[PATCH rdma-next v2 0/2] SG fix together with update to RDMA umem

[PATCH rdma-next v2 0/2] SG fix together with update to RDMA umem

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Changelog:
v2:
 * Changed implementation of first patch, based on our discussion with Christoph.
   https://lore.kernel.org/lkml/YNwaVTT0qmQdxaZz@infradead.org/
v1: https://lore.kernel.org/lkml/cover.1624955710.git.leonro@nvidia.com/
 * Fixed sg_page with a _dma_ API in the umem.c
v0: https://lore.kernel.org/lkml/cover.1624361199.git.leonro@nvidia.com

Maor Gottlieb (2):
  lib/scatterlist: Fix wrong update of orig_nents
  RDMA: Use dma_map_sgtable for map umem pages

 drivers/gpu/drm/drm_prime.c                 |  2 +-
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c |  2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c  |  2 +-
 drivers/infiniband/core/umem.c              | 33 +++-----
 drivers/infiniband/core/umem_dmabuf.c       |  1 -
 drivers/infiniband/hw/mlx4/mr.c             |  4 +-
 drivers/infiniband/hw/mlx5/mr.c             |  3 +-
 drivers/infiniband/sw/rdmavt/mr.c           |  2 +-
 drivers/infiniband/sw/rxe/rxe_mr.c          |  3 +-
 include/linux/scatterlist.h                 |  3 +-
 include/rdma/ib_umem.h                      |  6 +-
 include/rdma/ib_verbs.h                     | 28 +++++++
 lib/scatterlist.c                           | 88 ++++++++++++++-------
 tools/testing/scatterlist/main.c            | 15 +++-
 14 files changed, 128 insertions(+), 64 deletions(-)

-- 
2.31.1

[PATCH rdma-next v2 1/2] lib/scatterlist: Fix wrong update of orig_nents

[Leon Romanovsky]

From: Maor Gottlieb <maorg@nvidia.com>

orig_nents should represent the number of entries with pages,
but __sg_alloc_table_from_pages sets orig_nents as the number of
total entries in the table. This is wrong when the API is used for
dynamic allocation where not all the table entries are mapped with
pages. It wasn't observed until now, since RDMA umem who uses this
API in the dynamic form doesn't use orig_nents implicit or explicit
by the scatterlist APIs.

Fix it by:
1. Set orig_nents as number of entries with pages also in
   __sg_alloc_table_from_pages.
2. To fix the release flow, add a new output argument to
   __sg_alloc_table_from_pages which will be set to the
   number of total entries in the table. User like umem that use
   this function for dynamic allocation, should free the table by
   calling to sg_free_table_entries and pass the number of entries.

Fixes: 07da1223ec93 ("lib/scatterlist: Add support in dynamic allocation of SG table from pages")
Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/gpu/drm/drm_prime.c                 |  2 +-
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c |  2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c  |  2 +-
 drivers/infiniband/core/umem.c              |  5 +-
 include/linux/scatterlist.h                 |  3 +-
 include/rdma/ib_umem.h                      |  3 +-
 lib/scatterlist.c                           | 88 ++++++++++++++-------
 tools/testing/scatterlist/main.c            | 15 +++-
 8 files changed, 80 insertions(+), 40 deletions(-)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 2a54f86856af..1739d10a2c55 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -821,7 +821,7 @@ struct sg_table *drm_prime_pages_to_sg(struct drm_device *dev,
 	sge = __sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
 					  nr_pages << PAGE_SHIFT,
 					  max_segment,
-					  NULL, 0, GFP_KERNEL);
+					  NULL, 0, GFP_KERNEL, NULL);
 	if (IS_ERR(sge)) {
 		kfree(sg);
 		sg = ERR_CAST(sge);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 7487bab11f0b..c341d3e3386c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -155,7 +155,7 @@ static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
 alloc_table:
 	sg = __sg_alloc_table_from_pages(st, pvec, num_pages, 0,
 					 num_pages << PAGE_SHIFT, max_segment,
-					 NULL, 0, GFP_KERNEL);
+					 NULL, 0, GFP_KERNEL, NULL);
 	if (IS_ERR(sg)) {
 		ret = PTR_ERR(sg);
 		goto err;
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
index 0488042fb287..2ad889272b0a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
@@ -390,7 +390,7 @@ static int vmw_ttm_map_dma(struct vmw_ttm_tt *vmw_tt)
 				vsgt->num_pages, 0,
 				(unsigned long) vsgt->num_pages << PAGE_SHIFT,
 				dma_get_max_seg_size(dev_priv->drm.dev),
-				NULL, 0, GFP_KERNEL);
+				NULL, 0, GFP_KERNEL, NULL);
 		if (IS_ERR(sg)) {
 			ret = PTR_ERR(sg);
 			goto out_sg_alloc_fail;
diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 0eb40025075f..cf4197363346 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -59,7 +59,7 @@ static void __ib_umem_release(struct ib_device *dev, struct ib_umem *umem, int d
 		unpin_user_page_range_dirty_lock(sg_page(sg),
 			DIV_ROUND_UP(sg->length, PAGE_SIZE), make_dirty);
 
