| Message ID | 20230816151201.3655946-13-willy@infradead.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Remove _folio_dtor and _folio_order | expand |
On 16.08.23 17:12, Matthew Wilcox (Oracle) wrote: > Because THP_SWAP uses page->private for each page, we must not use > the space which overlaps that field for anything which would conflict > with that. We avoid the conflict on 32-bit systems by disallowing > THP_SWAP on 32-bit. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- > include/linux/mm_types.h | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 659c7b84726c..3880b3f2e321 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -340,8 +340,11 @@ struct folio { > atomic_t _pincount; > #ifdef CONFIG_64BIT > unsigned int _folio_nr_pages; > -#endif > + /* 4 byte gap here */ > /* private: the union with struct page is transitional */ > + /* Fix THP_SWAP to not use tail->private */ > + unsigned long _private_1; If you could give https://lkml.kernel.org/r/b887e764-ffa3-55ee-3c44-69cb15f8a115@redhat.com a quick glimpse to see if anything important jumps at you, that would be great. That really should be fixed.
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 659c7b84726c..3880b3f2e321 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -340,8 +340,11 @@ struct folio { atomic_t _pincount; #ifdef CONFIG_64BIT unsigned int _folio_nr_pages; -#endif + /* 4 byte gap here */ /* private: the union with struct page is transitional */ + /* Fix THP_SWAP to not use tail->private */ + unsigned long _private_1; +#endif }; struct page __page_1; }; @@ -362,6 +365,9 @@ struct folio { /* public: */ struct list_head _deferred_list; /* private: the union with struct page is transitional */ + unsigned long _avail_2a; + /* Fix THP_SWAP to not use tail->private */ + unsigned long _private_2a; }; struct page __page_2; }; @@ -386,12 +392,18 @@ FOLIO_MATCH(memcg_data, memcg_data); offsetof(struct page, pg) + sizeof(struct page)) FOLIO_MATCH(flags, _flags_1); FOLIO_MATCH(compound_head, _head_1); +#ifdef CONFIG_64BIT +FOLIO_MATCH(private, _private_1); +#endif #undef FOLIO_MATCH #define FOLIO_MATCH(pg, fl) \ static_assert(offsetof(struct folio, fl) == \ offsetof(struct page, pg) + 2 * sizeof(struct page)) FOLIO_MATCH(flags, _flags_2); FOLIO_MATCH(compound_head, _head_2); +FOLIO_MATCH(flags, _flags_2a); +FOLIO_MATCH(compound_head, _head_2a); +FOLIO_MATCH(private, _private_2a); #undef FOLIO_MATCH /*
Because THP_SWAP uses page->private for each page, we must not use the space which overlaps that field for anything which would conflict with that. We avoid the conflict on 32-bit systems by disallowing THP_SWAP on 32-bit. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- include/linux/mm_types.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)