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proc: add a reschedule point in proc_readfd_common()

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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>
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Eric Dumazet 2015-12-03 11:12:07 -08:00 committed by Al Viro
parent bc51b2a919
commit 3cc4a84e02
1 changed files with 1 additions and 0 deletions
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fs/proc/fd.c
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@ -258,6 +258,7 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx,
name, len, instantiate, p,
(void *)(unsigned long)fd))
goto out_fd_loop;
cond_resched();
rcu_read_lock();
}
rcu_read_unlock();