From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: [PATCH v2] Do a proper locking for mmap and block size change Date: Thu, 29 Nov 2012 14:48:40 -0500 Message-ID: <20121129194840.GC3490@shiny> References: <50B5CC5A.8060607@kernel.dk> <20121128194314.GF4939@ZenIV.linux.org.uk> <20121129191503.GB3490@shiny> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Chris Mason , Mikulas Patocka , Al Viro , Jens Axboe , Jeff Chua , Lai Jiangshan , Jan Kara , lkml , linux-fsdevel To: Linus Torvalds Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Thu, Nov 29, 2012 at 12:26:06PM -0700, Linus Torvalds wrote: > On Thu, Nov 29, 2012 at 11:15 AM, Chris Mason wrote: > > > > The fs/buffer.c part makes sense during a quick read. But > > fs/direct-io.c plays with i_blkbits too. The semaphore was fixing real > > bugs there. > > Ugh. I _hate_ direct-IO. What a mess. And yeah, it seems to be > incestuously playing games that should be in fs/buffer.c. I thought it > was doing the sane thing with the page cache. > > (I now realize that Mikulas was talking about this mess, while I > thought he was talking about the AIO code which is largely sane). It was all a trick to get you to say the AIO code was sane. It looks like we could use the private copy of i_blkbits that DIO is already recording. blkdev_get_blocks (called during DIO) is also checking i_blkbits, but I really don't get why that isn't byte based instead. DIO is already doing the shift & mask game. I think only clean_blockdev_aliases is intentionally using the inode's i_blkbits, but again that shouldn't be changing for filesystems so it seems safe to use the DIO copy. -chris