Re: [REGRESSION][BISECTED] Hibernation: WARNING at kernel/power/main.c:48 pm_restrict_gfp_mask (was: "[PATCH v1] PM: hibernate: Restrict GFP mask in hibernation_snapshot()")

[Mario Limonciello]

On 10/25/25 12:08 AM, Askar Safin wrote:
> "Rafael J. Wysocki" <rafael@xxxxxxxxxx>:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > Commit 12ffc3b1513e ("PM: Restrict swap use to later in the suspend
> > sequence") incorrectly removed a pm_restrict_gfp_mask() call from
> > hibernation_snapshot(), so memory allocations involving swap are not
> > prevented from being carried out in this code path any more which may
> > lead to serious breakage.
>
> #regzbot introduced: 449c9c02537a146ac97ef962327a221e21c9cab3
>
> This commit introduced regression: now I see WARNING every time when
> I hibernate. The bug reproduces both on real hardware and in Qemu.
>
> Here is script I used to reproduce this bug in Qemu:
> https://zerobin.net/?aadae7117a208c0a#Xh8aI5+u3pyk+vKwET7j+yXolLeoSLe/AedcvnNeCLs=
>
> Here is resulting log (dmesg) on current master (43e9ad0c55a3):
> https://zerobin.net/?471d17d0632e7f85#uYne0yUu+rP4KnDbOFFqtCrcDIi6UpQz2uIQw85lcdQ=
>
> Here is the most interesting part:
>
> [    1.735001] PM: Image saving progress:  90%
> [    1.746611] PM: Image saving progress: 100%
> [    1.747208] PM: Image saving done
> [    1.747403] PM: hibernation: Wrote 30164 kbytes in 0.13 seconds (232.03 MB/s)
> [    1.747837] PM: Image size after compression: 8908 kbytes
> [    1.748190] PM: S|
> [    1.750351] ------------[ cut here ]------------
> [    1.750627] WARNING: CPU: 0 PID: 1 at kernel/power/main.c:48 pm_restrict_gfp_mask+0x3b/0x40
>
> On real hardware exactly same thing happens (i. e. WARNING at kernel/power/main.c:48 pm_restrict_gfp_mask).

Thanks for the report, and especially for the simple reproducer!

This is pretty similar to the problem we had with hybrid sleep. [1]

Link: https://git.kernel.org/torvalds/c/469d80a3712c6 [1]

I believe this should help:

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 14e85ff23551..e15907f28c4c 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -721,6 +721,7 @@ static void power_down(void)
                kernel_restart(NULL);
                break;
        case HIBERNATION_PLATFORM:
+               pm_restore_gfp_mask();
                error = hibernation_platform_enter();
                if (error == -EAGAIN || error == -EBUSY) {
                        events_check_enabled = false;