[PATCH 1/5] lib/scatterlist: Fix offset type in sg_alloc_table_from_pages

[PATCH 1/5] lib/scatterlist: Fix offset type in sg_alloc_table_from_pages

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Scatterlist entries have an unsigned int for the offset so
correct the sg_alloc_table_from_pages function accordingly.

Since these are offsets withing a page, unsigned int is
wide enough.

Also converts callers which were using unsigned long locally
with the lower_32_bits annotation to make it explicitly
clear what is happening.

v2: Use offset_in_page. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Pawel Osciak <pawel@osciak.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Tomasz Stanislawski <t.stanislaws@samsung.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: linux-media@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com> (v1)
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
---
 drivers/media/v4l2-core/videobuf2-dma-contig.c | 4 ++--
 drivers/rapidio/devices/rio_mport_cdev.c       | 4 ++--
 include/linux/scatterlist.h                    | 2 +-
 lib/scatterlist.c                              | 2 +-
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 4f246d166111..2405077fdc71 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -479,7 +479,7 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 {
 	struct vb2_dc_buf *buf;
 	struct frame_vector *vec;
-	unsigned long offset;
+	unsigned int offset;
 	int n_pages, i;
 	int ret = 0;
 	struct sg_table *sgt;
@@ -507,7 +507,7 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 	buf->dev = dev;
 	buf->dma_dir = dma_dir;
 
-	offset = vaddr & ~PAGE_MASK;
+	offset = lower_32_bits(offset_in_page(vaddr));
 	vec = vb2_create_framevec(vaddr, size, dma_dir == DMA_FROM_DEVICE);
 	if (IS_ERR(vec)) {
 		ret = PTR_ERR(vec);
diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
index 5beb0c361076..5c1b6388122a 100644
--- a/drivers/rapidio/devices/rio_mport_cdev.c
+++ b/drivers/rapidio/devices/rio_mport_cdev.c
@@ -876,10 +876,10 @@ rio_dma_transfer(struct file *filp, u32 transfer_mode,
 	 * offset within the internal buffer specified by handle parameter.
 	 */
 	if (xfer->loc_addr) {
-		unsigned long offset;
+		unsigned int offset;
 		long pinned;
 
-		offset = (unsigned long)(uintptr_t)xfer->loc_addr & ~PAGE_MASK;
+		offset = lower_32_bits(offset_in_page(xfer->loc_addr));
 		nr_pages = PAGE_ALIGN(xfer->length + offset) >> PAGE_SHIFT;
 
 		page_list = kmalloc_array(nr_pages,
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 4b3286ac60c8..205aefb4ed93 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -263,7 +263,7 @@ int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
 int sg_alloc_table_from_pages(struct sg_table *sgt,
 	struct page **pages, unsigned int n_pages,
-	unsigned long offset, unsigned long size,
+	unsigned int offset, unsigned long size,
 	gfp_t gfp_mask);
 
 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index be7b4dd6b68d..dee0c5004e2f 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -391,7 +391,7 @@ EXPORT_SYMBOL(sg_alloc_table);
  */
 int sg_alloc_table_from_pages(struct sg_table *sgt,
 	struct page **pages, unsigned int n_pages,
-	unsigned long offset, unsigned long size,
+	unsigned int offset, unsigned long size,
 	gfp_t gfp_mask)
 {
 	unsigned int chunks;
-- 
2.9.4

[PATCH 2/5] lib/scatterlist: Avoid potential scatterlist entry overflow

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Since the scatterlist length field is an unsigned int, make
sure that sg_alloc_table_from_pages does not overflow it while
coallescing pages to a single entry.

v2: Drop reference to future use. Use UINT_MAX.
v3: max_segment must be page aligned.
v4: Do not rely on compiler to optimise out the rounddown.
    (Joonas Lahtinen)
v5: Simplified loops and use post-increments rather than
    pre-increments. Use PAGE_MASK and fix comment typo.
    (Andy Shevchenko)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 include/linux/scatterlist.h |  6 ++++++
 lib/scatterlist.c           | 31 ++++++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 205aefb4ed93..6dd2ddbc6230 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -21,6 +21,12 @@ struct scatterlist {
 };
 
 /*
+ * Since the above length field is an unsigned int, below we define the maximum
+ * length in bytes that can be stored in one scatterlist entry.
+ */
+#define SCATTERLIST_MAX_SEGMENT (UINT_MAX & PAGE_MASK)
+
+/*
  * These macros should be used after a dma_map_sg call has been done
  * to get bus addresses of each of the SG entries and their lengths.
  * You should only work with the number of sg entries dma_map_sg
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index dee0c5004e2f..7b2e74da2c44 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -394,17 +394,22 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 	unsigned int offset, unsigned long size,
 	gfp_t gfp_mask)
 {
-	unsigned int chunks;
-	unsigned int i;
-	unsigned int cur_page;
+	const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT;
+	unsigned int chunks, cur_page, seg_len, i;
 	int ret;
 	struct scatterlist *s;
 
 	/* compute number of contiguous chunks */
 	chunks = 1;
-	for (i = 1; i < n_pages; ++i)
-		if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
-			++chunks;
+	seg_len = 0;
+	for (i = 1; i < n_pages; i++) {
+		seg_len += PAGE_SIZE;
+		if (seg_len >= max_segment ||
+		    page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) {
+			chunks++;
+			seg_len = 0;
+		}
+	}
 
 	ret = sg_alloc_table(sgt, chunks, gfp_mask);
 	if (unlikely(ret))
@@ -413,17 +418,21 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 	/* merging chunks and putting them into the scatterlist */
 	cur_page = 0;
 	for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
-		unsigned long chunk_size;
-		unsigned int j;
+		unsigned int j, chunk_size;
 
 		/* look for the end of the current chunk */
-		for (j = cur_page + 1; j < n_pages; ++j)
-			if (page_to_pfn(pages[j]) !=
+		seg_len = 0;
+		for (j = cur_page + 1; j < n_pages; j++) {
+			seg_len += PAGE_SIZE;
+			if (seg_len >= max_segment ||
+			    page_to_pfn(pages[j]) !=
 			    page_to_pfn(pages[j - 1]) + 1)
 				break;
+		}
 
 		chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
-		sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
+		sg_set_page(s, pages[cur_page],
+			    min_t(unsigned long, size, chunk_size), offset);
 		size -= chunk_size;
 		offset = 0;
 		cur_page = j;
-- 
2.9.4

[PATCH v6 2/5] lib/scatterlist: Avoid potential scatterlist entry overflow

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Since the scatterlist length field is an unsigned int, make
sure that sg_alloc_table_from_pages does not overflow it while
coalescing pages to a single entry.

v2: Drop reference to future use. Use UINT_MAX.
v3: max_segment must be page aligned.
v4: Do not rely on compiler to optimise out the rounddown.
    (Joonas Lahtinen)
v5: Simplified loops and use post-increments rather than
    pre-increments. Use PAGE_MASK and fix comment typo.
    (Andy Shevchenko)
v6: Commit spelling fix.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 include/linux/scatterlist.h |  6 ++++++
 lib/scatterlist.c           | 31 ++++++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 205aefb4ed93..6dd2ddbc6230 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -21,6 +21,12 @@ struct scatterlist {
 };
 
 /*
+ * Since the above length field is an unsigned int, below we define the maximum
+ * length in bytes that can be stored in one scatterlist entry.
+ */
+#define SCATTERLIST_MAX_SEGMENT (UINT_MAX & PAGE_MASK)
+
+/*
  * These macros should be used after a dma_map_sg call has been done
  * to get bus addresses of each of the SG entries and their lengths.
  * You should only work with the number of sg entries dma_map_sg
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index dee0c5004e2f..7b2e74da2c44 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -394,17 +394,22 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 	unsigned int offset, unsigned long size,
 	gfp_t gfp_mask)
 {
-	unsigned int chunks;
-	unsigned int i;
-	unsigned int cur_page;
+	const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT;
+	unsigned int chunks, cur_page, seg_len, i;
 	int ret;
 	struct scatterlist *s;
 
 	/* compute number of contiguous chunks */
 	chunks = 1;
-	for (i = 1; i < n_pages; ++i)
-		if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
-			++chunks;
+	seg_len = 0;
+	for (i = 1; i < n_pages; i++) {
+		seg_len += PAGE_SIZE;
+		if (seg_len >= max_segment ||
+		    page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) {
+			chunks++;
+			seg_len = 0;
+		}
+	}
 
 	ret = sg_alloc_table(sgt, chunks, gfp_mask);
 	if (unlikely(ret))
@@ -413,17 +418,21 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 	/* merging chunks and putting them into the scatterlist */
 	cur_page = 0;
 	for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
-		unsigned long chunk_size;
-		unsigned int j;
+		unsigned int j, chunk_size;
 
 		/* look for the end of the current chunk */
-		for (j = cur_page + 1; j < n_pages; ++j)
-			if (page_to_pfn(pages[j]) !=
+		seg_len = 0;
+		for (j = cur_page + 1; j < n_pages; j++) {
+			seg_len += PAGE_SIZE;
+			if (seg_len >= max_segment ||
+			    page_to_pfn(pages[j]) !=
 			    page_to_pfn(pages[j - 1]) + 1)
 				break;
+		}
 
 		chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
-		sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
+		sg_set_page(s, pages[cur_page],
+			    min_t(unsigned long, size, chunk_size), offset);
 		size -= chunk_size;
 		offset = 0;
 		cur_page = j;
-- 
2.9.4

[PATCH 3/5] lib/scatterlist: Introduce and export __sg_alloc_table_from_pages

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Drivers like i915 benefit from being able to control the maxium
size of the sg coallesced segment while building the scatter-
gather list.

