (uuid_is_null(uuid)) {
+		xfs_warn(mp, "Filesystem has null UUID - can't mount");
+		return -EINVAL;
+	}
+
+	mutex_lock(&xfs_uuid_table_mutex);
+	for (i = 0, hole = -1; i < xfs_uuid_table_size; i++) {
+		if (uuid_is_null(&xfs_uuid_table[i])) {
+			hole = i;
+			continue;
+		}
+		if (uuid_equal(uuid, &xfs_uuid_table[i]))
+			goto out_duplicate;
+	}
+
+	if (hole < 0) {
+		xfs_uuid_table = kmem_realloc(xfs_uuid_table,
+			(xfs_uuid_table_size + 1) * sizeof(*xfs_uuid_table),
+			KM_SLEEP);
+		hole = xfs_uuid_table_size++;
+	}
+	xfs_uuid_table[hole] = *uuid;
+	mutex_unlock(&xfs_uuid_table_mutex);
+
+	return 0;
+
+ out_duplicate:
+	mutex_unlock(&xfs_uuid_table_mutex);
+	xfs_warn(mp, "Filesystem has duplicate UUID %pU - can't mount", uuid);
+	return -EINVAL;
+}
+
+STATIC void
+xfs_uuid_unmount(
+	struct xfs_mount	*mp)
+{
+	uuid_t			*uuid = &mp->m_sb.sb_uuid;
+	int			i;
+
+	if (mp->m_flags & XFS_MOUNT_NOUUID)
+		return;
+
+	mutex_lock(&xfs_uuid_table_mutex);
+	for (i = 0; i < xfs_uuid_table_size; i++) {
+		if (uuid_is_null(&xfs_uuid_table[i]))
+			continue;
+		if (!uuid_equal(uuid, &xfs_uuid_table[i]))
+			continue;
+		memset(&xfs_uuid_table[i], 0, sizeof(uuid_t));
+		break;
+	}
+	ASSERT(i < xfs_uuid_table_size);
+	mutex_unlock(&xfs_uuid_table_mutex);
+}
+
+
+STATIC void
+__xfs_free_perag(
+	struct rcu_head	*head)
+{
+	struct xfs_perag *pag = container_of(head, struct xfs_perag, rcu_head);
+
+	ASSERT(atomic_read(&pag->pag_ref) == 0);
+	kmem_free(pag);
+}
+
+/*
+ * Free up the per-ag resources associated with the mount structure.
+ */
+STATIC void
+xfs_free_perag(
+	xfs_mount_t	*mp)
+{
+	xfs_agnumber_t	agno;
+	struct xfs_perag *pag;
+
+	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+		spin_lock(&mp->m_perag_lock);
+		pag = radix_tree_delete(&mp->m_perag_tree, agno);
+		spin_unlock(&mp->m_perag_lock);
+		ASSERT(pag);
+		ASSERT(atomic_read(&pag->pag_ref) == 0);
+		xfs_buf_hash_destroy(pag);
+		mutex_destroy(&pag->pag_ici_reclaim_lock);
+		call_rcu(&pag->rcu_head, __xfs_free_perag);
+	}
+}
+
+/*
+ * Check size of device based on the (data/realtime) block count.
+ * Note: this check is used by the growfs code as well as mount.
+ */
+int
+xfs_sb_validate_fsb_count(
+	xfs_sb_t	*sbp,
+	uint64_t	nblocks)
+{
+	ASSERT(PAGE_SHIFT >= sbp->sb_blocklog);
+	ASSERT(sbp->sb_blocklog >= BBSHIFT);
+
+	/* Limited by ULONG_MAX of page cache index */
+	if (nblocks >> (PAGE_SHIFT - sbp->sb_blocklog) > ULONG_MAX)
+		return -EFBIG;
+	return 0;
+}
+
+int
+xfs_initialize_perag(
+	xfs_mount_t	*mp,
+	xfs_agnumber_t	agcount,
+	xfs_agnumber_t	*maxagi)
+{
+	xfs_agnumber_t	index;
+	xfs_agnumber_t	first_initialised = NULLAGNUMBER;
+	xfs_perag_t	*pag;
+	int		error = -ENOMEM;
+
+	/*
+	 * Walk the current per-ag tree so we don't try to initialise AGs
+	 * that already exist (growfs case). Allocate and insert all the
+	 * AGs we don't find ready for initialisation.
+	 */
+	for (index = 0; index < agcount; index++) {
+		pag = xfs_perag_get(mp, index);
+		if (pag) {
+			xfs_perag_put(pag);
+			continue;
+		}
+
+		pag = kmem_zalloc(sizeof(*pag), KM_MAYFAIL);
+		if (!pag)
+			goto out_unwind_new_pags;
+		pag->pag_agno = index;
+		pag->pag_mount = mp;
+		spin_lock_init(&pag->pag_ici_lock);
+		mutex_init(&pag->pag_ici_reclaim_lock);
+		INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
+		if (xfs_buf_hash_init(pag))
+			goto out_free_pag;
+		init_waitqueue_head(&pag->pagb_wait);
+		spin_lock_init(&pag->pagb_lock);
+		pag->pagb_count = 0;
+		pag->pagb_tree = RB_ROOT;
+
+		if (radix_tree_preload(GFP_NOFS))
+			goto out_hash_destroy;
+
+		spin_lock(&mp->m_perag_lock);
+		if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
+			BUG();
+			spin_unlock(&mp->m_perag_lock);
+			radix_tree_preload_end();
+			error = -EEXIST;
+			goto out_hash_destroy;
+		}
+		spin_unlock(&mp->m_perag_lock);
+		radix_tree_preload_end();
+		/* first new pag is fully initialized */
+		if (first_initialised == NULLAGNUMBER)
+			first_initialised = index;
+	}
+
+	index = xfs_set_inode_alloc(mp, agcount);
+
+	if (maxagi)
+		*maxagi = index;
+
+	mp->m_ag_prealloc_blocks = xfs_prealloc_blocks(mp);
+	return 0;
+
+out_hash_destroy:
+	xfs_buf_hash_destroy(pag);
+out_free_pag:
+	mutex_destroy(&pag->pag_ici_reclaim_lock);
+	kmem_free(pag);
+out_unwind_new_pags:
+	/* unwind any prior newly initialized pags */
+	for (index = first_initialised; index < agcount; index++) {
+		pag = radix_tree_delete(&mp->m_perag_tree, index);
+		if (!pag)
+			break;
+		xfs_buf_hash_destroy(pag);
+		mutex_destroy(&pag->pag_ici_reclaim_lock);
+		kmem_free(pag);
+	}
+	return error;
+}
+
+/*
+ * xfs_readsb
+ *
+ * Does the initial read of the superblock.
