Re: [PATCH v2 2/4] udmabuf: change folios array from kmalloc to kvmalloc

[Huan Yang]

在 2024/8/10 9:29, Kasireddy, Vivek 写道:
> [Some people who received this message don't often get email from vivek.kasireddy@xxxxxxxxx. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>
> Hi Huan,
>
> > 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@xxxxxxxx>
> > Acked-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >   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 475268d4ebb1..af2391cea0bf 100644
> > --- a/drivers/dma-buf/udmabuf.c
> > +++ b/drivers/dma-buf/udmabuf.c
> > @@ -73,7 +73,7 @@ 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;
> >
> > @@ -81,7 +81,7 @@ 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;
> >
> > @@ -189,8 +189,8 @@ 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);
> >   }
> >
> > @@ -315,14 +315,14 @@ 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),
> No strong opinion, but I'd prefer to keep the kvcalloc on the same line.
> Regardless,

This style is auto formatted by my clang-format with .clang-format set 
in kernel.

But, I chang into online:

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

checkpatch  also did not report any errors.

So, I can send the next version of the patch when needed.

Thanks.

> Acked-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
>
> > GFP_KERNEL);
> >        if (!ubuf->offsets) {
> >                ret = -ENOMEM;
> >                goto err;
> > @@ -336,7 +336,7 @@ 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;
> > @@ -346,7 +346,7 @@ 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;
> > @@ -375,7 +375,7 @@ static long udmabuf_create(struct miscdevice
> > *device,
> >                        }
> >                }
> >
> > -             kfree(folios);
> > +             kvfree(folios);
> >                fput(memfd);
> >                memfd = NULL;
> >        }
> > @@ -391,8 +391,8 @@ 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;
> >   }
> > --
> > 2.45.2