Introduce and export the __sg_alloc_table_from_pages function
which will allow it that control.

v2: Reorder parameters. (Chris Wilson)
v3: Fix incomplete reordering in v2.
v4: max_segment needs to be page aligned.
v5: Rebase.
v6: Rebase.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kernel@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 include/linux/scatterlist.h | 11 +++++----
 lib/scatterlist.c           | 58 +++++++++++++++++++++++++++++++++++----------
 2 files changed, 52 insertions(+), 17 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 6dd2ddbc6230..874b50c232de 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -267,10 +267,13 @@ void sg_free_table(struct sg_table *);
 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 		     struct scatterlist *, gfp_t, sg_alloc_fn *);
 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
-int sg_alloc_table_from_pages(struct sg_table *sgt,
-	struct page **pages, unsigned int n_pages,
-	unsigned int offset, unsigned long size,
-	gfp_t gfp_mask);
+int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+				unsigned int n_pages, unsigned int offset,
+				unsigned long size, unsigned int max_segment,
+				gfp_t gfp_mask);
+int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+			      unsigned int n_pages, unsigned int offset,
+			      unsigned long size, gfp_t gfp_mask);
 
 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 		      size_t buflen, off_t skip, bool to_buffer);
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 7b2e74da2c44..1a5900f9a057 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -370,14 +370,15 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
 EXPORT_SYMBOL(sg_alloc_table);
 
 /**
- * sg_alloc_table_from_pages - Allocate and initialize an sg table from
- *			       an array of pages
- * @sgt:	The sg table header to use
- * @pages:	Pointer to an array of page pointers
- * @n_pages:	Number of pages in the pages array
- * @offset:     Offset from start of the first page to the start of a buffer
- * @size:       Number of valid bytes in the buffer (after offset)
- * @gfp_mask:	GFP allocation mask
+ * __sg_alloc_table_from_pages - Allocate and initialize an sg table from
+ *			         an array of pages
+ * @sgt:	 The sg table header to use
+ * @pages:	 Pointer to an array of page pointers
+ * @n_pages:	 Number of pages in the pages array
+ * @offset:      Offset from start of the first page to the start of a buffer
+ * @size:        Number of valid bytes in the buffer (after offset)
+ * @max_segment: Maximum size of a scatterlist node in bytes (page aligned)
+ * @gfp_mask:	 GFP allocation mask
  *
  *  Description:
  *    Allocate and initialize an sg table from a list of pages. Contiguous
@@ -389,16 +390,18 @@ EXPORT_SYMBOL(sg_alloc_table);
  * Returns:
  *   0 on success, negative error on failure
  */
-int sg_alloc_table_from_pages(struct sg_table *sgt,
-	struct page **pages, unsigned int n_pages,
-	unsigned int offset, unsigned long size,
-	gfp_t gfp_mask)
+int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+				unsigned int n_pages, unsigned int offset,
+				unsigned long size, unsigned int max_segment,
+				gfp_t gfp_mask)
 {
-	const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT;
 	unsigned int chunks, cur_page, seg_len, i;
 	int ret;
 	struct scatterlist *s;
 
+	if (WARN_ON(!max_segment || offset_in_page(max_segment)))
+		return -EINVAL;
+
 	/* compute number of contiguous chunks */
 	chunks = 1;
 	seg_len = 0;
@@ -440,6 +443,35 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 
 	return 0;
 }
+EXPORT_SYMBOL(__sg_alloc_table_from_pages);
+
+/**
+ * sg_alloc_table_from_pages - Allocate and initialize an sg table from
+ *			       an array of pages
+ * @sgt:	 The sg table header to use
+ * @pages:	 Pointer to an array of page pointers
+ * @n_pages:	 Number of pages in the pages array
+ * @offset:      Offset from start of the first page to the start of a buffer
+ * @size:        Number of valid bytes in the buffer (after offset)
+ * @gfp_mask:	 GFP allocation mask
+ *
+ *  Description:
+ *    Allocate and initialize an sg table from a list of pages. Contiguous
+ *    ranges of the pages are squashed into a single scatterlist node. A user
+ *    may provide an offset at a start and a size of valid data in a buffer
+ *    specified by the page array. The returned sg table is released by
+ *    sg_free_table.
+ *
+ * Returns:
+ *   0 on success, negative error on failure
+ */
+int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+			      unsigned int n_pages, unsigned int offset,
+			      unsigned long size, gfp_t gfp_mask)
+{
+	return __sg_alloc_table_from_pages(sgt, pages, n_pages, offset, size,
+					   SCATTERLIST_MAX_SEGMENT, gfp_mask);
+}
 EXPORT_SYMBOL(sg_alloc_table_from_pages);
 
 void __sg_page_iter_start(struct sg_page_iter *piter,
-- 
2.9.4

[PATCH v7 3/5] lib/scatterlist: Introduce and export __sg_alloc_table_from_pages

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Drivers like i915 benefit from being able to control the maxium
size of the sg coalesced segment while building the scatter-
gather list.

Introduce and export the __sg_alloc_table_from_pages function
which will allow it that control.

v2: Reorder parameters. (Chris Wilson)
v3: Fix incomplete reordering in v2.
v4: max_segment needs to be page aligned.
v5: Rebase.
v6: Rebase.
v7: Fix spelling in commit and mention max segment size in
    __sg_alloc_table_from_pages kerneldoc. (Andrew Morton)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kernel@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/scatterlist.h | 11 +++++---
 lib/scatterlist.c           | 66 +++++++++++++++++++++++++++++++++------------
 2 files changed, 56 insertions(+), 21 deletions(-)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 6dd2ddbc6230..874b50c232de 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -267,10 +267,13 @@ void sg_free_table(struct sg_table *);
 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 		     struct scatterlist *, gfp_t, sg_alloc_fn *);
 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
-int sg_alloc_table_from_pages(struct sg_table *sgt,
-	struct page **pages, unsigned int n_pages,
-	unsigned int offset, unsigned long size,
-	gfp_t gfp_mask);
+int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+				unsigned int n_pages, unsigned int offset,
+				unsigned long size, unsigned int max_segment,
+				gfp_t gfp_mask);
+int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+			      unsigned int n_pages, unsigned int offset,
+			      unsigned long size, gfp_t gfp_mask);
 
 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 		      size_t buflen, off_t skip, bool to_buffer);
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 7b2e74da2c44..7c1c55f7daaa 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -370,35 +370,38 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
 EXPORT_SYMBOL(sg_alloc_table);
 
 /**
- * sg_alloc_table_from_pages - Allocate and initialize an sg table from
- *			       an array of pages
- * @sgt:	The sg table header to use
- * @pages:	Pointer to an array of page pointers
- * @n_pages:	Number of pages in the pages array
- * @offset:     Offset from start of the first page to the start of a buffer
- * @size:       Number of valid bytes in the buffer (after offset)
- * @gfp_mask:	GFP allocation mask
+ * __sg_alloc_table_from_pages - Allocate and initialize an sg table from
+ *			         an array of pages
+ * @sgt:	 The sg table header to use
+ * @pages:	 Pointer to an array of page pointers
+ * @n_pages:	 Number of pages in the pages array
+ * @offset:      Offset from start of the first page to the start of a buffer
+ * @size:        Number of valid bytes in the buffer (after offset)
+ * @max_segment: Maximum size of a scatterlist node in bytes (page aligned)
+ * @gfp_mask:	 GFP allocation mask
  *
  *  Description:
  *    Allocate and initialize an sg table from a list of pages. Contiguous
- *    ranges of the pages are squashed into a single scatterlist node. A user
- *    may provide an offset at a start and a size of valid data in a buffer
- *    specified by the page array. The returned sg table is released by
- *    sg_free_table.
+ *    ranges of the pages are squashed into a single scatterlist node up to the
+ *    maximum size specified in @max_segment. An user may provide an offset at a
+ *    start and a size of valid data in a buffer specified by the page array.
+ *    The returned sg table is released by sg_free_table.
  *
  * Returns:
  *   0 on success, negative error on failure
  */
-int sg_alloc_table_from_pages(struct sg_table *sgt,
-	struct page **pages, unsigned int n_pages,
-	unsigned int offset, unsigned long size,
-	gfp_t gfp_mask)
+int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+				unsigned int n_pages, unsigned int offset,
+				unsigned long size, unsigned int max_segment,
+				gfp_t gfp_mask)
 {
-	const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT;
 	unsigned int chunks, cur_page, seg_len, i;
 	int ret;
 	struct scatterlist *s;
 