+ */
+int
+xfs_readsb(
+	struct xfs_mount *mp,
+	int		flags)
+{
+	unsigned int	sector_size;
+	struct xfs_buf	*bp;
+	struct xfs_sb	*sbp = &mp->m_sb;
+	int		error;
+	int		loud = !(flags & XFS_MFSI_QUIET);
+	const struct xfs_buf_ops *buf_ops;
+
+	ASSERT(mp->m_sb_bp == NULL);
+	ASSERT(mp->m_ddev_targp != NULL);
+
+	/*
+	 * For the initial read, we must guess at the sector
+	 * size based on the block device.  It's enough to
+	 * get the sb_sectsize out of the superblock and
+	 * then reread with the proper length.
+	 * We don't verify it yet, because it may not be complete.
+	 */
+	sector_size = xfs_getsize_buftarg(mp->m_ddev_targp);
+	buf_ops = NULL;
+
+	/*
+	 * Allocate a (locked) buffer to hold the superblock. This will be kept
+	 * around at all times to optimize access to the superblock. Therefore,
+	 * set XBF_NO_IOACCT to make sure it doesn't hold the buftarg count
+	 * elevated.
+	 */
+reread:
+	error = xfs_buf_read_uncached(mp->m_ddev_targp, XFS_SB_DADDR,
+				      BTOBB(sector_size), XBF_NO_IOACCT, &bp,
+				      buf_ops);
+	if (error) {
+		if (loud)
+			xfs_warn(mp, "SB validate failed with error %d.", error);
+		/* bad CRC means corrupted metadata */
+		if (error == -EFSBADCRC)
+			error = -EFSCORRUPTED;
+		return error;
+	}
+
+	/*
+	 * Initialize the mount structure from the superblock.
+	 */
+	xfs_sb_from_disk(sbp, XFS_BUF_TO_SBP(bp));
+
+	/*
+	 * If we haven't validated the superblock, do so now before we try
+	 * to check the sector size and reread the superblock appropriately.
+	 */
+	if (sbp->sb_magicnum != XFS_SB_MAGIC) {
+		if (loud)
+			xfs_warn(mp, "Invalid superblock magic number");
+		error = -EINVAL;
+		goto release_buf;
+	}
+
+	/*
+	 * We must be able to do sector-sized and sector-aligned IO.
+	 */
+	if (sector_size > sbp->sb_sectsize) {
+		if (loud)
+			xfs_warn(mp, "device supports %u byte sectors (not %u)",
+				sector_size, sbp->sb_sectsize);
+		error = -ENOSYS;
+		goto release_buf;
+	}
+
+	if (buf_ops == NULL) {
+		/*
+		 * Re-read the superblock so the buffer is correctly sized,
+		 * and properly verified.
+		 */
+		xfs_buf_relse(bp);
+		sector_size = sbp->sb_sectsize;
+		buf_ops = loud ? &xfs_sb_buf_ops : &xfs_sb_quiet_buf_ops;
+		goto reread;
+	}
+
+	xfs_reinit_percpu_counters(mp);
+
+	/* no need to be quiet anymore, so reset the buf ops */
+	bp->b_ops = &xfs_sb_buf_ops;
+
+	mp->m_sb_bp = bp;
+	xfs_buf_unlock(bp);
+	return 0;
+
+release_buf:
+	xfs_buf_relse(bp);
+	return error;
+}
+
+/*
+ * Update alignment values based on mount options and sb values
+ */
+STATIC int
+xfs_update_alignment(xfs_mount_t *mp)
+{
+	xfs_sb_t	*sbp = &(mp->m_sb);
+
+	if (mp->m_dalign) {
+		/*
+		 * If stripe unit and stripe width are not multiples
+		 * of the fs blocksize turn off alignment.
+		 */
+		if ((BBTOB(mp->m_dalign) & mp->m_blockmask) ||
+		    (BBTOB(mp->m_swidth) & mp->m_blockmask)) {
+			xfs_warn(mp,
+		"alignment check failed: sunit/swidth vs. blocksize(%d)",
+				sbp->sb_blocksize);
+			return -EINVAL;
+		} else {
+			/*
+			 * Convert the stripe unit and width to FSBs.
+			 */
+			mp->m_dalign = XFS_BB_TO_FSBT(mp, mp->m_dalign);
+			if (mp->m_dalign && (sbp->sb_agblocks % mp->m_dalign)) {
+				xfs_warn(mp,
+			"alignment check failed: sunit/swidth vs. agsize(%d)",
+					 sbp->sb_agblocks);
+				return -EINVAL;
+			} else if (mp->m_dalign) {
+				mp->m_swidth = XFS_BB_TO_FSBT(mp, mp->m_swidth);
+			} else {
+				xfs_warn(mp,
+			"alignment check failed: sunit(%d) less than bsize(%d)",
+					 mp->m_dalign, sbp->sb_blocksize);
+				return -EINVAL;
+			}
+		}
+
+		/*
+		 * Update superblock with new values
+		 * and log changes
+		 */
+		if (xfs_sb_version_hasdalign(sbp)) {
+			if (sbp->sb_unit != mp->m_dalign) {
+				sbp->sb_unit = mp->m_dalign;
+				mp->m_update_sb = true;
+			}
+			if (sbp->sb_width != mp->m_swidth) {
+				sbp->sb_width = mp->m_swidth;
+				mp->m_update_sb = true;
+			}
+		} else {
+			xfs_warn(mp,
+	"cannot change alignment: superblock does not support data alignment");
+			return -EINVAL;
+		}
+	} else if ((mp->m_flags & XFS_MOUNT_NOALIGN) != XFS_MOUNT_NOALIGN &&
+		    xfs_sb_version_hasdalign(&mp->m_sb)) {
+			mp->m_dalign = sbp->sb_unit;
+			mp->m_swidth = sbp->sb_width;
+	}
+
+	return 0;
+}
+
+/*
+ * Set the maximum inode count for this filesystem
+ */
+STATIC void
+xfs_set_maxicount(xfs_mount_t *mp)
+{
+	xfs_sb_t	*sbp = &(mp->m_sb);
+	uint64_t	icount;
+
+	if (sbp->sb_imax_pct) {
+		/*
+		 * Make sure the maximum inode count is a multiple
+		 * of the units we allocate inodes in.
