[PATCH 0/2] Support direct I/O read and write for memory allocated by dmabuf

[PATCH 0/2] Support direct I/O read and write for memory allocated by dmabuf

[Lei Liu]

Use vm_insert_page to establish a mapping for the memory allocated
by dmabuf, thus supporting direct I/O read and write; and fix the
issue of incorrect memory statistics after mapping dmabuf memory.

Lei Liu (2):
  mm: dmabuf_direct_io: Support direct_io for memory allocated by dmabuf
  mm: dmabuf_direct_io: Fix memory statistics error for dmabuf allocated
    memory with direct_io support

 drivers/dma-buf/heaps/system_heap.c |  5 +++--
 fs/proc/task_mmu.c                  |  8 +++++++-
 include/linux/mm.h                  |  1 +
 mm/memory.c                         | 15 ++++++++++-----
 mm/rmap.c                           |  9 +++++----
 5 files changed, 26 insertions(+), 12 deletions(-)

-- 
2.34.1

[PATCH 1/2] mm: dmabuf_direct_io: Support direct_io for memory allocated by dmabuf

[Lei Liu]

1.Effects and reasons for lack of support:

Currently, memory allocated by dmabuf cannot be read from files using
direct_io. With the increasing use of AI models in mobile applications,
there is a growing need to load large model files occupying up to 3-4GB
into mobile memory. Presently, the only way to read is through
buffer_io, which limits performance. In low memory scenarios on 12GB RAM
smartphones, buffer_io requires additional memory, leading to a 3-4
times degradation in read performance with significant fluctuations.

The reason for the lack of support for direct_io reading is that the
current system establishes mappings for memory allocated by dmabuf using
remap_pfn_range, which includes the VM_PFN_MAP flag. When attempting
direct_io reads, the get_user_page process intercepts the VM_PFN_MAP
flag, preventing the page from being returned and resulting in read
failures.

2.Proposed solution:
  (1) Establish mmap mappings for memory allocated by dmabuf using the
vm_insert_page method to support direct_io read and write.

3.Advantages and benefits:
  (1) Faster and more stable reading speed.
  (2) Reduced pagecache memory usage.
  (3) Reduction in CPU data copying and unnecessary power consumption.

4.In a clean and stressapptest(a 16GB memory phone consumed 4GB of
  memory). A comparison of the time taken to read a 3.2GB large AI model
file using buffer_io and direct_io.

Read 3.21G AI large model file on mobilephone
Memstress  Rounds    DIO-Time/ms   BIO-Time/ms
             01        1432          2034
Clean        02        1406          2225
             03        1476          2097
           average     1438          2118
Memstress  Rounds    DIO-Time/ms   BIO-Time/ms
             01        1585          4821
Eat 4GB      02        1560          4957
             03        1519          4936
           average     1554          4905

Signed-off-by: Lei Liu <liulei.rjpt@vivo.com>
---
 drivers/dma-buf/heaps/system_heap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 9076d47ed2ef..87547791f9e1 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -203,8 +203,7 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
 	for_each_sgtable_page(table, &piter, vma->vm_pgoff) {
 		struct page *page = sg_page_iter_page(&piter);
 
-		ret = remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE,
-				      vma->vm_page_prot);
+		ret = vm_insert_page(vma, addr, page);
 		if (ret)
 			return ret;
 		addr += PAGE_SIZE;
-- 
2.34.1

[PATCH 2/2] mm: dmabuf_direct_io: Fix memory statistics error for dmabuf allocated memory with direct_io support

[Lei Liu]

The method of establishing mmap mapping for memory allocated by dmabuf
through vm_insert_page causes changes in the way dmabuf memory is
accounted for, primarily in the following three aspects:

(1) The memory usage of dmabuf is accounted for in mm->rss.

(2) /proc/self/smaps will account for the memory usage of dmabuf.

(3) Memory usage of dmabuf after mmap will be counted in Mapped in
/proc/meminfo.

By adding a VM_DMABUF_DIO_MAP flag, we address the memory accounting
issues in the three aspects mentioned above, ensuring that the memory
allocated by dmabuf with direct_io support does not undergo changes in
its memory accounting method.