+	if (WARN_ON(!max_segment || offset_in_page(max_segment)))
+		return -EINVAL;
+
 	/* compute number of contiguous chunks */
 	chunks = 1;
 	seg_len = 0;
@@ -440,6 +443,35 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 
 	return 0;
 }
+EXPORT_SYMBOL(__sg_alloc_table_from_pages);
+
+/**
+ * sg_alloc_table_from_pages - Allocate and initialize an sg table from
+ *			       an array of pages
+ * @sgt:	 The sg table header to use
+ * @pages:	 Pointer to an array of page pointers
+ * @n_pages:	 Number of pages in the pages array
+ * @offset:      Offset from start of the first page to the start of a buffer
+ * @size:        Number of valid bytes in the buffer (after offset)
+ * @gfp_mask:	 GFP allocation mask
+ *
+ *  Description:
+ *    Allocate and initialize an sg table from a list of pages. Contiguous
+ *    ranges of the pages are squashed into a single scatterlist node. A user
+ *    may provide an offset at a start and a size of valid data in a buffer
+ *    specified by the page array. The returned sg table is released by
+ *    sg_free_table.
+ *
+ * Returns:
+ *   0 on success, negative error on failure
+ */
+int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
+			      unsigned int n_pages, unsigned int offset,
+			      unsigned long size, gfp_t gfp_mask)
+{
+	return __sg_alloc_table_from_pages(sgt, pages, n_pages, offset, size,
+					   SCATTERLIST_MAX_SEGMENT, gfp_mask);
+}
 EXPORT_SYMBOL(sg_alloc_table_from_pages);
 
 void __sg_page_iter_start(struct sg_page_iter *piter,
-- 
2.9.4

[PATCH 4/5] drm/i915: Use __sg_alloc_table_from_pages for userptr allocations

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

With the addition of __sg_alloc_table_from_pages we can control
the maximum coallescing size and eliminate a separate path for
allocating backing store here.

Similar to 871dfbd67d4e ("drm/i915: Allow compaction upto
SWIOTLB max segment size") this enables more compact sg lists to
be created and so has a beneficial effect on workloads with many
and/or large objects of this class.

v2:
 * Rename helper to i915_sg_segment_size and fix swiotlb override.
 * Commit message update.

v3:
 * Actually include the swiotlb override fix.

v4:
 * Regroup parameters a bit. (Chris Wilson)

v5:
 * Rebase for swiotlb_max_segment.
 * Add DMA map failure handling as in abb0deacb5a6
   ("drm/i915: Fallback to single PAGE_SIZE segments for DMA remapping").

v6: Handle swiotlb_max_segment() returning 1. (Joonas Lahtinen)

v7: Rebase.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         | 15 +++++++
 drivers/gpu/drm/i915/i915_gem.c         |  6 +--
 drivers/gpu/drm/i915/i915_gem_userptr.c | 79 ++++++++++++---------------------
 3 files changed, 45 insertions(+), 55 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2c7456f4ed38..6383940e8d55 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2749,6 +2749,21 @@ static inline struct scatterlist *__sg_next(struct scatterlist *sg)
 	     (((__iter).curr += PAGE_SIZE) < (__iter).max) ||		\
 	     ((__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0))
 
+static inline unsigned int i915_sg_segment_size(void)
+{
+	unsigned int size = swiotlb_max_segment();
+
+	if (size == 0)
+		return SCATTERLIST_MAX_SEGMENT;
+
+	size = rounddown(size, PAGE_SIZE);
+	/* swiotlb_max_segment_size can return 1 byte when it means one page. */
+	if (size < PAGE_SIZE)
+		size = PAGE_SIZE;
+
+	return size;
+}
+
 static inline const struct intel_device_info *
 intel_info(const struct drm_i915_private *dev_priv)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6faabf34f142..a60885d6231b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2339,7 +2339,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	struct sgt_iter sgt_iter;
 	struct page *page;
 	unsigned long last_pfn = 0;	/* suppress gcc warning */
-	unsigned int max_segment;
+	unsigned int max_segment = i915_sg_segment_size();
 	gfp_t noreclaim;
 	int ret;
 
@@ -2350,10 +2350,6 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	GEM_BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
 	GEM_BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);
 
-	max_segment = swiotlb_max_segment();
-	if (!max_segment)
-		max_segment = rounddown(UINT_MAX, PAGE_SIZE);
-
 	st = kmalloc(sizeof(*st), GFP_KERNEL);
 	if (st == NULL)
 		return ERR_PTR(-ENOMEM);
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index ccd09e8419f5..60c10d4118ae 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -399,64 +399,42 @@ struct get_pages_work {
 	struct task_struct *task;
 };
 
-#if IS_ENABLED(CONFIG_SWIOTLB)
-#define swiotlb_active() swiotlb_nr_tbl()
-#else
-#define swiotlb_active() 0
-#endif
-
-static int
-st_set_pages(struct sg_table **st, struct page **pvec, int num_pages)
-{
-	struct scatterlist *sg;
-	int ret, n;
-
-	*st = kmalloc(sizeof(**st), GFP_KERNEL);
-	if (*st == NULL)
-		return -ENOMEM;
-
-	if (swiotlb_active()) {
-		ret = sg_alloc_table(*st, num_pages, GFP_KERNEL);
-		if (ret)
-			goto err;
-
-		for_each_sg((*st)->sgl, sg, num_pages, n)
-			sg_set_page(sg, pvec[n], PAGE_SIZE, 0);
-	} else {
-		ret = sg_alloc_table_from_pages(*st, pvec, num_pages,
-						0, num_pages << PAGE_SHIFT,
-						GFP_KERNEL);
-		if (ret)
-			goto err;
-	}
-
-	return 0;
-
-err:
-	kfree(*st);
-	*st = NULL;
-	return ret;
-}
-
 static struct sg_table *
-__i915_gem_userptr_set_pages(struct drm_i915_gem_object *obj,
-			     struct page **pvec, int num_pages)
+__i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj,
+			       struct page **pvec, int num_pages)
 {
-	struct sg_table *pages;
+	unsigned int max_segment = i915_sg_segment_size();
+	struct sg_table *st;
 	int ret;
 
-	ret = st_set_pages(&pages, pvec, num_pages);
-	if (ret)
+	st = kmalloc(sizeof(*st), GFP_KERNEL);
+	if (!st)
+		return ERR_PTR(-ENOMEM);
+
+alloc_table:
+	ret = __sg_alloc_table_from_pages(st, pvec, num_pages,
+					  0, num_pages << PAGE_SHIFT,
+					  max_segment,
+					  GFP_KERNEL);
+	if (ret) {
+		kfree(st);
 		return ERR_PTR(ret);
+	}
 
-	ret = i915_gem_gtt_prepare_pages(obj, pages);
+	ret = i915_gem_gtt_prepare_pages(obj, st);
 	if (ret) {
-		sg_free_table(pages);
-		kfree(pages);
+		sg_free_table(st);
+
+		if (max_segment > PAGE_SIZE) {
+			max_segment = PAGE_SIZE;
+			goto alloc_table;
+		}
+
+		kfree(st);
 		return ERR_PTR(ret);
 	}
 
-	return pages;
+	return st;
 }
 
 static int
@@ -540,7 +518,8 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
 		struct sg_table *pages = ERR_PTR(ret);
 
 		if (pinned == npages) {
-			pages = __i915_gem_userptr_set_pages(obj, pvec, npages);
+			pages = __i915_gem_userptr_alloc_pages(obj, pvec,
+							       npages);
 			if (!IS_ERR(pages)) {
 				__i915_gem_object_set_pages(obj, pages);
 				pinned = 0;
@@ -661,7 +640,7 @@ i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
 		pages = __i915_gem_userptr_get_pages_schedule(obj);
 		active = pages == ERR_PTR(-EAGAIN);
 	} else {
-		pages = __i915_gem_userptr_set_pages(obj, pvec, num_pages);
+		pages = __i915_gem_userptr_alloc_pages(obj, pvec, num_pages);
 		active = !IS_ERR(pages);
 	}
 	if (active)
-- 
2.9.4

[PATCH v8 4/5] drm/i915: Use __sg_alloc_table_from_pages for userptr allocations

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

With the addition of __sg_alloc_table_from_pages we can control
the maximum coalescing size and eliminate a separate path for
allocating backing store here.

