Re: [PATCH] block: modify __bio_add_page check to accept pages that don't start a new segment

2013-03-25 Thread Jan Vesely 
On Thu 07 Mar 2013 12:23:13 CET, Jan Vesely wrote:

 On Thu 21 Feb 2013 09:30:26 CET, Jan Vesely wrote:
 The original behavior was to refuse all pages after the maximum number of
 segments has been reached. However, some drivers (like st) craft their 
 buffers
 to potentially require exactly max segments and multiple pages in the last
 segment. This patch modifies the check to allow pages that can be merged into
 the last segment.

 This change fixes EBUSY failures when using large (1mb) tape block size in 
 high
 memory fragmentation condition.

 Signed-off-by: Jan Vesely jves...@redhat.com
 ---
  fs/bio.c |   26 --
  1 files changed, 16 insertions(+), 10 deletions(-)

 diff --git a/fs/bio.c b/fs/bio.c
 index b96fc6c..02efbd5 100644
 --- a/fs/bio.c
 +++ b/fs/bio.c
 @@ -500,7 +500,6 @@ static int __bio_add_page(struct request_queue *q, struct
 bio *bio, struct page
*page, unsigned int len, unsigned int offset,
unsigned short max_sectors)
  {
 -int retried_segments = 0;
  struct bio_vec *bvec;

  /*
 @@ -551,18 +550,12 @@ static int __bio_add_page(struct request_queue *q,
 struct bio *bio, struct page
  return 0;

  /*
 - * we might lose a segment or two here, but rather that than
 - * make this too complex.
 + * prepare segment count check, reduce segment count if possible
   */

 -while (bio-bi_phys_segments = queue_max_segments(q)) {
 -
 -if (retried_segments)
 -return 0;
 -
 -retried_segments = 1;
 +if (bio-bi_phys_segments = queue_max_segments(q))
  blk_recount_segments(q, bio);
 -}
 +

  /*
   * setup the new entry, we might clear it again later if we
 @@ -572,6 +565,19 @@ static int __bio_add_page(struct request_queue *q, 
 struct
 bio *bio, struct page
  bvec-bv_page = page;
  bvec-bv_len = len;
  bvec-bv_offset = offset;
 +
 +/*
 + * the other part of the segment count check, allow mergeable pages
 + */
 +if ((bio-bi_phys_segments  queue_max_segments(q)) ||
 +( (bio-bi_phys_segments == queue_max_segments(q)) 
 +!BIOVEC_PHYS_MERGEABLE(bvec - 1, bvec))) {
 +bvec-bv_page = NULL;
 +bvec-bv_len = 0;
 +bvec-bv_offset = 0;
 +return 0;
 +}
 +

  /*
   * if queue has other restrictions (eg varying max sector size

ping?

The described failure is a regression introduced in
46081b166415acb66d4b3150ecefcd9460bb48a1
st: Increase success probability in driver buffer allocation

I have added the signers to cc. I can resend the patch if it is 
necessary

thank you,

--
Jan Vesely jves...@redhat.com
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Re: [PATCH] block: modify __bio_add_page check to accept pages that don't start a new segment

2013-03-25 Thread Jens Axboe 
On Mon, Mar 25 2013, Jan Vesely wrote:
 On Thu 07 Mar 2013 12:23:13 CET, Jan Vesely wrote:
 
  On Thu 21 Feb 2013 09:30:26 CET, Jan Vesely wrote:
  The original behavior was to refuse all pages after the maximum number of
  segments has been reached. However, some drivers (like st) craft their 
  buffers
  to potentially require exactly max segments and multiple pages in the last
  segment. This patch modifies the check to allow pages that can be merged 
  into
  the last segment.
 
  This change fixes EBUSY failures when using large (1mb) tape block size in 
  high
  memory fragmentation condition.
 
  Signed-off-by: Jan Vesely jves...@redhat.com
  ---
   fs/bio.c |   26 --
   1 files changed, 16 insertions(+), 10 deletions(-)
 
  diff --git a/fs/bio.c b/fs/bio.c
  index b96fc6c..02efbd5 100644
  --- a/fs/bio.c
  +++ b/fs/bio.c
  @@ -500,7 +500,6 @@ static int __bio_add_page(struct request_queue *q, 
  struct
  bio *bio, struct page
 *page, unsigned int len, unsigned int offset,
 unsigned short max_sectors)
   {
  -int retried_segments = 0;
   struct bio_vec *bvec;
 
   /*
  @@ -551,18 +550,12 @@ static int __bio_add_page(struct request_queue *q,
  struct bio *bio, struct page
   return 0;
 
   /*
  - * we might lose a segment or two here, but rather that than
  - * make this too complex.
  + * prepare segment count check, reduce segment count if possible
*/
 
  -while (bio-bi_phys_segments = queue_max_segments(q)) {
  -
  -if (retried_segments)
  -return 0;
  -
  -retried_segments = 1;
  +if (bio-bi_phys_segments = queue_max_segments(q))
   blk_recount_segments(q, bio);
  -}
  +
 
   /*
* setup the new entry, we might clear it again later if we
  @@ -572,6 +565,19 @@ static int __bio_add_page(struct request_queue *q, 
  struct
  bio *bio, struct page
   bvec-bv_page = page;
   bvec-bv_len = len;
   bvec-bv_offset = offset;
  +
  +/*
  + * the other part of the segment count check, allow mergeable pages
  + */
  +if ((bio-bi_phys_segments  queue_max_segments(q)) ||
  +( (bio-bi_phys_segments == queue_max_segments(q)) 
  +!BIOVEC_PHYS_MERGEABLE(bvec - 1, bvec))) {
  +bvec-bv_page = NULL;
  +bvec-bv_len = 0;
  +bvec-bv_offset = 0;
  +return 0;
  +}
  +
 
   /*
* if queue has other restrictions (eg varying max sector size
 
 ping?
 
