block: Stack optimal I/O size

When stacking block devices ensure that optimal I/O size is scaled accordingly. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block: Stack optimal I/O size
When stacking block devices ensure that optimal I/O size is scaled accordingly. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Martin K. Petersen · Jens Axboe
1 parent 7c958e3264
Showing 1 changed file with 11 additions and 0 deletions Side-by-side Diff
block/blk-settings.c
@@ -7,6 +7,7 @@
 #include <linux/bio.h>
 #include <linux/blkdev.h>
 #include <linux/bootmem.h>	/* for max_pfn/max_low_pfn */
+#include <linux/gcd.h>
  
 #include "blk.h"
  
@@ -519,6 +520,16 @@
 		t->misaligned = 1;
 		return -1;
 	}
+
+	/* Find lcm() of optimal I/O size */
+	if (t->io_opt && b->io_opt)
+		t->io_opt = (t->io_opt * b->io_opt) / gcd(t->io_opt, b->io_opt);
+	else if (b->io_opt)
+		t->io_opt = b->io_opt;
+
+	/* Verify that optimal I/O size is a multiple of io_min */
+	if (t->io_min && t->io_opt % t->io_min)
+		return -1;
  
 	return 0;
 }
...	...	@@ -7,6 +7,7 @@
7	7	#include <linux/bio.h>
8	8	#include <linux/blkdev.h>
9	9	#include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
	10	+#include <linux/gcd.h>
10	11
11	12	#include "blk.h"
12	13
...	...	@@ -519,6 +520,16 @@
519	520	t->misaligned = 1;
520	521	return -1;
521	522	}
	523	+
	524	+ /* Find lcm() of optimal I/O size */
	525	+ if (t->io_opt && b->io_opt)
	526	+ t->io_opt = (t->io_opt * b->io_opt) / gcd(t->io_opt, b->io_opt);
	527	+ else if (b->io_opt)
	528	+ t->io_opt = b->io_opt;
	529	+
	530	+ /* Verify that optimal I/O size is a multiple of io_min */
	531	+ if (t->io_min && t->io_opt % t->io_min)
	532	+ return -1;
522	533
523	534	return 0;
524	535	}