block: Add bio_reset()
 

From: Kent Overstreet <koverstreet@google.com>

Reusing bios is something that's been highly frowned upon in the past,
but driver code keeps doing it anyways. If it's going to happen anyways,
we should provide a generic method.

This'll help with getting rid of bi_destructor.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
---
fs/bio.c | 8 ++++++++
include/linux/bio.h | 1 +
include/linux/blk_types.h | 6 ++++++
3 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/fs/bio.c b/fs/bio.c
index de0733e..90e4c3a 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -259,6 +259,14 @@ void bio_init(struct bio *bio)
}
EXPORT_SYMBOL(bio_init);

+void bio_reset(struct bio *bio)
+{
+ memset(bio, 0, BIO_RESET_OFFSET);
+ bio->bi_flags = 1 << BIO_UPTODATE;
+
+}
+EXPORT_SYMBOL(bio_reset);
+
/**
* bio_alloc_bioset - allocate a bio for I/O
* @gfp_mask: the GFP_ mask given to the slab allocator
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b27f16b..35f7c4d 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -228,6 +228,7 @@ extern struct bio *bio_clone(struct bio *, gfp_t);
struct bio *bio_clone_kmalloc(struct bio *, gfp_t);

extern void bio_init(struct bio *);
+extern void bio_reset(struct bio *);

extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dc0e399..4a47783 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -57,6 +57,10 @@ struct bio {
unsigned int bi_seg_front_size;
unsigned int bi_seg_back_size;

+ /*
+ * Everything starting with bi_max_vecs will be preserved by bio_reset()
+ */
+
unsigned int bi_max_vecs; /* max bvl_vecs we can hold */

atomic_t bi_cnt; /* pin count */
@@ -83,6 +87,8 @@ struct bio {
struct bio_vec bi_inline_vecs[0];
};

+#define BIO_RESET_OFFSET offsetof(struct bio, bi_max_vecs)
+
/*
* bio flags
*/
--
1.7.9.rc2

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block: Add bio_reset()
 

Hello,

On Thu, May 17, 2012 at 10:59:53PM -0400, koverstreet@google.com wrote:
> From: Kent Overstreet <koverstreet@google.com>
>
> Reusing bios is something that's been highly frowned upon in the past,
> but driver code keeps doing it anyways. If it's going to happen anyways,
> we should provide a generic method.
>
> This'll help with getting rid of bi_destructor.

It would be nice to explain a bit why this helps bi_destructor
removal.

> +#define BIO_RESET_OFFSET offsetof(struct bio, bi_max_vecs)

Maybe better named BIO_RESET_BYTES? As offset tends to indicate the
start of a region.

Thanks.

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block: Add bio_reset()
 

On Fri, May 18, 2012 at 09:16:08AM -0700, Tejun Heo wrote:
> Hello,
>
> On Thu, May 17, 2012 at 10:59:53PM -0400, koverstreet@google.com wrote:
> > From: Kent Overstreet <koverstreet@google.com>
> >
> > Reusing bios is something that's been highly frowned upon in the past,
> > but driver code keeps doing it anyways. If it's going to happen anyways,
> > we should provide a generic method.
> >
> > This'll help with getting rid of bi_destructor.
>
> It would be nice to explain a bit why this helps bi_destructor
> removal.

drivers/block/pktcdvd.c was open coding this - it was doing a bio_init()
and then resetting bi_destructor (and other stuff). The generic
bio_reset() means it doesn't have to know about bi_destructor anymore.

>
> > +#define BIO_RESET_OFFSET offsetof(struct bio, bi_max_vecs)
>
> Maybe better named BIO_RESET_BYTES? As offset tends to indicate the
> start of a region.

Yeah, that's a better name.

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block: Add bio_reset()
 

Reusing bios is something that's been highly frowned upon in the past,
but driver code keeps doing it anyways. If it's going to happen anyways,
we should provide a generic method.

This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
was open coding it, by doing a bio_init() and resetting bi_destructor.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
Change-Id: Ib0a43dfcb3f6c22a54da513d4a86be544b5ffd95
---
fs/bio.c | 8 ++++++++
include/linux/bio.h | 1 +
include/linux/blk_types.h | 6 ++++++
3 files changed, 15 insertions(+)

diff --git a/fs/bio.c b/fs/bio.c
index de0733e..7d8c29d 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -259,6 +259,14 @@ void bio_init(struct bio *bio)
}
EXPORT_SYMBOL(bio_init);

