PAGEFLAGS_EXTENDED and separate page flags for Head and Tail

[linux-2.6-omap-h63xx.git] / include / linux / page-flags.h

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 17deafa9eb9b4eec4cae6042f322bdcd4747819b..590cff32415d92528501410ccf98bab5d3a8a216 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -83,7 +83,12 @@ enum pageflags {
        PG_reserved,
        PG_private,             /* If pagecache, has fs-private data */
        PG_writeback,           /* Page is under writeback */
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+       PG_head,                /* A head page */
+       PG_tail,                /* A tail page */
+#else
        PG_compound,            /* A compound page */
+#endif
        PG_swapcache,           /* Swap page: swp_entry_t in private */
        PG_mappedtodisk,        /* Has blocks allocated on-disk */
        PG_reclaim,             /* To be reclaimed asap */
@@ -134,6 +139,10 @@ static inline int TestClearPage##uname(struct page *page)          \
 #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname)            \
        __SETPAGEFLAG(uname, lname)  __CLEARPAGEFLAG(uname, lname)
 
+#define PAGEFLAG_FALSE(uname)                                          \
+static inline int Page##uname(struct page *page)                       \
+                       { return 0; }
+
 #define TESTSCFLAG(uname, lname)                                       \
        TESTSETFLAG(uname, lname) TESTCLEARFLAG(uname, lname)
 
@@ -171,28 +180,19 @@ PAGEFLAG(Readahead, reclaim)              /* Reminder to do async read-ahead */
  */
 #define PageHighMem(__p) is_highmem(page_zone(__p))
 #else
-static inline int PageHighMem(struct page *page)
-{
-       return 0;
-}
+PAGEFLAG_FALSE(HighMem)
 #endif
 
 #ifdef CONFIG_SWAP
 PAGEFLAG(SwapCache, swapcache)
 #else
-static inline int PageSwapCache(struct page *page)
-{
-       return 0;
-}
+PAGEFLAG_FALSE(SwapCache)
 #endif
 
 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 PAGEFLAG(Uncached, uncached)
 #else
-static inline int PageUncached(struct page *)
-{
-       return 0;
-}
+PAGEFLAG_FALSE(Uncached)
 #endif
 
 static inline int PageUptodate(struct page *page)
@@ -253,6 +253,28 @@ static inline void set_page_writeback(struct page *page)
        test_set_page_writeback(page);
 }
 
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+/*
+ * System with lots of page flags available. This allows separate
+ * flags for PageHead() and PageTail() checks of compound pages so that bit
+ * tests can be used in performance sensitive paths. PageCompound is
+ * generally not used in hot code paths.
+ */
+__PAGEFLAG(Head, head)
+__PAGEFLAG(Tail, tail)
+
+static inline int PageCompound(struct page *page)
+{
+       return page->flags & ((1L << PG_head) | (1L << PG_tail));
+
+}
+#else
+/*
+ * Reduce page flag use as much as possible by overlapping
+ * compound page flags with the flags used for page cache pages. Possible
+ * because PageCompound is always set for compound pages and not for
+ * pages on the LRU and/or pagecache.
+ */
 TESTPAGEFLAG(Compound, compound)
 __PAGEFLAG(Head, compound)
 
@@ -283,5 +305,6 @@ static inline void __ClearPageTail(struct page *page)
        page->flags &= ~PG_head_tail_mask;
 }
 
+#endif /* !PAGEFLAGS_EXTENDED */
 #endif /* !__GENERATING_BOUNDS_H */
 #endif /* PAGE_FLAGS_H */