On Thu, 18 Nov 2010 13:02:43 -0600 Eric Sandeen <sandeen@xxxxxxxxxx> wrote: > On 11/18/10 12:36 PM, Andrew Morton wrote: > > On Thu, 18 Nov 2010 12:04:21 -0600 Eric Sandeen <sandeen@xxxxxxxxxx> wrote: > > > >> On 11/18/10 11:10 AM, Andrew Morton wrote: > >>> On Thu, 18 Nov 2010 08:55:18 -0600 Eric Sandeen <sandeen@xxxxxxxxxx> wrote: > >>> > >>>>> Can we just delete writeback_inodes_sb_nr_if_idle() and > >>>>> writeback_inodes_sb_if_idle()? The changelog for 17bd55d037a02 is > >>>>> pretty handwavy - do we know that deleting these things would make a > >>>>> jot of difference? > >>>> > >>>> Really? I thought it was pretty decent ;) > >>>> > >>>> Anyway, xfstests 204, "Test out ENOSPC flushing on small filesystems." > >>>> shows the problem clearly, IIRC. I should have included that in the > >>>> changelog, I suppose, sorry. > >>> > >>> Your email didn't really impart any information :( > >>> > >>> I suppose I could accidentally delete those nasty little functions in a > >>> drivers/parport patch then wait and see if anyone notices. > >>> > >> > >> Um, ok, then, to answer the question directly : > >> > >> No, please don't delete those functions, it will break ENOSPC handling > >> in ext4 as shown by xfstests regression test #204 ... > >> > > > > If those functions "fix" a testcase then it was by sheer luck, and the > > fs's ENOSPC handling is still busted. > > > > For a start writeback_inodes_sb_if_idle() is a no-op if the device > > isn't idle! > > so writeback is already in progress and it's already doing what we need, > right? Space is being freed up as we speak in that case. With no guarantee that it's being freed at a sufficient rate. > > Secondly, if the device _was_ idle, > > writeback_inodes_sb_if_idle() uses a work handoff to another thread, > > which means that the work might not get executed for another six weeks. > > We start it quite early, before things are critical. > > Yeah, it's not bulletproof but it is tons better. Translation: "it papers over a bug". Look, if this was a little best-effort poke-writeback-now performance tweak then fine. But as an attempt to prevent a synchronous and bogus ENOSPC error it's just hopeless. Guys, fix the thing for real, and take that hack out. -- 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
