On Thu, Dec 08, 2016 at 07:48:18AM +0100, Xin Zhou wrote: > Hi Liu, > > From the patch, is the snapshot disabled by disabling the COW in the mounting > path? > It seems the create_snapshot() in ioctl.c does not get changed.
Well, I think I made a mistake in this cover letter, snapshot still works while mounting with dax, but if a snapshot is taken, then we'll get -EIO while writing to dax inodes that belong to either snapshot tree or its source tree. So in fact, only a readonly snapshot makes sense in practice, I'll update the patch so that we only allow a readonly snapshot to be taken. COW is disabled by letting the dax mount option imply the "nodatacow" option. Thanks for spotting this! Thanks, -liubo > > I experienced some similar system but am a bit new to the brtfs code. > > Thanks, > Xin > > > > Subject: [PATCH 0/6] btrfs dax IOFrom: Liu Bo <bo.li.liu@xxxxxxxxxx>Date: > Wed, 7 Dec 2016 13:45:04 -0800Cc: Chris Mason <clm@xxxxxx>, Jan Kara > <jack@xxxxxxx>, David Sterba <dsterba@xxxxxxx> > This is a prelimanary patch set to add dax support for btrfs, with > this we can do normal read/write to dax files and can mmap dax files > to userspace so that applications have the ability to access > persistent memory directly. > > Please note that currently this is limited to nocow, i.e. all dax > inodes do not have COW behaviour. > > COW: no > mutliple device: no > clone/reflink: no > snapshot: no > compression: no > checksum: no > > Right now snapshot is disabled while mounting with -odax, but snapshot > can be created without -odax, and writing to a dax file in snapshot > will get -EIO. > > Clone/reflink is dealt with as same as snapshot, -EIO will be returned > when writing to shared extents. > > This has adopted the latest iomap framework for dax read/write > and dax mmap. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