-	sg_free_table(&umem->sg_head);
+	sg_free_table_entries(&umem->sg_head, umem->total_nents);
 }
 
 /**
@@ -229,8 +229,7 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,
 		sg = __sg_alloc_table_from_pages(&umem->sg_head, page_list, ret,
 				0, ret << PAGE_SHIFT,
 				ib_dma_max_seg_size(device), sg, npages,
-				GFP_KERNEL);
-		umem->sg_nents = umem->sg_head.nents;
+				GFP_KERNEL, &umem->total_nents);
 		if (IS_ERR(sg)) {
 			unpin_user_pages_dirty_lock(page_list, ret, 0);
 			ret = PTR_ERR(sg);
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index ecf87484814f..c796c165d5ee 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -282,6 +282,7 @@ typedef void (sg_free_fn)(struct scatterlist *, unsigned int);
 void __sg_free_table(struct sg_table *, unsigned int, unsigned int,
 		     sg_free_fn *);
 void sg_free_table(struct sg_table *);
+void sg_free_table_entries(struct sg_table *sgt, unsigned int num_entries);
 int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,
 		     struct scatterlist *, unsigned int, gfp_t, sg_alloc_fn *);
 int sg_alloc_table(struct sg_table *, unsigned int, gfp_t);
@@ -289,7 +290,7 @@ struct scatterlist *__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,
 		struct scatterlist *prv, unsigned int left_pages,
-		gfp_t gfp_mask);
+		gfp_t gfp_mask, unsigned int *total_nents);
 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);
diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h
index 676c57f5ca80..5a65212efc2e 100644
--- a/include/rdma/ib_umem.h
+++ b/include/rdma/ib_umem.h
@@ -27,8 +27,7 @@ struct ib_umem {
 	u32 is_dmabuf : 1;
 	struct work_struct	work;
 	struct sg_table sg_head;
-	int             nmap;
-	unsigned int    sg_nents;
+	unsigned int total_nents;
 };
 
 struct ib_umem_dmabuf {
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 27efa6178153..5cc41ae962ec 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -175,22 +175,11 @@ static void sg_kfree(struct scatterlist *sg, unsigned int nents)
 		kfree(sg);
 }
 
-/**
- * __sg_free_table - Free a previously mapped sg table
- * @table:	The sg table header to use
- * @max_ents:	The maximum number of entries per single scatterlist
- * @nents_first_chunk: Number of entries int the (preallocated) first
- * 	scatterlist chunk, 0 means no such preallocated first chunk
- * @free_fn:	Free function
- *
- *  Description:
- *    Free an sg table previously allocated and setup with
- *    __sg_alloc_table().  The @max_ents value must be identical to
- *    that previously used with __sg_alloc_table().
- *
- **/
-void __sg_free_table(struct sg_table *table, unsigned int max_ents,
-		     unsigned int nents_first_chunk, sg_free_fn *free_fn)
+static void __sg_free_table_entries(struct sg_table *table,
+				    unsigned int max_ents,
+				    unsigned int nents_first_chunk,
+				    sg_free_fn *free_fn,
+				    unsigned int num_entries)
 {
 	struct scatterlist *sgl, *next;
 	unsigned curr_max_ents = nents_first_chunk ?: max_ents;
@@ -199,8 +188,8 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents,
 		return;
 
 	sgl = table->sgl;
-	while (table->orig_nents) {
-		unsigned int alloc_size = table->orig_nents;
+	while (num_entries) {
+		unsigned int alloc_size = num_entries;
 		unsigned int sg_size;
 
 		/*
@@ -218,7 +207,7 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents,
 			next = NULL;
 		}
 
-		table->orig_nents -= sg_size;
+		num_entries -= sg_size;
 		if (nents_first_chunk)
 			nents_first_chunk = 0;
 		else
@@ -229,6 +218,43 @@ void __sg_free_table(struct sg_table *table, unsigned int max_ents,
 