+void bio_reset(struct bio *bio)
+{
+ memset(bio, 0, BIO_RESET_BYTES);
+ bio->bi_flags = 1 << BIO_UPTODATE;
+
+}
+EXPORT_SYMBOL(bio_reset);
+
/**
* bio_alloc_bioset - allocate a bio for I/O
* @gfp_mask: the GFP_ mask given to the slab allocator
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b27f16b..35f7c4d 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -228,6 +228,7 @@ extern struct bio *bio_clone(struct bio *, gfp_t);
struct bio *bio_clone_kmalloc(struct bio *, gfp_t);

extern void bio_init(struct bio *);
+extern void bio_reset(struct bio *);

extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dc0e399..6b7daf3 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -57,6 +57,10 @@ struct bio {
unsigned int bi_seg_front_size;
unsigned int bi_seg_back_size;

+ /*
+ * Everything starting with bi_max_vecs will be preserved by bio_reset()
+ */
+
unsigned int bi_max_vecs; /* max bvl_vecs we can hold */

atomic_t bi_cnt; /* pin count */
@@ -83,6 +87,8 @@ struct bio {
struct bio_vec bi_inline_vecs[0];
};

+#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
+
/*
* bio flags
*/
--
1.7.9.3.327.g2980b

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block: Add bio_reset()
 

Reusing bios is something that's been highly frowned upon in the past,
but driver code keeps doing it anyways. If it's going to happen anyways,
we should provide a generic method.

This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
was open coding it, by doing a bio_init() and resetting bi_destructor.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
Change-Id: Ib0a43dfcb3f6c22a54da513d4a86be544b5ffd95
---
fs/bio.c | 8 ++++++++
include/linux/bio.h | 1 +
include/linux/blk_types.h | 6 ++++++
3 files changed, 15 insertions(+)

diff --git a/fs/bio.c b/fs/bio.c
index 3667cef..240da21 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -259,6 +259,14 @@ void bio_init(struct bio *bio)
}
EXPORT_SYMBOL(bio_init);

+void bio_reset(struct bio *bio)
+{
+ memset(bio, 0, BIO_RESET_BYTES);
+ bio->bi_flags = 1 << BIO_UPTODATE;
+
+}
+EXPORT_SYMBOL(bio_reset);
+
/**
* bio_alloc_bioset - allocate a bio for I/O
* @gfp_mask: the GFP_ mask given to the slab allocator
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 4d94eb8..e5c2504 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -226,6 +226,7 @@ extern void __bio_clone(struct bio *, struct bio *);
extern struct bio *bio_clone(struct bio *, gfp_t);

extern void bio_init(struct bio *);
+extern void bio_reset(struct bio *);

extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dc0e399..6b7daf3 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -57,6 +57,10 @@ struct bio {
unsigned int bi_seg_front_size;
unsigned int bi_seg_back_size;

+ /*
+ * Everything starting with bi_max_vecs will be preserved by bio_reset()
+ */
+
unsigned int bi_max_vecs; /* max bvl_vecs we can hold */

atomic_t bi_cnt; /* pin count */
@@ -83,6 +87,8 @@ struct bio {
struct bio_vec bi_inline_vecs[0];
};

+#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
+
/*
* bio flags
*/
--
1.7.9.3.327.g2980b

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block: Add bio_reset()
 

On Fri, May 25, 2012 at 01:25:26PM -0700, Kent Overstreet wrote:
> Reusing bios is something that's been highly frowned upon in the past,
> but driver code keeps doing it anyways. If it's going to happen anyways,
> we should provide a generic method.
>
> This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
> was open coding it, by doing a bio_init() and resetting bi_destructor.
>
> Signed-off-by: Kent Overstreet <koverstreet@google.com>
> Change-Id: Ib0a43dfcb3f6c22a54da513d4a86be544b5ffd95
> ---
> fs/bio.c | 8 ++++++++
> include/linux/bio.h | 1 +
> include/linux/blk_types.h | 6 ++++++
> 3 files changed, 15 insertions(+)
>
> diff --git a/fs/bio.c b/fs/bio.c
> index 3667cef..240da21 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -259,6 +259,14 @@ void bio_init(struct bio *bio)
> }
> EXPORT_SYMBOL(bio_init);
>

Function comment please.

> +void bio_reset(struct bio *bio)
> +{
> + memset(bio, 0, BIO_RESET_BYTES);
> + bio->bi_flags = 1 << BIO_UPTODATE;
> +
> +}
> +EXPORT_SYMBOL(bio_reset);

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block: Add bio_reset()
 

On 05/28/2012 04:23 AM, Tejun Heo wrote:

> On Fri, May 25, 2012 at 01:25:26PM -0700, Kent Overstreet wrote:
>> Reusing bios is something that's been highly frowned upon in the past,
>> but driver code keeps doing it anyways. If it's going to happen anyways,
>> we should provide a generic method.
>>
>> This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
>> was open coding it, by doing a bio_init() and resetting bi_destructor.
>>
>> Signed-off-by: Kent Overstreet <koverstreet@google.com>
>> Change-Id: Ib0a43dfcb3f6c22a54da513d4a86be544b5ffd95
>> ---
>> fs/bio.c | 8 ++++++++
>> include/linux/bio.h | 1 +
>> include/linux/blk_types.h | 6 ++++++
>> 3 files changed, 15 insertions(+)
>>
>> diff --git a/fs/bio.c b/fs/bio.c
>> index 3667cef..240da21 100644
>> --- a/fs/bio.c
>> +++ b/fs/bio.c
>> @@ -259,6 +259,14 @@ void bio_init(struct bio *bio)
>> }
>> EXPORT_SYMBOL(bio_init);
>>
>
> Function comment please.


