Re: [PATCH mm-hotfixes-unstable v18 00/14] khugepaged: add mTHP collapse support

On Fri, May 22, 2026 at 01:47:24PM -0700, Andrew Morton wrote:

Hi Andrew et al,

On Fri, 22 May 2026 08:59:55 -0600 Nico Pache [off-list ref] wrote:

quoted

The following series provides khugepaged with the capability to collapse
anonymous memory regions to mTHPs.

Thanks, I've update mm.git's mm-unstable branch to this version.

It sounds like I might be dropping it soon, haven't started looking at
that yet.  But let's at least eyeball the latest version at this time.

Sashiko was able to apply this, so the base-it-on-hotfixes thing worked
well, thanks.  The AI checking made a few allegations:

This series appears to cause hangs on s390 in linux-next.
The issue is not easily reproducible, so it is not yet confirmed.
Any ideas for a reliable reproducer that exercises the code path below?

    [ 2749.385719] sysrq: Show Blocked State
    [ 2749.385730] task:khugepaged      state:D stack:0     pid:209   tgid:209   ppid:2      task_flags:0x200040 flags:0x00000000
    [ 2749.385735] Call Trace:
    [ 2749.385736]  [<0000017f63c8b226>] __schedule+0x316/0x890
    [ 2749.385740]  [<0000017f63c8b7dc>] schedule+0x3c/0xc0
    [ 2749.385743]  [<0000017f63c8b888>] schedule_preempt_disabled+0x28/0x40
    [ 2749.385746]  [<0000017f63c902ea>] rwsem_down_write_slowpath+0x2fa/0x8b0
    [ 2749.385749]  [<0000017f63c90910>] down_write+0x70/0x80
    [ 2749.385752]  [<0000017f6313407a>] collapse_huge_page+0x2ea/0x9e0
    [ 2749.385755]  [<0000017f6313491e>] mthp_collapse+0x1ae/0x1f0
    [ 2749.385757]  [<0000017f63134fda>] collapse_scan_pmd+0x67a/0x8f0
    [ 2749.385760]  [<0000017f6313751a>] collapse_single_pmd+0x15a/0x260
    [ 2749.385762]  [<0000017f6313792c>] collapse_scan_mm_slot.constprop.0+0x30c/0x470
    [ 2749.385765]  [<0000017f63137cb6>] khugepaged+0x226/0x240
    [ 2749.385768]  [<0000017f62db3128>] kthread+0x148/0x170
    [ 2749.385770]  [<0000017f62d2c238>] __ret_from_fork+0x48/0x220
    [ 2749.385772]  [<0000017f63c95d0a>] ret_from_fork+0xa/0x30

Thanks!