+		 */
+		icount = sbp->sb_dblocks * sbp->sb_imax_pct;
+		do_div(icount, 100);
+		do_div(icount, mp->m_ialloc_blks);
+		mp->m_maxicount = (icount * mp->m_ialloc_blks)  <<
+				   sbp->sb_inopblog;
+	} else {
+		mp->m_maxicount = 0;
+	}
+}
+
+/*
+ * Set the default minimum read and write sizes unless
+ * already specified in a mount option.
+ * We use smaller I/O sizes when the file system
+ * is being used for NFS service (wsync mount option).
+ */
+STATIC void
+xfs_set_rw_sizes(xfs_mount_t *mp)
+{
+	xfs_sb_t	*sbp = &(mp->m_sb);
+	int		readio_log, writeio_log;
+
+	if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)) {
+		if (mp->m_flags & XFS_MOUNT_WSYNC) {
+			readio_log = XFS_WSYNC_READIO_LOG;
+			writeio_log = XFS_WSYNC_WRITEIO_LOG;
+		} else {
+			readio_log = XFS_READIO_LOG_LARGE;
+			writeio_log = XFS_WRITEIO_LOG_LARGE;
+		}
+	} else {
+		readio_log = mp->m_readio_log;
+		writeio_log = mp->m_writeio_log;
+	}
+
+	if (sbp->sb_blocklog > readio_log) {
+		mp->m_readio_log = sbp->sb_blocklog;
+	} else {
+		mp->m_readio_log = readio_log;
+	}
+	mp->m_readio_blocks = 1 << (mp->m_readio_log - sbp->sb_blocklog);
+	if (sbp->sb_blocklog > writeio_log) {
+		mp->m_writeio_log = sbp->sb_blocklog;
+	} else {
+		mp->m_writeio_log = writeio_log;
+	}
+	mp->m_writeio_blocks = 1 << (mp->m_writeio_log - sbp->sb_blocklog);
+}
+
+/*
+ * precalculate the low space thresholds for dynamic speculative preallocation.
+ */
+void
+xfs_set_low_space_thresholds(
+	struct xfs_mount	*mp)
+{
+	int i;
+
+	for (i = 0; i < XFS_LOWSP_MAX; i++) {
+		uint64_t space = mp->m_sb.sb_dblocks;
+
+		do_div(space, 100);
+		mp->m_low_space[i] = space * (i + 1);
+	}
+}
+
+
+/*
+ * Set whether we're using inode alignment.
+ */
+STATIC void
+xfs_set_inoalignment(xfs_mount_t *mp)
+{
+	if (xfs_sb_version_hasalign(&mp->m_sb) &&
+		mp->m_sb.sb_inoalignmt >= xfs_icluster_size_fsb(mp))
+		mp->m_inoalign_mask = mp->m_sb.sb_inoalignmt - 1;
+	else
+		mp->m_inoalign_mask = 0;
+	/*
+	 * If we are using stripe alignment, check whether
+	 * the stripe unit is a multiple of the inode alignment
+	 */
+	if (mp->m_dalign && mp->m_inoalign_mask &&
+	    !(mp->m_dalign & mp->m_inoalign_mask))
+		mp->m_sinoalign = mp->m_dalign;
+	else
+		mp->m_sinoalign = 0;
+}
+
+/*
+ * Check that the data (and log if separate) is an ok size.
+ */
+STATIC int
+xfs_check_sizes(
+	struct xfs_mount *mp)
+{
+	struct xfs_buf	*bp;
+	xfs_daddr_t	d;
+	int		error;
+
+	d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
+	if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_dblocks) {
+		xfs_warn(mp, "filesystem size mismatch detected");
+		return -EFBIG;
+	}
+	error = xfs_buf_read_uncached(mp->m_ddev_targp,
+					d - XFS_FSS_TO_BB(mp, 1),
+					XFS_FSS_TO_BB(mp, 1), 0, &bp, NULL);
+	if (error) {
+		xfs_warn(mp, "last sector read failed");
+		return error;
+	}
+	xfs_buf_relse(bp);
+
+	if (mp->m_logdev_targp == mp->m_ddev_targp)
+		return 0;
+
+	d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_logblocks);
+	if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_logblocks) {
+		xfs_warn(mp, "log size mismatch detected");
+		return -EFBIG;
+	}
+	error = xfs_buf_read_uncached(mp->m_logdev_targp,
+					d - XFS_FSB_TO_BB(mp, 1),
+					XFS_FSB_TO_BB(mp, 1), 0, &bp, NULL);
+	if (error) {
+		xfs_warn(mp, "log device read failed");
+		return error;
+	}
+	xfs_buf_relse(bp);
+	return 0;
+}
+
+/*
+ * Clear the quotaflags in memory and in the superblock.
+ */
+int
+xfs_mount_reset_sbqflags(
+	struct xfs_mount	*mp)
+{
+	mp->m_qflags = 0;
+
+	/* It is OK to look at sb_qflags in the mount path without m_sb_lock. */
+	if (mp->m_sb.sb_qflags == 0)
+		return 0;
+	spin_lock(&mp->m_sb_lock);
+	mp->m_sb.sb_qflags = 0;
+	spin_unlock(&mp->m_sb_lock);
+
+	if (!xfs_fs_writable(mp, SB_FREEZE_WRITE))
+		return 0;
+
+	return xfs_sync_sb(mp, false);
+}
+
+uint64_t
+xfs_default_resblks(xfs_mount_t *mp)
+{
+	uint64_t resblks;
+
+	/*
+	 * We default to 5% or 8192 fsbs of space reserved, whichever is
+	 * smaller.  This is intended to cover concurrent allocation
+	 * transactions when we initially hit enospc. These each require a 4
+	 * block reservation. Hence by default we cover roughly 2000 concurrent
+	 * allocation reservations.
