diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index ffad7f2..d39e6d8 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -482,7 +482,9 @@
 		    be32_to_cpu(agfl->agfl_bno[i]) >= mp->m_sb.sb_agblocks)
 			return false;
 	}
-	return true;
+
+	return xfs_log_check_lsn(mp,
+				 be64_to_cpu(XFS_BUF_TO_AGFL(bp)->agfl_lsn));
 }
 
 static void
@@ -2259,9 +2261,13 @@
  {
 	struct xfs_agf	*agf = XFS_BUF_TO_AGF(bp);
 
-	if (xfs_sb_version_hascrc(&mp->m_sb) &&
-	    !uuid_equal(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid))
+	if (xfs_sb_version_hascrc(&mp->m_sb)) {
+		if (!uuid_equal(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid))
 			return false;
+		if (!xfs_log_check_lsn(mp,
+				be64_to_cpu(XFS_BUF_TO_AGF(bp)->agf_lsn)))
+			return false;
+	}
 
 	if (!(agf->agf_magicnum == cpu_to_be32(XFS_AGF_MAGIC) &&
 	      XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum)) &&
diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index 33df52d..aa187f7 100644
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -41,6 +41,7 @@
 #include "xfs_buf_item.h"
 #include "xfs_cksum.h"
 #include "xfs_dir2.h"
+#include "xfs_log.h"
 
 
 /*
@@ -266,6 +267,8 @@
 			return false;
 		if (be64_to_cpu(hdr3->info.blkno) != bp->b_bn)
 			return false;
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(hdr3->info.lsn)))
+			return false;
 	} else {
 		if (ichdr.magic != XFS_ATTR_LEAF_MAGIC)
 			return false;
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index f7d7ee7..235d026 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -32,6 +32,7 @@
 #include "xfs_trace.h"
 #include "xfs_cksum.h"
 #include "xfs_alloc.h"
+#include "xfs_log.h"
 
 /*
  * Cursor allocation zone.
@@ -243,8 +244,14 @@
 xfs_btree_lblock_verify_crc(
 	struct xfs_buf		*bp)
 {
-	if (xfs_sb_version_hascrc(&bp->b_target->bt_mount->m_sb))
+	struct xfs_btree_block	*block = XFS_BUF_TO_BLOCK(bp);
+	struct xfs_mount	*mp = bp->b_target->bt_mount;
+
+	if (xfs_sb_version_hascrc(&mp->m_sb)) {
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(block->bb_u.l.bb_lsn)))
+			return false;
 		return xfs_buf_verify_cksum(bp, XFS_BTREE_LBLOCK_CRC_OFF);
+	}
 
 	return true;
 }
@@ -275,8 +282,14 @@
 xfs_btree_sblock_verify_crc(
 	struct xfs_buf		*bp)
 {
-	if (xfs_sb_version_hascrc(&bp->b_target->bt_mount->m_sb))
+	struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
+	struct xfs_mount	*mp = bp->b_target->bt_mount;
+
+	if (xfs_sb_version_hascrc(&mp->m_sb)) {
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(block->bb_u.s.bb_lsn)))
+			return false;
 		return xfs_buf_verify_cksum(bp, XFS_BTREE_SBLOCK_CRC_OFF);
+	}
 
 	return true;
 }
diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index be43248..e89a0f8f 100644
--- a/fs/xfs/libxfs/xfs_da_btree.c
+++ b/fs/xfs/libxfs/xfs_da_btree.c
@@ -39,6 +39,7 @@
 #include "xfs_trace.h"
 #include "xfs_cksum.h"
 #include "xfs_buf_item.h"
+#include "xfs_log.h"
 
 /*
  * xfs_da_btree.c
@@ -150,6 +151,8 @@
 			return false;
 		if (be64_to_cpu(hdr3->info.blkno) != bp->b_bn)
 			return false;
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(hdr3->info.lsn)))
+			return false;
 	} else {
 		if (ichdr.magic != XFS_DA_NODE_MAGIC)
 			return false;
@@ -322,6 +325,7 @@
 	if (xfs_sb_version_hascrc(&mp->m_sb)) {
 		struct xfs_da3_node_hdr *hdr3 = bp->b_addr;
 
