Re: [PATCH 1/3] block: Allow mapping of vmalloc-ed buffers

[Bart Van Assche <bvanassche@acm.org>]

On 6/24/19 7:46 PM, Damien Le Moal wrote:
> To allow the SCSI subsystem scsi_execute_req() function to issue
> requests using large buffers that are better allocated with vmalloc()
> rather than kmalloc(), modify bio_map_kern() to allow passing a buffer
> allocated with the vmalloc() function. To do so, simply test the buffer
> address using is_vmalloc_addr() and use vmalloc_to_page() instead of
> virt_to_page() to obtain the pages of vmalloc-ed buffers.
> 
> Fixes: 515ce6061312 ("scsi: sd_zbc: Fix sd_zbc_report_zones() buffer allocation")
> Fixes: e76239a3748c ("block: add a report_zones method")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>   block/bio.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index ce797d73bb43..05afcaf655f3 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1501,6 +1501,8 @@ struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
>   	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
>   	unsigned long start = kaddr >> PAGE_SHIFT;
>   	const int nr_pages = end - start;
> +	bool is_vmalloc = is_vmalloc_addr(data);
> +	struct page *page;
>   	int offset, i;
>   	struct bio *bio;
>   
> @@ -1518,7 +1520,11 @@ struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
>   		if (bytes > len)
>   			bytes = len;
>   
> -		if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
> +		if (is_vmalloc)
> +			page = vmalloc_to_page(data);
> +		else
> +			page = virt_to_page(data);
> +		if (bio_add_pc_page(q, bio, page, bytes,
>   				    offset) < bytes) {
>   			/* we don't support partial mappings */
>   			bio_put(bio);

Reviewed-by: Bart Van Assche <bvanassche@acm.org>