This replaces scatterlist->page_link LSB encodings with SG_CHAIN and
SG_EMARK definitions without any functional change.
Signed-off-by: Anshuman Khandual <[email protected]>
---
include/linux/scatterlist.h | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 22b2131bcdcd..63d00bdb2fb3 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -65,16 +65,18 @@ struct sg_table {
*/
#define SG_MAGIC 0x87654321
+#define SG_CHAIN 0x01
+#define SG_EMARK 0x02
/*
* We overload the LSB of the page pointer to indicate whether it's
* a valid sg entry, or whether it points to the start of a new scatterlist.
* Those low bits are there for everyone! (thanks mason :-)
*/
-#define sg_is_chain(sg) ((sg)->page_link & 0x01)
-#define sg_is_last(sg) ((sg)->page_link & 0x02)
+#define sg_is_chain(sg) ((sg)->page_link & SG_CHAIN)
+#define sg_is_last(sg) ((sg)->page_link & SG_EMARK)
#define sg_chain_ptr(sg) \
- ((struct scatterlist *) ((sg)->page_link & ~0x03))
+ ((struct scatterlist *) ((sg)->page_link & ~(SG_CHAIN | SG_EMARK)))
/**
* sg_assign_page - Assign a given page to an SG entry
@@ -88,13 +90,13 @@ struct sg_table {
**/
static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
{
- unsigned long page_link = sg->page_link & 0x3;
+ unsigned long page_link = sg->page_link & (SG_CHAIN | SG_EMARK);
/*
* In order for the low bit stealing approach to work, pages
* must be aligned at a 32-bit boundary as a minimum.
*/
- BUG_ON((unsigned long) page & 0x03);
+ BUG_ON((unsigned long) page & (SG_CHAIN | SG_EMARK));
#ifdef CONFIG_DEBUG_SG
BUG_ON(sg->sg_magic != SG_MAGIC);
BUG_ON(sg_is_chain(sg));
@@ -130,7 +132,7 @@ static inline struct page *sg_page(struct scatterlist *sg)
BUG_ON(sg->sg_magic != SG_MAGIC);
BUG_ON(sg_is_chain(sg));
#endif
- return (struct page *)((sg)->page_link & ~0x3);
+ return (struct page *)((sg)->page_link & ~(SG_CHAIN | SG_EMARK));
}
/**
@@ -178,7 +180,8 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents,
* Set lowest bit to indicate a link pointer, and make sure to clear
* the termination bit if it happens to be set.
*/
- prv[prv_nents - 1].page_link = ((unsigned long) sgl | 0x01) & ~0x02;
+ prv[prv_nents - 1].page_link = ((unsigned long) sgl | SG_CHAIN)
+ & ~SG_EMARK;
}
/**
@@ -198,8 +201,8 @@ static inline void sg_mark_end(struct scatterlist *sg)
/*
* Set termination bit, clear potential chain bit
*/
- sg->page_link |= 0x02;
- sg->page_link &= ~0x01;
+ sg->page_link |= SG_EMARK;
+ sg->page_link &= ~SG_CHAIN;
}
/**
@@ -215,7 +218,7 @@ static inline void sg_unmark_end(struct scatterlist *sg)
#ifdef CONFIG_DEBUG_SG
BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
- sg->page_link &= ~0x02;
+ sg->page_link &= ~SG_EMARK;
}
/**
--
2.11.0
On Wed, 2018-02-14 at 10:28 +0530, Anshuman Khandual wrote:
> This replaces scatterlist->page_link LSB encodings with SG_CHAIN and
> SG_EMARK definitions without any functional change.
