On Fri, Jun 13, 2025 at 8:59 AM Pratyush Yadav <[email protected]> wrote: > > From: Pratyush Yadav <[email protected]> > > Currently, when restoring higher order folios, kho_restore_folio() only > calls prep_compound_page() on all the pages. That is not enough to > properly initialize the folios. The managed page count does not > get updated, the reserved flag does not get dropped, and page count does > not get initialized properly. > > Restoring a higher order folio with it results in the following BUG with > CONFIG_DEBUG_VM when attempting to free the folio: > > BUG: Bad page state in process test pfn:104e2b > page: refcount:1 mapcount:0 mapping:0000000000000000 > index:0xffffffffffffffff pfn:0x104e2b > flags: 0x2fffff80000000(node=0|zone=2|lastcpupid=0x1fffff) > raw: 002fffff80000000 0000000000000000 00000000ffffffff 0000000000000000 > raw: ffffffffffffffff 0000000000000000 00000001ffffffff 0000000000000000 > page dumped because: nonzero _refcount > [...] > Call Trace: > <TASK> > dump_stack_lvl+0x4b/0x70 > bad_page.cold+0x97/0xb2 > __free_frozen_pages+0x616/0x850 > [...] > > Combine the path for 0-order and higher order folios, initialize the > tail pages with a count of zero, and call adjust_managed_page_count() to > account for all the pages instead of just missing them. > > In addition, since all the KHO-preserved pages get marked with > MEMBLOCK_RSRV_NOINIT by deserialize_bitmap(), the reserved flag is not > actually set (as can also be seen from the flags of the dumped page in > the logs above). So drop the ClearPageReserved() calls. > > Fixes: fc33e4b44b271 ("kexec: enable KHO support for memory preservation") > Signed-off-by: Pratyush Yadav <[email protected]>
Reviewed-by: Pasha Tatashin <[email protected]>