+	 */
+	resblks = mp->m_sb.sb_dblocks;
+	do_div(resblks, 20);
+	resblks = min_t(uint64_t, resblks, 8192);
+	return resblks;
+}
+
+/* Ensure the summary counts are correct. */
+STATIC int
+xfs_check_summary_counts(
+	struct xfs_mount	*mp)
+{
+	/*
+	 * The AG0 superblock verifier rejects in-progress filesystems,
+	 * so we should never see the flag set this far into mounting.
+	 */
+	if (mp->m_sb.sb_inprogress) {
+		xfs_err(mp, "sb_inprogress set after log recovery??");
+		WARN_ON(1);
+		return -EFSCORRUPTED;
+	}
+
+	/*
+	 * Now the log is mounted, we know if it was an unclean shutdown or
+	 * not. If it was, with the first phase of recovery has completed, we
+	 * have consistent AG blocks on disk. We have not recovered EFIs yet,
+	 * but they are recovered transactionally in the second recovery phase
+	 * later.
+	 *
+	 * If the log was clean when we mounted, we can check the summary
+	 * counters.  If any of them are obviously incorrect, we can recompute
+	 * them from the AGF headers in the next step.
+	 */
+	if (XFS_LAST_UNMOUNT_WAS_CLEAN(mp) &&
+	    (mp->m_sb.sb_fdblocks > mp->m_sb.sb_dblocks ||
+	     !xfs_verify_icount(mp, mp->m_sb.sb_icount) ||
+	     mp->m_sb.sb_ifree > mp->m_sb.sb_icount))
+		mp->m_flags |= XFS_MOUNT_BAD_SUMMARY;
+
+	/*
+	 * We can safely re-initialise incore superblock counters from the
+	 * per-ag data. These may not be correct if the filesystem was not
+	 * cleanly unmounted, so we waited for recovery to finish before doing
+	 * this.
+	 *
+	 * If the filesystem was cleanly unmounted or the previous check did
+	 * not flag anything weird, then we can trust the values in the
+	 * superblock to be correct and we don't need to do anything here.
+	 * Otherwise, recalculate the summary counters.
+	 */
+	if ((!xfs_sb_version_haslazysbcount(&mp->m_sb) ||
+	     XFS_LAST_UNMOUNT_WAS_CLEAN(mp)) &&
+	    !(mp->m_flags & XFS_MOUNT_BAD_SUMMARY))
+		return 0;
+
+	return xfs_initialize_perag_data(mp, mp->m_sb.sb_agcount);
+}
+
+/*
+ * This function does the following on an initial mount of a file system:
+ *	- reads the superblock from disk and init the mount struct
+ *	- if we're a 32-bit kernel, do a size check on the superblock
+ *		so we don't mount terabyte filesystems
+ *	- init mount struct realtime fields
+ *	- allocate inode hash table for fs
+ *	- init directory manager
+ *	- perform recovery and init the log manager
+ */
+int
+xfs_mountfs(
+	struct xfs_mount	*mp)
+{
+	struct xfs_sb		*sbp = &(mp->m_sb);
+	struct xfs_inode	*rip;
+	uint64_t		resblks;
+	uint			quotamount = 0;
+	uint			quotaflags = 0;
+	int			error = 0;
+
+	xfs_sb_mount_common(mp, sbp);
+
+	/*
+	 * Check for a mismatched features2 values.  Older kernels read & wrote
+	 * into the wrong sb offset for sb_features2 on some platforms due to
+	 * xfs_sb_t not being 64bit size aligned when sb_features2 was added,
+	 * which made older superblock reading/writing routines swap it as a
+	 * 64-bit value.
+	 *
+	 * For backwards compatibility, we make both slots equal.
+	 *
+	 * If we detect a mismatched field, we OR the set bits into the existing
+	 * features2 field in case it has already been modified; we don't want
+	 * to lose any features.  We then update the bad location with the ORed
+	 * value so that older kernels will see any features2 flags. The
+	 * superblock writeback code ensures the new sb_features2 is copied to
+	 * sb_bad_features2 before it is logged or written to disk.
+	 */
+	if (xfs_sb_has_mismatched_features2(sbp)) {
+		xfs_warn(mp, "correcting sb_features alignment problem");
+		sbp->sb_features2 |= sbp->sb_bad_features2;
+		mp->m_update_sb = true;
+
+		/*
+		 * Re-check for ATTR2 in case it was found in bad_features2
+		 * slot.
+		 */
+		if (xfs_sb_version_hasattr2(&mp->m_sb) &&
+		   !(mp->m_flags & XFS_MOUNT_NOATTR2))
+			mp->m_flags |= XFS_MOUNT_ATTR2;
+	}
+
+	if (xfs_sb_version_hasattr2(&mp->m_sb) &&
+	   (mp->m_flags & XFS_MOUNT_NOATTR2)) {
+		xfs_sb_version_removeattr2(&mp->m_sb);
+		mp->m_update_sb = true;
+
+		/* update sb_versionnum for the clearing of the morebits */
+		if (!sbp->sb_features2)
+			mp->m_update_sb = true;
+	}
+
+	/* always use v2 inodes by default now */
+	if (!(mp->m_sb.sb_versionnum & XFS_SB_VERSION_NLINKBIT)) {
+		mp->m_sb.sb_versionnum |= XFS_SB_VERSION_NLINKBIT;
+		mp->m_update_sb = true;
+	}
+
+	/*
+	 * Check if sb_agblocks is aligned at stripe boundary
+	 * If sb_agblocks is NOT aligned turn off m_dalign since
+	 * allocator alignment is within an ag, therefore ag has
+	 * to be aligned at stripe boundary.