Similar to 871dfbd67d4e ("drm/i915: Allow compaction upto
SWIOTLB max segment size") this enables more compact sg lists to
be created and so has a beneficial effect on workloads with many
and/or large objects of this class.

v2:
 * Rename helper to i915_sg_segment_size and fix swiotlb override.
 * Commit message update.

v3:
 * Actually include the swiotlb override fix.

v4:
 * Regroup parameters a bit. (Chris Wilson)

v5:
 * Rebase for swiotlb_max_segment.
 * Add DMA map failure handling as in abb0deacb5a6
   ("drm/i915: Fallback to single PAGE_SIZE segments for DMA remapping").

v6: Handle swiotlb_max_segment() returning 1. (Joonas Lahtinen)

v7: Rebase.
v8: Commit spelling fix.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         | 15 +++++++
 drivers/gpu/drm/i915/i915_gem.c         |  6 +--
 drivers/gpu/drm/i915/i915_gem_userptr.c | 79 ++++++++++++---------------------
 3 files changed, 45 insertions(+), 55 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2c7456f4ed38..6383940e8d55 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2749,6 +2749,21 @@ static inline struct scatterlist *__sg_next(struct scatterlist *sg)
 	     (((__iter).curr += PAGE_SIZE) < (__iter).max) ||		\
 	     ((__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0))
 
+static inline unsigned int i915_sg_segment_size(void)
+{
+	unsigned int size = swiotlb_max_segment();
+
+	if (size == 0)
+		return SCATTERLIST_MAX_SEGMENT;
+
+	size = rounddown(size, PAGE_SIZE);
+	/* swiotlb_max_segment_size can return 1 byte when it means one page. */
+	if (size < PAGE_SIZE)
+		size = PAGE_SIZE;
+
+	return size;
+}
+
 static inline const struct intel_device_info *
 intel_info(const struct drm_i915_private *dev_priv)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6faabf34f142..a60885d6231b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2339,7 +2339,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	struct sgt_iter sgt_iter;
 	struct page *page;
 	unsigned long last_pfn = 0;	/* suppress gcc warning */
-	unsigned int max_segment;
+	unsigned int max_segment = i915_sg_segment_size();
 	gfp_t noreclaim;
 	int ret;
 
@@ -2350,10 +2350,6 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	GEM_BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
 	GEM_BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);
 
-	max_segment = swiotlb_max_segment();
-	if (!max_segment)
-		max_segment = rounddown(UINT_MAX, PAGE_SIZE);
-
 	st = kmalloc(sizeof(*st), GFP_KERNEL);
 	if (st == NULL)
 		return ERR_PTR(-ENOMEM);
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index ccd09e8419f5..60c10d4118ae 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -399,64 +399,42 @@ struct get_pages_work {
 	struct task_struct *task;
 };
 
-#if IS_ENABLED(CONFIG_SWIOTLB)
-#define swiotlb_active() swiotlb_nr_tbl()
-#else
-#define swiotlb_active() 0
-#endif
-
-static int
-st_set_pages(struct sg_table **st, struct page **pvec, int num_pages)
-{
-	struct scatterlist *sg;
-	int ret, n;
-
-	*st = kmalloc(sizeof(**st), GFP_KERNEL);
-	if (*st == NULL)
-		return -ENOMEM;
-
-	if (swiotlb_active()) {
-		ret = sg_alloc_table(*st, num_pages, GFP_KERNEL);
-		if (ret)
-			goto err;
-
-		for_each_sg((*st)->sgl, sg, num_pages, n)
-			sg_set_page(sg, pvec[n], PAGE_SIZE, 0);
-	} else {
-		ret = sg_alloc_table_from_pages(*st, pvec, num_pages,
-						0, num_pages << PAGE_SHIFT,
-						GFP_KERNEL);
-		if (ret)
-			goto err;
-	}
-
-	return 0;
-
-err:
-	kfree(*st);
-	*st = NULL;
-	return ret;
-}
-
 static struct sg_table *
-__i915_gem_userptr_set_pages(struct drm_i915_gem_object *obj,
-			     struct page **pvec, int num_pages)
+__i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj,
+			       struct page **pvec, int num_pages)
 {
-	struct sg_table *pages;
+	unsigned int max_segment = i915_sg_segment_size();
+	struct sg_table *st;
 	int ret;
 
-	ret = st_set_pages(&pages, pvec, num_pages);
-	if (ret)
+	st = kmalloc(sizeof(*st), GFP_KERNEL);
+	if (!st)
+		return ERR_PTR(-ENOMEM);
+
+alloc_table:
+	ret = __sg_alloc_table_from_pages(st, pvec, num_pages,
+					  0, num_pages << PAGE_SHIFT,
+					  max_segment,
+					  GFP_KERNEL);
+	if (ret) {
+		kfree(st);
 		return ERR_PTR(ret);
+	}
 
-	ret = i915_gem_gtt_prepare_pages(obj, pages);
+	ret = i915_gem_gtt_prepare_pages(obj, st);
 	if (ret) {
-		sg_free_table(pages);
-		kfree(pages);
+		sg_free_table(st);
+
+		if (max_segment > PAGE_SIZE) {
+			max_segment = PAGE_SIZE;
+			goto alloc_table;
+		}
+
+		kfree(st);
 		return ERR_PTR(ret);
 	}
 
-	return pages;
+	return st;
 }
 
 static int
@@ -540,7 +518,8 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
 		struct sg_table *pages = ERR_PTR(ret);
 
 		if (pinned == npages) {
-			pages = __i915_gem_userptr_set_pages(obj, pvec, npages);
+			pages = __i915_gem_userptr_alloc_pages(obj, pvec,
+							       npages);
 			if (!IS_ERR(pages)) {
 				__i915_gem_object_set_pages(obj, pages);
 				pinned = 0;
@@ -661,7 +640,7 @@ i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
 		pages = __i915_gem_userptr_get_pages_schedule(obj);
 		active = pages == ERR_PTR(-EAGAIN);
 	} else {
-		pages = __i915_gem_userptr_set_pages(obj, pvec, num_pages);
+		pages = __i915_gem_userptr_alloc_pages(obj, pvec, num_pages);
 		active = !IS_ERR(pages);
 	}
 	if (active)
-- 
2.9.4

[PATCH 5/5] tools/testing/scatterlist: Test new __sg_alloc_table_from_pages

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Exercise the new __sg_alloc_table_from_pages API (and through
it also the old sg_alloc_table_from_pages), checking that the
created table has the expected number of segments depending on
the sequence of input pages and other conditions.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: linux-kernel@vger.kernel.org
---
 tools/testing/scatterlist/Makefile   |  30 +++++++++
 tools/testing/scatterlist/linux/mm.h | 125 +++++++++++++++++++++++++++++++++++
 tools/testing/scatterlist/main.c     | 112 +++++++++++++++++++++++++++++++
 3 files changed, 267 insertions(+)
 create mode 100644 tools/testing/scatterlist/Makefile
 create mode 100644 tools/testing/scatterlist/linux/mm.h
 create mode 100644 tools/testing/scatterlist/main.c

