Messages in this thread | | | Date | Fri, 17 Oct 2014 15:52:14 +0000 (UTC) | From | Mathieu Desnoyers <> | Subject | Re: [PATCH v11 07/21] dax,ext2: Replace XIP read and write with DAX I/O |
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----- Original Message ----- > From: "Matthew Wilcox" <willy@linux.intel.com> > To: "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com> > Cc: "Matthew Wilcox" <matthew.r.wilcox@intel.com>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, > linux-kernel@vger.kernel.org > Sent: Friday, October 17, 2014 12:33:31 AM > Subject: Re: [PATCH v11 07/21] dax,ext2: Replace XIP read and write with DAX I/O > > On Thu, Oct 16, 2014 at 03:51:12PM -0400, Matthew Wilcox wrote: > > On Thu, Oct 16, 2014 at 11:50:27AM +0200, Mathieu Desnoyers wrote: > > > > + if (rw == WRITE) { > > > > + if (!buffer_mapped(bh)) { > > > > + retval = -EIO; > > > > + /* FIXME: fall back to buffered I/O */ > > > > > > Fallback on buffered I/O would void guarantee about having data stored > > > into persistent memory after write returns. Not sure we actually want > > > that. > > > > Yeah, I think that comment is just stale. I can't see a way in which > > buffered I/O would succeed after DAX I/O falis. > > On further consideration, I think the whole thing is just foolish. > I don't see how get_block(create == 1) can return success *and* a buffer > that is !mapped.
Perhaps a safe approach could be to put a BUG_ON() to check this assumption ?
Thanks,
Mathieu
> > So I did this nice simplification: > > - if (rw == WRITE) { > - if (!buffer_mapped(bh)) { > - retval = -EIO; > - /* FIXME: fall back to buffered I/O > */ > - break; > - } > - hole = false; > - } else { > - hole = !buffer_written(bh); > - } > + hole = (rw != WRITE) && !buffer_written(bh); > > (compile-tested only; I'm going to run all the changes through xfstests > next week when I'm back home before sending out a v12). >
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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