diff options
authorDan Streetman <ddstreet@ieee.org>2017-02-27 14:26:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-27 18:43:45 -0800
commitfd5bb66cd934987e49557455b6497fc006521940 (patch)
parentzswap: clear compressor or zpool param if invalid at init (diff)
zswap: don't param_set_charp while holding spinlock
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: c99b42c3529e ("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>
1 files changed, 13 insertions, 7 deletions
diff --git a/mm/zswap.c b/mm/zswap.c
index 9e8565d9c66b..eedc27894b10 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -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());
- } else {
- spin_unlock(&zswap_pools_lock);
- pool = zswap_pool_create(type, compressor);
- spin_lock(&zswap_pools_lock);
+ spin_unlock(&zswap_pools_lock);
+ if (!pool)
+ pool = zswap_pool_create(type, compressor);
if (pool)
ret = param_set_charp(s, kp);
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