[V3,1/3] block: Allow mapping of vmalloc-ed buffers

Commit Message

Damien Le Moal June 26, 2019, 6:54 a.m. UTC

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: [e-mail]
Signed-off-by: Damien Le Moal <[e-mail]>
Reviewed-by: Bart Van Assche <[e-mail]>
---
 block/bio.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig June 26, 2019, 1:17 p.m. UTC | #1

This is still missing the proper vmalloc flushing and invalidation.

We can't leave that to the callers as is very subtle and trivial
to get wrong, as shown by your couple of previous attempts.

Patch

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);