Re: [PATCH V5 1/3] block: Allow mapping of vmalloc-ed buffers

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On Thu, Jun 27, 2019 at 5:31 PM Damien Le Moal <damien.lemoal@xxxxxxx> 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 vmalloc().
>
> To do so, detect vmalloc-ed buffers using is_vmalloc_addr(). For
> vmalloc-ed buffers, flush the buffer using flush_kernel_vmap_range(),
> use vmalloc_to_page() instead of virt_to_page() to obtain the pages of
> the buffer, and invalidate the buffer addresses with
> invalidate_kernel_vmap_range() on completion of read BIOs. This last
> point is executed using the function bio_invalidate_vmalloc_pages()
> which is defined only if the architecture defines
> ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE, that is, if the architecture
> actually needs the invalidation done.
>
> Fixes: 515ce6061312 ("scsi: sd_zbc: Fix sd_zbc_report_zones() buffer allocation")
> Fixes: e76239a3748c ("block: add a report_zones method")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
> ---
>  block/bio.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index ce797d73bb43..bbba5f08b2ef 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -16,6 +16,7 @@
>  #include <linux/workqueue.h>
>  #include <linux/cgroup.h>
>  #include <linux/blk-cgroup.h>
> +#include <linux/highmem.h>
>
>  #include <trace/events/block.h>
>  #include "blk.h"
> @@ -1479,8 +1480,22 @@ void bio_unmap_user(struct bio *bio)
>         bio_put(bio);
>  }
>
> +static void bio_invalidate_vmalloc_pages(struct bio *bio)
> +{
> +#ifdef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
> +       if (bio->bi_private && !op_is_write(bio_op(bio))) {
> +               unsigned long i, len = 0;
> +
> +               for (i = 0; i < bio->bi_vcnt; i++)
> +                       len += bio->bi_io_vec[i].bv_len;
> +               invalidate_kernel_vmap_range(bio->bi_private, len);
> +       }
> +#endif
> +}
> +
>  static void bio_map_kern_endio(struct bio *bio)
>  {
> +       bio_invalidate_vmalloc_pages(bio);
>         bio_put(bio);
>  }
>
> @@ -1501,6 +1516,8 @@ 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;
>
> @@ -1508,6 +1525,11 @@ struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
>         if (!bio)
>                 return ERR_PTR(-ENOMEM);
>
> +       if (is_vmalloc) {
> +               flush_kernel_vmap_range(data, len);
> +               bio->bi_private = data;
> +       }
> +
>         offset = offset_in_page(kaddr);
>         for (i = 0; i < nr_pages; i++) {
>                 unsigned int bytes = PAGE_SIZE - offset;
> @@ -1518,7 +1540,11 @@ 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 = virt_to_page(data);
> +               else
> +                       page = vmalloc_to_page(data);
> +               if (bio_add_pc_page(q, bio, page, bytes,
>                                     offset) < bytes) {
>                         /* we don't support partial mappings */
>                         bio_put(bio);
> @@ -1531,6 +1557,7 @@ struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
>         }
>
>         bio->bi_end_io = bio_map_kern_endio;
> +
>         return bio;
>  }
>  EXPORT_SYMBOL(bio_map_kern);
> --
> 2.21.0
>

Looks fine:

Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>

-- 
Ming Lei



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