On Tue, Jul 4, 2023 at 3:04 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > On Tue, Jul 4, 2023 at 2:28 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Tue, 4 Jul 2023 13:22:54 -0700 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > > > > On Tue, Jul 4, 2023 at 9:18 AM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Tue, 4 Jul 2023 09:00:19 +0100 Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > > Thanks! I'll investigate this later today. After discussing with > > > > > > > > > Andrew, we would like to disable CONFIG_PER_VMA_LOCK by default until > > > > > > > > > the issue is fixed. I'll post a patch shortly. > > > > > > > > > > > > > > > > Posted at: https://lore.kernel.org/all/20230703182150.2193578-1-surenb@xxxxxxxxxx/ > > > > > > > > > > > > > > As that change fixes something in 6.4, why not cc: stable on it as well? > > > > > > > > > > > > Sorry, I thought since per-VMA locks were introduced in 6.4 and this > > > > > > patch is fixing 6.4 I didn't need to send it to stable for older > > > > > > versions. Did I miss something? > > > > > > > > > > 6.4.y is a stable kernel tree right now, so yes, it needs to be included > > > > > there :) > > > > > > > > I'm in wait-a-few-days-mode on this. To see if we have a backportable > > > > fix rather than disabling the feature in -stable. > > > > > > Ok, I think we have a fix posted at [2] and it's cleanly applies to > > > 6.4.y stable branch as well. However fork() performance might slightly > > > regress, therefore disabling per-VMA locks by default for now seems to > > > be preferable even with this fix (see discussion at > > > https://lore.kernel.org/all/54cd9ffb-8f4b-003f-c2d6-3b6b0d2cb7d9@xxxxxxxxxx/). > > > IOW, both [1] and [2] should be applied to 6.4.y stable. Both apply > > > cleanly and I CC'ed stable on [2]. Greg, should I send [1] separately > > > to stable@vger? > > > > > > [1] https://lore.kernel.org/all/20230703182150.2193578-1-surenb@xxxxxxxxxx/ > > > > This one isn't sufficient for .configs which already have > > PER_VMA_LOCK=y. Using `depends on BROKEN' would be better. > > > > > [2] https://lore.kernel.org/all/20230704200656.2526715-1-surenb@xxxxxxxxxx/ > > > > > > > We're still awaiting tester input on this? > > Yeah, and it seems to be negative... Anyway, I'll post a dependency on BROKEN. I posted the patchset at https://lore.kernel.org/all/20230705063711.2670599-1-surenb@xxxxxxxxxx/ CC'ing stable@vger with the cover letter explaining the situation. The negative report might have been a fluke, so let's wait for more testing. In the meantime we can disable the feature by applying the last patch in that series. > > > > > I think a clean new fully-changelogged two-patch series would be the > > best way to handle this. Please ensure that the [0/2] intro clearly > > explains what we're proposing here, and why. Done. > > > > Also, "might slightly regress" is a bit weak. These things are > > measurable, no? Because a better solution would be to fix 6.4.x and > > mainline and leave it at that. They are measurable and they were included in the fix I posted. I added the numbers in the new cover letter as well. Thanks, Suren. > >