 	table->sgl = NULL;
 }
+
+/**
+ * sg_free_table_entries - Free a previously allocated sg table according to
+ *                         the total number of entries in the table.
+ * @table:	 The mapped sg table header
+ * @num_entries: The number of entries in the table.
+ *
+ **/
+void sg_free_table_entries(struct sg_table *table, unsigned int num_entries)
+{
+	__sg_free_table_entries(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree,
+				num_entries);
+}
+EXPORT_SYMBOL(sg_free_table_entries);
+
+/**
+ * __sg_free_table - Free a previously mapped sg table
+ * @table:	The sg table header to use
+ * @max_ents:	The maximum number of entries per single scatterlist
+ * @total_ents:	The total number of entries in the table
+ * @nents_first_chunk: Number of entries int the (preallocated) first
+ *                     scatterlist chunk, 0 means no such preallocated
+ *                     first chunk
+ * @free_fn:	Free function
+ *
+ *  Description:
+ *    Free an sg table previously allocated and setup with
+ *    __sg_alloc_table().  The @max_ents value must be identical to
+ *    that previously used with __sg_alloc_table().
+ *
+ **/
+void __sg_free_table(struct sg_table *table, unsigned int max_ents,
+		     unsigned int nents_first_chunk, sg_free_fn *free_fn)
+{
+	__sg_free_table_entries(table, max_ents, nents_first_chunk, free_fn,
+				table->orig_nents);
+}
 EXPORT_SYMBOL(__sg_free_table);
 
 /**
@@ -238,7 +264,8 @@ EXPORT_SYMBOL(__sg_free_table);
  **/
 void sg_free_table(struct sg_table *table)
 {
-	__sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree);
+	__sg_free_table_entries(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree,
+				table->orig_nents);
 }
 EXPORT_SYMBOL(sg_free_table);
 
@@ -368,7 +395,8 @@ EXPORT_SYMBOL(sg_alloc_table);
 static struct scatterlist *get_next_sg(struct sg_table *table,
 				       struct scatterlist *cur,
 				       unsigned long needed_sges,
-				       gfp_t gfp_mask)
+				       gfp_t gfp_mask,
+				       unsigned int *total_nents)
 {
 	struct scatterlist *new_sg, *next_sg;
 	unsigned int alloc_size;
@@ -386,12 +414,14 @@ static struct scatterlist *get_next_sg(struct sg_table *table,
 		return ERR_PTR(-ENOMEM);
 	sg_init_table(new_sg, alloc_size);
 	if (cur) {
+		if (total_nents)
+			*total_nents += alloc_size - 1;
 		__sg_chain(next_sg, new_sg);
-		table->orig_nents += alloc_size - 1;
 	} else {
 		table->sgl = new_sg;
-		table->orig_nents = alloc_size;
 		table->nents = 0;
+		if (total_nents)
+			*total_nents = alloc_size;
 	}
 	return new_sg;
 }
@@ -408,6 +438,7 @@ static struct scatterlist *get_next_sg(struct sg_table *table,
  * @prv:	 Last populated sge in sgt
  * @left_pages:  Left pages caller have to set after this call
  * @gfp_mask:	 GFP allocation mask
+ * @total_nents: Output of total number of entries in the table
  *
  * Description:
  *    If @prv is NULL, allocate and initialize an sg table from a list of pages,
@@ -419,7 +450,8 @@ static struct scatterlist *get_next_sg(struct sg_table *table,
  *
  * Returns:
  *   Last SGE in sgt on success, PTR_ERR on otherwise.
- *   The allocation in @sgt must be released by sg_free_table.
+ *   The allocation in @sgt must be released by sg_free_table or
+ *   sg_free_table_entries.
  *
  * Notes:
  *   If this function returns non-0 (eg failure), the caller must call
@@ -429,7 +461,7 @@ struct scatterlist *__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,
 		struct scatterlist *prv, unsigned int left_pages,
-		gfp_t gfp_mask)
+		gfp_t gfp_mask, unsigned int *total_nents)
 {
 	unsigned int chunks, cur_page, seg_len, i, prv_len = 0;
 	unsigned int added_nents = 0;
@@ -496,7 +528,8 @@ struct scatterlist *__sg_alloc_table_from_pages(struct sg_table *sgt,
 		}
 
 		/* Pass how many chunks might be left */
-		s = get_next_sg(sgt, s, chunks - i + left_pages, gfp_mask);
+		s = get_next_sg(sgt, s, chunks - i + left_pages, gfp_mask,
+				total_nents);
 		if (IS_ERR(s)) {
 			/*
 			 * Adjust entry length to be as before function was
@@ -515,6 +548,7 @@ struct scatterlist *__sg_alloc_table_from_pages(struct sg_table *sgt,
 		cur_page = j;
 	}
 	sgt->nents += added_nents;
+	sgt->orig_nents = sgt->nents;
 out:
 	if (!left_pages)
 		sg_mark_end(s);
@@ -547,7 +581,7 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
 			      unsigned long size, gfp_t gfp_mask)
 {
 	return PTR_ERR_OR_ZERO(__sg_alloc_table_from_pages(sgt, pages, n_pages,
-			offset, size, UINT_MAX, NULL, 0, gfp_mask));
+			offset, size, UINT_MAX, NULL, 0, gfp_mask, NULL));
 }
 EXPORT_SYMBOL(sg_alloc_table_from_pages);
 
diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
index 652254754b4c..00576c86971e 100644
--- a/tools/testing/scatterlist/main.c
+++ b/tools/testing/scatterlist/main.c
@@ -88,11 +88,14 @@ int main(void)
 		struct page *pages[MAX_PAGES];
 		struct sg_table st;
 		struct scatterlist *sg;
+		unsigned int total_nents;
 
 		set_pages(pages, test->pfn, test->num_pages);
 
 		sg = __sg_alloc_table_from_pages(&st, pages, test->num_pages, 0,
-				test->size, test->max_seg, NULL, left_pages, GFP_KERNEL);
+						 test->size, test->max_seg,
+						 NULL, left_pages, GFP_KERNEL,
+						 &total_nents);
 		assert(PTR_ERR_OR_ZERO(sg) == test->alloc_ret);
 
 		if (test->alloc_ret)
@@ -100,8 +103,9 @@ int main(void)
 
 		if (test->pfn_app) {
 			set_pages(pages, test->pfn_app, test->num_pages);
-			sg = __sg_alloc_table_from_pages(&st, pages, test->num_pages, 0,
-					test->size, test->max_seg, sg, 0, GFP_KERNEL);
+			sg = __sg_alloc_table_from_pages(
+				&st, pages, test->num_pages, 0, test->size,
+				test->max_seg, sg, 0, GFP_KERNEL, &total_nents);
 
 			assert(PTR_ERR_OR_ZERO(sg) == test->alloc_ret);
 		}
@@ -110,7 +114,10 @@ int main(void)
 		if (!test->pfn_app)
 			VALIDATE(st.orig_nents == test->expected_segments, &st, test);
 
-		sg_free_table(&st);
+		if (test->pfn_app)
+			sg_free_table_entries(&st, total_nents);
+		else
+			sg_free_table(&st);
 	}
 
 	assert(i == (sizeof(tests) / sizeof(tests[0])) - 1);
-- 
2.31.1

Re: [PATCH rdma-next v2 1/2] lib/scatterlist: Fix wrong update of orig_nents

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH rdma-next v2 1/2] lib/scatterlist: Fix wrong update of orig_nents

[Jason Gunthorpe]

On Sun, Jul 18, 2021 at 02:09:12PM +0300, Leon Romanovsky wrote:
> @@ -386,12 +414,14 @@ static struct scatterlist *get_next_sg(struct sg_table *table,
>  		return ERR_PTR(-ENOMEM);
>  	sg_init_table(new_sg, alloc_size);
>  	if (cur) {
> +		if (total_nents)
> +			*total_nents += alloc_size - 1;
>  		__sg_chain(next_sg, new_sg);
> -		table->orig_nents += alloc_size - 1;
>  	} else {
>  		table->sgl = new_sg;
> -		table->orig_nents = alloc_size;
>  		table->nents = 0;

Why does this still touch nents?

> @@ -515,6 +548,7 @@ struct scatterlist *__sg_alloc_table_from_pages(struct sg_table *sgt,
>  		cur_page = j;
>  	}
>  	sgt->nents += added_nents;
> +	sgt->orig_nents = sgt->nents;

And here too?

nents should only be set by the dma mapper, right?


I'm also trying to understand why it is OK to pass in NULL for
total_nents?

Any situation where _sg_alloc_table_from_pages() returns with
sgt->orig_nents != total_nents requires the use of
sg_free_table_entries()

It looks like there is some trouble here:

	for (i = 0; i < chunks; i++) {
		s = get_next_sg(sgt, s, chunks - i + left_pages, gfp_mask,
				total_nents);
		if (IS_ERR(s)) {

This will update total_nents but after a few loops it can exit without
synchronizing sgt->orig_nents - thus any caller handling an error
return from __sg_alloc_table_from_pages() must not pass in NULL and
must use sg_free_table_entries()

So I would see two options:

 1) Remove the possiblity to return NULL and fix all callers to use
    sg_free_table_entries() on error

 2) Once __sg_alloc_table_from_pages() fails the sg_table is corrupted
    and the user must call sg_free_table_entries().
    ie forcibly store total_nents in the orig_nents and thus destroy
    the ability to continue to use the sg_table.

