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Subject[PATCH v1] zram: don't retry compress incompressible page
Date
It doesn't make sense for us to retry to compress an uncompressible
page (comp_len == PAGE_SIZE) in zsmalloc slowpath, because we will
be storing it uncompressed anyway. We can avoid wasting time on
another compression attempt. It is enough to take lock
(zcomp_stream_get) and execute the code below.

Signed-off-by: Alexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: Dmitry Rokosov <ddrokosov@sberdevices.ru>
---
drivers/block/zram/zram_drv.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index cb253d80d72b..bb9dd8b64176 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1413,9 +1413,20 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
handle = zs_malloc(zram->mem_pool, comp_len,
GFP_NOIO | __GFP_HIGHMEM |
__GFP_MOVABLE);
- if (handle)
+ if (!handle)
+ return -ENOMEM;
+
+ if (comp_len != PAGE_SIZE)
goto compress_again;
- return -ENOMEM;
+
+ /*
+ * If the page is not compressible, you need to acquire the lock and
+ * execute the code below. The zcomp_stream_get() call is needed to
+ * disable the cpu hotplug and grab the zstrm buffer back.
+ * It is necessary that the dereferencing of the zstrm variable below
+ * occurs correctly.
+ */
+ zstrm = zcomp_stream_get(zram->comp);
}

alloced_pages = zs_get_total_pages(zram->mem_pool);
--
2.30.1
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