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

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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@xxxxxxxxxxxxxxx
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
---
  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@xxxxxxx>



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