+	 */
+	error = xfs_update_alignment(mp);
+	if (error)
+		goto out;
+
+	xfs_alloc_compute_maxlevels(mp);
+	xfs_bmap_compute_maxlevels(mp, XFS_DATA_FORK);
+	xfs_bmap_compute_maxlevels(mp, XFS_ATTR_FORK);
+	xfs_ialloc_compute_maxlevels(mp);
+	xfs_rmapbt_compute_maxlevels(mp);
+	xfs_refcountbt_compute_maxlevels(mp);
+
+	xfs_set_maxicount(mp);
+
+	/* enable fail_at_unmount as default */
+	mp->m_fail_unmount = true;
+
+	error = xfs_sysfs_init(&mp->m_kobj, &xfs_mp_ktype, NULL, mp->m_fsname);
+	if (error)
+		goto out;
+
+	error = xfs_sysfs_init(&mp->m_stats.xs_kobj, &xfs_stats_ktype,
+			       &mp->m_kobj, "stats");
+	if (error)
+		goto out_remove_sysfs;
+
+	error = xfs_error_sysfs_init(mp);
+	if (error)
+		goto out_del_stats;
+
+	error = xfs_errortag_init(mp);
+	if (error)
+		goto out_remove_error_sysfs;
+
+	error = xfs_uuid_mount(mp);
+	if (error)
+		goto out_remove_errortag;
+
+	/*
+	 * Set the minimum read and write sizes
+	 */
+	xfs_set_rw_sizes(mp);
+
+	/* set the low space thresholds for dynamic preallocation */
+	xfs_set_low_space_thresholds(mp);
+
+	/*
+	 * Set the inode cluster size.
+	 * This may still be overridden by the file system
+	 * block size if it is larger than the chosen cluster size.
+	 *
+	 * For v5 filesystems, scale the cluster size with the inode size to
+	 * keep a constant ratio of inode per cluster buffer, but only if mkfs
+	 * has set the inode alignment value appropriately for larger cluster
+	 * sizes.
+	 */
+	mp->m_inode_cluster_size = XFS_INODE_BIG_CLUSTER_SIZE;
+	if (xfs_sb_version_hascrc(&mp->m_sb)) {
+		int	new_size = mp->m_inode_cluster_size;
+
+		new_size *= mp->m_sb.sb_inodesize / XFS_DINODE_MIN_SIZE;
+		if (mp->m_sb.sb_inoalignmt >= XFS_B_TO_FSBT(mp, new_size))
+			mp->m_inode_cluster_size = new_size;
+	}
+
+	/*
+	 * If enabled, sparse inode chunk alignment is expected to match the
+	 * cluster size. Full inode chunk alignment must match the chunk size,
+	 * but that is checked on sb read verification...
+	 */
+	if (xfs_sb_version_hassparseinodes(&mp->m_sb) &&
+	    mp->m_sb.sb_spino_align !=
+			XFS_B_TO_FSBT(mp, mp->m_inode_cluster_size)) {
+		xfs_warn(mp,
+	"Sparse inode block alignment (%u) must match cluster size (%llu).",
+			 mp->m_sb.sb_spino_align,
+			 XFS_B_TO_FSBT(mp, mp->m_inode_cluster_size));
+		error = -EINVAL;
+		goto out_remove_uuid;
+	}
+
+	/*
+	 * Set inode alignment fields
+	 */
+	xfs_set_inoalignment(mp);
+
+	/*
+	 * Check that the data (and log if separate) is an ok size.
+	 */
+	error = xfs_check_sizes(mp);
+	if (error)
+		goto out_remove_uuid;
+
+	/*
+	 * Initialize realtime fields in the mount structure
+	 */
+	error = xfs_rtmount_init(mp);
+	if (error) {
+		xfs_warn(mp, "RT mount failed");
+		goto out_remove_uuid;
+	}
+
+	/*
+	 *  Copies the low order bits of the timestamp and the randomly
+	 *  set "sequence" number out of a UUID.
+	 */
+	mp->m_fixedfsid[0] =
+		(get_unaligned_be16(&sbp->sb_uuid.b[8]) << 16) |
+		 get_unaligned_be16(&sbp->sb_uuid.b[4]);
+	mp->m_fixedfsid[1] = get_unaligned_be32(&sbp->sb_uuid.b[0]);
+
+	error = xfs_da_mount(mp);
+	if (error) {
+		xfs_warn(mp, "Failed dir/attr init: %d", error);
+		goto out_remove_uuid;
+	}
+
+	/*
+	 * Initialize the precomputed transaction reservations values.
+	 */
+	xfs_trans_init(mp);
+
+	/*
+	 * Allocate and initialize the per-ag data.
+	 */
+	error = xfs_initialize_perag(mp, sbp->sb_agcount, &mp->m_maxagi);
+	if (error) {
+		xfs_warn(mp, "Failed per-ag init: %d", error);
+		goto out_free_dir;
+	}
+
+	if (!sbp->sb_logblocks) {
+		xfs_warn(mp, "no log defined");
+		XFS_ERROR_REPORT("xfs_mountfs", XFS_ERRLEVEL_LOW, mp);
+		error = -EFSCORRUPTED;
+		goto out_free_perag;
+	}
+
+	/*
+	 * Log's mount-time initialization. The first part of recovery can place
+	 * some items on the AIL, to be handled when recovery is finished or
+	 * cancelled.
+	 */
+	error = xfs_log_mount(mp, mp->m_logdev_targp,
+			      XFS_FSB_TO_DADDR(mp, sbp->sb_logstart),
+			      XFS_FSB_TO_BB(mp, sbp->sb_logblocks));
+	if (error) {
+		xfs_warn(mp, "log mount failed");
+		goto out_fail_wait;
+	}
+
+	/* Make sure the summary counts are ok. */
+	error = xfs_check_summary_counts(mp);
+	if (error)
+		goto out_log_dealloc;
+
+	/*
+	 * Get and sanity-check the root inode.
+	 * Save the pointer to it in the mount structure.
+	 */
+	error = xfs_iget(mp, NULL, sbp->sb_rootino, XFS_IGET_UNTRUSTED,
+			 XFS_ILOCK_EXCL, &rip);
+	if (error) {
+		xfs_warn(mp,
+			"Failed to read root inode 0x%llx, error %d",
+			sbp->sb_rootino, -error);
+		goto out_log_dealloc;
+	}
+
+	ASSERT(rip != NULL);
+
+	if (unlikely(!S_ISDIR(VFS_I(rip)->i_mode))) {
+		xfs_warn(mp, "corrupted root inode %llu: not a directory",
+			(unsigned long long)rip->i_ino);
+		xfs_iunlock(rip, XFS_ILOCK_EXCL);
+		XFS_ERROR_REPORT("xfs_mountfs_int(2)", XFS_ERRLEVEL_LOW,
+				 mp);
+		error = -EFSCORRUPTED;
+		goto out_rele_rip;
+	}
+	mp->m_rootip = rip;	/* save it */
+
+	xfs_iunlock(rip, XFS_ILOCK_EXCL);
+
+	/*
+	 * Initialize realtime inode pointers in the mount structure
+	 */
+	error = xfs_rtmount_inodes(mp);
+	if (error) {
+		/*
+		 * Free up the root inode.