    This is what sg_alloc_table_from_pages() already has to do

Further upon success of __sg_alloc_table_from_pages() it should be
true that sgt->orig_nents == total_nents so the ib_umem change is
confusing. total_nents should be removed from the struct and only the
failure paths in the function calling __sg_alloc_table_from_pages()
need a stack local variable and sg_free_table_entries()

IMHO this API may have become unwieldly and complicated, I wonder if
this is better:

   struct sg_append_table state;

   sg_append_init(&state, sgt, gfp_mask);

   while (..)
     ret = sg_append_pages(&state, pages, n_pages, ..)
     if (ret)
	 sg_append_abort(&state); // Frees the sgt and puts it to NULL
   sg_append_complete(&state)

Which allows sg_alloc_table_from_pages() to be written as

   struct sg_append_table state;
   sg_append_init(&state, sgt, gfp_mask);
   ret = sg_append_pages(&state,pages, n_pages, offset, size, UINT_MAX)
   if (ret) {
      sg_append_abort(&state);
      return ret;
   }
   sg_append_complete(&state);
   return 0;

And then the API can manage all of this in some sane and
understandable way.

Jason

Re: [PATCH rdma-next v2 1/2] lib/scatterlist: Fix wrong update of orig_nents

[Christoph Hellwig]

On Thu, Jul 22, 2021 at 10:00:40AM -0300, Jason Gunthorpe wrote:
> this is better:
> 
>    struct sg_append_table state;
> 
>    sg_append_init(&state, sgt, gfp_mask);
> 
>    while (..)
>      ret = sg_append_pages(&state, pages, n_pages, ..)
>      if (ret)
> 	 sg_append_abort(&state); // Frees the sgt and puts it to NULL
>    sg_append_complete(&state)
> 
> Which allows sg_alloc_table_from_pages() to be written as
> 
>    struct sg_append_table state;
>    sg_append_init(&state, sgt, gfp_mask);
>    ret = sg_append_pages(&state,pages, n_pages, offset, size, UINT_MAX)
>    if (ret) {
>       sg_append_abort(&state);
>       return ret;
>    }
>    sg_append_complete(&state);
>    return 0;
> 
> And then the API can manage all of this in some sane and
> understandable way.

That would be a lot easier to use for sure.  Not sure how invasive the
changes would be, though.

Re: [PATCH rdma-next v2 1/2] lib/scatterlist: Fix wrong update of orig_nents

[Jason Gunthorpe]

On Thu, Jul 22, 2021 at 02:07:51PM +0100, Christoph Hellwig wrote:
> On Thu, Jul 22, 2021 at 10:00:40AM -0300, Jason Gunthorpe wrote:
> > this is better:
> > 
> >    struct sg_append_table state;
> > 
> >    sg_append_init(&state, sgt, gfp_mask);
> > 
> >    while (..)
> >      ret = sg_append_pages(&state, pages, n_pages, ..)
> >      if (ret)
> > 	 sg_append_abort(&state); // Frees the sgt and puts it to NULL
> >    sg_append_complete(&state)
> > 
> > Which allows sg_alloc_table_from_pages() to be written as
> > 
> >    struct sg_append_table state;
> >    sg_append_init(&state, sgt, gfp_mask);
> >    ret = sg_append_pages(&state,pages, n_pages, offset, size, UINT_MAX)
> >    if (ret) {
> >       sg_append_abort(&state);
> >       return ret;
> >    }
> >    sg_append_complete(&state);
> >    return 0;
> > 
> > And then the API can manage all of this in some sane and
> > understandable way.
> 
> That would be a lot easier to use for sure.  Not sure how invasive the
> changes would be, though.

Looks pretty good, Maor can you try it?

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1739d10a2c556e..6c8e761ab389e8 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -806,27 +806,27 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops =  {
 struct sg_table *drm_prime_pages_to_sg(struct drm_device *dev,
 				       struct page **pages, unsigned int nr_pages)
 {
-	struct sg_table *sg;
-	struct scatterlist *sge;
+	struct sg_table *sgt;
 	size_t max_segment = 0;
+	int ret;
 
-	sg = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
-	if (!sg)
+	sgt = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
+	if (!sgt)
 		return ERR_PTR(-ENOMEM);
 
 	if (dev)
 		max_segment = dma_max_mapping_size(dev->dev);
 	if (max_segment == 0)
 		max_segment = UINT_MAX;
-	sge = __sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
-					  nr_pages << PAGE_SHIFT,
-					  max_segment,
-					  NULL, 0, GFP_KERNEL, NULL);
-	if (IS_ERR(sge)) {
-		kfree(sg);
-		sg = ERR_CAST(sge);
+
+	ret = sg_alloc_table_from_pages_segment(sgt, pages, nr_pages, 0,
+						nr_pages << PAGE_SHIFT,
+						max_segment, GFP_KERNEL);
+	if (ret) {
+		kfree(sgt);
+		return ERR_PTR(ret);
 	}
-	return sg;
+	return sgt;
 }
 EXPORT_SYMBOL(drm_prime_pages_to_sg);
 
