diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index ddd45e5..2251a49 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -177,6 +177,7 @@
 		up_write(&mp->m_peraglock);
 	}
 	tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFS);
+	tp->t_flags |= XFS_TRANS_RESERVE;
 	if ((error = xfs_trans_reserve(tp, XFS_GROWFS_SPACE_RES(mp),
 			XFS_GROWDATA_LOG_RES(mp), 0, 0, 0))) {
 		xfs_trans_cancel(tp, 0);
@@ -499,8 +500,9 @@
 	unsigned long		s;
 
 	/* If inval is null, report current values and return */
-
 	if (inval == (__uint64_t *)NULL) {
+		if (!outval)
+			return EINVAL;
 		outval->resblks = mp->m_resblks;
 		outval->resblks_avail = mp->m_resblks_avail;
 		return 0;
@@ -563,8 +565,10 @@
 		}
 	}
 out:
-	outval->resblks = mp->m_resblks;
-	outval->resblks_avail = mp->m_resblks_avail;
+	if (outval) {
+		outval->resblks = mp->m_resblks;
+		outval->resblks_avail = mp->m_resblks_avail;
+	}
 	XFS_SB_UNLOCK(mp, s);
 
 	if (fdblks_delta) {
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 3f2b9f2..ab50621 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -489,13 +489,13 @@
 	if (unlikely(rt)) {
 		resrtextents = qblocks = resaligned;
 		resrtextents /= mp->m_sb.sb_rextsize;
-  		resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
-  		quota_flag = XFS_QMOPT_RES_RTBLKS;
-  	} else {
-  		resrtextents = 0;
+		resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
+		quota_flag = XFS_QMOPT_RES_RTBLKS;
+	} else {
+		resrtextents = 0;
 		resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
-  		quota_flag = XFS_QMOPT_RES_REGBLKS;
-  	}
+		quota_flag = XFS_QMOPT_RES_REGBLKS;
+	}
 
 	/*
 	 * Allocate and setup the transaction
@@ -788,18 +788,12 @@
 		nimaps = 0;
 		while (nimaps == 0) {
 			tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);
+			tp->t_flags |= XFS_TRANS_RESERVE;
 			nres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
 			error = xfs_trans_reserve(tp, nres,
 					XFS_WRITE_LOG_RES(mp),
 					0, XFS_TRANS_PERM_LOG_RES,
 					XFS_WRITE_LOG_COUNT);
-			if (error == ENOSPC) {
-				error = xfs_trans_reserve(tp, 0,
-						XFS_WRITE_LOG_RES(mp),
-						0,
-						XFS_TRANS_PERM_LOG_RES,
-						XFS_WRITE_LOG_COUNT);
-			}
 			if (error) {
 				xfs_trans_cancel(tp, 0);
 				return XFS_ERROR(error);
@@ -917,8 +911,8 @@
 		 * from unwritten to real. Do allocations in a loop until
 		 * we have covered the range passed in.
 		 */
-
 		tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);
+		tp->t_flags |= XFS_TRANS_RESERVE;
 		error = xfs_trans_reserve(tp, resblks,
 				XFS_WRITE_LOG_RES(mp), 0,
 				XFS_TRANS_PERM_LOG_RES,
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 39cf6f32..31453ca 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -725,7 +725,7 @@
 	bhv_vnode_t	*rvp = NULL;
 	int		readio_log, writeio_log;
 	xfs_daddr_t	d;
-	__uint64_t	ret64;
+	__uint64_t	resblks;
 	__int64_t	update_flags;
 	uint		quotamount, quotaflags;
 	int		agno;
@@ -842,6 +842,7 @@
 	 */
 	if ((mfsi_flags & XFS_MFSI_SECOND) == 0 &&
 	    (mp->m_flags & XFS_MOUNT_NOUUID) == 0) {
+		__uint64_t	ret64;
 		if (xfs_uuid_mount(mp)) {
 			error = XFS_ERROR(EINVAL);
 			goto error1;
@@ -1135,13 +1136,27 @@
 		goto error4;
 	}
 
-
 	/*
 	 * Complete the quota initialisation, post-log-replay component.
 	 */
 	if ((error = XFS_QM_MOUNT(mp, quotamount, quotaflags, mfsi_flags)))
 		goto error4;
 
+	/*
+	 * 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.
+	 *
+	 * We default to 5% or 1024 fsbs of space reserved, whichever is smaller.
+	 * This may drive us straight to ENOSPC on mount, but that implies
+	 * we were already there on the last unmount.
+	 */
+	resblks = min_t(__uint64_t, mp->m_sb.sb_dblocks / 20, 1024);
+	xfs_reserve_blocks(mp, &resblks, NULL);
+
 	return 0;
 
  error4:
@@ -1181,6 +1196,7 @@
 #if defined(DEBUG) || defined(INDUCE_IO_ERROR)
 	int64_t		fsid;
 #endif
+	__uint64_t	resblks;
 
 	/*
 	 * We can potentially deadlock here if we have an inode cluster
@@ -1209,6 +1225,23 @@
 		xfs_binval(mp->m_rtdev_targp);
 	}
 
+	/*
+	 * 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 aboslutely 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;
+	xfs_reserve_blocks(mp, &resblks, NULL);
+
 	xfs_log_sbcount(mp, 1);
 	xfs_unmountfs_writesb(mp);
 	xfs_unmountfs_wait(mp); 		/* wait for async bufs */