+		 */
+		xfs_warn(mp, "failed to read RT inodes");
+		goto out_rele_rip;
+	}
+
+	/*
+	 * If this is a read-only mount defer the superblock updates until
+	 * the next remount into writeable mode.  Otherwise we would never
+	 * perform the update e.g. for the root filesystem.
+	 */
+	if (mp->m_update_sb && !(mp->m_flags & XFS_MOUNT_RDONLY)) {
+		error = xfs_sync_sb(mp, false);
+		if (error) {
+			xfs_warn(mp, "failed to write sb changes");
+			goto out_rtunmount;
+		}
+	}
+
+	/*
+	 * Initialise the XFS quota management subsystem for this mount
+	 */
+	if (XFS_IS_QUOTA_RUNNING(mp)) {
+		error = xfs_qm_newmount(mp, &quotamount, &quotaflags);
+		if (error)
+			goto out_rtunmount;
+	} else {
+		ASSERT(!XFS_IS_QUOTA_ON(mp));
+
+		/*
+		 * If a file system had quotas running earlier, but decided to
+		 * mount without -o uquota/pquota/gquota options, revoke the
+		 * quotachecked license.
+		 */
+		if (mp->m_sb.sb_qflags & XFS_ALL_QUOTA_ACCT) {
+			xfs_notice(mp, "resetting quota flags");
+			error = xfs_mount_reset_sbqflags(mp);
+			if (error)
+				goto out_rtunmount;
+		}
+	}
+
+	/*
+	 * Finish recovering the file system.  This part needed to be delayed
+	 * until after the root and real-time bitmap inodes were consistently
+	 * read in.
+	 */
+	error = xfs_log_mount_finish(mp);
+	if (error) {
+		xfs_warn(mp, "log mount finish failed");
+		goto out_rtunmount;
+	}
+
+	/*
+	 * Now the log is fully replayed, we can transition to full read-only
+	 * mode for read-only mounts. This will sync all the metadata and clean
+	 * the log so that the recovery we just performed does not have to be
+	 * replayed again on the next mount.
+	 *
+	 * We use the same quiesce mechanism as the rw->ro remount, as they are
+	 * semantically identical operations.
+	 */
+	if ((mp->m_flags & (XFS_MOUNT_RDONLY|XFS_MOUNT_NORECOVERY)) ==
+							XFS_MOUNT_RDONLY) {
+		xfs_quiesce_attr(mp);
+	}
+
+	/*
+	 * Complete the quota initialisation, post-log-replay component.
+	 */
+	if (quotamount) {
+		ASSERT(mp->m_qflags == 0);
+		mp->m_qflags = quotaflags;
+
+		xfs_qm_mount_quotas(mp);
+	}
+
+	/*
+	 * Now we are mounted, reserve a small amount of unused space for
+	 * privileged transactions. This is needed so that transaction
+	 * space required for critical operations can dip into this pool
+	 * when at ENOSPC. This is needed for operations like create with
+	 * attr, unwritten extent conversion at ENOSPC, etc. Data allocations
+	 * are not allowed to use this reserved space.
+	 *
+	 * This may drive us straight to ENOSPC on mount, but that implies
+	 * we were already there on the last unmount. Warn if this occurs.
+	 */
+	if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
+		resblks = xfs_default_resblks(mp);
+		error = xfs_reserve_blocks(mp, &resblks, NULL);
+		if (error)
+			xfs_warn(mp,
+	"Unable to allocate reserve blocks. Continuing without reserve pool.");
+
+		/* Recover any CoW blocks that never got remapped. */
+		error = xfs_reflink_recover_cow(mp);
+		if (error) {
+			xfs_err(mp,
+	"Error %d recovering leftover CoW allocations.", error);
+			xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+			goto out_quota;
+		}
+
+		/* Reserve AG blocks for future btree expansion. */
+		error = xfs_fs_reserve_ag_blocks(mp);
+		if (error && error != -ENOSPC)
+			goto out_agresv;
+	}
+
+	return 0;
+
+ out_agresv:
+	xfs_fs_unreserve_ag_blocks(mp);
+ out_quota:
+	xfs_qm_unmount_quotas(mp);
+ out_rtunmount:
+	xfs_rtunmount_inodes(mp);
+ out_rele_rip:
+	xfs_irele(rip);
+	/* Clean out dquots that might be in memory after quotacheck. */
+	xfs_qm_unmount(mp);
+	/*
+	 * Cancel all delayed reclaim work and reclaim the inodes directly.
+	 * We have to do this /after/ rtunmount and qm_unmount because those
+	 * two will have scheduled delayed reclaim for the rt/quota inodes.
+	 *
+	 * This is slightly different from the unmountfs call sequence
+	 * because we could be tearing down a partially set up mount.  In
+	 * particular, if log_mount_finish fails we bail out without calling
+	 * qm_unmount_quotas and therefore rely on qm_unmount to release the
+	 * quota inodes.
+	 */
+	cancel_delayed_work_sync(&mp->m_reclaim_work);
+	xfs_reclaim_inodes(mp, SYNC_WAIT);
+ out_log_dealloc:
+	mp->m_flags |= XFS_MOUNT_UNMOUNTING;
+	xfs_log_mount_cancel(mp);
+ out_fail_wait:
+	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
+		xfs_wait_buftarg(mp->m_logdev_targp);
+	xfs_wait_buftarg(mp->m_ddev_targp);
+ out_free_perag:
+	xfs_free_perag(mp);
+ out_free_dir:
+	xfs_da_unmount(mp);
+ out_remove_uuid:
+	xfs_uuid_unmount(mp);
+ out_remove_errortag:
+	xfs_errortag_del(mp);
+ out_remove_error_sysfs:
+	xfs_error_sysfs_del(mp);
+ out_del_stats:
+	xfs_sysfs_del(&mp->m_stats.xs_kobj);
+ out_remove_sysfs:
+	xfs_sysfs_del(&mp->m_kobj);
+ out:
+	return error;
+}
+
+/*
+ * This flushes out the inodes,dquots and the superblock, unmounts the
+ * log and makes sure that incore structures are freed.
