From: Theodore Ts'o Subject: Re: [PATCH 2/2] ext4: make use of sb_getblk_gfp Date: Thu, 2 Jul 2015 10:17:54 -0400 Message-ID: <20150702141754.GA9456@thunk.org> References: <1435645609-20387-1-git-send-email-kernel@kyup.com> <1435645609-20387-2-git-send-email-kernel@kyup.com> <20150702061427.GB3108@thunk.org> <5594D742.6040202@kyup.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: Nikolay Borisov Return-path: Content-Disposition: inline In-Reply-To: <5594D742.6040202@kyup.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thu, Jul 02, 2015 at 09:16:34AM +0300, Nikolay Borisov wrote: > > Just a question that popped to my mind after discussing with a colleague > - Is GFP_NOFS enough here or should it be GFP_NOIO? Presumably the > latter is a stronger guarantee that we are not going to hit any > fs/writeback related code? GFP_NOFS is fine here; file system code calls the I/O codepaths, but device driver code doesn't call fs code. Put another way, if there are pages that are backed by a block device, which can be cleaned without going through the FS code paths, it's fine to let that happen while we are inside file system code. - Ted