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Message-ID: <IA0PR11MB7185DF242D3F61BFE8429F35F8962@IA0PR11MB7185.namprd11.prod.outlook.com>
Date: Thu, 29 Aug 2024 06:39:52 +0000
From: "Kasireddy, Vivek" <vivek.kasireddy@...el.com>
To: Huan Yang <link@...o.com>, Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>, Gerd Hoffmann
<kraxel@...hat.com>, "linux-media@...r.kernel.org"
<linux-media@...r.kernel.org>, "dri-devel@...ts.freedesktop.org"
<dri-devel@...ts.freedesktop.org>, "linaro-mm-sig@...ts.linaro.org"
<linaro-mm-sig@...ts.linaro.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>
CC: "opensource.kernel@...o.com" <opensource.kernel@...o.com>
Subject: RE: [PATCH v4 4/5] udmabuf: udmabuf_create codestyle cleanup
Hi Huan,
> Subject: [PATCH v4 4/5] udmabuf: udmabuf_create codestyle cleanup
>
> There are some variables in udmabuf_create that are only used inside the
> loop. Therefore, there is no need to declare them outside the scope.
> This patch moved it into loop.
>
> It is difficult to understand the loop condition of the code that adds
> folio to the unpin_list.
>
> This patch move item folio pin and record into a single function, when
> pinned success, the outer loop of this patch iterates through folios,
> while the inner loop correctly sets the folio and corresponding offset
> into the udmabuf starting from the offset. if reach to pgcnt or nr_folios,
> end of loop.
>
> If item size is huge, folios may use vmalloc to get memory, which can't
> cache but return into pcp(or buddy) when vfree. So, each pin may waste
> some time in folios array alloc.
> This patch also reuse of folios when iter create head, just use max size
> of item.
>
> Signed-off-by: Huan Yang <link@...o.com>
> ---
> drivers/dma-buf/udmabuf.c | 165 +++++++++++++++++++++++---------------
> 1 file changed, 101 insertions(+), 64 deletions(-)
>
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index 0bbc9df36c0a..eb55bb4a5fcc 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -321,17 +321,87 @@ static int export_udmabuf(struct udmabuf *ubuf,
> return dma_buf_fd(buf, flags);
> }
>
> +static int __udmabuf_pin_list_folios(struct udmabuf_create_item *item,
I think the name udmabuf_pin_folios() for this function would be simple and apt.
> + struct udmabuf *ubuf,
> + struct folio **folios)
> +{
> + struct file *memfd = NULL;
> + pgoff_t pgoff, ipgcnt, upgcnt = ubuf->pagecount;
> + u32 cur_folio, cur_pgcnt;
> + struct folio **ubuf_folios;
> + pgoff_t *ubuf_offsets;
> + long nr_folios;
> + loff_t end, start;
> + int ret;
> +
> + memfd = fget(item->memfd);
> + ret = check_memfd_seals(memfd);
> + if (ret < 0)
> + goto err;
Please move the above hunk to udmabuf_create(). Lets just have pinning and
processing of folios in this function.
> +
> + start = item->offset;
> + ipgcnt = item->size >> PAGE_SHIFT;
I think it would be a bit more clear to have udmabuf_create() pass start and size
values directly to this function instead of item. And rename ipgcnt to something
like subpgcnt or nr_subpgs.
> + end = start + (ipgcnt << PAGE_SHIFT) - 1;
> +
> + nr_folios = memfd_pin_folios(memfd, start, end, folios, ipgcnt,
> &pgoff);
> + if (nr_folios <= 0) {
> + kvfree(folios);
Please free folios in udmabuf_create() which is where it was allocated.
> + ret = nr_folios ? nr_folios : -EINVAL;
> + goto err;
> + }
> +
> + cur_pgcnt = 0;
> + ubuf_folios = ubuf->folios;
> + ubuf_offsets = ubuf->offsets;
Please initialize these temp variables at declaration time above. No strong
opinion but I am not sure if they are really helpful here. Something like
upgcnt would be OK as it definitely improves readability.
> +
> + for (cur_folio = 0; cur_folio < nr_folios; ++cur_folio) {
> + pgoff_t subpgoff = pgoff;
> + long fsize = folio_size(folios[cur_folio]);
The return type for folio_size() is size_t. Please use that for consistency.
> +
> + ret = add_to_unpin_list(&ubuf->unpin_list, folios[cur_folio]);
> + if (ret < 0) {
> + kfree(folios);
> + goto err;
> + }
> +
> + for (; subpgoff < fsize; subpgoff += PAGE_SIZE) {
> + ubuf->folios[upgcnt] = folios[cur_folio];
> + ubuf->offsets[upgcnt] = subpgoff;
> + ++upgcnt;
> +
> + if (++cur_pgcnt >= ipgcnt)
> + goto end;
> + }
> +
> + /**
> + * Only first folio in item may start from offset,
I prefer to use the term range instead of item, in this context.
> + * so remain folio start from 0.
