zram: don't use highmem for the bounce buffer in zram_bvec_{read,write}

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

Link: https://lkml.kernel.org/r/20230411171459.567614-9-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 2d01544..0182316 100644 (file)
--- 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);
        }