[PATCH] xfs: introduce xfs_validate_stripe_factors()

[Gao Xiang <hsiangkao@redhat.com>]

Introduce a common helper to consolidate stripe validation process.
Also make kernel code xfs_validate_sb_common() use it first.

Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---

kernel side of:
https://lore.kernel.org/r/20201007140402.14295-3-hsiangkao@aol.com
with update suggested by Darrick:
 - stretch columns for commit message;
 - add comments to hasdalign check;
 - break old sunit / swidth != 0 check into two seperate checks;
 - update an error message description.

also use bytes for sunit / swidth representation, so users can
see values in the unique unit.

see
https://lore.kernel.org/r/20201007140402.14295-1-hsiangkao@aol.com
for the background.

 fs/xfs/libxfs/xfs_sb.c | 65 +++++++++++++++++++++++++++++++++++-------
 fs/xfs/libxfs/xfs_sb.h |  3 ++
 2 files changed, 57 insertions(+), 11 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 5aeafa59ed27..cb2a7aa0ad51 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -360,21 +360,18 @@ xfs_validate_sb_common(
 		}
 	}
 
-	if (sbp->sb_unit) {
-		if (!xfs_sb_version_hasdalign(sbp) ||
-		    sbp->sb_unit > sbp->sb_width ||
-		    (sbp->sb_width % sbp->sb_unit) != 0) {
-			xfs_notice(mp, "SB stripe unit sanity check failed");
-			return -EFSCORRUPTED;
-		}
-	} else if (xfs_sb_version_hasdalign(sbp)) {
+	/*
+	 * Either (sb_unit and !hasdalign) or (!sb_unit and hasdalign)
+	 * would imply the image is corrupted.
+	 */
+	if (!sbp->sb_unit ^ !xfs_sb_version_hasdalign(sbp)) {
 		xfs_notice(mp, "SB stripe alignment sanity check failed");
 		return -EFSCORRUPTED;
-	} else if (sbp->sb_width) {
-		xfs_notice(mp, "SB stripe width sanity check failed");
-		return -EFSCORRUPTED;
 	}
 
+	if (!xfs_validate_stripe_factors(mp, XFS_FSB_TO_B(mp, sbp->sb_unit),
+					 XFS_FSB_TO_B(mp, sbp->sb_width), 0))
+		return -EFSCORRUPTED;
 
 	if (xfs_sb_version_hascrc(&mp->m_sb) &&
 	    sbp->sb_blocksize < XFS_MIN_CRC_BLOCKSIZE) {
@@ -1233,3 +1230,49 @@ xfs_sb_get_secondary(
 	*bpp = bp;
 	return 0;
 }
+
+/*
+ * sunit, swidth, sectorsize(optional with 0) should be all in bytes,
+ * so users won't be confused by values in error messages.
+ */
+bool
+xfs_validate_stripe_factors(
+	struct xfs_mount	*mp,
+	__s64			sunit,
+	__s64			swidth,
+	int			sectorsize)
+{
+	if (sectorsize && sunit % sectorsize) {
+		xfs_notice(mp,
+"stripe unit (%lld) must be a multiple of the sector size (%d)",
+			   sunit, sectorsize);
+		return false;
+	}
+
+	if (sunit && !swidth) {
+		xfs_notice(mp,
+"invalid stripe unit (%lld) and stripe width of 0", sunit);
+		return false;
+	}
+
+	if (!sunit && swidth) {
+		xfs_notice(mp,
+"invalid stripe width (%lld) and stripe unit of 0", swidth);
+		return false;
+	}
+
+	if (sunit > swidth) {
+		xfs_notice(mp,
+"stripe unit (%lld) is larger than the stripe width (%lld)", sunit, swidth);
+		return false;
+	}
+
+	if (sunit && (swidth % sunit)) {
+		xfs_notice(mp,
+"stripe width (%lld) must be a multiple of the stripe unit (%lld)",
+			   swidth, sunit);
+		return false;
+	}
+	return true;
+}
+
diff --git a/fs/xfs/libxfs/xfs_sb.h b/fs/xfs/libxfs/xfs_sb.h
index 92465a9a5162..2d3504eb9886 100644
--- a/fs/xfs/libxfs/xfs_sb.h
+++ b/fs/xfs/libxfs/xfs_sb.h
@@ -42,4 +42,7 @@ extern int	xfs_sb_get_secondary(struct xfs_mount *mp,
 				struct xfs_trans *tp, xfs_agnumber_t agno,
 				struct xfs_buf **bpp);
 
+extern bool	xfs_validate_stripe_factors(struct xfs_mount *mp,
+				__s64 sunit, __s64 swidth, int sectorsize);
+
 #endif	/* __XFS_SB_H__ */
-- 
2.18.1