diff --git a/tools/testing/scatterlist/Makefile b/tools/testing/scatterlist/Makefile
new file mode 100644
index 000000000000..0867e0ef32d6
--- /dev/null
+++ b/tools/testing/scatterlist/Makefile
@@ -0,0 +1,30 @@
+CFLAGS += -I. -I../../include -g -O2 -Wall -fsanitize=address
+LDFLAGS += -fsanitize=address
+TARGETS = main
+OFILES = main.o scatterlist.o
+
+ifeq ($(BUILD), 32)
+        CFLAGS += -m32
+        LDFLAGS += -m32
+endif
+
+targets: include $(TARGETS)
+
+main: $(OFILES)
+
+clean:
+	$(RM) $(TARGETS) $(OFILES) scatterlist.c linux/scatterlist.h linux/highmem.h linux/kmemleak.h asm/io.h
+	@rmdir asm
+
+scatterlist.c: ../../../lib/scatterlist.c
+	@sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@
+
+.PHONY: include
+
+include: ../../../include/linux/scatterlist.h
+	@mkdir -p linux
+	@mkdir -p asm
+	@touch asm/io.h
+	@touch linux/highmem.h
+	@touch linux/kmemleak.h
+	@cp $< linux/scatterlist.h
diff --git a/tools/testing/scatterlist/linux/mm.h b/tools/testing/scatterlist/linux/mm.h
new file mode 100644
index 000000000000..ccbb248ebdc1
--- /dev/null
+++ b/tools/testing/scatterlist/linux/mm.h
@@ -0,0 +1,125 @@
+#ifndef _LINUX_MM_H
+#define _LINUX_MM_H
+
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+
+typedef unsigned long dma_addr_t;
+
+#define unlikely
+
+#define BUG_ON(x) assert(!(x))
+
+#define WARN_ON(condition) ({                                           \
+        int __ret_warn_on = !!(condition);                              \
+        unlikely(__ret_warn_on);                                        \
+})
+
+#define WARN_ON_ONCE(condition) ({                              \
+        int __ret_warn_on = !!(condition);                      \
+        if (unlikely(__ret_warn_on))                            \
+                assert(0);                                      \
+        unlikely(__ret_warn_on);                                \
+})
+
+#define PAGE_SIZE	(4096)
+#define PAGE_SHIFT	(12)
+#define PAGE_MASK	(~(PAGE_SIZE-1))
+
+#define __ALIGN_KERNEL(x, a)            __ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1)
+#define __ALIGN_KERNEL_MASK(x, mask)    (((x) + (mask)) & ~(mask))
+#define ALIGN(x, a)             __ALIGN_KERNEL((x), (a))
+
+#define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
+
+#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
+
+#define virt_to_page(x)	((void *)x)
+#define page_address(x)	((void *)x)
+
+static inline unsigned long page_to_phys(struct page *page)
+{
+	assert(0);
+
+	return 0;
+}
+
+#define page_to_pfn(page) ((unsigned long)(page) / PAGE_SIZE)
+#define pfn_to_page(pfn) (void *)((pfn) * PAGE_SIZE)
+#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
+
+#define __min(t1, t2, min1, min2, x, y) ({              \
+        t1 min1 = (x);                                  \
+        t2 min2 = (y);                                  \
+        (void) (&min1 == &min2);                        \
+        min1 < min2 ? min1 : min2; })
+
+#define ___PASTE(a,b) a##b
+#define __PASTE(a,b) ___PASTE(a,b)
+
+#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+#define min(x, y)                                       \
+        __min(typeof(x), typeof(y),                     \
+              __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),   \
+              x, y)
+
+#define min_t(type, x, y)                               \
+        __min(type, type,                               \
+              __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),   \
+              x, y)
+
+#define preemptible() (1)
+
+static inline void *kmap(struct page *page)
+{
+	assert(0);
+
+	return NULL;
+}
+
+static inline void *kmap_atomic(struct page *page)
+{
+	assert(0);
+
+	return NULL;
+}
+
+static inline void kunmap(void *addr)
+{
+	assert(0);
+}
+
+static inline void kunmap_atomic(void *addr)
+{
+	assert(0);
+}
+
+static inline unsigned long __get_free_page(unsigned int flags)
+{
+	return (unsigned long)malloc(PAGE_SIZE);
+}
+
+static inline void free_page(unsigned long page)
+{
+	free((void *)page);
+}
+
+static inline void *kmalloc(unsigned int size, unsigned int flags)
+{
+	return malloc(size);
+}
+
+#define kfree(x) free(x)
+
+#define kmemleak_alloc(a, b, c, d)
+#define kmemleak_free(a)
+
+#define PageSlab(p) (0)
+#define flush_kernel_dcache_page(p)
+
+#endif
diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
new file mode 100644
index 000000000000..edf9b2960734
--- /dev/null
+++ b/tools/testing/scatterlist/main.c
@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <assert.h>
+
+#include <linux/scatterlist.h>
+
+#define MAX_PAGES (64)
+
+static unsigned
+_set_pages(struct page **pages, const unsigned *array, unsigned num)
+{
+	unsigned int i;
+
+	assert(num < MAX_PAGES);
+
+	for (i = 0; i < num; i++)
+		pages[i] = (struct page *)(unsigned long)
+			   ((1 + array[i]) * PAGE_SIZE);
+
+	return num;
+}
+
+#define set_pages(p, a) _set_pages((p), (a), sizeof(a) / sizeof(a[0]))
+
+#define check_and_free(_st, _ret, _nents) \
+{ \
+	assert((_ret) == 0); \
+	assert((_st)->nents == _nents); \
+	assert((_st)->orig_nents == _nents); \
+	sg_free_table(_st); \
+}
+
+static int
+alloc_tbl(struct sg_table *st, struct page **pages, unsigned nr_pages,
+	  unsigned offset, unsigned size, unsigned max)
+{
+	return __sg_alloc_table_from_pages(st, pages, nr_pages, offset, size,
+					   max, GFP_KERNEL);
+}
+
+int main(void)
+{
+	const unsigned int sgmax = SCATTERLIST_MAX_SEGMENT;
+	struct page *pages[MAX_PAGES];
+	struct sg_table st;
+	int ret;
+
+	ret = set_pages(pages, ((unsigned []){ 0 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, PAGE_SIZE + 1);
+	assert(ret == -EINVAL);
+
+	ret = set_pages(pages, ((unsigned []){ 0 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, 0);
+	assert(ret == -EINVAL);
+
+	ret = set_pages(pages, ((unsigned []){ 0 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 1);
+
+	ret = set_pages(pages, ((unsigned []){ 0 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret, sgmax);
+	check_and_free(&st, ret, 1);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 1);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 2 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 2);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 3 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 2);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 3, 4 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 2);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 3, 4, 5 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 2);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 3, 4, 6 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 3);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 2, 4, 6, 8 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 5);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 2, 3, 4 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, sgmax);
+	check_and_free(&st, ret, 1);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 2, 3, 4 }));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, 2 * PAGE_SIZE);
+	check_and_free(&st, ret, 3);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 2, 3, 4, 5}));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, 2 * PAGE_SIZE);
+	check_and_free(&st, ret, 3);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 2, 3, 4, 5, 6}));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, 2 * PAGE_SIZE);
+	check_and_free(&st, ret, 4);
+
+	ret = set_pages(pages, ((unsigned []){ 0, 1, 3, 4, 5, 6}));
+	ret = alloc_tbl(&st, pages, ret, 0, ret * PAGE_SIZE, 2 * PAGE_SIZE);
+	check_and_free(&st, ret, 3);
+
+	return 0;
+}
-- 
2.9.4

[PATCH v2 5/5] tools/testing/scatterlist: Test new __sg_alloc_table_from_pages

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Exercise the new __sg_alloc_table_from_pages API (and through
it also the old sg_alloc_table_from_pages), checking that the
created table has the expected number of segments depending on
the sequence of input pages and other conditions.

v2: Move to data driven for readability.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: linux-kernel@vger.kernel.org
---
 tools/testing/scatterlist/Makefile   |  30 +++++++++
 tools/testing/scatterlist/linux/mm.h | 125 +++++++++++++++++++++++++++++++++++
 tools/testing/scatterlist/main.c     |  74 +++++++++++++++++++++
 3 files changed, 229 insertions(+)
 create mode 100644 tools/testing/scatterlist/Makefile
 create mode 100644 tools/testing/scatterlist/linux/mm.h
 create mode 100644 tools/testing/scatterlist/main.c

