xfsprogs/xfsprogs-mkfs-avoid-divide-by-zero-when-hardware-reports-opti.patch

From 99a3f52e337d9c785315e64a599755bc6f7b2118 Mon Sep 17 00:00:00 2001
From: Jeff Mahoney <jeffm@suse.com>
Date: Wed, 1 Aug 2018 17:06:45 -0500
Subject: [PATCH] mkfs: avoid divide-by-zero when hardware reports optimal i/o
 size as 0
References: bsc#1089777
Patch-mainline: v4.18.0-rc1
Git-commit: 99a3f52e337d9c785315e64a599755bc6f7b2118

Commit 051b4e37f5e (mkfs: factor AG alignment) factored out the
AG alignment code into a separate function.  It got rid of
redundant checks for dswidth != 0 since calc_stripe_factors was
supposed to guarantee that if dsunit is non-zero dswidth will be
as well.  Unfortunately, there's hardware out there that reports its
optimal i/o size as larger than the maximum i/o size, which the kernel
treats as broken and zeros out the optimal i/o size.

To resolve this we can check the topology before consuming it, and
ignore the bad stripe geometry.

Fixes: 051b4e37f5e (mkfs: factor AG alignment)
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
[sandeen: remove guessing heuristic, just warn and ignore bad data.]
Reviewed-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---
 mkfs/xfs_mkfs.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -2292,11 +2292,20 @@ _("data stripe width (%d) must be a mult
 
 	/* if no stripe config set, use the device default */
 	if (!dsunit) {
-		dsunit = ft->dsunit;
-		dswidth = ft->dswidth;
-		use_dev = true;
+		/* Ignore nonsense from device.  XXX add more validation */
+		if (ft->dsunit && ft->dswidth == 0) {
+			fprintf(stderr,
+_("%s: Volume reports stripe unit of %d bytes and stripe width of 0, ignoring.\n"),
+				progname, BBTOB(ft->dsunit));
+			ft->dsunit = 0;
+			ft->dswidth = 0;
+		} else {
+			dsunit = ft->dsunit;
+			dswidth = ft->dswidth;
+			use_dev = true;
+		}
 	} else {
-		/* check and warn is alignment is sub-optimal */
+		/* check and warn if user-specified alignment is sub-optimal */
 		if (ft->dsunit && ft->dsunit != dsunit) {
 			fprintf(stderr,
 _("%s: Specified data stripe unit %d is not the same as the volume stripe unit %d\n"),