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index c341d3e3386ccb..a2c5e1b30f425f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -131,6 +131,7 @@ static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 	const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
 	unsigned int max_segment = i915_sg_segment_size();
+	struct sg_append_table state;
 	struct sg_table *st;
 	unsigned int sg_page_sizes;
 	struct scatterlist *sg;
@@ -153,13 +154,11 @@ static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
 	spin_unlock(&i915->mm.notifier_lock);
 
 alloc_table:
-	sg = __sg_alloc_table_from_pages(st, pvec, num_pages, 0,
-					 num_pages << PAGE_SHIFT, max_segment,
-					 NULL, 0, GFP_KERNEL, NULL);
-	if (IS_ERR(sg)) {
-		ret = PTR_ERR(sg);
+	ret = sg_alloc_table_from_pages_segment(st, pvec, num_pages, 0,
+						num_pages << PAGE_SHIFT,
+						max_segment, GFP_KERNEL);
+	if (ret)
 		goto err;
-	}
 
 	ret = i915_gem_gtt_prepare_pages(obj, st);
 	if (ret) {
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
index 2ad889272b0a15..56214bcc6c5280 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
@@ -386,15 +386,12 @@ static int vmw_ttm_map_dma(struct vmw_ttm_tt *vmw_tt)
 		if (unlikely(ret != 0))
 			return ret;
 
-		sg = __sg_alloc_table_from_pages(&vmw_tt->sgt, vsgt->pages,
-				vsgt->num_pages, 0,
-				(unsigned long) vsgt->num_pages << PAGE_SHIFT,
-				dma_get_max_seg_size(dev_priv->drm.dev),
-				NULL, 0, GFP_KERNEL, NULL);
-		if (IS_ERR(sg)) {
-			ret = PTR_ERR(sg);
+		ret = sg_alloc_table_from_pages_segment(
+			vmw_tt->sgt, vsgt->pages, vsgt->num_pages, 0,
+			(unsigned long)vsgt->num_pages << PAGE_SHIFT,
+			dma_get_max_seg_size(dev_priv->drm.dev), GFP_KERNEL);
+		if (ret)
 			goto out_sg_alloc_fail;
-		}
 
 		if (vsgt->num_pages > vmw_tt->sgt.orig_nents) {
 			uint64_t over_alloc =
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 5cc41ae962ec1d..53de1ec77326be 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -556,6 +556,25 @@ struct scatterlist *__sg_alloc_table_from_pages(struct sg_table *sgt,
 }
 EXPORT_SYMBOL(__sg_alloc_table_from_pages);
 
+int sg_alloc_table_from_pages_segment(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)
+{
+	struct sg_append_table state;
+	int ret;
+
+	sg_append_init(&state, sgt, max_segment, gfp_mask);
+	ret = sg_append_pages(&state, pages, n_pages, offset, size);
+	if (ret) {
+		sg_append_abort(&state);
+		return ret;
+	}
+	sg_append_complete(&state);
+	return 0;
+}
+EXPORT_SYMBOL(sg_alloc_table_from_pages_segment);
+
 /**
  * sg_alloc_table_from_pages - Allocate and initialize an sg table from
  *			       an array of pages
@@ -580,8 +599,8 @@ 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 PTR_ERR_OR_ZERO(__sg_alloc_table_from_pages(sgt, pages, n_pages,
-			offset, size, UINT_MAX, NULL, 0, gfp_mask, NULL));
+	return sg_alloc_table_from_pages_segment(sgt, pages, n_pages, offset,
+						 size, UINT_MAX, gfp_mask);
 }
 EXPORT_SYMBOL(sg_alloc_table_from_pages);
 

[PATCH rdma-next v2 2/2] RDMA: Use dma_map_sgtable for map umem pages

[Leon Romanovsky]

From: Maor Gottlieb <maorg@nvidia.com>

In order to avoid incorrect usage of sg_table fields, change umem to
use dma_map_sgtable for map the pages for DMA. Since dma_map_sgtable
update the nents field (number of DMA entries), there is no need
anymore for nmap variable, hence do some cleanups accordingly.

Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/infiniband/core/umem.c        | 28 +++++++++++----------------
 drivers/infiniband/core/umem_dmabuf.c |  1 -
 drivers/infiniband/hw/mlx4/mr.c       |  4 ++--
 drivers/infiniband/hw/mlx5/mr.c       |  3 ++-
 drivers/infiniband/sw/rdmavt/mr.c     |  2 +-
 drivers/infiniband/sw/rxe/rxe_mr.c    |  3 ++-
 include/rdma/ib_umem.h                |  3 ++-
 include/rdma/ib_verbs.h               | 28 +++++++++++++++++++++++++++
 8 files changed, 48 insertions(+), 24 deletions(-)

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index cf4197363346..77c2df1c91d1 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -51,11 +51,11 @@ static void __ib_umem_release(struct ib_device *dev, struct ib_umem *umem, int d
 	struct scatterlist *sg;
 	unsigned int i;
 
