From: Eric Sandeen Subject: Re: [PATCH 3/3] ext4: Block mmapped writes while the fs is frozen Date: Wed, 18 May 2011 09:03:27 -0500 Message-ID: <4DD3D1AF.9060809@redhat.com> References: <1305066574-1573-1-git-send-email-jack@suse.cz> <1305066574-1573-4-git-send-email-jack@suse.cz> <20110517151108.GB6653@infradead.org> <20110518075614.GB25632@quack.suse.cz> <20110518080731.GA2759@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Jan Kara , Ted Tso , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Christoph Hellwig Return-path: In-Reply-To: <20110518080731.GA2759@infradead.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 5/18/11 3:07 AM, Christoph Hellwig wrote: > On Wed, May 18, 2011 at 09:56:14AM +0200, Jan Kara wrote: >> __block_page_mkwrite() and return some error value (EAGAIN translating to >> VM_FAULT_RETRY would look logical, I just have to think off better error >> value for VM_FAULT_NOPAGE). But vfs_check_frozen() cannot be in >> __block_page_mkwrite() since ext4 needs to call that with a transaction >> started so that would create a deadlock and we need to call >> vfs_check_frozen() somewhere so that we don't busyloop. >> >> I can call vfs_check_frozen() inside block_page_mkwrite() but it would be a >> bit surprising difference from __block_page_mkwrite() to me. Not sure what >> the cleanest solution would be here... > > block_page_mkwrite is supposed to be used directly by filesystems and > do all the right things. IIRC Eric even mentioned he added > vfs_check_frozen to it for RHEL, but forgot to push it upstream. Well, I tried, but it was rejected IIRC. Still, mea culpa.... I can resurrect what I did for RHEL5 and repost if desired... -Eric