On Fri, Jul 9, 2021 at 4:33 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 9 Jul 2021 16:23:18 -0700 Evan Green <evgreen@xxxxxxxxxxxx> wrote: > > > On Fri, Jul 9, 2021 at 3:20 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Fri, 9 Jul 2021 10:50:48 -0700 Evan Green <evgreen@xxxxxxxxxxxx> wrote: > > > > > > > Currently it's not possible to enable hibernation without also enabling > > > > generic swap for a given swap area. These two use cases are not the > > > > same. For example there may be users who want to enable hibernation, > > > > but whose drives don't have the write endurance for generic swap > > > > activities. > > > > > > > > Add a new SWAP_FLAG_NOSWAP that adds a swap region but refuses to allow > > > > generic swapping to it. This region can still be wired up for use in > > > > suspend-to-disk activities, but will never have regular pages swapped to > > > > it. > > > > > > > > Swap regions with SWAP_FLAG_NOSWAP set will not appear in /proc/meminfo > > > > under SwapTotal and SwapFree, since they are not usable as general swap. > > > > > > > > > > This patch doesn't appear to set SWAP_FLAG_NOSWAP anywhere. Perhaps > > > there's another patch somewhere which changes the hibernation code? If > > > so, can we please have both patches in a series? > > > > There's no other patch, in the kernel at least. SWAP_FLAG_* is exposed > > to usermode, which would set it when calling swapon(2). Once this > > patch is accepted, I'll have to add the option into util-linux [1], so > > that I can use it in my init scripts. > > > > Said a different way, this patch isn't about altering how hibernate > > behaves, but about giving usermode the freedom to set up hibernate and > > swap independently. > > OK, can we please get this into the changelog? And it would be helpful > to describe how this will be invoked via swapon(8). Sure, I can augment the commit text to include some of this, and what it would likely look like from the commandline. I'll send a v3 for that. > > And I expect an update to the swapon syscall's manpage will be in order. > Yes! I was originally planning to do that once this was accepted, but can also spin it up in parallel if requested. -Evan
