linux-kernel - Re: [patch] aio: remove aio-max-nr and instead use the memlock rlimit to limit the number of pages pinned for the aio completion ring

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Date:	Thu, 12 Mar 2009 04:33:20 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Benjamin LaHaise <bcrl@...ck.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Jeff Moyer <jmoyer@...hat.com>, Avi Kivity <avi@...hat.com>,
	linux-aio <linux-aio@...ck.org>, zach.brown@...cle.com,
	linux-kernel@...r.kernel.org,
	Davide Libenzi <davidel@...ilserver.org>
Subject: Re: [patch] aio: remove aio-max-nr and instead use the memlock rlimit
 to limit the number of pages pinned for the aio completion ring

Benjamin LaHaise a écrit :
> On Thu, Mar 12, 2009 at 04:24:42AM +0100, Eric Dumazet wrote:
>>         if (!IS_ERR(req->ki_eventfd))
>>                 fput(req->ki_eventfd);   /* BANG : can be called from interrupt context */
> ...
>> Thank you
> 
> That's a bug in the eventfd code, not aio.  Davide: please fix.
> 

Hmm... what about fget_light() ... is it Davide fault too ?

aio breaks the fget_light() concept too, if process is mono threaded.

/*
 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
 * You can use this only if it is guranteed that the current task already
 * holds a refcnt to that file. That check has to be done at fget() only
 * and a flag is returned to be passed to the corresponding fput_light().
 * There must not be a cloning between an fget_light/fput_light pair.
 */
struct file *fget_light(unsigned int fd, int *fput_needed)
{
        struct file *file;
        struct files_struct *files = current->files;

        *fput_needed = 0;
        if (likely((atomic_read(&files->count) == 1))) {
                file = fcheck_files(files, fd);
        } else {
                rcu_read_lock();
                file = fcheck_files(files, fd);
                if (file) {
                        if (atomic_long_inc_not_zero(&file->f_count))
                                *fput_needed = 1;
                        else
                                /* Didn't get the reference, someone's freed */
                                file = NULL;
                }
                rcu_read_unlock();
        }

        return file;
}



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