Re: [PATCH 7/9] mm: Free up PG_slab

[Matthew Wilcox <willy@infradead.org>]

On Thu, Mar 21, 2024 at 02:24:45PM +0000, Matthew Wilcox (Oracle) wrote:
> Reclaim the Slab page flag by using a spare bit in PageType.  We are
> perennially short of page flags for various purposes, and now that
> the original SLAB allocator has been retired, SLUB does not use the
> mapcount/page_type field.  This lets us remove a number of special cases
> for ignoring mapcount on Slab pages.

Update vmcoreinfo:

diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
index 23c125c2e243..1d5eadd9dd61 100644
--- a/kernel/vmcore_info.c
+++ b/kernel/vmcore_info.c
@@ -198,7 +198,8 @@ static int __init crash_save_vmcoreinfo_init(void)
 	VMCOREINFO_NUMBER(PG_private);
 	VMCOREINFO_NUMBER(PG_swapcache);
 	VMCOREINFO_NUMBER(PG_swapbacked);
-	VMCOREINFO_NUMBER(PG_slab);
+#define PAGE_SLAB_MAPCOUNT_VALUE	(~PG_slab)
+	VMCOREINFO_NUMBER(PAGE_SLAB_MAPCOUNT_VALUE);
 #ifdef CONFIG_MEMORY_FAILURE
 	VMCOREINFO_NUMBER(PG_hwpoison);
 #endif