[PATCH 08/17] zram: don't use highmem for the bounce buffer in zram_bvec_{read,write}

[Christoph Hellwig <hch@xxxxxx>]

There is no point in allocation a highmem page when we instantly need
to copy from it.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 drivers/block/zram/zram_drv.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 2d0154489f0327..0182316b2a901d 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1431,7 +1431,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 	page = bvec->bv_page;
 	if (is_partial_io(bvec)) {
 		/* Use a temporary buffer to decompress the page */
-		page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
+		page = alloc_page(GFP_NOIO);
 		if (!page)
 			return -ENOMEM;
 	}
@@ -1440,12 +1440,8 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 	if (unlikely(ret))
 		goto out;
 
-	if (is_partial_io(bvec)) {
-		void *src = kmap_atomic(page);
-
-		memcpy_to_bvec(bvec, src + offset);
-		kunmap_atomic(src);
-	}
+	if (is_partial_io(bvec))
+		memcpy_to_bvec(bvec, page_address(page) + offset);
 out:
 	if (is_partial_io(bvec))
 		__free_page(page);
@@ -1589,12 +1585,11 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 
 	vec = *bvec;
 	if (is_partial_io(bvec)) {
-		void *dst;
 		/*
 		 * This is a partial IO. We need to read the full page
 		 * before to write the changes.
 		 */
-		page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
+		page = alloc_page(GFP_NOIO);
 		if (!page)
 			return -ENOMEM;
 
@@ -1602,9 +1597,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 		if (ret)
 			goto out;
 
-		dst = kmap_atomic(page);
-		memcpy_from_bvec(dst + offset, bvec);
-		kunmap_atomic(dst);
+		memcpy_from_bvec(page_address(page) + offset, bvec);
 
 		bvec_set_page(&vec, page, PAGE_SIZE, 0);
 	}
-- 
2.39.2