On Wed, 24 Nov 2010 12:03:43 +1100 Nick Piggin <npiggin@xxxxxxxxx> wrote: > On Tue, Nov 23, 2010 at 01:58:24PM -0500, Chris Mason wrote: > > > > My original btrfs patch just exported the bdi_ funcs so that btrfs could > > > > do the above internally. But Christoph objected, and I think he's > > > > right. We should either give everyone a bdi or make sure the writeback > > > > func kicks only one filesystem. > > > > > > Well it's just kicking the writeback thread, and it will writeback > > > from that particular sb. > > > > Hmmm? It will writeback for all the SBs on that bdi. In the current > > form that ext4 uses, that gets pretty expensive if you have a bunch of > > large partitions and you're only running out of space on one of them. > > Right. But if the bdi has writeback in progress (which would be most > of the time, on a busy filesystem), writeback_if_idle doesn't do > anything, and it is happy just for the background writeback to > eventually get around to writing out for us. That doesn't work if you're running btfs (apparently short for "busticated filesystem") because the bdi-per-sb thing carefully hid the information which you're looking for. We still don't have a fix for this bug yet, it appears, btw. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
