proc: add a reschedule point in proc_readfd_common()
User can pass an arbitrary large buffer to getdents().
It is typically a 32KB buffer used by libc scandir() implementation.
When scanning /proc/{pid}/fd, we can hold cpu way too long,
so add a cond_resched() to be kind with other tasks.
We've seen latencies of more than 50ms on real workloads.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 3c2a915..56afa5e 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -258,6 +258,7 @@
name, len, instantiate, p,
(void *)(unsigned long)fd))
goto out_fd_loop;
+ cond_resched();
rcu_read_lock();
}
rcu_read_unlock();