The patch titled
Subject: zram: don't use highmem for the bounce buffer in zram_bvec_{read,write}
has been added to the -mm mm-unstable branch. Its filename is
zram-dont-use-highmem-for-the-bounce-buffer-in-zram_bvec_readwrite.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-dont-use-highmem-for-the-bounce-buffer-in-zram_bvec_readwrite.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Christoph Hellwig <hch@xxxxxx>
Subject: zram: don't use highmem for the bounce buffer in zram_bvec_{read,write}
Date: Tue, 11 Apr 2023 19:14:50 +0200
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@xxxxxx
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 17 +++++------------
1 file changed, 5 insertions(+), 12 deletions(-)
--- a/drivers/block/zram/zram_drv.c~zram-dont-use-highmem-for-the-bounce-buffer-in-zram_bvec_readwrite
+++ a/drivers/block/zram/zram_drv.c
@@ -1431,7 +1431,7 @@ static int zram_bvec_read(struct zram *z
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 *z
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 *
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 *
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);
}
_
Patches currently in -mm which might be from hch@xxxxxx are
zram-always-compile-read_from_bdev_sync.patch
zram-remove-valid_io_request.patch
zram-make-zram_bio_discard-more-self-contained.patch
zram-simplify-bvec-iteration-in-__zram_make_request.patch
zram-move-discard-handling-to-zram_submit_bio.patch
zram-return-early-on-error-in-zram_bvec_rw.patch
zram-refactor-highlevel-read-and-write-handling.patch
zram-dont-use-highmem-for-the-bounce-buffer-in-zram_bvec_readwrite.patch
zram-rename-__zram_bvec_read-to-zram_read_page.patch
zram-directly-call-zram_read_page-in-writeback_store.patch
zram-refactor-zram_bdev_read.patch
zram-dont-pass-a-bvec-to-__zram_bvec_write.patch
zram-refactor-zram_bdev_write.patch
zram-pass-a-page-to-read_from_bdev.patch
zram-dont-return-errors-from-read_from_bdev_async.patch
zram-fix-synchronous-reads.patch
zram-return-errors-from-read_from_bdev_sync.patch