+ */
+void
+xfs_unmountfs(
+	struct xfs_mount	*mp)
+{
+	uint64_t		resblks;
+	int			error;
+
+	xfs_icache_disable_reclaim(mp);
+	xfs_fs_unreserve_ag_blocks(mp);
+	xfs_qm_unmount_quotas(mp);
+	xfs_rtunmount_inodes(mp);
+	xfs_irele(mp->m_rootip);
+
+	/*
+	 * We can potentially deadlock here if we have an inode cluster
+	 * that has been freed has its buffer still pinned in memory because
+	 * the transaction is still sitting in a iclog. The stale inodes
+	 * on that buffer will have their flush locks held until the
+	 * transaction hits the disk and the callbacks run. the inode
+	 * flush takes the flush lock unconditionally and with nothing to
+	 * push out the iclog we will never get that unlocked. hence we
+	 * need to force the log first.
+	 */
+	xfs_log_force(mp, XFS_LOG_SYNC);
+
+	/*
+	 * Wait for all busy extents to be freed, including completion of
+	 * any discard operation.
+	 */
+	xfs_extent_busy_wait_all(mp);
+	flush_workqueue(xfs_discard_wq);
+
+	/*
+	 * We now need to tell the world we are unmounting. This will allow
+	 * us to detect that the filesystem is going away and we should error
+	 * out anything that we have been retrying in the background. This will
+	 * prevent neverending retries in AIL pushing from hanging the unmount.
+	 */
+	mp->m_flags |= XFS_MOUNT_UNMOUNTING;
+
+	/*
+	 * Flush all pending changes from the AIL.
+	 */
+	xfs_ail_push_all_sync(mp->m_ail);
+
+	/*
+	 * And reclaim all inodes.  At this point there should be no dirty
+	 * inodes and none should be pinned or locked, but use synchronous
+	 * reclaim just to be sure. We can stop background inode reclaim
+	 * here as well if it is still running.
+	 */
+	cancel_delayed_work_sync(&mp->m_reclaim_work);
+	xfs_reclaim_inodes(mp, SYNC_WAIT);
+
+	xfs_qm_unmount(mp);
+
+	/*
+	 * Unreserve any blocks we have so that when we unmount we don't account
+	 * the reserved free space as used. This is really only necessary for
+	 * lazy superblock counting because it trusts the incore superblock
+	 * counters to be absolutely correct on clean unmount.
+	 *
+	 * We don't bother correcting this elsewhere for lazy superblock
+	 * counting because on mount of an unclean filesystem we reconstruct the
+	 * correct counter value and this is irrelevant.
+	 *
+	 * For non-lazy counter filesystems, this doesn't matter at all because
+	 * we only every apply deltas to the superblock and hence the incore
+	 * value does not matter....
+	 */
+	resblks = 0;
+	error = xfs_reserve_blocks(mp, &resblks, NULL);
+	if (error)
+		xfs_warn(mp, "Unable to free reserved block pool. "
+				"Freespace may not be correct on next mount.");
+
+	error = xfs_log_sbcount(mp);
+	if (error)
+		xfs_warn(mp, "Unable to update superblock counters. "
+				"Freespace may not be correct on next mount.");
+
+
+	xfs_log_unmount(mp);
+	xfs_da_unmount(mp);
+	xfs_uuid_unmount(mp);
+
+#if defined(DEBUG)
+	xfs_errortag_clearall(mp);
+#endif
+	xfs_free_perag(mp);
+
+	xfs_errortag_del(mp);
+	xfs_error_sysfs_del(mp);
+	xfs_sysfs_del(&mp->m_stats.xs_kobj);
+	xfs_sysfs_del(&mp->m_kobj);
+}
+
+/*
+ * Determine whether modifications can proceed. The caller specifies the minimum
+ * freeze level for which modifications should not be allowed. This allows
+ * certain operations to proceed while the freeze sequence is in progress, if
+ * necessary.
+ */
+bool
+xfs_fs_writable(
+	struct xfs_mount	*mp,
+	int			level)
+{
+	ASSERT(level > SB_UNFROZEN);
+	if ((mp->m_super->s_writers.frozen >= level) ||
+	    XFS_FORCED_SHUTDOWN(mp) || (mp->m_flags & XFS_MOUNT_RDONLY))
+		return false;
+
+	return true;
+}
+
+/*
+ * xfs_log_sbcount
+ *
+ * Sync the superblock counters to disk.
+ *
+ * Note this code can be called during the process of freezing, so we use the
+ * transaction allocator that does not block when the transaction subsystem is
+ * in its frozen state.
+ */
+int
+xfs_log_sbcount(xfs_mount_t *mp)
+{
+	/* allow this to proceed during the freeze sequence... */
+	if (!xfs_fs_writable(mp, SB_FREEZE_COMPLETE))
+		return 0;
+
+	/*
+	 * we don't need to do this if we are updating the superblock
+	 * counters on every modification.
+	 */
+	if (!xfs_sb_version_haslazysbcount(&mp->m_sb))
+		return 0;
+
+	return xfs_sync_sb(mp, true);
+}
+
+/*
+ * Deltas for the inode count are +/-64, hence we use a large batch size
+ * of 128 so we don't need to take the counter lock on every update.
+ */
+#define XFS_ICOUNT_BATCH	128
+int
+xfs_mod_icount(
+	struct xfs_mount	*mp,
+	int64_t			delta)
+{
+	percpu_counter_add_batch(&mp->m_icount, delta, XFS_ICOUNT_BATCH);
+	if (__percpu_counter_compare(&mp->m_icount, 0, XFS_ICOUNT_BATCH) < 0) {
+		ASSERT(0);
+		percpu_counter_add(&mp->m_icount, -delta);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int
+xfs_mod_ifree(
+	struct xfs_mount	*mp,
+	int64_t			delta)
+{
+	percpu_counter_add(&mp->m_ifree, delta);
+	if (percpu_counter_compare(&mp->m_ifree, 0) < 0) {
+		ASSERT(0);
+		percpu_counter_add(&mp->m_ifree, -delta);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+/*
+ * Deltas for the block count can vary from 1 to very large, but lock contention
+ * only occurs on frequent small block count updates such as in the delayed
+ * allocation path for buffered writes (page a time updates). Hence we set
+ * a large batch count (1024) to minimise global counter updates except when
+ * we get near to ENOSPC and we have to be very accurate with our updates.