+		memset(hdr3, 0, sizeof(struct xfs_da3_node_hdr));
 		ichdr.magic = XFS_DA3_NODE_MAGIC;
 		hdr3->info.blkno = cpu_to_be64(bp->b_bn);
 		hdr3->info.owner = cpu_to_be64(args->dp->i_ino);
diff --git a/fs/xfs/libxfs/xfs_dir2_block.c b/fs/xfs/libxfs/xfs_dir2_block.c
index 4778d1d..9c10e2b 100644
--- a/fs/xfs/libxfs/xfs_dir2_block.c
+++ b/fs/xfs/libxfs/xfs_dir2_block.c
@@ -34,6 +34,7 @@
 #include "xfs_error.h"
 #include "xfs_trace.h"
 #include "xfs_cksum.h"
+#include "xfs_log.h"
 
 /*
  * Local function prototypes.
@@ -71,6 +72,8 @@
 			return false;
 		if (be64_to_cpu(hdr3->blkno) != bp->b_bn)
 			return false;
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(hdr3->lsn)))
+			return false;
 	} else {
 		if (hdr3->magic != cpu_to_be32(XFS_DIR2_BLOCK_MAGIC))
 			return false;
diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c
index 824131e..af71a84f 100644
--- a/fs/xfs/libxfs/xfs_dir2_data.c
+++ b/fs/xfs/libxfs/xfs_dir2_data.c
@@ -31,6 +31,7 @@
 #include "xfs_trans.h"
 #include "xfs_buf_item.h"
 #include "xfs_cksum.h"
+#include "xfs_log.h"
 
 /*
  * Check the consistency of the data block.
@@ -224,6 +225,8 @@
 			return false;
 		if (be64_to_cpu(hdr3->blkno) != bp->b_bn)
 			return false;
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(hdr3->lsn)))
+			return false;
 	} else {
 		if (hdr3->magic != cpu_to_be32(XFS_DIR2_DATA_MAGIC))
 			return false;
diff --git a/fs/xfs/libxfs/xfs_dir2_leaf.c b/fs/xfs/libxfs/xfs_dir2_leaf.c
index f300240..3923e1f 100644
--- a/fs/xfs/libxfs/xfs_dir2_leaf.c
+++ b/fs/xfs/libxfs/xfs_dir2_leaf.c
@@ -33,6 +33,7 @@
 #include "xfs_trans.h"
 #include "xfs_buf_item.h"
 #include "xfs_cksum.h"
+#include "xfs_log.h"
 
 /*
  * Local function declarations.
@@ -164,6 +165,8 @@
 			return false;
 		if (be64_to_cpu(leaf3->info.blkno) != bp->b_bn)
 			return false;
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(leaf3->info.lsn)))
+			return false;
 	} else {
 		if (leaf->hdr.info.magic != cpu_to_be16(magic))
 			return false;
diff --git a/fs/xfs/libxfs/xfs_dir2_node.c b/fs/xfs/libxfs/xfs_dir2_node.c
index cc28e92..70b0cb2 100644
--- a/fs/xfs/libxfs/xfs_dir2_node.c
+++ b/fs/xfs/libxfs/xfs_dir2_node.c
@@ -33,6 +33,7 @@
 #include "xfs_trans.h"
 #include "xfs_buf_item.h"
 #include "xfs_cksum.h"
+#include "xfs_log.h"
 
 /*
  * Function declarations.
@@ -97,6 +98,8 @@
 			return false;
 		if (be64_to_cpu(hdr3->blkno) != bp->b_bn)
 			return false;
+		if (!xfs_log_check_lsn(mp, be64_to_cpu(hdr3->lsn)))
+			return false;
 	} else {
 		if (hdr->magic != cpu_to_be32(XFS_DIR2_FREE_MAGIC))
 			return false;
diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 54deb2d..70c1db9 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -38,6 +38,7 @@
 #include "xfs_icreate_item.h"
 #include "xfs_icache.h"
 #include "xfs_trace.h"
+#include "xfs_log.h"
 
 
 /*
@@ -2500,9 +2501,14 @@
 	struct xfs_mount *mp = bp->b_target->bt_mount;
 	struct xfs_agi	*agi = XFS_BUF_TO_AGI(bp);
 