 The described failure is a regression introduced in
 46081b166415acb66d4b3150ecefcd9460bb48a1
 st: Increase success probability in driver buffer allocation
 
 I have added the signers to cc. I can resend the patch if it is 
 necessary

Can you resend the patch? The above is mangled for me.

-- 
Jens Axboe

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Re: [PATCH] block: modify __bio_add_page check to accept pages that don't start a new segment

2013-03-07 Thread Jan Vesely 

Hi Jens,

I have added you to cc, I'm not sure who to bug to get this patch 
merged.


thanks,
Jan Vesely

On Thu 21 Feb 2013 09:30:26 CET, Jan Vesely wrote:

The original behavior was to refuse all pages after the maximum number of
segments has been reached. However, some drivers (like st) craft their buffers
to potentially require exactly max segments and multiple pages in the last
segment. This patch modifies the check to allow pages that can be merged into
the last segment.

This change fixes EBUSY failures when using large (1mb) tape block size in high
memory fragmentation condition.

Signed-off-by: Jan Vesely jves...@redhat.com
---
 fs/bio.c |   26 --
 1 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/bio.c b/fs/bio.c
index b96fc6c..02efbd5 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -500,7 +500,6 @@ static int __bio_add_page(struct request_queue *q, struct
bio *bio, struct page
   *page, unsigned int len, unsigned int offset,
   unsigned short max_sectors)
 {
-int retried_segments = 0;
 struct bio_vec *bvec;

 /*
@@ -551,18 +550,12 @@ static int __bio_add_page(struct request_queue *q,
struct bio *bio, struct page
 return 0;

 /*
- * we might lose a segment or two here, but rather that than
- * make this too complex.
+ * prepare segment count check, reduce segment count if possible
  */

-while (bio-bi_phys_segments = queue_max_segments(q)) {
-
-if (retried_segments)
-return 0;
-
-retried_segments = 1;
+if (bio-bi_phys_segments = queue_max_segments(q))
 blk_recount_segments(q, bio);
-}
+

 /*
  * setup the new entry, we might clear it again later if we
@@ -572,6 +565,19 @@ static int __bio_add_page(struct request_queue *q, struct
bio *bio, struct page
 bvec-bv_page = page;
 bvec-bv_len = len;
 bvec-bv_offset = offset;
+
+/*
+ * the other part of the segment count check, allow mergeable pages
+ */
+if ((bio-bi_phys_segments  queue_max_segments(q)) ||
+( (bio-bi_phys_segments == queue_max_segments(q)) 
+!BIOVEC_PHYS_MERGEABLE(bvec - 1, bvec))) {
+bvec-bv_page = NULL;
+bvec-bv_len = 0;
+bvec-bv_offset = 0;
+return 0;
+}
+

 /*
  * if queue has other restrictions (eg varying max sector size


--
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[PATCH] block: modify __bio_add_page check to accept pages that don't start a new segment

2013-02-21 Thread Jan Vesely 

The original behavior was to refuse all pages after the maximum number of
segments has been reached. However, some drivers (like st) craft their buffers
to potentially require exactly max segments and multiple pages in the last
segment. This patch modifies the check to allow pages that can be merged into
the last segment.

This change fixes EBUSY failures when using large (1mb) tape block size in high
memory fragmentation condition.

Signed-off-by: Jan Vesely jves...@redhat.com
---
 fs/bio.c |   26 --
 1 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/bio.c b/fs/bio.c
index b96fc6c..02efbd5 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -500,7 +500,6 @@ static int __bio_add_page(struct request_queue *q, struct 
bio *bio, struct page

  *page, unsigned int len, unsigned int offset,
  unsigned short max_sectors)
 {
-   int retried_segments = 0;
struct bio_vec *bvec;

/*
@@ -551,18 +550,12 @@ static int __bio_add_page(struct request_queue *q, struct 
bio *bio, struct page

return 0;

/*
-* we might lose a segment or two here, but rather that than
-* make this too complex.
+* prepare segment count check, reduce segment count if possible
 */

-   while (bio-bi_phys_segments = queue_max_segments(q)) {
-
-   if (retried_segments)
-   return 0;
-
-   retried_segments = 1;
+   if (bio-bi_phys_segments = queue_max_segments(q))
blk_recount_segments(q, bio);
-   }
+

/*
 * setup the new entry, we might clear it again later if we
@@ -572,6 +565,19 @@ static int __bio_add_page(struct request_queue *q, struct 
bio *bio, struct page

bvec-bv_page = page;
bvec-bv_len = len;
bvec-bv_offset = offset;
+   
+   /*
+* the other part of the segment count check, allow mergeable pages
+*/
+   if ((bio-bi_phys_segments  queue_max_segments(q)) ||
+   ( (bio-bi_phys_segments == queue_max_segments(q)) 
+   !BIOVEC_PHYS_MERGEABLE(bvec - 1, bvec))) {
+   bvec-bv_page = NULL;
+   bvec-bv_len = 0;
+   bvec-bv_offset = 0;
+   return 0;
+   }
+

/*
 * if queue has other restrictions (eg varying max sector size
--
1.7.1
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