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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>
This commit is contained in:
Martin K. Petersen 2009-07-31 11:49:12 -04:00 committed by Jens Axboe
parent 7c958e3264
commit 70dd5bf3b9
1 changed files with 11 additions and 0 deletions
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11
block/blk-settings.c
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@ -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"
@ -520,6 +521,16 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
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;
}
EXPORT_SYMBOL(blk_stack_limits);