Signed-off-by: Lei Liu <liulei.rjpt@vivo.com>
---
 drivers/dma-buf/heaps/system_heap.c |  2 ++
 fs/proc/task_mmu.c                  |  8 +++++++-
 include/linux/mm.h                  |  1 +
 mm/memory.c                         | 15 ++++++++++-----
 mm/rmap.c                           |  9 +++++----
 5 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 87547791f9e1..1d6f08b1dc5b 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -200,6 +200,8 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
 	struct sg_page_iter piter;
 	int ret;
 
+	vm_flags_set(vma, VM_DMABUF_DIO);
+
 	for_each_sgtable_page(table, &piter, vma->vm_pgoff) {
 		struct page *page = sg_page_iter_page(&piter);
 
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 71e5039d940d..8070fdd4ac7b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -784,7 +784,13 @@ static void smap_gather_stats(struct vm_area_struct *vma,
 	/* Invalid start */
 	if (start >= vma->vm_end)
 		return;
-
+	/*
+	 * The memory of DMABUF needs to be mmaped using vm_insert_page in order to
+	 * support direct_io. It will not with VM_PFNMAP flag, but it does have the
+	 * VM_DMABUF_DIO flag memory will be counted in the process's RSS.
+	 */
+	if (vma->vm_flags & VM_DMABUF_DIO)
+		return;
 	if (vma->vm_file && shmem_mapping(vma->vm_file->f_mapping)) {
 		/*
 		 * For shared or readonly shmem mappings we know that all
diff --git a/include/linux/mm.h b/include/linux/mm.h
index eb7c96d24ac0..86d23f1a9717 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -283,6 +283,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_UFFD_MISSING	0
 #endif /* CONFIG_MMU */
 #define VM_PFNMAP	0x00000400	/* Page-ranges managed without "struct page", just pure PFN */
+#define VM_DMABUF_DIO	0x00000800	/* Memory accounting for dmabuf support direct_io */
 #define VM_UFFD_WP	0x00001000	/* wrprotect pages tracking */
 
 #define VM_LOCKED	0x00002000
diff --git a/mm/memory.c b/mm/memory.c
index d10e616d7389..8b126ce0f788 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1003,7 +1003,8 @@ copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma
 			VM_WARN_ON_FOLIO(PageAnonExclusive(page), folio);
 		} else {
 			folio_dup_file_rmap_ptes(folio, page, nr);
-			rss[mm_counter_file(folio)] += nr;
+			if (likely(!(src_vma->vm_flags & VM_DMABUF_DIO)))
+				rss[mm_counter_file(folio)] += nr;
 		}
 		if (any_writable)
 			pte = pte_mkwrite(pte, src_vma);
@@ -1031,7 +1032,8 @@ copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma
 		VM_WARN_ON_FOLIO(PageAnonExclusive(page), folio);
 	} else {
 		folio_dup_file_rmap_pte(folio, page);
-		rss[mm_counter_file(folio)]++;
+		if (likely(!(src_vma->vm_flags & VM_DMABUF_DIO)))
+			rss[mm_counter_file(folio)]++;
 	}
 
 copy_pte:
@@ -1488,7 +1490,8 @@ static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb,
 		}
 		if (pte_young(ptent) && likely(vma_has_recency(vma)))
 			folio_mark_accessed(folio);
-		rss[mm_counter(folio)] -= nr;
+		if (likely(!(vma->vm_flags & VM_DMABUF_DIO)))
+			rss[mm_counter(folio)] -= nr;
 	} else {
 		/* We don't need up-to-date accessed/dirty bits. */
 		clear_full_ptes(mm, addr, pte, nr, tlb->fullmm);
@@ -1997,7 +2000,8 @@ static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte,
 		return -EBUSY;
 	/* Ok, finally just insert the thing.. */
 	folio_get(folio);
-	inc_mm_counter(vma->vm_mm, mm_counter_file(folio));
+	if (likely(!(vma->vm_flags & VM_DMABUF_DIO)))
+		inc_mm_counter(vma->vm_mm, mm_counter_file(folio));
 	folio_add_file_rmap_pte(folio, page, vma);
 	set_pte_at(vma->vm_mm, addr, pte, mk_pte(page, prot));
 	return 0;
@@ -4641,7 +4645,8 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
 	if (write)
 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 
-	add_mm_counter(vma->vm_mm, mm_counter_file(folio), HPAGE_PMD_NR);
+	if (likely(!(vma->vm_flags & VM_DMABUF_DIO)))
+		add_mm_counter(vma->vm_mm, mm_counter_file(folio), HPAGE_PMD_NR);
 	folio_add_file_rmap_pmd(folio, page, vma);
 
