----- Original Message ----- > From: "Matthew Wilcox" <willy@xxxxxxxxxxxxxxx> > To: "Mathieu Desnoyers" <mathieu.desnoyers@xxxxxxxxxxxx> > Cc: "Matthew Wilcox" <matthew.r.wilcox@xxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, > linux-kernel@xxxxxxxxxxxxxxx > 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>