[PATCH v2 12/12] cachefiles: make on-demand read killable

libaokun
2024-05-15T08:56:44Z

From: Baokun Li <libaokun1@huawei.com>

Replacing wait_for_completion() with wait_for_completion_killable() in
cachefiles_ondemand_send_req() allows us to kill processes that might
trigger a hunk_task if the daemon is abnormal.

But now only CACHEFILES_OP_READ is killable, because OP_CLOSE and OP_OPEN
is initiated from kworker context and the signal is prohibited in these
kworker.

Note that when the req in xas changes, i.e. xas_load(&xas) != req, it
means that a process will complete the current request soon, so wait
again for the request to be completed.

Suggested-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
---
fs/cachefiles/ondemand.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index a511d0a89109..bdc2d6dbadce 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -544,8 +544,25 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
goto out;

wake_up_all(&cache->daemon_pollwq);
- wait_for_completion(&req->done);
- ret = req->error;
+wait:
+ ret = wait_for_completion_killable(&req->done);
+ if (!ret) {
+ ret = req->error;
+ } else {
+ xas_reset(&xas);
+ xas_lock(&xas);
+ if (xas_load(&xas) == req) {
+ xas_store(&xas, NULL);
+ ret = -EINTR;
+ }
+ xas_unlock(&xas);
+
+ /* Someone will complete it soon. */
+ if (ret != -EINTR) {
+ cpu_relax();
+ goto wait;
+ }
+ }
cachefiles_req_put(req);
return ret;
out:
--
2.39.2