 	/*
diff --git a/mm/rmap.c b/mm/rmap.c
index e8fc5ecb59b2..17cab358acc1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1441,10 +1441,10 @@ static __always_inline void __folio_add_file_rmap(struct folio *folio,
 	VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
 
 	nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
-	if (nr_pmdmapped)
+	if (nr_pmdmapped && !(vma->vm_flags & VM_DMABUF_DIO))
 		__mod_node_page_state(pgdat, folio_test_swapbacked(folio) ?
 			NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, nr_pmdmapped);
-	if (nr)
+	if (nr && !(vma->vm_flags & VM_DMABUF_DIO))
 		__lruvec_stat_mod_folio(folio, NR_FILE_MAPPED, nr);
 
 	/* See comments in folio_add_anon_rmap_*() */
@@ -1545,7 +1545,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 		/* NR_{FILE/SHMEM}_PMDMAPPED are not maintained per-memcg */
 		if (folio_test_anon(folio))
 			__lruvec_stat_mod_folio(folio, NR_ANON_THPS, -nr_pmdmapped);
-		else
+		else if (likely(!(vma->vm_flags & VM_DMABUF_DIO)))
 			__mod_node_page_state(pgdat,
 					folio_test_swapbacked(folio) ?
 					NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED,
@@ -1553,7 +1553,8 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 	}
 	if (nr) {
 		idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
-		__lruvec_stat_mod_folio(folio, idx, -nr);
+		if (likely(!(vma->vm_flags & VM_DMABUF_DIO)))
+			__lruvec_stat_mod_folio(folio, idx, -nr);
 
 		/*
 		 * Queue anon large folio for deferred split if at least one
-- 
2.34.1

[PATCH 1/2] mm: dmabuf_direct_io: Support direct_io for memory allocated by dmabuf

[Lei Liu]

1.Effects and reasons for lack of support:

Currently, memory allocated by dmabuf cannot be read from files using
direct_io. With the increasing use of AI models in mobile applications,
there is a growing need to load large model files occupying up to 3-4GB
into mobile memory. Presently, the only way to read is through
buffer_io, which limits performance. In low memory scenarios on 12GB RAM
smartphones, buffer_io requires additional memory, leading to a 3-4
times degradation in read performance with significant fluctuations.

The reason for the lack of support for direct_io reading is that the
current system establishes mappings for memory allocated by dmabuf using
remap_pfn_range, which includes the VM_PFN_MAP flag. When attempting
direct_io reads, the get_user_page process intercepts the VM_PFN_MAP
flag, preventing the page from being returned and resulting in read
failures.

2.Proposed solution:
  (1) Establish mmap mappings for memory allocated by dmabuf using the
vm_insert_page method to support direct_io read and write.

3.Advantages and benefits:
  (1) Faster and more stable reading speed.
  (2) Reduced pagecache memory usage.
  (3) Reduction in CPU data copying and unnecessary power consumption.

4.In a clean and stressapptest(a 16GB memory phone consumed 4GB of
  memory). A comparison of the time taken to read a 3.2GB large AI model
file using buffer_io and direct_io.

Read 3.21G AI large model file on mobilephone
Memstress  Rounds    DIO-Time/ms   BIO-Time/ms
             01        1432          2034
Clean        02        1406          2225
             03        1476          2097
           average     1438          2118
Memstress  Rounds    DIO-Time/ms   BIO-Time/ms
             01        1585          4821
Eat 4GB      02        1560          4957
             03        1519          4936
           average     1554          4905

Signed-off-by: Lei Liu <liulei.rjpt@vivo.com>
---
 drivers/dma-buf/heaps/system_heap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 9076d47ed2ef..87547791f9e1 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -203,8 +203,7 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
 	for_each_sgtable_page(table, &piter, vma->vm_pgoff) {
 		struct page *page = sg_page_iter_page(&piter);
 
-		ret = remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE,
-				      vma->vm_page_prot);
+		ret = vm_insert_page(vma, addr, page);
 		if (ret)
 			return ret;
 		addr += PAGE_SIZE;
-- 
2.34.1