> + */
> + pgoff = 0;
> + }
> +end:
> + ubuf->pagecount = upgcnt;
> + fput(memfd);
> +
> + return 0;
> +
> +err:
> + ubuf->pagecount = upgcnt;
> + if (memfd)
> + fput(memfd);
> +
> + return ret;
> +}
> +
> static long udmabuf_create(struct miscdevice *device,
> struct udmabuf_create_list *head,
> struct udmabuf_create_item *list)
> {
> - pgoff_t pgoff, pgcnt, pglimit, pgbuf = 0;
> - long nr_folios, ret = -EINVAL;
> - struct file *memfd = NULL;
> - struct folio **folios;
> + pgoff_t pgcnt = 0, pglimit, max_ipgcnt = 0;
> + long ret = -EINVAL;
> struct udmabuf *ubuf;
> - u32 i, j, k, flags;
> - loff_t end;
> + struct folio **folios = NULL;
> + u32 i, flags;
>
> ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
> if (!ubuf)
> @@ -340,82 +410,50 @@ static long udmabuf_create(struct miscdevice
> *device,
> INIT_LIST_HEAD(&ubuf->unpin_list);
> pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
> for (i = 0; i < head->count; i++) {
> - if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))
> + pgoff_t itempgcnt;
> +
> + if (!PAGE_ALIGNED(list[i].offset))
> goto err;
> - if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
> + if (!PAGE_ALIGNED(list[i].size))
> goto err;
> - ubuf->pagecount += list[i].size >> PAGE_SHIFT;
> - if (ubuf->pagecount > pglimit)
> +
> + itempgcnt = list[i].size >> PAGE_SHIFT;
> + pgcnt += itempgcnt;
> +
> + if (pgcnt > pglimit)
> goto err;
> +
> + max_ipgcnt = max_t(unsigned long, itempgcnt, max_ipgcnt);
Is this optimization really necessary given that, in practice, the userspace provides
only a few ranges? It can stay but please pull these changes into a separate patch.
Thanks,
Vivek
> }
>
> - if (!ubuf->pagecount)
> + if (!pgcnt)
> goto err;
>
> - ubuf->folios = kvmalloc_array(ubuf->pagecount, sizeof(*ubuf-
> >folios),
> + ubuf->folios = kvmalloc_array(pgcnt, sizeof(*ubuf->folios),
> GFP_KERNEL);
> if (!ubuf->folios) {
> ret = -ENOMEM;
> goto err;
> }
> - ubuf->offsets = kvcalloc(ubuf->pagecount, sizeof(*ubuf->offsets),
> - GFP_KERNEL);
> +
> + ubuf->offsets = kvcalloc(pgcnt, sizeof(*ubuf->offsets), GFP_KERNEL);
> if (!ubuf->offsets) {
> ret = -ENOMEM;
> goto err;
> }
>
> - pgbuf = 0;
> - for (i = 0; i < head->count; i++) {
> - memfd = fget(list[i].memfd);
> - ret = check_memfd_seals(memfd);
> - if (ret < 0)
> - goto err;
> -
> - pgcnt = list[i].size >> PAGE_SHIFT;
> - folios = kvmalloc_array(pgcnt, sizeof(*folios), GFP_KERNEL);
> - if (!folios) {
> - ret = -ENOMEM;
> - goto err;
> - }
> + folios = kvmalloc_array(max_ipgcnt, sizeof(*folios), GFP_KERNEL);
> + if (!folios) {
> + ret = -ENOMEM;
> + goto err;
> + }
>
> - end = list[i].offset + (pgcnt << PAGE_SHIFT) - 1;
> - ret = memfd_pin_folios(memfd, list[i].offset, end,
> - folios, pgcnt, &pgoff);
> - if (ret <= 0) {
> - kvfree(folios);
> - if (!ret)
> - ret = -EINVAL;
> + for (i = 0; i < head->count; i++) {
> + ret = __udmabuf_pin_list_folios(&list[i], ubuf, folios);
> + if (ret)
> goto err;
> - }
> -
> - nr_folios = ret;
> - pgoff >>= PAGE_SHIFT;
> - for (j = 0, k = 0; j < pgcnt; j++) {
> - ubuf->folios[pgbuf] = folios[k];
> - ubuf->offsets[pgbuf] = pgoff << PAGE_SHIFT;
> -
> - if (j == 0 || ubuf->folios[pgbuf-1] != folios[k]) {
> - ret = add_to_unpin_list(&ubuf->unpin_list,
> - folios[k]);
> - if (ret < 0) {
> - kfree(folios);
> - goto err;
> - }
> - }
> -
> - pgbuf++;
> - if (++pgoff == folio_nr_pages(folios[k])) {
> - pgoff = 0;
> - if (++k == nr_folios)
> - break;
> - }
> - }
> -
> - kvfree(folios);
> - fput(memfd);
> - memfd = NULL;
> }
> + kvfree(folios);
>
> flags = head->flags & UDMABUF_FLAGS_CLOEXEC ? O_CLOEXEC : 0;
> ret = export_udmabuf(ubuf, device, flags);
> @@ -425,9 +463,8 @@ static long udmabuf_create(struct miscdevice
> *device,
> return ret;
>
> err:
> - if (memfd)
> - fput(memfd);
> unpin_all_folios(&ubuf->unpin_list);
> + kvfree(folios);
> kvfree(ubuf->offsets);
> kvfree(ubuf->folios);
> kfree(ubuf);
> --
> 2.45.2
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