Merge branch 'for-linus' of git://git.kernel.dk/linux-block

Pull block layer fix from Jens Axboe:
 "Just one patch in this pull request, fixing a regression caused by a
  'mathematically correct' change to lcm()"

* 'for-linus' of git://git.kernel.dk/linux-block:
  block: fix blk_stack_limits() regression due to lcm() change

3 files changed, 15 insertions, 3 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 6ed2cbe..12600bf 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -585,7 +585,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 				     b->physical_block_size);
 
 	t->io_min = max(t->io_min, b->io_min);
-	t->io_opt = lcm(t->io_opt, b->io_opt);
+	t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
 
 	t->cluster &= b->cluster;
 	t->discard_zeroes_data &= b->discard_zeroes_data;
@@ -616,7 +616,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 		    b->raid_partial_stripes_expensive);
 
 	/* Find lowest common alignment_offset */
-	t->alignment_offset = lcm(t->alignment_offset, alignment)
+	t->alignment_offset = lcm_not_zero(t->alignment_offset, alignment)
 		% max(t->physical_block_size, t->io_min);
 
 	/* Verify that new alignment_offset is on a logical block boundary */
@@ -643,7 +643,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 						      b->max_discard_sectors);
 		t->discard_granularity = max(t->discard_granularity,
 					     b->discard_granularity);
-		t->discard_alignment = lcm(t->discard_alignment, alignment) %
+		t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) %
 			t->discard_granularity;
 	}
 
diff --git a/include/linux/lcm.h b/include/linux/lcm.h
index 7bf01d7..1ce79a7 100644
--- a/include/linux/lcm.h
+++ b/include/linux/lcm.h
@@ -4,5 +4,6 @@
 #include <linux/compiler.h>
 
 unsigned long lcm(unsigned long a, unsigned long b) __attribute_const__;
+unsigned long lcm_not_zero(unsigned long a, unsigned long b) __attribute_const__;
 
 #endif /* _LCM_H */
diff --git a/lib/lcm.c b/lib/lcm.c
index e97dbd5..03d7fcb 100644
--- a/lib/lcm.c
+++ b/lib/lcm.c
@@ -12,3 +12,14 @@ unsigned long lcm(unsigned long a, unsigned long b)
 		return 0;
 }
 EXPORT_SYMBOL_GPL(lcm);
+
+unsigned long lcm_not_zero(unsigned long a, unsigned long b)
+{
+	unsigned long l = lcm(a, b);
+
+	if (l)
+		return l;
+
+	return (b ? : a);
+}
+EXPORT_SYMBOL_GPL(lcm_not_zero);