[Linaro-mm-sig] Re: [PATCH 2/5] udmabuf: change folios array from kmalloc to kvmalloc

Am 01.08.24 um 12:45 schrieb Huan Yang:

When PAGE_SIZE 4096, MAX_PAGE_ORDER 10, 64bit machine, page_alloc only support 4MB. If above this, trigger this warn and return NULL.

udmabuf can change size limit, if change it to 3072(3GB), and then alloc 3GB udmabuf, will fail create.

[ 4080.876581] ------------[ cut here ]------------ [ 4080.876843] WARNING: CPU: 3 PID: 2015 at mm/page_alloc.c:4556 __alloc_pages+0x2c8/0x350 [ 4080.878839] RIP: 0010:__alloc_pages+0x2c8/0x350 [ 4080.879470] Call Trace: [ 4080.879473] <TASK> [ 4080.879473] ? __alloc_pages+0x2c8/0x350 [ 4080.879475] ? __warn.cold+0x8e/0xe8 [ 4080.880647] ? __alloc_pages+0x2c8/0x350 [ 4080.880909] ? report_bug+0xff/0x140 [ 4080.881175] ? handle_bug+0x3c/0x80 [ 4080.881556] ? exc_invalid_op+0x17/0x70 [ 4080.881559] ? asm_exc_invalid_op+0x1a/0x20 [ 4080.882077] ? udmabuf_create+0x131/0x400

Because MAX_PAGE_ORDER, kmalloc can max alloc 4096 * (1 << 10), 4MB memory, each array entry is pointer(8byte), so can save 524288 pages(2GB).

Further more, costly order(order 3) may not be guaranteed that it can be applied for, due to fragmentation.

This patch change udmabuf array use kvmalloc_array, this can fallback alloc into vmalloc, which can guarantee allocation for any size and does not affect the performance of kmalloc allocations.

Signed-off-by: Huan Yang link@vivo.com

Acked-by: Christian König christian.koenig@amd.com

---

drivers/dma-buf/udmabuf.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index d69aeada7367..a915714c5dce 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -83,7 +83,7 @@ static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map) dma_resv_assert_held(buf->resv);

• pages = kmalloc_array(ubuf->pagecount, sizeof(*pages), GFP_KERNEL);

• pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages), GFP_KERNEL); if (!pages) return -ENOMEM;

@@ -91,7 +91,7 @@ static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map) pages[pg] = &ubuf->folios[pg]->page; vaddr = vm_map_ram(pages, ubuf->pagecount, -1);

• kfree(pages);

• kvfree(pages); if (!vaddr) return -EINVAL;

@@ -203,8 +203,8 @@ static void release_udmabuf(struct dma_buf *buf) put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL); unpin_all_folios(&ubuf->unpin_list);

• kfree(ubuf->offsets);
• kfree(ubuf->folios);

• kvfree(ubuf->offsets);
• kvfree(ubuf->folios); kfree(ubuf); }

@@ -330,14 +330,14 @@ static long udmabuf_create(struct miscdevice *device, if (!ubuf->pagecount) goto err;

• ubuf->folios = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),

• 		    GFP_KERNEL);
  

• ubuf->folios = kvmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),

• 		      GFP_KERNEL);
  

  if (!ubuf->folios) { ret = -ENOMEM; goto err; }

• ubuf->offsets = kcalloc(ubuf->pagecount, sizeof(*ubuf->offsets),

• 		GFP_KERNEL);
  

• ubuf->offsets =

• kvcalloc(ubuf->pagecount, sizeof(*ubuf->offsets), GFP_KERNEL);
  

  if (!ubuf->offsets) { ret = -ENOMEM; goto err;

@@ -351,7 +351,7 @@ static long udmabuf_create(struct miscdevice *device, goto err; pgcnt = list[i].size >> PAGE_SHIFT;

• folios = kmalloc_array(pgcnt, sizeof(*folios), GFP_KERNEL);
  

• folios = kvmalloc_array(pgcnt, sizeof(*folios), GFP_KERNEL);
  

  if (!folios) { ret = -ENOMEM; goto err;

@@ -361,7 +361,7 @@ static long udmabuf_create(struct miscdevice *device, ret = memfd_pin_folios(memfd, list[i].offset, end, folios, pgcnt, &pgoff); if (ret <= 0) {

• 	kfree(folios);
  

• 	kvfree(folios);
  if (!ret)
  	ret = -EINVAL;
  goto err;
  

@@ -390,7 +390,7 @@ static long udmabuf_create(struct miscdevice *device, } }

• kfree(folios);
  

• kvfree(folios);
  

  fput(memfd); memfd = NULL; }

@@ -406,8 +406,8 @@ static long udmabuf_create(struct miscdevice *device, if (memfd) fput(memfd); unpin_all_folios(&ubuf->unpin_list);

• kfree(ubuf->offsets);
• kfree(ubuf->folios);

• kvfree(ubuf->offsets);
• kvfree(ubuf->folios); kfree(ubuf); return ret; }