Messages in this thread | | | Date | Mon, 18 Mar 2024 13:14:44 +0000 | From | Matthew Wilcox <> | Subject | Re: [PATCH 01/12] mm/ksm: catch tail page abnormal in page_stable_node |
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On Mon, Mar 18, 2024 at 08:14:30PM +0800, alexs@kernel.org wrote: > From: Alex Shi <alexs@kernel.org> > > commit 19138349ed59 ("mm/migrate: Add folio_migrate_flags()") change the > meaning of func page_stable_node() to check the compound head for tail > 'page' instead of tail page self. > But seems both semantics are same at results, the func always return NULL > for tail page. So adding a bug monitor here in case of abnormal.
No. I didn't object to you doing this to convince yourself, but there's no way we should have this upstream.
If we did have large KSM folios (and I don't think we should!), you'd crash the kernel instead of silently doing the right thing.
> static inline struct ksm_stable_node *page_stable_node(struct page *page) > { > - return folio_stable_node(page_folio(page)); > + struct ksm_stable_node *node; > + > + node = folio_stable_node(page_folio(page)); > + VM_BUG_ON_PAGE(PageTail(page) && node, page); > + > + return node; > }
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