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authorDan Streetman <ddstreet@ieee.org>2017-02-27 14:26:53 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-17 09:35:27 +0100
commitc4eafbc2ba115bf6a4dbbc12874e16aa7f0c7283 (patch)
tree79cd3cb27f878cdbe29645f667caf13ef5ba2e83 /mm
parenteeca23f21cfb78bf537e1575874862cee91f7688 (diff)
zswap: don't param_set_charp while holding spinlock
commit fd5bb66cd934987e49557455b6497fc006521940 upstream. 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> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/zswap.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/mm/zswap.c b/mm/zswap.c
index 70775d37747a..568015e2fe7a 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -752,18 +752,22 @@ 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);