From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Hillf Danton <hdanton@sina.com>,
	Kairui Song <ryncsn@gmail.com>,
	Minchan Kim <minchan@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Yosry Ahmed <yosry.ahmed@linux.dev>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.6.y 2/4] zram: move post-processing target allocation
Date: Fri,  4 Sep 2026 16:32:01 -0400
Message-ID: <20260904203203.1546745-2-sashal@kernel.org>
In-Reply-To: <20260904203203.1546745-1-sashal@kernel.org>
References: <2026090305-dimly-backboned-037d@gregkh>
 <20260904203203.1546745-1-sashal@kernel.org>
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From: Sergey Senozhatsky <senozhatsky@chromium.org>

[ Upstream commit 7e1b0212d4d59281a80c836841539a91b724bf24 ]

Allocate post-processing target in place_pp_slot().  This simplifies
scan_slots_for_writeback() and scan_slots_for_recompress() loops because
we don't need to track pps pointer state anymore.  Previously we have to
explicitly NULL the point if it has been added to a post-processing bucket
or re-use previously allocated pointer otherwise and make sure we don't
leak the memory in the end.

We are also fine doing GFP_NOIO allocation, as post-processing can be
called under memory pressure so we better pick as many slots as we can as
soon as we can and start post-processing them, possibly saving the memory.
Allocation failure there is not fatal, we will post-process whatever we
put into the buckets on previous iterations.

Link: https://lkml.kernel.org/r/20250303022425.285971-12-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 894913e2d35c ("zram: fix out-of-bounds access in writeback_store()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/block/zram/zram_drv.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index d547f2d251fd2..3b87e89a9a496 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -636,12 +636,20 @@ static ssize_t writeback_store(struct device *dev,
 	u64 nr_pages = zram->disksize >> PAGE_SHIFT;
 	unsigned long lo = 0, hi = nr_pages;
 	struct zram_pp_ctl *pp_ctl = NULL;
+	struct zram_wb_ctl *wb_ctl = NULL;
+	char *args, *param, *val;
 	ssize_t ret = len;
 	int err, mode = 0;
 	struct bio bio;
 	struct bio_vec bio_vec;
 	unsigned long blk_idx = 0;
 
+	/* Keep the newer writeback setup context available for its fix. */
+	(void)wb_ctl;
+	(void)args;
+	(void)param;
+	(void)val;
+
 	guard(rwsem_write)(&zram->init_lock);
 	if (!init_done(zram))
 		return -EINVAL;
@@ -649,9 +657,6 @@ static ssize_t writeback_store(struct device *dev,
 	if (!zram->backing_dev)
 		return -ENODEV;
 
-	nr_pages = zram->disksize >> PAGE_SHIFT;
-	hi = nr_pages;
-
 	pp_ctl = init_pp_ctl();
 	if (!pp_ctl)
 		return -ENOMEM;
-- 
2.53.0