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Message-ID: <20250805101946.1774112-1-senozhatsky@chromium.org>
Date: Tue, 5 Aug 2025 19:19:29 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jens Axboe <axboe@...nel.dk>,
Minchan Kim <minchan@...nel.org>,
linux-kernel@...r.kernel.org,
linux-block@...r.kernel.org,
Sergey Senozhatsky <senozhatsky@...omium.org>,
Seyediman Seyedarab <imandevel@...il.com>
Subject: [PATCH] zram: protect recomp_algorithm_show() with ->init_lock
sysfs handlers should be called under ->init_lock and are not
supposed to unlock it until return, otherwise e.g. a concurrent
reset() can occur. There is one handler that breaks that rule:
recomp_algorithm_show().
Move ->init_lock handling outside of __comp_algorithm_show()
(also drop it and call zcomp_available_show() directly) so that
the entire recomp_algorithm_show() loop is protected by the
lock, as opposed to protecting individual iterations.
Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
Reported-by: Seyediman Seyedarab <imandevel@...il.com>
---
drivers/block/zram/zram_drv.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 8acad3cc6e6e..9ac271b82780 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1225,18 +1225,6 @@ static void comp_algorithm_set(struct zram *zram, u32 prio, const char *alg)
zram->comp_algs[prio] = alg;
}
-static ssize_t __comp_algorithm_show(struct zram *zram, u32 prio,
- char *buf, ssize_t at)
-{
- ssize_t sz;
-
- down_read(&zram->init_lock);
- sz = zcomp_available_show(zram->comp_algs[prio], buf, at);
- up_read(&zram->init_lock);
-
- return sz;
-}
-
static int __comp_algorithm_store(struct zram *zram, u32 prio, const char *buf)
{
char *compressor;
@@ -1387,8 +1375,12 @@ static ssize_t comp_algorithm_show(struct device *dev,
char *buf)
{
struct zram *zram = dev_to_zram(dev);
+ ssize_t sz;
- return __comp_algorithm_show(zram, ZRAM_PRIMARY_COMP, buf, 0);
+ down_read(&zram->init_lock);
+ sz = zcomp_available_show(zram->comp_algs[ZRAM_PRIMARY_COMP], buf, 0);
+ up_read(&zram->init_lock);
+ return sz;
}
static ssize_t comp_algorithm_store(struct device *dev,
@@ -1412,14 +1404,15 @@ static ssize_t recomp_algorithm_show(struct device *dev,
ssize_t sz = 0;
u32 prio;
+ down_read(&zram->init_lock);
for (prio = ZRAM_SECONDARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
if (!zram->comp_algs[prio])
continue;
sz += sysfs_emit_at(buf, sz, "#%d: ", prio);
- sz += __comp_algorithm_show(zram, prio, buf, sz);
+ sz += zcomp_available_show(zram->comp_algs[prio], buf, sz);
}
-
+ up_read(&zram->init_lock);
return sz;
}
--
2.50.1.565.gc32cd1483b-goog
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