[PATCH v4 4/5] udmabuf: udmabuf_create codestyle cleanup

[Kasireddy, Vivek]

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 at vivo.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