[PATCH] additional bio list helpers

[PATCH] additional bio list helpers

[Bryn M. Reeves]

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Add a couple of extra helper routines to drivers/md/dm-bio-list.h. This
patch is required for the current dm-loop patch.

Kind regards,

Bryn.
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Add additional bio list helpers to dm-bio-list.h:

bio_list_empty
bio_list_nr
bio_list_join
bio_list_join_init
bio_list_merge_init
bio_list_push

These are used by dm-loop for manipulating lists of bios to be
resubmitted by the fs I/O code.

Signed-off-by: Heinz Mauelshagen <hjm@redhat.com>
Signed-off-by: Bryn Reeves <breeves@redhat.com>

===================================================================
diff --git a/drivers/md/dm-bio-list.h b/drivers/md/dm-bio-list.h
index da43496..301efae 100644
--- a/drivers/md/dm-bio-list.h
+++ b/drivers/md/dm-bio-list.h
@@ -14,11 +14,33 @@ struct bio_list {
 	struct bio *tail;
 };
 
+static inline int  bio_list_empty(struct bio_list *bl)
+{
+	return bl->head == NULL && bl->tail == NULL;
+}
+
+#define BIO_LIST_HEAD(bl)	struct bio_list bl = { NULL, NULL }
+
 static inline void bio_list_init(struct bio_list *bl)
 {
 	bl->head = bl->tail = NULL;
 }
 
+#define bio_for_each(bio, bl) \
+	for (bio = (bl)->head; bio; bio = bio->bi_next)
+
+static inline int bio_list_nr(struct bio_list *bl)
+{
+	int i=0;
+	struct bio *bio;
+
+	if(bio_list_empty(bl))
+		return i;
+	bio_for_each(bio, bl)
+		i++;
+	return i;
+}
+
 static inline void bio_list_add(struct bio_list *bl, struct bio *bio)
 {
 	bio->bi_next = NULL;
@@ -33,9 +55,6 @@ static inline void bio_list_add(struct bio_list *bl, struct bio *bio)
 
 static inline void bio_list_merge(struct bio_list *bl, struct bio_list *bl2)
 {
-	if (!bl2->head)
-		return;
-
 	if (bl->tail)
 		bl->tail->bi_next = bl2->head;
 	else
@@ -58,6 +77,40 @@ static inline void bio_list_merge_head(struct bio_list *bl,
 	bl->head = bl2->head;
 }
 
+static inline void bio_list_join(struct bio_list *bl, struct bio_list *bl2)
+{
+	if (bio_list_empty(bl2))
+		return;
+
+	bl2->tail->bi_next = bl->head;
+	bl->head = bl2->head;
+
+	if (!bl->tail)
+		bl->tail = bl2->tail;
+}
+
+static inline void bio_list_join_init(struct bio_list *bl, struct bio_list *bl2)
+{
+	bio_list_join(bl, bl2);
+	bio_list_init(bl2);
+}
+
+static inline void bio_list_merge_init(struct bio_list *bl,
+				       struct bio_list *bl2)
+{
+	bio_list_merge(bl, bl2);
+	bio_list_init(bl2);
+}
+
+static inline void bio_list_push(struct bio_list *bl, struct bio *bio)
+{
+	bio->bi_next = bl->head;
+	bl->head = bio;
+
+	if (!bl->tail)
+		bl->tail = bio;
+}
+
 static inline struct bio *bio_list_pop(struct bio_list *bl)
 {
 	struct bio *bio = bl->head;

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Re: [PATCH] additional bio list helpers

[Kiyoshi Ueda]

Hi Bryn,

On Tue, 06 Feb 2007 11:00:15 +0000, "Bryn M. Reeves" <breeves@redhat.com> wrote:
> @@ -33,9 +55,6 @@ static inline void bio_list_add(struct bio_list *bl, struct bio *bio)
>  
>  static inline void bio_list_merge(struct bio_list *bl, struct bio_list *bl2)
>  {
> -	if (!bl2->head)
> -		return;
> -
>  	if (bl->tail)
>  		bl->tail->bi_next = bl2->head;
>  	else

This one breaks the bio_list if bl2 is a empty list.
Probably missed to add like below?
-----------------------------------
+	if (bio_list_empty(bl2))
+		return;
-----------------------------------

Other small comments are below:

> @@ -14,11 +14,33 @@ struct bio_list {
>  	struct bio *tail;
>  };
>  
> +static inline int  bio_list_empty(struct bio_list *bl)
> +{
> +	return bl->head == NULL && bl->tail == NULL;
> +}

I think that bl->tail is always NULL when bl->head is NULL,
unless the bio_list is corrupted.  So no need to check bl->tail.

