diff options
| author | Matteo Croce <mcroce@microsoft.com> | 2021-06-07 21:02:36 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-06-07 14:11:47 -0700 |
| commit | c07aea3ef4d4076f18f567b98ed01e082e02ed51 (patch) | |
| tree | f52beca6a7fefeb1f14f7fb92efa914a3682b86f /include | |
| parent | 35cba15a504bf4f585bb9d78f47b22b28a1a06b2 (diff) | |
mm: add a signature in struct page
This is needed by the page_pool to avoid recycling a page not allocated
via page_pool.
The page->signature field is aliased to page->lru.next and
page->compound_head, but it can't be set by mistake because the
signature value is a bad pointer, and can't trigger a false positive
in PageTail() because the last bit is 0.
Co-developed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mm.h | 11 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 7 | ||||
| -rw-r--r-- | include/linux/poison.h | 3 |
3 files changed, 16 insertions, 5 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index c274f75efcf9..a0434e8c2617 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1668,10 +1668,11 @@ struct address_space *page_mapping(struct page *page); static inline bool page_is_pfmemalloc(const struct page *page) { /* - * Page index cannot be this large so this must be - * a pfmemalloc page. + * lru.next has bit 1 set if the page is allocated from the + * pfmemalloc reserves. Callers may simply overwrite it if + * they do not need to preserve that information. */ - return page->index == -1UL; + return (uintptr_t)page->lru.next & BIT(1); } /* @@ -1680,12 +1681,12 @@ static inline bool page_is_pfmemalloc(const struct page *page) */ static inline void set_page_pfmemalloc(struct page *page) { - page->index = -1UL; + page->lru.next = (void *)BIT(1); } static inline void clear_page_pfmemalloc(struct page *page) { - page->index = 0; + page->lru.next = NULL; } /* diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5aacc1c10a45..ed6862eacb52 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -97,6 +97,13 @@ struct page { }; struct { /* page_pool used by netstack */ /** + * @pp_magic: magic value to avoid recycling non + * page_pool allocated pages. + */ + unsigned long pp_magic; + struct page_pool *pp; + unsigned long _pp_mapping_pad; + /** * @dma_addr: might require a 64-bit value on * 32-bit architectures. */ diff --git a/include/linux/poison.h b/include/linux/poison.h index aff1c9250c82..d62ef5a6b4e9 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -78,4 +78,7 @@ /********** security/ **********/ #define KEY_DESTROY 0xbd +/********** net/core/page_pool.c **********/ +#define PP_SIGNATURE (0x40 + POISON_POINTER_DELTA) + #endif |