[4/4] md: fast clone bio in bio_clone_mddev()
diff mbox

Message ID 1486275733-7268-5-git-send-email-tom.leiming@gmail.com
State New
Headers show

Commit Message

Ming Lei Feb. 5, 2017, 6:22 a.m. UTC
Firstly bio_clone_mddev() is used in raid normal I/O and isn't
in resync I/O path.

Secondly all the direct access to bvec table in raid happens on
resync I/O except for write behind of raid1, in which we still
use bio_clone() for allocating new bvec table.

So this patch replaces bio_clone() with bio_clone_fast()
in bio_clone_mddev().

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/md/md.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Christoph Hellwig Feb. 6, 2017, 8:54 a.m. UTC | #1
On Sun, Feb 05, 2017 at 02:22:13PM +0800, Ming Lei wrote:
> Firstly bio_clone_mddev() is used in raid normal I/O and isn't
> in resync I/O path.
> 
> Secondly all the direct access to bvec table in raid happens on
> resync I/O except for write behind of raid1, in which we still
> use bio_clone() for allocating new bvec table.
> 
> So this patch replaces bio_clone() with bio_clone_fast()
> in bio_clone_mddev().

Having the _fast in the name would be really useful for the
reader.  And as far as I can tell in the callers mddev is never
NULL and neither is ->bio_set, so replacing bio_clone_mddev with
raw calls to bio_clone_fast would be my preference.
Ming Lei Feb. 6, 2017, 10:43 a.m. UTC | #2
On Mon, Feb 6, 2017 at 4:54 PM, Christoph Hellwig <hch@infradead.org> wrote:
> On Sun, Feb 05, 2017 at 02:22:13PM +0800, Ming Lei wrote:
>> Firstly bio_clone_mddev() is used in raid normal I/O and isn't
>> in resync I/O path.
>>
>> Secondly all the direct access to bvec table in raid happens on
>> resync I/O except for write behind of raid1, in which we still
>> use bio_clone() for allocating new bvec table.
>>
>> So this patch replaces bio_clone() with bio_clone_fast()
>> in bio_clone_mddev().
>
> Having the _fast in the name would be really useful for the
> reader.  And as far as I can tell in the callers mddev is never
> NULL and neither is ->bio_set, so replacing bio_clone_mddev with

In theory, ->bio_set still might be NULL in case of failed memory allocation,
please see md_run().

> raw calls to bio_clone_fast would be my preference.



Thanks,
Ming Lei
Christoph Hellwig Feb. 6, 2017, 2:24 p.m. UTC | #3
On Mon, Feb 06, 2017 at 06:43:32PM +0800, Ming Lei wrote:
> In theory, ->bio_set still might be NULL in case of failed memory allocation,
> please see md_run().

And that's something that should be fixed.  Silently not having mempool
is very bad behavior.

Patch
diff mbox

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 704be11355a9..7d176f025add 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -193,10 +193,14 @@  EXPORT_SYMBOL_GPL(bio_alloc_mddev);
 struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
 			    struct mddev *mddev)
 {
+	struct bio_set *bs;
+
 	if (!mddev || !mddev->bio_set)
-		return bio_clone(bio, gfp_mask);
+		bs = fs_bio_set;
+	else
+		bs = mddev->bio_set;
 
-	return bio_clone_bioset(bio, gfp_mask, mddev->bio_set);
+	return bio_clone_fast(bio, gfp_mask, bs);
 }
 EXPORT_SYMBOL_GPL(bio_clone_mddev);