diff options
| author | Dan Streetman <ddstreet@ieee.org> | 2017-02-27 14:26:53 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-02-27 18:43:45 -0800 |
| commit | fd5bb66cd934987e49557455b6497fc006521940 (patch) | |
| tree | d238fc3900b464c335b8719703ee1bfd9743c719 | |
| parent | bae21db88b7075662f28a0aa57e97016a2fdabfd (diff) | |
| download | lwn-fd5bb66cd934987e49557455b6497fc006521940.tar.gz lwn-fd5bb66cd934987e49557455b6497fc006521940.zip | |
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>
| -rw-r--r-- | mm/zswap.c | 20 |
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()); list_del_rcu(&pool->list); - } 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); 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 */ |