btrfs: integrity-checker: convert block context kmap's to kmap_local_page

btrfsic_read_block() (which calls kmap()) and
btrfsic_release_block_ctx() (which calls kunmap()) are always called
within a single thread of execution.

Therefore the mappings created within these calls can be a thread local
mapping.

Convert the kmap() of bloc_ctx->pagev to kmap_local_page().  Luckily the
unmap loops backwards through the array pointer so no adjustment needs
to be made to the unmapping order.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index 6cc8296..1695086 100644 (file)
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -1555,10 +1555,11 @@ static void btrfsic_release_block_ctx(struct btrfsic_block_data_ctx *block_ctx)
                BUG_ON(!block_ctx->pagev);
                num_pages = (block_ctx->len + (u64)PAGE_SIZE - 1) >>
                            PAGE_SHIFT;
+               /* Pages must be unmapped in reverse order */
                while (num_pages > 0) {
                        num_pages--;
                        if (block_ctx->datav[num_pages]) {
-                               kunmap(block_ctx->pagev[num_pages]);
+                               kunmap_local(block_ctx->datav[num_pages]);
                                block_ctx->datav[num_pages] = NULL;
                        }
                        if (block_ctx->pagev[num_pages]) {
@@ -1637,7 +1638,7 @@ static int btrfsic_read_block(struct btrfsic_state *state,
                i = j;
        }
        for (i = 0; i < num_pages; i++)
-               block_ctx->datav[i] = kmap(block_ctx->pagev[i]);
+               block_ctx->datav[i] = kmap_local_page(block_ctx->pagev[i]);
 
        return block_ctx->len;
 }