[PATCH 1/2] zram: remove BD_CAP_SYNCHRONOUS_IO with writeback feature

[Minchan Kim]

If zram supports writeback feature, it's no more syncrhonous
device beause we need asynchronous IO opeation.

Do not pretend to be syncrhonous IO device.
It makes system very sluggish as waiting IO completion from
upper layer.

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 drivers/block/zram/zram_drv.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 7436b2d27fa3..8610987b7b5a 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1699,6 +1699,11 @@ static int zram_add(void)
 
 	zram->disk->queue->backing_dev_info->capabilities |=
 			(BDI_CAP_STABLE_WRITES | BDI_CAP_SYNCHRONOUS_IO);
+#if CONFIG_ZRAM_WRITEBACK
+	if (zram->backing_dev)
+		zram->disk->queue->backing_dev_info->capabilities &=
+			~BDI_CAP_SYNCHRONOUS_IO;
+#endif
 	add_disk(zram->disk);
 
 	ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
-- 
2.18.0.345.g5c9ce644c3-goog


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