From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Both by the comments and the implementation, you are allowed to test
the flags of tail pages, but not set or clear the flags of tail pages.
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
---
include/linux/page-flags.h | 40 ++++++++++++++++++++--------------------
1 file changed, 20 insertions(+), 20 deletions(-)
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 593a5505bbb4..8588c4628a7d 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -178,7 +178,7 @@ static inline int PagePoisoned(const struct page *page)
* PF_ONLY_HEAD:
* for compound page, callers only ever operate on the head page.
*
- * PF_NO_TAIL:
+ * PF_TAIL_READ:
* modifications of the page flag must be done on small or head pages,
* checks can be done on tail pages too.
*
@@ -193,7 +193,7 @@ static inline int PagePoisoned(const struct page *page)
#define PF_ONLY_HEAD(page, modify) ({ \
VM_BUG_ON_PGFLAGS(PageTail(page), page); \
PF_POISONED_CHECK(page); })
-#define PF_NO_TAIL(page, modify) ({ \
+#define PF_TAIL_READ(page, modify) ({ \
VM_BUG_ON_PGFLAGS(modify && PageTail(page), page); \
PF_POISONED_CHECK(compound_head(page)); })
#define PF_NO_COMPOUND(page, modify) ({ \
@@ -269,7 +269,7 @@ static inline int TestClearPage##uname(struct page *page) { return 0; }
#define TESTSCFLAG_FALSE(uname) \
TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
-__PAGEFLAG(Locked, locked, PF_NO_TAIL)
+__PAGEFLAG(Locked, locked, PF_TAIL_READ)
PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
PAGEFLAG(Referenced, referenced, PF_HEAD)
@@ -280,8 +280,8 @@ PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(LRU, lru, PF_HEAD)
PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
TESTCLEARFLAG(Active, active, PF_HEAD)
-__PAGEFLAG(Slab, slab, PF_NO_TAIL)
-__PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
+__PAGEFLAG(Slab, slab, PF_TAIL_READ)
+__PAGEFLAG(SlobFree, slob_free, PF_TAIL_READ)
PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems */
/* Xen */
@@ -292,9 +292,9 @@ PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);
PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
__CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
-PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
- __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
- __SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
+PAGEFLAG(SwapBacked, swapbacked, PF_TAIL_READ)
+ __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_TAIL_READ)
+ __SETPAGEFLAG(SwapBacked, swapbacked, PF_TAIL_READ)
/*
* Private page markings that may be used by the filesystem that owns the page
@@ -311,13 +311,13 @@ PAGEFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
* Only test-and-set exist for PG_writeback. The unconditional operators are
* risky: they bypass page accounting.
*/
-TESTPAGEFLAG(Writeback, writeback, PF_NO_TAIL)
- TESTSCFLAG(Writeback, writeback, PF_NO_TAIL)
-PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)
+TESTPAGEFLAG(Writeback, writeback, PF_TAIL_READ)
+ TESTSCFLAG(Writeback, writeback, PF_TAIL_READ)
+PAGEFLAG(MappedToDisk, mappedtodisk, PF_TAIL_READ)
/* PG_readahead is only used for reads; PG_reclaim is only for writes */
-PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
- TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
+PAGEFLAG(Reclaim, reclaim, PF_TAIL_READ)
+ TESTCLEARFLAG(Reclaim, reclaim, PF_TAIL_READ)
PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
@@ -340,8 +340,8 @@ static __always_inline int PageSwapCache(struct page *page)
return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
}
-SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
-CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
+SETPAGEFLAG(SwapCache, swapcache, PF_TAIL_READ)
+CLEARPAGEFLAG(SwapCache, swapcache, PF_TAIL_READ)
#else
PAGEFLAG_FALSE(SwapCache)
#endif
@@ -351,9 +351,9 @@ PAGEFLAG(Unevictable, unevictable, PF_HEAD)
TESTCLEARFLAG(Unevictable, unevictable, PF_HEAD)
#ifdef CONFIG_MMU
-PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
- __CLEARPAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
- TESTSCFLAG(Mlocked, mlocked, PF_NO_TAIL)
+PAGEFLAG(Mlocked, mlocked, PF_TAIL_READ)
+ __CLEARPAGEFLAG(Mlocked, mlocked, PF_TAIL_READ)
+ TESTSCFLAG(Mlocked, mlocked, PF_TAIL_READ)
#else
PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
TESTSCFLAG_FALSE(Mlocked)
@@ -477,7 +477,7 @@ static __always_inline void SetPageUptodate(struct page *page)
set_bit(PG_uptodate, &page->flags);
}
-CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)
+CLEARPAGEFLAG(Uptodate, uptodate, PF_TAIL_READ)
int test_clear_page_writeback(struct page *page);
int __test_set_page_writeback(struct page *page, bool keep_write);
@@ -763,7 +763,7 @@ static inline int page_has_private(struct page *page)
#undef PF_ANY
#undef PF_HEAD
#undef PF_ONLY_HEAD
-#undef PF_NO_TAIL
+#undef PF_TAIL_READ
#undef PF_NO_COMPOUND
#endif /* !__GENERATING_BOUNDS_H */
--
2.16.3