And please make this inline in header. We should not
EXPORT_SYMBOL a memset. (Even the memset gets inlined by
compiler.

Boaz

>
>> +void bio_reset(struct bio *bio)
>> +{
>> + memset(bio, 0, BIO_RESET_BYTES);
>> + bio->bi_flags = 1 << BIO_UPTODATE;
>> +
>> +}
>> +EXPORT_SYMBOL(bio_reset);
>


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block: Add bio_reset()
 

Reusing bios is something that's been highly frowned upon in the past,
but driver code keeps doing it anyways. If it's going to happen anyways,
we should provide a generic method.

This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
was open coding it, by doing a bio_init() and resetting bi_destructor.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
---
fs/bio.c | 10 ++++++++++
include/linux/bio.h | 1 +
include/linux/blk_types.h | 6 ++++++
3 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/fs/bio.c b/fs/bio.c
index 1c6c8b7..252e253 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -261,6 +261,16 @@ void bio_init(struct bio *bio)
}
EXPORT_SYMBOL(bio_init);

+void bio_reset(struct bio *bio)
+{
+ /* Clear all flags below BIO_OWNS_VEC */
+ unsigned long flags = bio->bi_flags & (~0UL << BIO_OWNS_VEC);
+
+ memset(bio, 0, BIO_RESET_BYTES);
+ bio->bi_flags = flags|(1 << BIO_UPTODATE);
+}
+EXPORT_SYMBOL(bio_reset);
+
/**
* bio_alloc_bioset - allocate a bio for I/O
* @gfp_mask: the GFP_ mask given to the slab allocator
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 2643589..ba60319 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -226,6 +226,7 @@ extern void __bio_clone(struct bio *, struct bio *);
extern struct bio *bio_clone(struct bio *, gfp_t);

extern void bio_init(struct bio *);
+extern void bio_reset(struct bio *);

extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 293547e..40411e2 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -59,6 +59,10 @@ struct bio {
unsigned int bi_seg_front_size;
unsigned int bi_seg_back_size;

+ /*
+ * Everything starting with bi_max_vecs will be preserved by bio_reset()
+ */
+
unsigned int bi_max_vecs; /* max bvl_vecs we can hold */

atomic_t bi_cnt; /* pin count */
@@ -93,6 +97,8 @@ struct bio {
struct bio_vec bi_inline_vecs[0];
};

+#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
+
/*
* bio flags
*/
--
1.7.7.3

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block: Add bio_reset()
 

On 07/24/2012 11:11 PM, Kent Overstreet wrote:

> Reusing bios is something that's been highly frowned upon in the past,
> but driver code keeps doing it anyways. If it's going to happen anyways,
> we should provide a generic method.
>
> This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
> was open coding it, by doing a bio_init() and resetting bi_destructor.
>
> Signed-off-by: Kent Overstreet <koverstreet@google.com>
> ---
> fs/bio.c | 10 ++++++++++
> include/linux/bio.h | 1 +
> include/linux/blk_types.h | 6 ++++++
> 3 files changed, 17 insertions(+), 0 deletions(-)
>
> diff --git a/fs/bio.c b/fs/bio.c
> index 1c6c8b7..252e253 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -261,6 +261,16 @@ void bio_init(struct bio *bio)
> }
> EXPORT_SYMBOL(bio_init);
>
> +void bio_reset(struct bio *bio)
> +{
> + /* Clear all flags below BIO_OWNS_VEC */
> + unsigned long flags = bio->bi_flags & (~0UL << BIO_OWNS_VEC);
> +


Hey I have not seen these FLAGS thing before. Are these new?

Anyway. Please NO!!! for one you need to put a big fat comment
over at flags definitions. And two what happens when one adds
a new flag. Is it reset or not reset?

I'd rather you define a flags mask for those that need to be
preserved, at header, plus a comment that any needed-to-be-preserved
cross init flags, must be added to the mask.

Never, ever, hide such crap so deep in the code.

