[PATCH 3/4] mkfs: complain about impossible log size constraints

From: "Darrick J. Wong" <djwong@kernel.org>
To: sandeen@sandeen.net, djwong@kernel.org
Cc: linux-xfs@vger.kernel.org
Subject: [PATCH 3/4] mkfs: complain about impossible log size constraints
Date: Tue, 12 Jul 2022 18:09:53 -0700	[thread overview]
Message-ID: <165767459394.891854.2338822152912053034.stgit@magnolia> (raw)
In-Reply-To: <165767457703.891854.2108521135190969641.stgit@magnolia>

From: Darrick J. Wong <djwong@kernel.org>

xfs/042 trips over an impossible fs geometry when nrext64 is enabled.
The minimum log size calculation comes out to 4287 blocks, but the mkfs
parameters specify an AG size of 4096 blocks.  This eventually causes
mkfs to complain that the autoselected log size doesn't meet the minimum
size, but we could be a little more explicit in pointing out that the
two size constraints make for an impossible geometry.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 mkfs/xfs_mkfs.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index db322b3a..61ac1a4a 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -3401,6 +3401,13 @@ _("external log device size %lld blocks too small, must be at least %lld blocks\
 	 * an AG.
 	 */
 	max_logblocks = libxfs_alloc_ag_max_usable(mp) - 1;
+	if (max_logblocks < min_logblocks) {
+		fprintf(stderr,
+_("max log size %d smaller than min log size %d\n"),
+				max_logblocks,
+				min_logblocks);
+		usage();
+	}
 
 	/* internal log - if no size specified, calculate automatically */
 	if (!cfg->logblocks) {