diff --git a/tools/testing/scatterlist/Makefile b/tools/testing/scatterlist/Makefile
new file mode 100644
index 000000000000..0867e0ef32d6
--- /dev/null
+++ b/tools/testing/scatterlist/Makefile
@@ -0,0 +1,30 @@
+CFLAGS += -I. -I../../include -g -O2 -Wall -fsanitize=address
+LDFLAGS += -fsanitize=address
+TARGETS = main
+OFILES = main.o scatterlist.o
+
+ifeq ($(BUILD), 32)
+        CFLAGS += -m32
+        LDFLAGS += -m32
+endif
+
+targets: include $(TARGETS)
+
+main: $(OFILES)
+
+clean:
+	$(RM) $(TARGETS) $(OFILES) scatterlist.c linux/scatterlist.h linux/highmem.h linux/kmemleak.h asm/io.h
+	@rmdir asm
+
+scatterlist.c: ../../../lib/scatterlist.c
+	@sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@
+
+.PHONY: include
+
+include: ../../../include/linux/scatterlist.h
+	@mkdir -p linux
+	@mkdir -p asm
+	@touch asm/io.h
+	@touch linux/highmem.h
+	@touch linux/kmemleak.h
+	@cp $< linux/scatterlist.h
diff --git a/tools/testing/scatterlist/linux/mm.h b/tools/testing/scatterlist/linux/mm.h
new file mode 100644
index 000000000000..ccbb248ebdc1
--- /dev/null
+++ b/tools/testing/scatterlist/linux/mm.h
@@ -0,0 +1,125 @@
+#ifndef _LINUX_MM_H
+#define _LINUX_MM_H
+
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+
+typedef unsigned long dma_addr_t;
+
+#define unlikely
+
+#define BUG_ON(x) assert(!(x))
+
+#define WARN_ON(condition) ({                                           \
+        int __ret_warn_on = !!(condition);                              \
+        unlikely(__ret_warn_on);                                        \
+})
+
+#define WARN_ON_ONCE(condition) ({                              \
+        int __ret_warn_on = !!(condition);                      \
+        if (unlikely(__ret_warn_on))                            \
+                assert(0);                                      \
+        unlikely(__ret_warn_on);                                \
+})
+
+#define PAGE_SIZE	(4096)
+#define PAGE_SHIFT	(12)
+#define PAGE_MASK	(~(PAGE_SIZE-1))
+
+#define __ALIGN_KERNEL(x, a)            __ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1)
+#define __ALIGN_KERNEL_MASK(x, mask)    (((x) + (mask)) & ~(mask))
+#define ALIGN(x, a)             __ALIGN_KERNEL((x), (a))
+
+#define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
+
+#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
+
+#define virt_to_page(x)	((void *)x)
+#define page_address(x)	((void *)x)
+
+static inline unsigned long page_to_phys(struct page *page)
+{
+	assert(0);
+
+	return 0;
+}
+
+#define page_to_pfn(page) ((unsigned long)(page) / PAGE_SIZE)
+#define pfn_to_page(pfn) (void *)((pfn) * PAGE_SIZE)
+#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
+
+#define __min(t1, t2, min1, min2, x, y) ({              \
+        t1 min1 = (x);                                  \
+        t2 min2 = (y);                                  \
+        (void) (&min1 == &min2);                        \
+        min1 < min2 ? min1 : min2; })
+
+#define ___PASTE(a,b) a##b
+#define __PASTE(a,b) ___PASTE(a,b)
+
+#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+#define min(x, y)                                       \
+        __min(typeof(x), typeof(y),                     \
+              __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),   \
+              x, y)
+
+#define min_t(type, x, y)                               \
+        __min(type, type,                               \
+              __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),   \
+              x, y)
+
+#define preemptible() (1)
+
+static inline void *kmap(struct page *page)
+{
+	assert(0);
+
+	return NULL;
+}
+
+static inline void *kmap_atomic(struct page *page)
+{
+	assert(0);
+
+	return NULL;
+}
+
+static inline void kunmap(void *addr)
+{
+	assert(0);
+}
+
+static inline void kunmap_atomic(void *addr)
+{
+	assert(0);
+}
+
+static inline unsigned long __get_free_page(unsigned int flags)
+{
+	return (unsigned long)malloc(PAGE_SIZE);
+}
+
+static inline void free_page(unsigned long page)
+{
+	free((void *)page);
+}
+
+static inline void *kmalloc(unsigned int size, unsigned int flags)
+{
+	return malloc(size);
+}
+
+#define kfree(x) free(x)
+
+#define kmemleak_alloc(a, b, c, d)
+#define kmemleak_free(a)
+
+#define PageSlab(p) (0)
+#define flush_kernel_dcache_page(p)
+
+#endif
diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
new file mode 100644
index 000000000000..8ca5c8703eb7
--- /dev/null
+++ b/tools/testing/scatterlist/main.c
@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <assert.h>
+
+#include <linux/scatterlist.h>
+
+#define MAX_PAGES (64)
+
+static void set_pages(struct page **pages, const unsigned *array, unsigned num)
+{
+	unsigned int i;
+
+	assert(num < MAX_PAGES);
+	for (i = 0; i < num; i++)
+		pages[i] = (struct page *)(unsigned long)
+			   ((1 + array[i]) * PAGE_SIZE);
+}
+
+#define pfn(...) (unsigned []){ __VA_ARGS__ }
+
+int main(void)
+{
+	const unsigned int sgmax = SCATTERLIST_MAX_SEGMENT;
+	struct test {
+		int alloc_ret;
+		unsigned num_pages;
+		unsigned *pfn;
+		unsigned size;
+		unsigned int max_seg;
+		unsigned int expected_segments;
+	} *test, tests[] = {
+		{ -EINVAL, 1, pfn(0), PAGE_SIZE, PAGE_SIZE + 1, 1 },
+		{ -EINVAL, 1, pfn(0), PAGE_SIZE, 0, 1 },
+		{ -EINVAL, 1, pfn(0), PAGE_SIZE, sgmax + 1, 1 },
+		{ 0, 1, pfn(0), PAGE_SIZE, sgmax, 1 },
+		{ 0, 1, pfn(0), 1, sgmax, 1 },
+		{ 0, 2, pfn(0, 1), 2 * PAGE_SIZE, sgmax, 1 },
+		{ 0, 3, pfn(0, 1, 3), 3 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 4, pfn(0, 1, 3, 4), 4 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 5, pfn(0, 1, 3, 4, 5), 5 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 5, pfn(0, 1, 3, 4, 6), 5 * PAGE_SIZE, sgmax, 3 },
+		{ 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, sgmax, 1 },
+		{ 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
+		{ 0, 6, pfn(0, 1, 2, 3, 4, 5), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
+		{ 0, 6, pfn(0, 2, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 4 },
+		{ 0, 6, pfn(0, 1, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
+		{ 0, 0, NULL, 0, 0, 0 },
+	};
+	unsigned i;
+
+	for (i = 0, test = tests; test->expected_segments; test++, i++) {
+		struct page *pages[MAX_PAGES];
+		struct sg_table st;
+		int ret;
+
+		set_pages(pages, test->pfn, test->num_pages);
+
+		ret = __sg_alloc_table_from_pages(&st, pages, test->num_pages,
+						  0, test->size, test->max_seg,
+						  GFP_KERNEL);
+		assert(ret == test->alloc_ret);
+
+		if (test->alloc_ret)
+			continue;
+
+		assert(st.nents == test->expected_segments);
+		assert(st.orig_nents == test->expected_segments);
+
+		sg_free_table(&st);
+	}
+
+	assert(i == (sizeof(tests) / sizeof(tests[0])) - 1);
+
+	return 0;
+}
-- 
2.9.5

Re: [PATCH v2 5/5] tools/testing/scatterlist: Test new __sg_alloc_table_from_pages

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-09-05 11:24:03)
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> Exercise the new __sg_alloc_table_from_pages API (and through
> it also the old sg_alloc_table_from_pages), checking that the
> created table has the expected number of segments depending on
> the sequence of input pages and other conditions.
> 
> v2: Move to data driven for readability.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: linux-kernel@vger.kernel.org
> ---
>  tools/testing/scatterlist/Makefile   |  30 +++++++++
>  tools/testing/scatterlist/linux/mm.h | 125 +++++++++++++++++++++++++++++++++++
>  tools/testing/scatterlist/main.c     |  74 +++++++++++++++++++++
>  3 files changed, 229 insertions(+)
>  create mode 100644 tools/testing/scatterlist/Makefile
>  create mode 100644 tools/testing/scatterlist/linux/mm.h
>  create mode 100644 tools/testing/scatterlist/main.c
> 
> diff --git a/tools/testing/scatterlist/Makefile b/tools/testing/scatterlist/Makefile
> new file mode 100644
> index 000000000000..0867e0ef32d6
> --- /dev/null
> +++ b/tools/testing/scatterlist/Makefile
> @@ -0,0 +1,30 @@
> +CFLAGS += -I. -I../../include -g -O2 -Wall -fsanitize=address
> +LDFLAGS += -fsanitize=address
> +TARGETS = main
> +OFILES = main.o scatterlist.o
> +
> +ifeq ($(BUILD), 32)
> +        CFLAGS += -m32
> +        LDFLAGS += -m32
> +endif

Hmm, are there no HOST_CFLAGS? No. I wonder how menuconfig/xconfig get
compiled.

HOSTCC, HOSTCFLAGS.

hostprogs-y := main
always := $(hostprogs-y)

But nothing else seems to use HOSTCC in testing/selftests

> +targets: include $(TARGETS)
> +
> +main: $(OFILES)
> +
> +clean:
> +       $(RM) $(TARGETS) $(OFILES) scatterlist.c linux/scatterlist.h linux/highmem.h linux/kmemleak.h asm/io.h
> +       @rmdir asm
> +
> +scatterlist.c: ../../../lib/scatterlist.c
> +       @sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@

I think I would have used

#define __always_inline inline
#include "../../../lib/scatterlist.c"

> diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
> new file mode 100644
> index 000000000000..8ca5c8703eb7
> --- /dev/null
> +++ b/tools/testing/scatterlist/main.c
> @@ -0,0 +1,74 @@
> +#include <stdio.h>
> +#include <assert.h>
> +
> +#include <linux/scatterlist.h>
> +
> +#define MAX_PAGES (64)
> +
> +static void set_pages(struct page **pages, const unsigned *array, unsigned num)
> +{
> +       unsigned int i;
> +
> +       assert(num < MAX_PAGES);
> +       for (i = 0; i < num; i++)
> +               pages[i] = (struct page *)(unsigned long)
> +                          ((1 + array[i]) * PAGE_SIZE);

pfn_to_page(PFN_BIAS + array[i]) ? Ah, that relies on headers. Ok.