-	if (umem->nmap > 0)
-		ib_dma_unmap_sg(dev, umem->sg_head.sgl, umem->sg_nents,
-				DMA_BIDIRECTIONAL);
+	if (dirty)
+		ib_dma_unmap_sgtable_attrs(dev, &umem->sg_head,
+					   DMA_BIDIRECTIONAL, 0);
 
-	for_each_sg(umem->sg_head.sgl, sg, umem->sg_nents, i)
+	for_each_sgtable_sg(&umem->sg_head, sg, i)
 		unpin_user_page_range_dirty_lock(sg_page(sg),
 			DIV_ROUND_UP(sg->length, PAGE_SIZE), make_dirty);
 
@@ -111,7 +111,7 @@ unsigned long ib_umem_find_best_pgsz(struct ib_umem *umem,
 	/* offset into first SGL */
 	pgoff = umem->address & ~PAGE_MASK;
 
-	for_each_sg(umem->sg_head.sgl, sg, umem->nmap, i) {
+	for_each_sgtable_dma_sg(&umem->sg_head, sg, i) {
 		/* Walk SGL and reduce max page size if VA/PA bits differ
 		 * for any address.
 		 */
@@ -121,7 +121,7 @@ unsigned long ib_umem_find_best_pgsz(struct ib_umem *umem,
 		 * the maximum possible page size as the low bits of the iova
 		 * must be zero when starting the next chunk.
 		 */
-		if (i != (umem->nmap - 1))
+		if (i != (umem->sg_head.nents - 1))
 			mask |= va;
 		pgoff = 0;
 	}
@@ -240,16 +240,10 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,
 	if (access & IB_ACCESS_RELAXED_ORDERING)
 		dma_attr |= DMA_ATTR_WEAK_ORDERING;
 
-	umem->nmap =
-		ib_dma_map_sg_attrs(device, umem->sg_head.sgl, umem->sg_nents,
-				    DMA_BIDIRECTIONAL, dma_attr);
-
-	if (!umem->nmap) {
-		ret = -ENOMEM;
+	ret = ib_dma_map_sgtable_attrs(device, &umem->sg_head,
+				       DMA_BIDIRECTIONAL, dma_attr);
+	if (ret)
 		goto umem_release;
-	}
-
-	ret = 0;
 	goto out;
 
 umem_release:
@@ -309,8 +303,8 @@ int ib_umem_copy_from(void *dst, struct ib_umem *umem, size_t offset,
 		return -EINVAL;
 	}
 
-	ret = sg_pcopy_to_buffer(umem->sg_head.sgl, umem->sg_nents, dst, length,
-				 offset + ib_umem_offset(umem));
+	ret = sg_pcopy_to_buffer(umem->sg_head.sgl, umem->sg_head.orig_nents,
+				 dst, length, offset + ib_umem_offset(umem));
 
 	if (ret < 0)
 		return ret;
diff --git a/drivers/infiniband/core/umem_dmabuf.c b/drivers/infiniband/core/umem_dmabuf.c
index c6e875619fac..2884e4526d78 100644
--- a/drivers/infiniband/core/umem_dmabuf.c
+++ b/drivers/infiniband/core/umem_dmabuf.c
@@ -57,7 +57,6 @@ int ib_umem_dmabuf_map_pages(struct ib_umem_dmabuf *umem_dmabuf)
 
 	umem_dmabuf->umem.sg_head.sgl = umem_dmabuf->first_sg;
 	umem_dmabuf->umem.sg_head.nents = nmap;
-	umem_dmabuf->umem.nmap = nmap;
 	umem_dmabuf->sgt = sgt;
 
 wait_fence:
diff --git a/drivers/infiniband/hw/mlx4/mr.c b/drivers/infiniband/hw/mlx4/mr.c
index 50becc0e4b62..ab5dc8eac7f8 100644
--- a/drivers/infiniband/hw/mlx4/mr.c
+++ b/drivers/infiniband/hw/mlx4/mr.c
@@ -200,7 +200,7 @@ int mlx4_ib_umem_write_mtt(struct mlx4_ib_dev *dev, struct mlx4_mtt *mtt,
 	mtt_shift = mtt->page_shift;
 	mtt_size = 1ULL << mtt_shift;
 
-	for_each_sg(umem->sg_head.sgl, sg, umem->nmap, i) {
+	for_each_sgtable_dma_sg(&umem->sg_head, sg, i) {
 		if (cur_start_addr + len == sg_dma_address(sg)) {
 			/* still the same block */
 			len += sg_dma_len(sg);
@@ -273,7 +273,7 @@ int mlx4_ib_umem_calc_optimal_mtt_size(struct ib_umem *umem, u64 start_va,
 
 	*num_of_mtts = ib_umem_num_dma_blocks(umem, PAGE_SIZE);
 