-	if (xfs_sb_version_hascrc(&mp->m_sb) &&
-	    !uuid_equal(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid))
+	if (xfs_sb_version_hascrc(&mp->m_sb)) {
+		if (!uuid_equal(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid))
 			return false;
+		if (!xfs_log_check_lsn(mp,
+				be64_to_cpu(XFS_BUF_TO_AGI(bp)->agi_lsn)))
+			return false;
+	}
+
 	/*
 	 * Validate the magic number of the agi block.
 	 */
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 4742514..a0b071d 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -35,6 +35,7 @@
 #include "xfs_bmap_btree.h"
 #include "xfs_alloc_btree.h"
 #include "xfs_ialloc_btree.h"
+#include "xfs_log.h"
 
 /*
  * Physical superblock buffer manipulations. Shared with libxfs in userspace.
@@ -163,6 +164,15 @@
 "Filesystem can not be safely mounted by this kernel.");
 			return -EINVAL;
 		}
+	} else if (xfs_sb_version_hascrc(sbp)) {
+		/*
+		 * We can't read verify the sb LSN because the read verifier is
+		 * called before the log is allocated and processed. We know the
+		 * log is set up before write verifier (!check_version) calls,
+		 * so just check it here.
+		 */
+		if (!xfs_log_check_lsn(mp, sbp->sb_lsn))
+			return -EFSCORRUPTED;
 	}
 
 	if (xfs_sb_version_has_pquotino(sbp)) {
diff --git a/fs/xfs/libxfs/xfs_symlink_remote.c b/fs/xfs/libxfs/xfs_symlink_remote.c
index b9884aa..cb6fd20 100644
--- a/fs/xfs/libxfs/xfs_symlink_remote.c
+++ b/fs/xfs/libxfs/xfs_symlink_remote.c
@@ -31,6 +31,7 @@
 #include "xfs_cksum.h"
 #include "xfs_trans.h"
 #include "xfs_buf_item.h"
+#include "xfs_log.h"
 
 
 /*
@@ -60,6 +61,7 @@
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return 0;
 
+	memset(dsl, 0, sizeof(struct xfs_dsymlink_hdr));
 	dsl->sl_magic = cpu_to_be32(XFS_SYMLINK_MAGIC);
 	dsl->sl_offset = cpu_to_be32(offset);
 	dsl->sl_bytes = cpu_to_be32(size);
@@ -116,6 +118,8 @@
 		return false;
 	if (dsl->sl_owner == 0)
 		return false;
+	if (!xfs_log_check_lsn(mp, be64_to_cpu(dsl->sl_lsn)))
+		return false;
 
 	return true;
 }
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index aaadee0..0c8ef76 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -3165,11 +3165,19 @@
 	}
 
 	if (log->l_curr_block >= log->l_logBBsize) {
+		/*
+		 * Rewind the current block before the cycle is bumped to make
+		 * sure that the combined LSN never transiently moves forward
+		 * when the log wraps to the next cycle. This is to support the
+		 * unlocked sample of these fields from xlog_valid_lsn(). Most
+		 * other cases should acquire l_icloglock.
+		 */
+		log->l_curr_block -= log->l_logBBsize;
+		ASSERT(log->l_curr_block >= 0);
+		smp_wmb();
 		log->l_curr_cycle++;
 		if (log->l_curr_cycle == XLOG_HEADER_MAGIC_NUM)
 			log->l_curr_cycle++;
-		log->l_curr_block -= log->l_logBBsize;
-		ASSERT(log->l_curr_block >= 0);
 	}
 	ASSERT(iclog == log->l_iclog);
 	log->l_iclog = iclog->ic_next;
@@ -4023,3 +4031,45 @@
 	return 1;
 }
 
