[PATCH 58/58] xfs: validate the realtime geometry in xfs_validate_sb_common

[Christoph Hellwig <hch@lst.de>]

From: "Darrick J. Wong" <darrick.wong@oracle.com>

Source kernel commit: f8e566c0f5e1fd8de33ccec6eb1ff815cd4b0dc3

Validate the geometry of the realtime geometry when we mount the
filesystem, so that we don't abruptly shut down the filesystem later on.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 libxfs/libxfs_priv.h | 22 ++++++++++++++++++++++
 libxfs/xfs_sb.c      | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/libxfs/libxfs_priv.h b/libxfs/libxfs_priv.h
index 85fcccb6..70c70479 100644
--- a/libxfs/libxfs_priv.h
+++ b/libxfs/libxfs_priv.h
@@ -265,6 +265,28 @@ static inline uint64_t div64_u64_rem(uint64_t dividend, uint64_t divisor,
 	return dividend / divisor;
 }
 
+/**
+ * div_u64 - unsigned 64bit divide with 32bit divisor
+ * @dividend: unsigned 64bit dividend
+ * @divisor: unsigned 32bit divisor
+ *
+ * This is the most common 64bit divide and should be used if possible,
+ * as many 32bit archs can optimize this variant better than a full 64bit
+ * divide.
+ */
+static inline uint64_t div_u64(uint64_t dividend, uint32_t divisor)
+{
+	uint32_t remainder;
+	return div_u64_rem(dividend, divisor, &remainder);
+}
+
+static inline uint64_t howmany_64(uint64_t x, uint32_t y)
+{
+	x += y - 1;
+	do_div(x, y);
+	return x;
+}
+
 #define min_t(type,x,y) \
 	({ type __x = (x); type __y = (y); __x < __y ? __x: __y; })
 #define max_t(type,x,y) \
diff --git a/libxfs/xfs_sb.c b/libxfs/xfs_sb.c
index e26b9016..d37d60b3 100644
--- a/libxfs/xfs_sb.c
+++ b/libxfs/xfs_sb.c
@@ -325,6 +325,38 @@ xfs_validate_sb_common(
 		return -EFSCORRUPTED;
 	}
 
+	/* Validate the realtime geometry; stolen from xfs_repair */
+	if (sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE ||
+	    sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE) {
+		xfs_notice(mp,
+			"realtime extent sanity check failed");
+		return -EFSCORRUPTED;
+	}
+
+	if (sbp->sb_rblocks == 0) {
+		if (sbp->sb_rextents != 0 || sbp->sb_rbmblocks != 0 ||
+		    sbp->sb_rextslog != 0 || sbp->sb_frextents != 0) {
+			xfs_notice(mp,
+				"realtime zeroed geometry check failed");
+			return -EFSCORRUPTED;
+		}
+	} else {
+		uint64_t	rexts;
+		uint64_t	rbmblocks;
+
+		rexts = div_u64(sbp->sb_rblocks, sbp->sb_rextsize);
+		rbmblocks = howmany_64(sbp->sb_rextents,
+				       NBBY * sbp->sb_blocksize);
+
+		if (sbp->sb_rextents != rexts ||
+		    sbp->sb_rextslog != xfs_highbit32(sbp->sb_rextents) ||
+		    sbp->sb_rbmblocks != rbmblocks) {
+			xfs_notice(mp,
+				"realtime geometry sanity check failed");
+			return -EFSCORRUPTED;
+		}
+	}
+
 	if (sbp->sb_unit) {
 		if (!xfs_sb_version_hasdalign(sbp) ||
 		    sbp->sb_unit > sbp->sb_width ||
-- 
2.26.2