On 10/30/2012 03:14 PM, NeilBrown wrote: > On Tue, 30 Oct 2012 13:14:24 -0700 "Darrick J. Wong" > <darrick.wong@xxxxxxxxxx> wrote: > >> On Tue, Oct 30, 2012 at 08:19:41AM -0400, Martin K. Petersen wrote: >>>>>>>> "Neil" == NeilBrown <neilb@xxxxxxx> writes: >>> <> > So I see a need for 2 flags here. Yes that was my thought too. We need two flags. The FS should communicate it's capabilities as well. > The first one is set by the device or transport to say "I would prefer > stable writes if possible". > The second is set by the filesystem, either because it has its own needs, or > because it sees the first flag set on the device and chooses to honour it. > The VFS/VM would act based on this second flag, and devices like md/RAID5 > would set the first flag, and assume writes are stable if the second flag is > also set. > > This implies that setting that second flag must be handled synchronously by > the filesystem, so that the device doesn't see the flag set until the > filesystem has committed to honouring it. That seems to make a mount (or > remount) option the safest way to set it. > I think I do not like any mount option or any other tuneable. With the block device stating it's needs and the FS confirming on it's capability then I do not see how reverting that decision by admin can be any good. Any overrides by an admin would then just be a bug. > Comments? > > NeilBrown > Thanks Boaz -- 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