> +#define bio_for_each(bio, bl) \
> +	for (bio = (bl)->head; bio; bio = bio->bi_next)
> +
> +static inline int bio_list_nr(struct bio_list *bl)
> +{
> +	int i=0;
> +	struct bio *bio;
> +
> +	if(bio_list_empty(bl))
> +		return i;

I think that this check in not needed because it is covered
by bio_for_each() below.

> +	bio_for_each(bio, bl)
> +		i++;
> +	return i;
> +}


> @@ -58,6 +77,40 @@ static inline void bio_list_merge_head(struct bio_list *bl,
>  	bl->head = bl2->head;
>  }
>  
> +static inline void bio_list_join(struct bio_list *bl, struct bio_list *bl2)
> +{
> +	if (bio_list_empty(bl2))
> +		return;
> +
> +	bl2->tail->bi_next = bl->head;
> +	bl->head = bl2->head;
> +
> +	if (!bl->tail)
> +		bl->tail = bl2->tail;
> +}
> +
> +static inline void bio_list_join_init(struct bio_list *bl, struct bio_list *bl2)
> +{
> +	bio_list_join(bl, bl2);
> +	bio_list_init(bl2);
> +}

I think that bio_list_join() is same as existing bio_list_merge_head().

Regards,
Kiyoshi Ueda

Re: [PATCH] additional bio list helpers

[Bryn M. Reeves]

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Hi Kiyoshi,

Kiyoshi Ueda wrote:
> This one breaks the bio_list if bl2 is a empty list.
> Probably missed to add like below?
> -----------------------------------
> +	if (bio_list_empty(bl2))
> +		return;
> -----------------------------------

Quite right - fixed, thanks!

> I think that bl->tail is always NULL when bl->head is NULL,
> unless the bio_list is corrupted.  So no need to check bl->tail.

This was actually already changed in my git copy, but I forgot to
re-generate the patch before posting - apologies!

> I think that this check in not needed because it is covered
> by bio_for_each() below.

Agreed!

> I think that bio_list_join() is same as existing bio_list_merge_head().

Also agreed - thanks for catching these. This one also isn't used by
dm-loop anyway.

Revised patch attached - this time just including the changes actually
needed by the dm-loop patch:

bio_list_empty
bio_for_each
bio_list_nr
bio_list_merge_init

Kind regards,

Bryn.

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[-- Attachment #2: dm-bio-list-helpers.patch --]
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Add additional bio list helpers to dm-bio-list.h:

bio_list_empty
bio_for_each
bio_list_nr
bio_list_merge_init

These are used by dm-loop for manipulating lists of bios to be
resubmitted by the fs I/O code.

Signed-off-by: Bryn Reeves <breeves@redhat.com>

===================================================================
diff --git a/drivers/md/dm-bio-list.h b/drivers/md/dm-bio-list.h
index da43496..6db7644 100644
--- a/drivers/md/dm-bio-list.h
+++ b/drivers/md/dm-bio-list.h
@@ -14,11 +14,31 @@ struct bio_list {
 	struct bio *tail;
 };
 
+static inline int  bio_list_empty(struct bio_list *bl)
+{
+	return bl->head == NULL;
+}
+
+#define BIO_LIST_HEAD(bl)	struct bio_list bl = { NULL, NULL }
+
 static inline void bio_list_init(struct bio_list *bl)
 {
 	bl->head = bl->tail = NULL;
 }
 
+#define bio_for_each(bio, bl) \
+	for (bio = (bl)->head; bio; bio = bio->bi_next)
+
+static inline int bio_list_nr(struct bio_list *bl)
+{
+	int i=0;
+	struct bio *bio;
+
+	bio_for_each(bio, bl)
+		i++;
+	return i;
+}
+
 static inline void bio_list_add(struct bio_list *bl, struct bio *bio)
 {
 	bio->bi_next = NULL;
@@ -58,6 +78,13 @@ static inline void bio_list_merge_head(struct bio_list *bl,
 	bl->head = bl2->head;
 }
 
+static inline void bio_list_merge_init(struct bio_list *bl,
+				       struct bio_list *bl2)
+{
+	bio_list_merge(bl, bl2);
+	bio_list_init(bl2);
+}
+
 static inline struct bio *bio_list_pop(struct bio_list *bl)
 {
 	struct bio *bio = bl->head;

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