From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Hj7ctWdU" Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 46ACF1B6; Tue, 5 Dec 2023 23:21:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3qSq0ZgSYyFQdhkNKKx+ay2VTuWMWagkFjN44scFJGI=; b=Hj7ctWdUPYGChKSXbjiG3ceuLC qJJdvlVYftwJ0JmFiiq7KgA3kS4RlnIA/MDhNrvJyEEBExXyzpZoszMTkmDa/0AcbWk3X3RegC55V 7demvhkD/2Vm6MNZiLt23BUpT9dBqEkmj0CKPAbAJm+oIUuXhDVeLjwJaZkW3WPEmdGuSLkwjyd9+ YyBHijcvKAnO2bAVJAUvyMRdWxJKRyTYJ1uvpasFg0q82cLUXzhXq4Wu/L7v1jx64IWttFDdMu/ca 3J1JyfBFyObPGWrCPbNdP80bglMjq75SOxMB3QIX6GX/sagc2ovosgUjghAazuSh7ZC/geNc3PWxS jsvebKrQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1rAmCo-009HjE-0N; Wed, 06 Dec 2023 07:20:26 +0000 Date: Tue, 5 Dec 2023 23:20:26 -0800 From: Christoph Hellwig To: Yu Kuai Cc: Christoph Hellwig , axboe@kernel.dk, roger.pau@citrix.com, colyli@suse.de, kent.overstreet@gmail.com, joern@lazybastard.org, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, sth@linux.ibm.com, hoeppner@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, jejb@linux.ibm.com, martin.petersen@oracle.com, clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, nico@fluxnic.net, xiang@kernel.org, chao@kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, agruenba@redhat.com, jack@suse.com, konishi.ryusuke@gmail.com, willy@infradead.org, akpm@linux-foundation.org, hare@suse.de, p.raghav@samsung.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-bcachefs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, gfs2@lists.linux.dev, linux-nilfs@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, "yukuai (C)" Subject: Re: [PATCH -next RFC 01/14] block: add some bdev apis Message-ID: References: <20231205123728.1866699-1-yukuai1@huaweicloud.com> <20231205123728.1866699-2-yukuai1@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-nilfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Dec 06, 2023 at 02:50:56PM +0800, Yu Kuai wrote: > I'm a litter confused, so there are 3 use cases: > 1) use GFP_USER, default gfp from bdev_alloc. > 2) use GFP_KERNEL > 3) use GFP_NOFS > > I understand that you're suggesting memalloc_nofs_save() to distinguish > 2 and 3, but how can I distinguish 1? You shouldn't. Diverging from the default flags except for clearing the FS or IO flags is simply a bug. Note that things like block2mtd should probably also ensure a noio allocation if they aren't doing that yet. > > - use memalloc_nofs_save in extet instead of using > > mapping_gfp_constraint to clear it from the mapping flags > > - remove __ext4_sb_bread_gfp and just have buffer.c helper that does > > the right thing (either by changing the calling conventions of an > > existing one, or adding a new one). > > Thanks for the suggestions, but I'm not sure how to do this yet, I must > read more ext4 code. the nofs save part should be trivial. You can just skip the rest for now as it's not needed for this patch series.