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: Jordan Glover <Golden_Miller83@protonmail.ch>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 34c125e..9180f67 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -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);
 }
 

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 51f5202..093aa57 100644 (file)
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -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]);
 }
 

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 06dad7a..d4ae67d 100644 (file)
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -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);

diff --git a/tools/virtio/linux/scatterlist.h b/tools/virtio/linux/scatterlist.h
index 9a45f90..369ee30 100644 (file)
--- a/tools/virtio/linux/scatterlist.h
+++ b/tools/virtio/linux/scatterlist.h
@@ -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]);
 }