> +}
> +
> +#define pfn(...) (unsigned []){ __VA_ARGS__ }
> +
> +int main(void)
> +{
> +       const unsigned int sgmax = SCATTERLIST_MAX_SEGMENT;
> +       struct test {
> +               int alloc_ret;
> +               unsigned num_pages;
> +               unsigned *pfn;
> +               unsigned size;
> +               unsigned int max_seg;
> +               unsigned int expected_segments;
> +       } *test, tests[] = {
> +               { -EINVAL, 1, pfn(0), PAGE_SIZE, PAGE_SIZE + 1, 1 },
> +               { -EINVAL, 1, pfn(0), PAGE_SIZE, 0, 1 },
> +               { -EINVAL, 1, pfn(0), PAGE_SIZE, sgmax + 1, 1 },
> +               { 0, 1, pfn(0), PAGE_SIZE, sgmax, 1 },
> +               { 0, 1, pfn(0), 1, sgmax, 1 },
> +               { 0, 2, pfn(0, 1), 2 * PAGE_SIZE, sgmax, 1 },
> +               { 0, 3, pfn(0, 1, 3), 3 * PAGE_SIZE, sgmax, 2 },
> +               { 0, 4, pfn(0, 1, 3, 4), 4 * PAGE_SIZE, sgmax, 2 },
> +               { 0, 5, pfn(0, 1, 3, 4, 5), 5 * PAGE_SIZE, sgmax, 2 },
> +               { 0, 5, pfn(0, 1, 3, 4, 6), 5 * PAGE_SIZE, sgmax, 3 },
> +               { 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, sgmax, 1 },
> +               { 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
> +               { 0, 6, pfn(0, 1, 2, 3, 4, 5), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
> +               { 0, 6, pfn(0, 2, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 4 },
> +               { 0, 6, pfn(0, 1, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },

All ascending. Interesting challenge for 3,2,1,0; it can be coalesced,
we just don't. I wonder if we are missing some like that. But for the
moment, 0, 2, 1, would be a good addition to the above set.

Is there any value in checking overflows in this interface?

Lgtm, throw in a couple of inverted positions,
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris

Re: [Intel-gfx] [PATCH v2 5/5] tools/testing/scatterlist: Test new __sg_alloc_table_from_pages

[Tvrtko Ursulin]

On 06/09/2017 11:48, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2017-09-05 11:24:03)
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> Exercise the new __sg_alloc_table_from_pages API (and through
>> it also the old sg_alloc_table_from_pages), checking that the
>> created table has the expected number of segments depending on
>> the sequence of input pages and other conditions.
>>
>> v2: Move to data driven for readability.
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: linux-kernel@vger.kernel.org
>> ---
>>   tools/testing/scatterlist/Makefile   |  30 +++++++++
>>   tools/testing/scatterlist/linux/mm.h | 125 +++++++++++++++++++++++++++++++++++
>>   tools/testing/scatterlist/main.c     |  74 +++++++++++++++++++++
>>   3 files changed, 229 insertions(+)
>>   create mode 100644 tools/testing/scatterlist/Makefile
>>   create mode 100644 tools/testing/scatterlist/linux/mm.h
>>   create mode 100644 tools/testing/scatterlist/main.c
>>
>> diff --git a/tools/testing/scatterlist/Makefile b/tools/testing/scatterlist/Makefile
>> new file mode 100644
>> index 000000000000..0867e0ef32d6
>> --- /dev/null
>> +++ b/tools/testing/scatterlist/Makefile
>> @@ -0,0 +1,30 @@
>> +CFLAGS += -I. -I../../include -g -O2 -Wall -fsanitize=address
>> +LDFLAGS += -fsanitize=address
>> +TARGETS = main
>> +OFILES = main.o scatterlist.o
>> +
>> +ifeq ($(BUILD), 32)
>> +        CFLAGS += -m32
>> +        LDFLAGS += -m32
>> +endif
> 
> Hmm, are there no HOST_CFLAGS? No. I wonder how menuconfig/xconfig get
> compiled.
> 
> HOSTCC, HOSTCFLAGS.
> 
> hostprogs-y := main
> always := $(hostprogs-y)
> 
> But nothing else seems to use HOSTCC in testing/selftests

I lifted it frim an existing makefile. I think this means no one was 
interested in building tests while doing a cross compile.

>> +targets: include $(TARGETS)
>> +
>> +main: $(OFILES)
>> +
>> +clean:
>> +       $(RM) $(TARGETS) $(OFILES) scatterlist.c linux/scatterlist.h linux/highmem.h linux/kmemleak.h asm/io.h
>> +       @rmdir asm
>> +
>> +scatterlist.c: ../../../lib/scatterlist.c
>> +       @sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@
> 
> I think I would have used
> 
> #define __always_inline inline
> #include "../../../lib/scatterlist.c"

Again, I lifted the approach from one of the existing tests. It might be 
beneficial to have a local copy when debugging, but it is probably very 
marginal and both approaches look OK.

>> diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
>> new file mode 100644
>> index 000000000000..8ca5c8703eb7
>> --- /dev/null
>> +++ b/tools/testing/scatterlist/main.c
>> @@ -0,0 +1,74 @@
>> +#include <stdio.h>
>> +#include <assert.h>
>> +
>> +#include <linux/scatterlist.h>
>> +
>> +#define MAX_PAGES (64)
>> +
>> +static void set_pages(struct page **pages, const unsigned *array, unsigned num)
>> +{
>> +       unsigned int i;
>> +
>> +       assert(num < MAX_PAGES);
>> +       for (i = 0; i < num; i++)
>> +               pages[i] = (struct page *)(unsigned long)
>> +                          ((1 + array[i]) * PAGE_SIZE);
> 
> pfn_to_page(PFN_BIAS + array[i]) ? Ah, that relies on headers. Ok.
> 
>> +}
>> +
>> +#define pfn(...) (unsigned []){ __VA_ARGS__ }
>> +
>> +int main(void)
>> +{
>> +       const unsigned int sgmax = SCATTERLIST_MAX_SEGMENT;
>> +       struct test {
>> +               int alloc_ret;
>> +               unsigned num_pages;
>> +               unsigned *pfn;
>> +               unsigned size;
>> +               unsigned int max_seg;
>> +               unsigned int expected_segments;
>> +       } *test, tests[] = {
>> +               { -EINVAL, 1, pfn(0), PAGE_SIZE, PAGE_SIZE + 1, 1 },
>> +               { -EINVAL, 1, pfn(0), PAGE_SIZE, 0, 1 },
>> +               { -EINVAL, 1, pfn(0), PAGE_SIZE, sgmax + 1, 1 },
>> +               { 0, 1, pfn(0), PAGE_SIZE, sgmax, 1 },
>> +               { 0, 1, pfn(0), 1, sgmax, 1 },
>> +               { 0, 2, pfn(0, 1), 2 * PAGE_SIZE, sgmax, 1 },
>> +               { 0, 3, pfn(0, 1, 3), 3 * PAGE_SIZE, sgmax, 2 },
>> +               { 0, 4, pfn(0, 1, 3, 4), 4 * PAGE_SIZE, sgmax, 2 },
>> +               { 0, 5, pfn(0, 1, 3, 4, 5), 5 * PAGE_SIZE, sgmax, 2 },
>> +               { 0, 5, pfn(0, 1, 3, 4, 6), 5 * PAGE_SIZE, sgmax, 3 },
>> +               { 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, sgmax, 1 },
>> +               { 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
>> +               { 0, 6, pfn(0, 1, 2, 3, 4, 5), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
>> +               { 0, 6, pfn(0, 2, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 4 },
>> +               { 0, 6, pfn(0, 1, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
> 
> All ascending. Interesting challenge for 3,2,1,0; it can be coalesced,
> we just don't. I wonder if we are missing some like that. But for the

Hm, how do you think descending pages could be coalesced? By 
re-arranging the pages? But that would break everything, do I don't get it.

> moment, 0, 2, 1, would be a good addition to the above set.
> 
> Is there any value in checking overflows in this interface?

Overflows as in size > num_pages * PAGE_SIZE as passed in to 
__sg_alloc_table_from_pages ? It is not checked in the implementation at 
the moment and it looks it is harmless.

There is one test above which checks for underflow (size < num_pages * 
PAGE_SIZE).

> Lgtm, throw in a couple of inverted positions,
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Will do, thanks!

Regards,

Tvrtko

Re: [Intel-gfx] [PATCH v2 5/5] tools/testing/scatterlist: Test new __sg_alloc_table_from_pages

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-09-06 13:10:57)
> 
> On 06/09/2017 11:48, Chris Wilson wrote:
> > All ascending. Interesting challenge for 3,2,1,0; it can be coalesced,
> > we just don't. I wonder if we are missing some like that. But for the
> 
> Hm, how do you think descending pages could be coalesced? By 
> re-arranging the pages? But that would break everything, do I don't get it.

Wishful thinking; I wasn't considering the order inside the object, just
their physical addresses.
> 
> > moment, 0, 2, 1, would be a good addition to the above set.
> > 
> > Is there any value in checking overflows in this interface?
> 
> Overflows as in size > num_pages * PAGE_SIZE as passed in to 
> __sg_alloc_table_from_pages ? It is not checked in the implementation at 
> the moment and it looks it is harmless.

Just thinking aloud if there was a way to get a mult/add overflow. That
we do page size coalescing, the only avenue is from a buggy max_seg.