-	for_each_sg(umem->sg_head.sgl, sg, umem->nmap, i) {
+	for_each_sgtable_dma_sg(&umem->sg_head, sg, i) {
 		/*
 		 * Initialization - save the first chunk start as the
 		 * current_block_start - block means contiguous pages.
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index 3263851ea574..4954fb9eb6dc 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1226,7 +1226,8 @@ int mlx5_ib_update_mr_pas(struct mlx5_ib_mr *mr, unsigned int flags)
 	orig_sg_length = sg.length;
 
 	cur_mtt = mtt;
-	rdma_for_each_block (mr->umem->sg_head.sgl, &biter, mr->umem->nmap,
+	rdma_for_each_block (mr->umem->sg_head.sgl, &biter,
+			     mr->umem->sg_head.nents,
 			     BIT(mr->page_shift)) {
 		if (cur_mtt == (void *)mtt + sg.length) {
 			dma_sync_single_for_device(ddev, sg.addr, sg.length,
diff --git a/drivers/infiniband/sw/rdmavt/mr.c b/drivers/infiniband/sw/rdmavt/mr.c
index 34b7af6ab9c2..d955c8c4acc4 100644
--- a/drivers/infiniband/sw/rdmavt/mr.c
+++ b/drivers/infiniband/sw/rdmavt/mr.c
@@ -410,7 +410,7 @@ struct ib_mr *rvt_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 	mr->mr.page_shift = PAGE_SHIFT;
 	m = 0;
 	n = 0;
-	for_each_sg_page (umem->sg_head.sgl, &sg_iter, umem->nmap, 0) {
+	for_each_sg_page (umem->sg_head.sgl, &sg_iter, umem->sg_head.nents, 0) {
 		void *vaddr;
 
 		vaddr = page_address(sg_page_iter_page(&sg_iter));
diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
index 1ee5bd8291e5..ba534b6c67f0 100644
--- a/drivers/infiniband/sw/rxe/rxe_mr.c
+++ b/drivers/infiniband/sw/rxe/rxe_mr.c
@@ -141,7 +141,8 @@ int rxe_mr_init_user(struct rxe_pd *pd, u64 start, u64 length, u64 iova,
 	if (length > 0) {
 		buf = map[0]->buf;
 
-		for_each_sg_page(umem->sg_head.sgl, &sg_iter, umem->nmap, 0) {
+		for_each_sg_page(umem->sg_head.sgl, &sg_iter,
+				 umem->sg_head.nents, 0) {
 			if (num_buf >= RXE_BUF_PER_MAP) {
 				map++;
 				buf = map[0]->buf;
diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h
index 5a65212efc2e..3f5576877072 100644
--- a/include/rdma/ib_umem.h
+++ b/include/rdma/ib_umem.h
@@ -76,7 +76,8 @@ static inline void __rdma_umem_block_iter_start(struct ib_block_iter *biter,
 						struct ib_umem *umem,
 						unsigned long pgsz)
 {
-	__rdma_block_iter_start(biter, umem->sg_head.sgl, umem->nmap, pgsz);
+	__rdma_block_iter_start(biter, umem->sg_head.sgl, umem->sg_head.nents,
+				pgsz);
 }
 
 /**
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 371df1c80aeb..2dba30849731 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -4057,6 +4057,34 @@ static inline void ib_dma_unmap_sg_attrs(struct ib_device *dev,
 				   dma_attrs);
 }
 
+/**
+ * ib_dma_map_sgtable_attrs - Map a scatter/gather table to DMA addresses
+ * @dev: The device for which the DMA addresses are to be created
+ * @sg: The sg_table object describing the buffer
+ * @direction: The direction of the DMA
+ * @attrs: Optional DMA attributes for the map operation
+ */
+static inline int ib_dma_map_sgtable_attrs(struct ib_device *dev,
+					   struct sg_table *sgt,
+					   enum dma_data_direction direction,
+					   unsigned long dma_attrs)
+{
+	if (ib_uses_virt_dma(dev)) {
+		ib_dma_virt_map_sg(dev, sgt->sgl, sgt->orig_nents);
+		return 0;
+	}
+	return dma_map_sgtable(dev->dma_device, sgt, direction, dma_attrs);
+}
+
+static inline void ib_dma_unmap_sgtable_attrs(struct ib_device *dev,
+					      struct sg_table *sgt,
+					      enum dma_data_direction direction,
+					      unsigned long dma_attrs)
+{
+	if (!ib_uses_virt_dma(dev))
+		dma_unmap_sgtable(dev->dma_device, sgt, direction, dma_attrs);
+}
+
 /**
  * ib_dma_map_sg - Map a scatter/gather list to DMA addresses
  * @dev: The device for which the DMA addresses are to be created
-- 
2.31.1

Re: [PATCH rdma-next v2 2/2] RDMA: Use dma_map_sgtable for map umem pages

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>