+/*
+ * Verify that an LSN stamped into a piece of metadata is valid. This is
+ * intended for use in read verifiers on v5 superblocks.
+ */
+bool
+xfs_log_check_lsn(
+	struct xfs_mount	*mp,
+	xfs_lsn_t		lsn)
+{
+	struct xlog		*log = mp->m_log;
+	bool			valid;
+
+	/*
+	 * norecovery mode skips mount-time log processing and unconditionally
+	 * resets the in-core LSN. We can't validate in this mode, but
+	 * modifications are not allowed anyways so just return true.
+	 */
+	if (mp->m_flags & XFS_MOUNT_NORECOVERY)
+		return true;
+
+	/*
+	 * Some metadata LSNs are initialized to NULL (e.g., the agfl). This is
+	 * handled by recovery and thus safe to ignore here.
+	 */
+	if (lsn == NULLCOMMITLSN)
+		return true;
+
+	valid = xlog_valid_lsn(mp->m_log, lsn);
+
+	/* warn the user about what's gone wrong before verifier failure */
+	if (!valid) {
+		spin_lock(&log->l_icloglock);
+		xfs_warn(mp,
+"Corruption warning: Metadata has LSN (%d:%d) ahead of current LSN (%d:%d). "
+"Please unmount and run xfs_repair (>= v4.3) to resolve.",
+			 CYCLE_LSN(lsn), BLOCK_LSN(lsn),
+			 log->l_curr_cycle, log->l_curr_block);
+		spin_unlock(&log->l_icloglock);
+	}
+
+	return valid;
+}
diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
index 09d91d3..aa533a7 100644
--- a/fs/xfs/xfs_log.h
+++ b/fs/xfs/xfs_log.h
@@ -181,5 +181,6 @@
 void	xfs_log_work_queue(struct xfs_mount *mp);
 void	xfs_log_worker(struct work_struct *work);
 void	xfs_log_quiesce(struct xfs_mount *mp);
+bool	xfs_log_check_lsn(struct xfs_mount *, xfs_lsn_t);
 
 #endif	/* __XFS_LOG_H__ */
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 950f3f9..8daba74 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -560,4 +560,55 @@
 	remove_wait_queue(wq, &wait);
 }
 
+/*
+ * The LSN is valid so long as it is behind the current LSN. If it isn't, this
+ * means that the next log record that includes this metadata could have a
+ * smaller LSN. In turn, this means that the modification in the log would not
+ * replay.
+ */
+static inline bool
+xlog_valid_lsn(
+	struct xlog	*log,
+	xfs_lsn_t	lsn)
+{
+	int		cur_cycle;
+	int		cur_block;
+	bool		valid = true;
+
+	/*
+	 * First, sample the current lsn without locking to avoid added
+	 * contention from metadata I/O. The current cycle and block are updated
+	 * (in xlog_state_switch_iclogs()) and read here in a particular order
+	 * to avoid false negatives (e.g., thinking the metadata LSN is valid
+	 * when it is not).
+	 *
+	 * The current block is always rewound before the cycle is bumped in
+	 * xlog_state_switch_iclogs() to ensure the current LSN is never seen in
+	 * a transiently forward state. Instead, we can see the LSN in a
+	 * transiently behind state if we happen to race with a cycle wrap.
+	 */
+	cur_cycle = ACCESS_ONCE(log->l_curr_cycle);
+	smp_rmb();
+	cur_block = ACCESS_ONCE(log->l_curr_block);
+
+	if ((CYCLE_LSN(lsn) > cur_cycle) ||
+	    (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) {
+		/*
+		 * If the metadata LSN appears invalid, it's possible the check
+		 * above raced with a wrap to the next log cycle. Grab the lock
+		 * to check for sure.
+		 */
+		spin_lock(&log->l_icloglock);
+		cur_cycle = log->l_curr_cycle;
+		cur_block = log->l_curr_block;
+		spin_unlock(&log->l_icloglock);
+
+		if ((CYCLE_LSN(lsn) > cur_cycle) ||
+		    (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block))
+			valid = false;
+	}
+
+	return valid;
+}
+
 #endif	/* __XFS_LOG_PRIV_H__ */
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 512a094..f8f1363 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -4609,9 +4609,19 @@
 	int		error;
 
 	/* find the tail of the log */
-	if ((error = xlog_find_tail(log, &head_blk, &tail_blk)))
+	error = xlog_find_tail(log, &head_blk, &tail_blk);
+	if (error)
 		return error;
 
+	/*
+	 * The superblock was read before the log was available and thus the LSN
+	 * could not be verified. Check the superblock LSN against the current
+	 * LSN now that it's known.
+	 */
+	if (xfs_sb_version_hascrc(&log->l_mp->m_sb) &&
+	    !xfs_log_check_lsn(log->l_mp, log->l_mp->m_sb.sb_lsn))
+		return -EINVAL;
+
 	if (tail_blk != head_blk) {
 		/* There used to be a comment here:
 		 *