linux-kernel - Re: [PATCH] mm: Support madvise_willneed override by Filesystems

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Date:   Wed, 3 Jul 2019 21:03:42 +0300
From:   Boaz Harrosh <openosd@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Dave Chinner <david@...morbit.com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Chinner <dchinner@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-bcache@...r.kernel.org,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Zach Brown <zach.brown@...com>, Jens Axboe <axboe@...nel.dk>,
        Josef Bacik <josef@...icpanda.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH] mm: Support madvise_willneed override by Filesystems

On 03/07/2019 20:21, Jan Kara wrote:
> On Wed 03-07-19 04:04:57, Boaz Harrosh wrote:
>> On 19/06/2019 11:21, Jan Kara wrote:
>> <>
<>
>> Hi Jan
>>
>> Funny I'm sitting on the same patch since LSF last. I need it too for other
>> reasons. I have not seen, have you pushed your patch yet?
>> (Is based on old v4.20)
> 
> Your patch is wrong due to lock ordering. You should not call vfs_fadvise()
> under mmap_sem. So we need to do a similar dance like madvise_remove(). I
> have to get to writing at least XFS fix so that the madvise change gets
> used and post the madvise patch with it... Sorry it takes me so long.
> 
> 								Honza

Ha Sorry I was not aware of this. Lockdep did not catch it on my setup
because my setup does not have any locking conflicts with mmap_sem on the
WILL_NEED path.

But surly you are right because the all effort is to fix the locking problems.

I will also try in a day or two to do as you suggest, and look at madvise_remove()
once I have a bit of time. Who ever gets to be less busy ...

Thank you for your help
Boaz