[PATCH 05/16] page-flags: define behavior of FS/IO-related flags on compound pages

[Kirill A. Shutemov]

It seems we don't have compound page on FS/IO path currently.
Use PF_NO_COMPOUND to catch if we have.

The odd exception is PG_dirty: sound uses compound pages and maps them
with PTEs. PF_NO_COMPOUND triggers VM_BUG_ON() in set_page_dirty() on
handling shared fault.  Let's use PF_HEAD for PG_dirty.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 include/linux/page-flags.h | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 26102813f0ac..63db7483c264 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -245,16 +245,16 @@ static inline int __TestClearPage##uname(struct page *page) { return 0; }
 	TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)
 
 __PAGEFLAG(Locked, locked, PF_NO_TAIL)
-PAGEFLAG(Error, error, PF_ANY) TESTCLEARFLAG(Error, error, PF_ANY)
+PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
 PAGEFLAG(Referenced, referenced, PF_ANY) TESTCLEARFLAG(Referenced, referenced, PF_ANY)
 	__SETPAGEFLAG(Referenced, referenced, PF_ANY)
-PAGEFLAG(Dirty, dirty, PF_ANY) TESTSCFLAG(Dirty, dirty, PF_ANY)
-	__CLEARPAGEFLAG(Dirty, dirty, PF_ANY)
+PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
+	__CLEARPAGEFLAG(Dirty, dirty, PF_HEAD)
 PAGEFLAG(LRU, lru, PF_ANY) __CLEARPAGEFLAG(LRU, lru, PF_ANY)
 PAGEFLAG(Active, active, PF_ANY) __CLEARPAGEFLAG(Active, active, PF_ANY)
 	TESTCLEARFLAG(Active, active, PF_ANY)
 __PAGEFLAG(Slab, slab, PF_ANY)
-PAGEFLAG(Checked, checked, PF_ANY)		/* Used by some filesystems */
+PAGEFLAG(Checked, checked, PF_NO_COMPOUND)	   /* Used by some filesystems */
 PAGEFLAG(Pinned, pinned, PF_ANY) TESTSCFLAG(Pinned, pinned, PF_ANY)	/* Xen */
 PAGEFLAG(SavePinned, savepinned, PF_ANY);			/* Xen */
 PAGEFLAG(Foreign, foreign, PF_ANY);				/* Xen */
@@ -280,12 +280,15 @@ 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_ANY) TESTSCFLAG(Writeback, writeback, PF_ANY)
-PAGEFLAG(MappedToDisk, mappedtodisk, PF_ANY)
+TESTPAGEFLAG(Writeback, writeback, PF_NO_COMPOUND)
+	TESTSCFLAG(Writeback, writeback, PF_NO_COMPOUND)
+PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_COMPOUND)
 
 /* PG_readahead is only used for reads; PG_reclaim is only for writes */
-PAGEFLAG(Reclaim, reclaim, PF_ANY) TESTCLEARFLAG(Reclaim, reclaim, PF_ANY)
-PAGEFLAG(Readahead, reclaim, PF_ANY) TESTCLEARFLAG(Readahead, reclaim, PF_ANY)
+PAGEFLAG(Reclaim, reclaim, PF_NO_COMPOUND)
+	TESTCLEARFLAG(Reclaim, reclaim, PF_NO_COMPOUND)
+PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
+	TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)
 
 #ifdef CONFIG_HIGHMEM
 /*
@@ -401,7 +404,7 @@ static inline int PageUptodate(struct page *page)
 static inline void __SetPageUptodate(struct page *page)
 {
 	smp_wmb();
-	__set_bit(PG_uptodate, &(page)->flags);
+	__set_bit(PG_uptodate, &page->flags);
 }
 
 static inline void SetPageUptodate(struct page *page)
@@ -412,7 +415,7 @@ static inline void SetPageUptodate(struct page *page)
 	 * uptodate are actually visible before PageUptodate becomes true.
 	 */
 	smp_wmb();
-	set_bit(PG_uptodate, &(page)->flags);
+	set_bit(PG_uptodate, &page->flags);
 }
 
 CLEARPAGEFLAG(Uptodate, uptodate, PF_ANY)
-- 
2.5.1

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