From: David Howells <dhowells@redhat.com>
Subject: Re: [PATCH 2/3] fscache/cachefiles: optionally use SEEK_DATA instead of ->bmap.
Date: Mon, 20 Apr 2015 12:21:42 +0100
Message-ID: <3914.1429528902@warthog.procyon.org.uk>
References: <20150420052752.26554.52672.stgit@notabene.brown> <20150420052558.26554.97143.stgit@notabene.brown>
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Cc: dhowells@redhat.com, Chris Mason <clm@fb.com>,
	Al Viro <viro@ZenIV.linux.org.uk>, Josef Bacik <jbacik@fb.com>,
	David Sterba <dsterba@suse.cz>, linux-cachefs@vger.kernel.org,
	Dave Chinner <david@fromorbit.com>,
	linux-kernel@vger.kernel.org,
	Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org
To: NeilBrown <neilb@suse.de>
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NeilBrown <neilb@suse.de> wrote:

> @@ -721,24 +733,45 @@ int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op,

We can actually do better than this what you've done here for
cachefiles_read_or_alloc_pages().  We can use SEEK_DATA to check the beginning
of a run of pages and then SEEK_HOLE to see how many pages are covered.

David