linux-kernel - Re: [PATCH 04/12] mm: add support for async page locking

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Message-ID: <20200526215925.GC6781@cmpxchg.org>
Date:   Tue, 26 May 2020 17:59:25 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org
Subject: Re: [PATCH 04/12] mm: add support for async page locking

On Tue, May 26, 2020 at 01:51:15PM -0600, Jens Axboe wrote:
> Normally waiting for a page to become unlocked, or locking the page,
> requires waiting for IO to complete. Add support for lock_page_async()
> and wait_on_page_locked_async(), which are callback based instead. This

wait_on_page_locked_async() is actually in the next patch, requiring
some back and forth to review. I wonder if this and the next patch
could be merged to have the new API and callers introduced together?

> allows a caller to get notified when a page becomes unlocked, rather
> than wait for it.
> 
> We add a new iocb field, ki_waitq, to pass in the necessary data for this
> to happen. We can unionize this with ki_cookie, since that is only used
> for polled IO. Polled IO can never co-exist with async callbacks, as it is
> (by definition) polled completions. struct wait_page_key is made public,
> and we define struct wait_page_async as the interface between the caller
> and the core.
> 
> Signed-off-by: Jens Axboe <axboe@...nel.dk>

Acked-by: Johannes Weiner <hannes@...xchg.org>