[PATCH 2/2] md:Rewrite the md_write_start().

[PATCH 2/2] md:Rewrite the md_write_start().

[majianpeng]

Remove the judgement "bio_data_dir(bi) != WRITE" in md_write_start().Put
it before call md_write_start.

Signed-off-by: majianpeng <majianpeng@gmail.com>
---
 drivers/md/md.c     |    4 +---
 drivers/md/md.h     |    2 +-
 drivers/md/raid1.c  |    4 ++--
 drivers/md/raid10.c |    3 ++-
 drivers/md/raid5.c  |    3 ++-
 5 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1c2f904..e009f1d 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7198,11 +7198,9 @@ void md_done_sync(struct mddev *mddev, int blocks, int ok)
  * in superblock) before writing, schedule a superblock update
  * and wait for it to complete.
  */
-void md_write_start(struct mddev *mddev, struct bio *bi)
+void md_write_start(struct mddev *mddev)
 {
 	int did_change = 0;
-	if (bio_data_dir(bi) != WRITE)
-		return;
 
 	BUG_ON(mddev->ro == 1);
 	if (mddev->ro == 2) {
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 7b4a3c3..906e3db 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -593,7 +593,7 @@ extern struct md_thread *md_register_thread(
 extern void md_unregister_thread(struct md_thread **threadp);
 extern void md_wakeup_thread(struct md_thread *thread);
 extern void md_check_recovery(struct mddev *mddev);
-extern void md_write_start(struct mddev *mddev, struct bio *bi);
+extern void md_write_start(struct mddev *mddev);
 extern void md_write_end(struct mddev *mddev);
 extern void md_done_sync(struct mddev *mddev, int blocks, int ok);
 extern void md_error(struct mddev *mddev, struct md_rdev *rdev);
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 835de71..4bfa77d 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -893,8 +893,8 @@ static void make_request(struct mddev *mddev, struct bio * bio)
 	 * thread has put up a bar for new requests.
 	 * Continue immediately if no resync is active currently.
 	 */
-
-	md_write_start(mddev, bio); /* wait on superblock update early */
+	if (rw == WRITE)
+		md_write_start(mddev); /* wait on superblock update early */
 
 	if (bio_data_dir(bio) == WRITE &&
 	    bio->bi_sector + bio->bi_size/512 > mddev->suspend_lo &&
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 987db37..b10cb99 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1098,7 +1098,8 @@ static void make_request(struct mddev *mddev, struct bio * bio)
 		return;
 	}
 
-	md_write_start(mddev, bio);
+	if (rw == WRITE)
+		md_write_start(mddev);
 
 	/*
 	 * Register the new request and wait if the reconstruction
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5653125..8e330f8 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3983,7 +3983,8 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 	     chunk_aligned_read(mddev,bi))
 		return;
 
-	md_write_start(mddev, bi);
+	if (rw == WRITE)
+		md_write_start(mddev);
 
 	logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
 	last_sector = bi->bi_sector + (bi->bi_size>>9);
-- 
1.7.5.4



--------------
majianpeng

Re: [PATCH 2/2] md:Rewrite the md_write_start().

[Dan Williams]

On Sat, Jun 2, 2012 at 1:16 AM, majianpeng <majianpeng@gmail.com> wrote:
> Remove the judgement "bio_data_dir(bi) != WRITE" in md_write_start().Put
> it before call md_write_start.
>
> Signed-off-by: majianpeng <majianpeng@gmail.com>
> ---
>  drivers/md/md.c     |    4 +---
>  drivers/md/md.h     |    2 +-
>  drivers/md/raid1.c  |    4 ++--
>  drivers/md/raid10.c |    3 ++-
>  drivers/md/raid5.c  |    3 ++-
>  5 files changed, 8 insertions(+), 8 deletions(-)

If the deletions had outnumbered the insertions then maybe, but I
think just like kfree() allowing NULL pointers it's cleaner if the
caller need not worry.

--
Dan
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Re: Re: [PATCH 2/2] md:Rewrite the md_write_start().

[majianpeng]

On Sun, 3 Jun 2012 14:11:41 -0700, Dan Williams wrote:
>On Sat, Jun 2, 2012 at 1:16 AM, majianpeng <majianpeng@gmail.com> wrote:
>> Remove the judgement "bio_data_dir(bi) != WRITE" in md_write_start().Put
>> it before call md_write_start.
>>
>> Signed-off-by: majianpeng <majianpeng@gmail.com>
>> ---
>> ?drivers/md/md.c ? ? | ? ?4 +---
>> ?drivers/md/md.h ? ? | ? ?2 +-
>> ?drivers/md/raid1.c ?| ? ?4 ++--
>> ?drivers/md/raid10.c | ? ?3 ++-
>> ?drivers/md/raid5.c ?| ? ?3 ++-
>> ?5 files changed, 8 insertions(+), 8 deletions(-)
>
>If the deletions had outnumbered the insertions then maybe, but I
>think just like kfree() allowing NULL pointers it's cleaner if the
>caller need not worry.
>
>--
>Dan
The patch had a anthor reason: first check,if read so not call function.
Call function takes long time than check statment.

Re: [PATCH 2/2] md:Rewrite the md_write_start().

[NeilBrown]

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On Mon, 4 Jun 2012 09:03:57 +0800 majianpeng <majianpeng@gmail.com> wrote:

> On Sun, 3 Jun 2012 14:11:41 -0700, Dan Williams wrote:
> >On Sat, Jun 2, 2012 at 1:16 AM, majianpeng <majianpeng@gmail.com> wrote:
> >> Remove the judgement "bio_data_dir(bi) != WRITE" in md_write_start().Put
> >> it before call md_write_start.
> >>
> >> Signed-off-by: majianpeng <majianpeng@gmail.com>
> >> ---
> >> ?drivers/md/md.c ? ? | ? ?4 +---
> >> ?drivers/md/md.h ? ? | ? ?2 +-
> >> ?drivers/md/raid1.c ?| ? ?4 ++--
> >> ?drivers/md/raid10.c | ? ?3 ++-
> >> ?drivers/md/raid5.c ?| ? ?3 ++-
> >> ?5 files changed, 8 insertions(+), 8 deletions(-)
> >
> >If the deletions had outnumbered the insertions then maybe, but I
> >think just like kfree() allowing NULL pointers it's cleaner if the
> >caller need not worry.
> >
> >--
> >Dan
> The patch had a anthor reason: first check,if read so not call function.
> Call function takes long time than check statment.
> 

This is micro-optimisation that really isn't worth spending any time on.

NeilBrown

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