+ */
+#define XFS_FDBLOCKS_BATCH	1024
+int
+xfs_mod_fdblocks(
+	struct xfs_mount	*mp,
+	int64_t			delta,
+	bool			rsvd)
+{
+	int64_t			lcounter;
+	long long		res_used;
+	s32			batch;
+
+	if (delta > 0) {
+		/*
+		 * If the reserve pool is depleted, put blocks back into it
+		 * first. Most of the time the pool is full.
+		 */
+		if (likely(mp->m_resblks == mp->m_resblks_avail)) {
+			percpu_counter_add(&mp->m_fdblocks, delta);
+			return 0;
+		}
+
+		spin_lock(&mp->m_sb_lock);
+		res_used = (long long)(mp->m_resblks - mp->m_resblks_avail);
+
+		if (res_used > delta) {
+			mp->m_resblks_avail += delta;
+		} else {
+			delta -= res_used;
+			mp->m_resblks_avail = mp->m_resblks;
+			percpu_counter_add(&mp->m_fdblocks, delta);
+		}
+		spin_unlock(&mp->m_sb_lock);
+		return 0;
+	}
+
+	/*
+	 * Taking blocks away, need to be more accurate the closer we
+	 * are to zero.
+	 *
+	 * If the counter has a value of less than 2 * max batch size,
+	 * then make everything serialise as we are real close to
+	 * ENOSPC.
+	 */
+	if (__percpu_counter_compare(&mp->m_fdblocks, 2 * XFS_FDBLOCKS_BATCH,
+				     XFS_FDBLOCKS_BATCH) < 0)
+		batch = 1;
+	else
+		batch = XFS_FDBLOCKS_BATCH;
+
+	percpu_counter_add_batch(&mp->m_fdblocks, delta, batch);
+	if (__percpu_counter_compare(&mp->m_fdblocks, mp->m_alloc_set_aside,
+				     XFS_FDBLOCKS_BATCH) >= 0) {
+		/* we had space! */
+		return 0;
+	}
+
+	/*
+	 * lock up the sb for dipping into reserves before releasing the space
+	 * that took us to ENOSPC.
+	 */
+	spin_lock(&mp->m_sb_lock);
+	percpu_counter_add(&mp->m_fdblocks, -delta);
+	if (!rsvd)
+		goto fdblocks_enospc;
+
+	lcounter = (long long)mp->m_resblks_avail + delta;
+	if (lcounter >= 0) {
+		mp->m_resblks_avail = lcounter;
+		spin_unlock(&mp->m_sb_lock);
+		return 0;
+	}
+	printk_once(KERN_WARNING
+		"Filesystem \"%s\": reserve blocks depleted! "
+		"Consider increasing reserve pool size.",
+		mp->m_fsname);
+fdblocks_enospc:
+	spin_unlock(&mp->m_sb_lock);
+	return -ENOSPC;
+}
+
+int
+xfs_mod_frextents(
+	struct xfs_mount	*mp,
+	int64_t			delta)
+{
+	int64_t			lcounter;
+	int			ret = 0;
+
+	spin_lock(&mp->m_sb_lock);
+	lcounter = mp->m_sb.sb_frextents + delta;
+	if (lcounter < 0)
+		ret = -ENOSPC;
+	else
+		mp->m_sb.sb_frextents = lcounter;
+	spin_unlock(&mp->m_sb_lock);
+	return ret;
+}
+
+/*
+ * xfs_getsb() is called to obtain the buffer for the superblock.
+ * The buffer is returned locked and read in from disk.
+ * The buffer should be released with a call to xfs_brelse().
+ *
+ * If the flags parameter is BUF_TRYLOCK, then we'll only return
+ * the superblock buffer if it can be locked without sleeping.
+ * If it can't then we'll return NULL.
+ */
+struct xfs_buf *
+xfs_getsb(
+	struct xfs_mount	*mp,
+	int			flags)
+{
+	struct xfs_buf		*bp = mp->m_sb_bp;
+
+	if (!xfs_buf_trylock(bp)) {
+		if (flags & XBF_TRYLOCK)
+			return NULL;
+		xfs_buf_lock(bp);
+	}
+
+	xfs_buf_hold(bp);
+	ASSERT(bp->b_flags & XBF_DONE);
+	return bp;
+}
+
+/*
+ * Used to free the superblock along various error paths.
+ */
+void
+xfs_freesb(
+	struct xfs_mount	*mp)
+{
+	struct xfs_buf		*bp = mp->m_sb_bp;
+
+	xfs_buf_lock(bp);
+	mp->m_sb_bp = NULL;
+	xfs_buf_relse(bp);
+}
+
+/*
+ * If the underlying (data/log/rt) device is readonly, there are some
+ * operations that cannot proceed.
+ */
+int
+xfs_dev_is_read_only(
+	struct xfs_mount	*mp,
+	char			*message)
+{
+	if (xfs_readonly_buftarg(mp->m_ddev_targp) ||
+	    xfs_readonly_buftarg(mp->m_logdev_targp) ||
+	    (mp->m_rtdev_targp && xfs_readonly_buftarg(mp->m_rtdev_targp))) {
+		xfs_notice(mp, "%s required on read-only device.", message);
+		xfs_notice(mp, "write access unavailable, cannot proceed.");
+		return -EROFS;
+	}
+	return 0;
+}
+
+/* Force the summary counters to be recalculated at next mount. */
+void
+xfs_force_summary_recalc(
+	struct xfs_mount	*mp)
+{
+	if (!xfs_sb_version_haslazysbcount(&mp->m_sb))
+		return;
+
+	spin_lock(&mp->m_sb_lock);
+	mp->m_flags |= XFS_MOUNT_BAD_SUMMARY;
+	spin_unlock(&mp->m_sb_lock);
+}