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 34c125e2d90c094c98759e127d2f93780cd65788..9180f67746b4ea5d1a16bb7b584718d685cd37a1 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 51f52020ad5fdd44ab4fdfa6ad2e0063c4780947..093aa57120b0cf1f40c2a75f28612331c6e6f6e0 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 06dad7a072fd66385032f541f3c9f77b6d440235..d4ae67d6cd1e2e9a3a0e208c094011d3ca6e42d2 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 9a45f90e2d08974c42c6e6dc242b5cfd35d5e120..369ee308b6686ca4a106581b91f8d382e45c79e8 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]);
 }