dm integrity: use bvec_kmap_local in integrity_metadata

Using local kmaps slightly reduces the chances to stray writes, and
the bvec interface cleans up the code a little bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Author: Christoph Hellwig

drivers/md/dm-integrity.c

@@ -1770,7 +1770,7 @@ static void integrity_metadata(struct work_struct *w)
 			char *mem, *checksums_ptr;
 
 again:
-			mem = (char *)kmap_atomic(bv.bv_page) + bv.bv_offset;
+			mem = bvec_kmap_local(&bv);
 			pos = 0;
 			checksums_ptr = checksums;
 			do {
@@ -1780,7 +1780,7 @@ static void integrity_metadata(struct work_struct *w)
 				pos += ic->sectors_per_block << SECTOR_SHIFT;
 				sector += ic->sectors_per_block;
 			} while (pos < bv.bv_len && sectors_to_process && checksums != checksums_onstack);
-			kunmap_atomic(mem);
+			kunmap_local(mem);
 
 			r = dm_integrity_rw_tag(ic, checksums, &dio->metadata_block, &dio->metadata_offset,
 						checksums_ptr - checksums, dio->op == REQ_OP_READ ? TAG_CMP : TAG_WRITE);