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Date:   Thu, 22 Oct 2020 15:10:37 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Hao Xu <haoxu@linux.alibaba.com>
Cc:     Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org,
        linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH RFC] mm: fix the sync buffered read to the old way
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On Thu, Oct 22, 2020 at 09:58:34PM +0800, Hao Xu wrote:
> The commit 324bcf54c449 changed the code path of async buffered reads
> to go with the page_cache_sync_readahead() way when readahead is
> disabled, meanwhile the sync buffered reads are forced to do IO in the
> above way as well, which makes it go to a more complex code path.

But ->readpage is (increasingly) synchronous while readahead should be
used to start async I/Os.  I'm pretty sure Jens meant to do exactly what
he did.