[PATCH] Decrease number of pointer derefs in multipath.c

[PATCH] Decrease number of pointer derefs in multipath.c

[Jesper Juhl]

Hi,

Here's a small patch to decrease the number of pointer derefs in
drivers/md/multipath.c

Benefits of the patch:
 - Fewer pointer dereferences should make the code slightly faster.
 - Size of generated code is smaller
 - improved readability

Please consider applying.


Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
---

 drivers/md/multipath.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

orig:
   text    data     bss     dec     hex filename
   3747      68       0    3815     ee7 drivers/md/multipath.o

patched:
   text    data     bss     dec     hex filename
   3736      68       0    3804     edc drivers/md/multipath.o

--- linux-2.6.15-rc5-git1-orig/drivers/md/multipath.c	2005-12-04 18:47:49.000000000 +0100
+++ linux-2.6.15-rc5-git1/drivers/md/multipath.c	2005-12-08 21:30:57.000000000 +0100
@@ -308,6 +308,7 @@ static void print_multipath_conf (multip
 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
 {
 	multipath_conf_t *conf = mddev->private;
+	struct request_queue *q;
 	int found = 0;
 	int path;
 	struct multipath_info *p;
@@ -316,8 +317,8 @@ static int multipath_add_disk(mddev_t *m
 
 	for (path=0; path<mddev->raid_disks; path++) 
 		if ((p=conf->multipaths+path)->rdev == NULL) {
-			blk_queue_stack_limits(mddev->queue,
-					       rdev->bdev->bd_disk->queue);
+			q = rdev->bdev->bd_disk->queue;
+			blk_queue_stack_limits(mddev->queue, q);
 
 		/* as we don't honour merge_bvec_fn, we must never risk
 		 * violating it, so limit ->max_sector to one PAGE, as
@@ -325,7 +326,7 @@ static int multipath_add_disk(mddev_t *m
 		 * (Note: it is very unlikely that a device with
 		 * merge_bvec_fn will be involved in multipath.)
 		 */
-			if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
+			if (q->merge_bvec_fn &&
 			    mddev->queue->max_sectors > (PAGE_SIZE>>9))
 				blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 

Re: [PATCH] Decrease number of pointer derefs in multipath.c

[Ingo Molnar]

* Jesper Juhl <jesper.juhl@gmail.com> wrote:

> Hi,
> 
> Here's a small patch to decrease the number of pointer derefs in
> drivers/md/multipath.c
> 
> Benefits of the patch:
>  - Fewer pointer dereferences should make the code slightly faster.
>  - Size of generated code is smaller
>  - improved readability
> 
> Please consider applying.
> 
> 
> Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>

looks good to me.

Acked-by: Ingo Molnar <mingo@elte.hu>

	Ingo