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authorAnshuman Khandual <khandual@linux.vnet.ibm.com>2018-02-15 09:03:56 +0530
committerJens Axboe <axboe@kernel.dk>2018-02-28 12:23:35 -0700
commit723fbf563a6a9cefbd3c58e95694583ad1cb8704 (patch)
treee7f7886eb7ee80e276e7efe6c56f95c36708240e /include/linux
parent468f098734ab095b72d8af26bcd4bcb2ed31a3be (diff)
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lib/scatterlist: Add SG_CHAIN and SG_END macros for LSB encodings
This replaces scatterlist->page_link LSB encodings with SG_CHAIN and SG_END definitions without any functional change. Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/scatterlist.h23
1 files changed, 13 insertions, 10 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 22b2131bcdcd..b6fe1815f5c4 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 0x01UL
+#define SG_END 0x02UL
/*
* 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_END)
#define sg_chain_ptr(sg) \
- ((struct scatterlist *) ((sg)->page_link & ~0x03))
+ ((struct scatterlist *) ((sg)->page_link & ~(SG_CHAIN | SG_END)))
/**
* 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_END);
/*
* 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_END));
#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_END));
}
/**
@@ -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_END;
}
/**
@@ -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_END;
+ 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_END;
}
/**