zswap: don't param_set_charp while holding spinlock (fd5bb66c) · Commits · 戴 / test

Change the zpool/compressor param callback function to release the zswap_pools_lock spinlock before calling param_set_charp, since that function may sleep when it calls kmalloc with GFP_KERNEL. While this problem has existed for a while, I wasn't able to trigger it using a tight loop changing either/both the zpool and compressor params; I think it's very unlikely to be an issue on the stable kernels, especially since most zswap users will change the compressor and/or zpool from sysfs only one time each boot - or zero times, if they add the params to the kernel boot. Fixes: ("zswap: use charp for zswap param strings") Link: http://lkml.kernel.org/r/20170126155821.4545-1-ddstreet@ieee.org Signed-off-by:

Dan Streetman <dan.streetman@canonical.com> Reported-by:

Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/zswap.c

+13 −7

Original line number	Diff line number	Diff line
		@@ -704,18 +704,22 @@ static int __zswap_param_set(const char val, const struct kernel_param kp,
		pool = zswap_pool_find_get(type, compressor);
		if (pool) {
		zswap_pool_debug("using existing", pool);
		WARN_ON(pool == zswap_pool_current());
		list_del_rcu(&pool->list);
		} else {
		}

		spin_unlock(&zswap_pools_lock);

		if (!pool)
		pool = zswap_pool_create(type, compressor);
		spin_lock(&zswap_pools_lock);
		}

		if (pool)
		ret = param_set_charp(s, kp);
		else
		ret = -EINVAL;

		spin_lock(&zswap_pools_lock);

		if (!ret) {
		put_pool = zswap_pool_current();
		list_add_rcu(&pool->list, &zswap_pools);
		@@ -727,7 +731,11 @@ static int __zswap_param_set(const char val, const struct kernel_param kp,
		*/
		list_add_tail_rcu(&pool->list, &zswap_pools);
		put_pool = pool;
		} else if (!zswap_has_pool) {
		}

		spin_unlock(&zswap_pools_lock);

		if (!zswap_has_pool && !pool) {
		/* if initial pool creation failed, and this pool creation also
		* failed, maybe both compressor and zpool params were bad.
		* Allow changing this param, so pool creation will succeed
		@@ -738,8 +746,6 @@ static int __zswap_param_set(const char val, const struct kernel_param kp,
		ret = param_set_charp(s, kp);
		}

		spin_unlock(&zswap_pools_lock);

		/* drop the ref from either the old current pool,
		* or the new pool we failed to add
		*/

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