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Commit 9544bc53 authored by Jens Axboe's avatar Jens Axboe
Browse files

sg: remove ->sg_magic member 



This was introduced more than a decade ago when sg chaining was
added, but we never really caught anything with it. The scatterlist
entry size can be critical, since drivers allocate it, so remove
the magic member. Recently it's been triggering allocation stalls
and failures in NVMe.

Tested-by: default avatarJordan Glover <Golden_Miller83@protonmail.ch>
Acked-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 49f1c610

drivers/gpu/drm/i915/i915_drv.h

+0 −3
Original line number Diff line number Diff line
@@ -2238,9 +2238,6 @@ static inline struct scatterlist *____sg_next(struct scatterlist *sg) 
 **/

static inline struct scatterlist *__sg_next(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	return sg_is_last(sg) ? NULL : ____sg_next(sg);

}

include/linux/scatterlist.h

+0 −18
Original line number Diff line number Diff line
@@ -9,9 +9,6 @@ 
#include <asm/io.h>



struct scatterlist {

#ifdef CONFIG_DEBUG_SG

	unsigned long	sg_magic;

#endif

	unsigned long	page_link;

	unsigned int	offset;

	unsigned int	length;
@@ -64,7 +61,6 @@ struct sg_table { 
 *

 */



#define SG_MAGIC	0x87654321

#define SG_CHAIN	0x01UL

#define SG_END		0x02UL
@@ -98,7 +94,6 @@ static inline void sg_assign_page(struct scatterlist *sg, struct page *page) 
	 */

	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));

#endif

	sg->page_link = page_link | (unsigned long) page;
@@ -129,7 +124,6 @@ static inline void sg_set_page(struct scatterlist *sg, struct page *page, 
static inline struct page *sg_page(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

	BUG_ON(sg_is_chain(sg));

#endif

	return (struct page *)((sg)->page_link & ~(SG_CHAIN | SG_END));
@@ -195,9 +189,6 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 
 **/

static inline void sg_mark_end(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	/*

	 * Set termination bit, clear potential chain bit

	 */
@@ -215,9 +206,6 @@ static inline void sg_mark_end(struct scatterlist *sg) 
 **/

static inline void sg_unmark_end(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	sg->page_link &= ~SG_END;

}
@@ -260,12 +248,6 @@ static inline void *sg_virt(struct scatterlist *sg) 
static inline void sg_init_marker(struct scatterlist *sgl,

				  unsigned int nents)

{

#ifdef CONFIG_DEBUG_SG

	unsigned int i;



	for (i = 0; i < nents; i++)

		sgl[i].sg_magic = SG_MAGIC;

#endif

	sg_mark_end(&sgl[nents - 1]);

}

lib/scatterlist.c

+0 −6
Original line number Diff line number Diff line
@@ -24,9 +24,6 @@ 
 **/

struct scatterlist *sg_next(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	if (sg_is_last(sg))

		return NULL;
@@ -111,10 +108,7 @@ struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) 
	for_each_sg(sgl, sg, nents, i)

		ret = sg;



#ifdef CONFIG_DEBUG_SG

	BUG_ON(sgl[0].sg_magic != SG_MAGIC);

	BUG_ON(!sg_is_last(ret));

#endif

	return ret;

}

EXPORT_SYMBOL(sg_last);

tools/virtio/linux/scatterlist.h

+0 −18
Original line number Diff line number Diff line
@@ -36,7 +36,6 @@ static inline void sg_assign_page(struct scatterlist *sg, struct page *page) 
	 */

	BUG_ON((unsigned long) page & 0x03);

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

	BUG_ON(sg_is_chain(sg));

#endif

	sg->page_link = page_link | (unsigned long) page;
@@ -67,7 +66,6 @@ static inline void sg_set_page(struct scatterlist *sg, struct page *page, 
static inline struct page *sg_page(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

	BUG_ON(sg_is_chain(sg));

#endif

	return (struct page *)((sg)->page_link & ~0x3);
@@ -116,9 +114,6 @@ static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, 
 **/

static inline void sg_mark_end(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	/*

	 * Set termination bit, clear potential chain bit

	 */
@@ -136,17 +131,11 @@ static inline void sg_mark_end(struct scatterlist *sg) 
 **/

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;

}



static inline struct scatterlist *sg_next(struct scatterlist *sg)

{

#ifdef CONFIG_DEBUG_SG

	BUG_ON(sg->sg_magic != SG_MAGIC);

#endif

	if (sg_is_last(sg))

		return NULL;
@@ -160,13 +149,6 @@ static inline struct scatterlist *sg_next(struct scatterlist *sg) 
static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)

{

	memset(sgl, 0, sizeof(*sgl) * nents);

#ifdef CONFIG_DEBUG_SG

	{

		unsigned int i;

		for (i = 0; i < nents; i++)

			sgl[i].sg_magic = SG_MAGIC;

	}

#endif

	sg_mark_end(&sgl[nents - 1]);

}