[ndctl PATCH] ndctl, create-namespace: fix minimum alignment detection

From: Dan Williams <dan.j.williams@intel.com>
To: linux-nvdimm@lists.01.org
Cc: Maciej Ramotowski <maciej.ramotowski@intel.com>
Subject: [ndctl PATCH] ndctl, create-namespace: fix minimum alignment detection
Date: Sat, 03 Mar 2018 13:49:07 -0800	[thread overview]
Message-ID: <152011374766.14937.7017387737157056826.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)

Commit 0c31ce0a2875 "ndctl, create-namespace: fix --align= default..."
tried to make casual testing with nfit_test easier by auto-detecting the
alignment. However, this auto-detection always falls back to 4K
alignment on kernels that do not export the region 'resource' attribute.
Those kernels, like v4.9.4, may also be missing this fix: commit
cd755677d944 "libnvdimm, pfn: fix memmap reservation size versus 4K
alignment".

Given the chance to fail to initialize a namespace in the 4K case on
older kernels, be more conservative about falling back to 4K alignment.

Link: https://github.com/pmem/ndctl/issues/34
Reported-by: Maciej Ramotowski <maciej.ramotowski@intel.com>
Fixes: 0c31ce0a2875 ("ndctl, create-namespace: fix --align= default...")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 ndctl/namespace.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/ndctl/namespace.c b/ndctl/namespace.c
index ceb9e7a9b8af..aef356abbee1 100644
--- a/ndctl/namespace.c
+++ b/ndctl/namespace.c
@@ -462,7 +462,7 @@ static int validate_namespace_options(struct ndctl_region *region,
 		struct ndctl_namespace *ndns, struct parsed_parameters *p)
 {
 	const char *region_name = ndctl_region_get_devname(region);
-	unsigned long long size_align = SZ_4K, units = 1;
+	unsigned long long size_align = SZ_4K, units = 1, resource;
 	unsigned int ways;
 	int rc = 0;
 
@@ -563,8 +563,9 @@ static int validate_namespace_options(struct ndctl_region *region,
 		 * the nfit_test use case where it is backed by vmalloc
 		 * memory.
 		 */
-		if (param.align_default && (ndctl_region_get_resource(region)
-					& (SZ_2M - 1))) {
+		resource = ndctl_region_get_resource(region);
+		if (param.align_default && resource < ULLONG_MAX
+				&& (resource & (SZ_2M - 1))) {
 			debug("%s: falling back to a 4K alignment\n",
 					region_name);
 			p->align = SZ_4K;

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