From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [PATCH 1/3] fs: allow short direct-io reads to be completed via buffered IO Date: Tue, 4 May 2010 10:14:18 +1000 Message-ID: <20100504001418.GH2591@dastard> References: <20100503172702.GB3961@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@vger.kernel.org To: Josef Bacik Return-path: Content-Disposition: inline In-Reply-To: <20100503172702.GB3961@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mon, May 03, 2010 at 01:27:02PM -0400, Josef Bacik wrote: > This is similar to what already happens in the write case. If we have a short > read while doing O_DIRECT, instead of just returning, fallthrough and try to > read the rest via buffered IO. BTRFS needs this because if we encounter a > compressed or inline extent during DIO, we need to fallback on buffered. If the > extent is compressed we need to read the entire thing into memory and > de-compress it into the users pages. I have tested this with fsx and everything > works great. Thanks, Won't this mean that any direct IO read that spans EOF (i.e. get a short read) now attempt a buffered IO (that will fail) before returning? Cheers, Dave. -- Dave Chinner david@fromorbit.com