Going back to the makefile, perhaps add the magic for ubsan as well?
-fsanitize=address -fsanitize=undefined
-Chris

[PATCH v3 5/5] tools/testing/scatterlist: Test new __sg_alloc_table_from_pages

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Exercise the new __sg_alloc_table_from_pages API (and through
it also the old sg_alloc_table_from_pages), checking that the
created table has the expected number of segments depending on
the sequence of input pages and other conditions.

v2: Move to data driven for readability.
v3: Add some more testcases and -fsanitize=undefined. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 tools/testing/scatterlist/Makefile   |  30 +++++++++
 tools/testing/scatterlist/linux/mm.h | 125 +++++++++++++++++++++++++++++++++++
 tools/testing/scatterlist/main.c     |  79 ++++++++++++++++++++++
 3 files changed, 234 insertions(+)
 create mode 100644 tools/testing/scatterlist/Makefile
 create mode 100644 tools/testing/scatterlist/linux/mm.h
 create mode 100644 tools/testing/scatterlist/main.c

diff --git a/tools/testing/scatterlist/Makefile b/tools/testing/scatterlist/Makefile
new file mode 100644
index 000000000000..933c3a6e4d77
--- /dev/null
+++ b/tools/testing/scatterlist/Makefile
@@ -0,0 +1,30 @@
+CFLAGS += -I. -I../../include -g -O2 -Wall -fsanitize=address
+LDFLAGS += -fsanitize=address -fsanitize=undefined
+TARGETS = main
+OFILES = main.o scatterlist.o
+
+ifeq ($(BUILD), 32)
+        CFLAGS += -m32
+        LDFLAGS += -m32
+endif
+
+targets: include $(TARGETS)
+
+main: $(OFILES)
+
+clean:
+	$(RM) $(TARGETS) $(OFILES) scatterlist.c linux/scatterlist.h linux/highmem.h linux/kmemleak.h asm/io.h
+	@rmdir asm
+
+scatterlist.c: ../../../lib/scatterlist.c
+	@sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@
+
+.PHONY: include
+
+include: ../../../include/linux/scatterlist.h
+	@mkdir -p linux
+	@mkdir -p asm
+	@touch asm/io.h
+	@touch linux/highmem.h
+	@touch linux/kmemleak.h
+	@cp $< linux/scatterlist.h
diff --git a/tools/testing/scatterlist/linux/mm.h b/tools/testing/scatterlist/linux/mm.h
new file mode 100644
index 000000000000..ccbb248ebdc1
--- /dev/null
+++ b/tools/testing/scatterlist/linux/mm.h
@@ -0,0 +1,125 @@
+#ifndef _LINUX_MM_H
+#define _LINUX_MM_H
+
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+
+typedef unsigned long dma_addr_t;
+
+#define unlikely
+
+#define BUG_ON(x) assert(!(x))
+
+#define WARN_ON(condition) ({                                           \
+        int __ret_warn_on = !!(condition);                              \
+        unlikely(__ret_warn_on);                                        \
+})
+
+#define WARN_ON_ONCE(condition) ({                              \
+        int __ret_warn_on = !!(condition);                      \
+        if (unlikely(__ret_warn_on))                            \
+                assert(0);                                      \
+        unlikely(__ret_warn_on);                                \
+})
+
+#define PAGE_SIZE	(4096)
+#define PAGE_SHIFT	(12)
+#define PAGE_MASK	(~(PAGE_SIZE-1))
+
+#define __ALIGN_KERNEL(x, a)            __ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1)
+#define __ALIGN_KERNEL_MASK(x, mask)    (((x) + (mask)) & ~(mask))
+#define ALIGN(x, a)             __ALIGN_KERNEL((x), (a))
+
+#define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE)
+
+#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
+
+#define virt_to_page(x)	((void *)x)
+#define page_address(x)	((void *)x)
+
+static inline unsigned long page_to_phys(struct page *page)
+{
+	assert(0);
+
+	return 0;
+}
+
+#define page_to_pfn(page) ((unsigned long)(page) / PAGE_SIZE)
+#define pfn_to_page(pfn) (void *)((pfn) * PAGE_SIZE)
+#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
+
+#define __min(t1, t2, min1, min2, x, y) ({              \
+        t1 min1 = (x);                                  \
+        t2 min2 = (y);                                  \
+        (void) (&min1 == &min2);                        \
+        min1 < min2 ? min1 : min2; })
+
+#define ___PASTE(a,b) a##b
+#define __PASTE(a,b) ___PASTE(a,b)
+
+#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+#define min(x, y)                                       \
+        __min(typeof(x), typeof(y),                     \
+              __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),   \
+              x, y)
+
+#define min_t(type, x, y)                               \
+        __min(type, type,                               \
+              __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),   \
+              x, y)
+
+#define preemptible() (1)
+
+static inline void *kmap(struct page *page)
+{
+	assert(0);
+
+	return NULL;
+}
+
+static inline void *kmap_atomic(struct page *page)
+{
+	assert(0);
+
+	return NULL;
+}
+
+static inline void kunmap(void *addr)
+{
+	assert(0);
+}
+
+static inline void kunmap_atomic(void *addr)
+{
+	assert(0);
+}
+
+static inline unsigned long __get_free_page(unsigned int flags)
+{
+	return (unsigned long)malloc(PAGE_SIZE);
+}
+
+static inline void free_page(unsigned long page)
+{
+	free((void *)page);
+}
+
+static inline void *kmalloc(unsigned int size, unsigned int flags)
+{
+	return malloc(size);
+}
+
+#define kfree(x) free(x)
+
+#define kmemleak_alloc(a, b, c, d)
+#define kmemleak_free(a)
+
+#define PageSlab(p) (0)
+#define flush_kernel_dcache_page(p)
+
+#endif
diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
new file mode 100644
index 000000000000..0a1464181226
--- /dev/null
+++ b/tools/testing/scatterlist/main.c
@@ -0,0 +1,79 @@
+#include <stdio.h>
+#include <assert.h>
+
+#include <linux/scatterlist.h>
+
+#define MAX_PAGES (64)
+
+static void set_pages(struct page **pages, const unsigned *array, unsigned num)
+{
+	unsigned int i;
+
+	assert(num < MAX_PAGES);
+	for (i = 0; i < num; i++)
+		pages[i] = (struct page *)(unsigned long)
+			   ((1 + array[i]) * PAGE_SIZE);
+}
+
+#define pfn(...) (unsigned []){ __VA_ARGS__ }
+
+int main(void)
+{
+	const unsigned int sgmax = SCATTERLIST_MAX_SEGMENT;
+	struct test {
+		int alloc_ret;
+		unsigned num_pages;
+		unsigned *pfn;
+		unsigned size;
+		unsigned int max_seg;
+		unsigned int expected_segments;
+	} *test, tests[] = {
+		{ -EINVAL, 1, pfn(0), PAGE_SIZE, PAGE_SIZE + 1, 1 },
+		{ -EINVAL, 1, pfn(0), PAGE_SIZE, 0, 1 },
+		{ -EINVAL, 1, pfn(0), PAGE_SIZE, sgmax + 1, 1 },
+		{ 0, 1, pfn(0), PAGE_SIZE, sgmax, 1 },
+		{ 0, 1, pfn(0), 1, sgmax, 1 },
+		{ 0, 2, pfn(0, 1), 2 * PAGE_SIZE, sgmax, 1 },
+		{ 0, 2, pfn(1, 0), 2 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 3, pfn(0, 1, 2), 3 * PAGE_SIZE, sgmax, 1 },
+		{ 0, 3, pfn(0, 2, 1), 3 * PAGE_SIZE, sgmax, 3 },
+		{ 0, 3, pfn(0, 1, 3), 3 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 3, pfn(1, 2, 4), 3 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 3, pfn(1, 3, 4), 3 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 4, pfn(0, 1, 3, 4), 4 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 5, pfn(0, 1, 3, 4, 5), 5 * PAGE_SIZE, sgmax, 2 },
+		{ 0, 5, pfn(0, 1, 3, 4, 6), 5 * PAGE_SIZE, sgmax, 3 },
+		{ 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, sgmax, 1 },
+		{ 0, 5, pfn(0, 1, 2, 3, 4), 5 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
+		{ 0, 6, pfn(0, 1, 2, 3, 4, 5), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
+		{ 0, 6, pfn(0, 2, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 4 },
+		{ 0, 6, pfn(0, 1, 3, 4, 5, 6), 6 * PAGE_SIZE, 2 * PAGE_SIZE, 3 },
+		{ 0, 0, NULL, 0, 0, 0 },
+	};
+	unsigned int i;
+
+	for (i = 0, test = tests; test->expected_segments; test++, i++) {
+		struct page *pages[MAX_PAGES];
+		struct sg_table st;
+		int ret;
+
+		set_pages(pages, test->pfn, test->num_pages);
+
+		ret = __sg_alloc_table_from_pages(&st, pages, test->num_pages,
+						  0, test->size, test->max_seg,
+						  GFP_KERNEL);
+		assert(ret == test->alloc_ret);
+
+		if (test->alloc_ret)
+			continue;
+
+		assert(st.nents == test->expected_segments);
+		assert(st.orig_nents == test->expected_segments);
+
+		sg_free_table(&st);
+	}
+
+	assert(i == (sizeof(tests) / sizeof(tests[0])) - 1);
+
+	return 0;
+}
-- 
2.9.5