>
> Signed-off-by: Anshuman Khandual <[email protected]>
> ---
> include/linux/scatterlist.h | 23 +++++++++++++----------
> 1 file changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/scatterlist.h
> b/include/linux/scatterlist.h
> index 22b2131bcdcd..63d00bdb2fb3 100644
> --- a/include/linux/scatterlist.h
> +++ b/include/linux/scatterlist.h
> @@ -65,16 +65,18 @@ struct sg_table {
> */
>
> #define SG_MAGIC 0x87654321
> +#define SG_CHAIN 0x01
> +#define SG_EMARK 0x02
SG_EMARK sounds strange, what about SG_END?
--
Johannes Thumshirn Storage
jthu
[email protected] +49 911 74053 689
SUSE
LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane
Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38
9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
On Wed, 2018-02-14 at 10:28 +0530, Anshuman Khandual wrote:
> +#define SG_CHAIN 0x01
> +#define SG_EMARK 0x02
Hello Anshuman,
As you probably know constants that do not have a suffix are of type int. Please
consider to add suffix "UL" to these constants to avoid that the compiler could
take an undesired decision when e.g. converting ~SG_CHAIN from int to unsigned
long.
Thanks,
Bart.
On 14/02/18 08:32, Johannes Thumshirn wrote:
> On Wed, 2018-02-14 at 10:28 +0530, Anshuman Khandual wrote:
>> This replaces scatterlist->page_link LSB encodings with SG_CHAIN and
>> SG_EMARK definitions without any functional change.
>>
>> Signed-off-by: Anshuman Khandual <[email protected]>
>> ---
>> include/linux/scatterlist.h | 23 +++++++++++++----------
>> 1 file changed, 13 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/linux/scatterlist.h
>> b/include/linux/scatterlist.h
>> index 22b2131bcdcd..63d00bdb2fb3 100644
>> --- a/include/linux/scatterlist.h
>> +++ b/include/linux/scatterlist.h
>> @@ -65,16 +65,18 @@ struct sg_table {
>> */
>>
>> #define SG_MAGIC 0x87654321
>> +#define SG_CHAIN 0x01
>> +#define SG_EMARK 0x02
>
> SG_EMARK sounds strange, what about SG_END?
+1 on SG_END.
Btw, just a cleanup for readability or you have further work in this area?
Regards,
Tvrtko
On 02/14/2018 09:41 PM, Tvrtko Ursulin wrote:
>
> On 14/02/18 08:32, Johannes Thumshirn wrote:
>> On Wed, 2018-02-14 at 10:28 +0530, Anshuman Khandual wrote:
>>> This replaces scatterlist->page_link LSB encodings with SG_CHAIN and
>>> SG_EMARK definitions without any functional change.
>>>
>>> Signed-off-by: Anshuman Khandual <[email protected]>
>>> ---
>>> include/linux/scatterlist.h | 23 +++++++++++++----------
>>> 1 file changed, 13 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/include/linux/scatterlist.h
>>> b/include/linux/scatterlist.h
>>> index 22b2131bcdcd..63d00bdb2fb3 100644
>>> --- a/include/linux/scatterlist.h
>>> +++ b/include/linux/scatterlist.h
>>> @@ -65,16 +65,18 @@ struct sg_table {
>>> */
>>> #define SG_MAGIC 0x87654321
>>> +#define SG_CHAIN 0x01
>>> +#define SG_EMARK 0x02
>>
>> SG_EMARK sounds strange, what about SG_END?
>
> +1 on SG_END.
>
> Btw, just a cleanup for readability or you have further work in this area?
Sure, will replace with SG_END. I was trying something else on virtio drivers
on POWER platform and just came across this.
On 02/14/2018 09:33 PM, Bart Van Assche wrote:
> On Wed, 2018-02-14 at 10:28 +0530, Anshuman Khandual wrote:
>> +#define SG_CHAIN 0x01
>> +#define SG_EMARK 0x02
>
> Hello Anshuman,
>
> As you probably know constants that do not have a suffix are of type int. Please
> consider to add suffix "UL" to these constants to avoid that the compiler could
> take an undesired decision when e.g. converting ~SG_CHAIN from int to unsigned
> long.
Sure, will do.