Boaz

> + memset(bio, 0, BIO_RESET_BYTES);
> + bio->bi_flags = flags|(1 << BIO_UPTODATE);
> +}
> +EXPORT_SYMBOL(bio_reset);
> +
> /**
> * bio_alloc_bioset - allocate a bio for I/O
> * @gfp_mask: the GFP_ mask given to the slab allocator
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 2643589..ba60319 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -226,6 +226,7 @@ extern void __bio_clone(struct bio *, struct bio *);
> extern struct bio *bio_clone(struct bio *, gfp_t);
>
> extern void bio_init(struct bio *);
> +extern void bio_reset(struct bio *);
>
> extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
> extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 293547e..40411e2 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -59,6 +59,10 @@ struct bio {
> unsigned int bi_seg_front_size;
> unsigned int bi_seg_back_size;
>
> + /*
> + * Everything starting with bi_max_vecs will be preserved by bio_reset()
> + */
> +
> unsigned int bi_max_vecs; /* max bvl_vecs we can hold */
>
> atomic_t bi_cnt; /* pin count */
> @@ -93,6 +97,8 @@ struct bio {
> struct bio_vec bi_inline_vecs[0];
> };
>
> +#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
> +
> /*
> * bio flags
> */


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block: Add bio_reset()
 

On Wed, Jul 25, 2012 at 02:19:27PM +0300, Boaz Harrosh wrote:
> On 07/24/2012 11:11 PM, Kent Overstreet wrote:
>
> > Reusing bios is something that's been highly frowned upon in the past,
> > but driver code keeps doing it anyways. If it's going to happen anyways,
> > we should provide a generic method.
> >
> > This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
> > was open coding it, by doing a bio_init() and resetting bi_destructor.
> >
> > Signed-off-by: Kent Overstreet <koverstreet@google.com>
> > ---
> > fs/bio.c | 10 ++++++++++
> > include/linux/bio.h | 1 +
> > include/linux/blk_types.h | 6 ++++++
> > 3 files changed, 17 insertions(+), 0 deletions(-)
> >
> > diff --git a/fs/bio.c b/fs/bio.c
> > index 1c6c8b7..252e253 100644
> > --- a/fs/bio.c
> > +++ b/fs/bio.c
> > @@ -261,6 +261,16 @@ void bio_init(struct bio *bio)
> > }
> > EXPORT_SYMBOL(bio_init);
> >
> > +void bio_reset(struct bio *bio)
> > +{
> > + /* Clear all flags below BIO_OWNS_VEC */
> > + unsigned long flags = bio->bi_flags & (~0UL << BIO_OWNS_VEC);
> > +
>
>
> Hey I have not seen these FLAGS thing before. Are these new?
>
> Anyway. Please NO!!! for one you need to put a big fat comment
> over at flags definitions. And two what happens when one adds
> a new flag. Is it reset or not reset?
>
> I'd rather you define a flags mask for those that need to be
> preserved, at header, plus a comment that any needed-to-be-preserved
> cross init flags, must be added to the mask.

Yeah, that's a much better idea. Do you think this is clear enough?

diff --git a/fs/bio.c b/fs/bio.c
index 1c6c8b7..c7f3442 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -261,6 +261,15 @@ void bio_init(struct bio *bio)
}
EXPORT_SYMBOL(bio_init);

+void bio_reset(struct bio *bio)
+{
+ unsigned long flags = bio->bi_flags & (~0UL << BIO_RESET_BITS);
+
+ memset(bio, 0, BIO_RESET_BYTES);
+ bio->bi_flags = flags|(1 << BIO_UPTODATE);
+}
+EXPORT_SYMBOL(bio_reset);
+
/**
* bio_alloc_bioset - allocate a bio for I/O
* @gfp_mask: the GFP_ mask given to the slab allocator
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 2643589..ba60319 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -226,6 +226,7 @@ extern void __bio_clone(struct bio *, struct bio *);
extern struct bio *bio_clone(struct bio *, gfp_t);

extern void bio_init(struct bio *);
+extern void bio_reset(struct bio *);

extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 293547e..769799f 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -59,6 +59,10 @@ struct bio {
unsigned int bi_seg_front_size;
unsigned int bi_seg_back_size;

+ /*
+ * Everything starting with bi_max_vecs will be preserved by bio_reset()
+ */
+
unsigned int bi_max_vecs; /* max bvl_vecs we can hold */

atomic_t bi_cnt; /* pin count */
@@ -93,6 +97,8 @@ struct bio {
struct bio_vec bi_inline_vecs[0];
};

+#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
+
/*
* bio flags
*/
@@ -108,6 +114,9 @@ struct bio {
#define BIO_FS_INTEGRITY 9 /* fs owns integrity data, not block layer */
#define BIO_QUIET 10 /* Make BIO Quiet */
#define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
+
+#define BIO_RESET_BITS 12 /* Flags starting here get preserved by bio_reset() */
+
#define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))

/*

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