We have enough page flags after vmemmap no longer uses section ids. Reserve 5 of the 6 saved flags for functionality that is currently under development in the VM. The new flags are only available if either of these conditions are met: 1. 64 Bit system. (then we have 8 more free of the 32) 2. !NUMA. In that case 2 bits are needed for the zone id which leaves 30 page flag bits. Of those we use 24. 6 left. 3. !SPARSEMEM. In that case we use 5 bits of the 30 available for the node. 1 leftover. 4. SPARSEMEM_VMEMMAP. Case 3 applies. The remaining case is classic sparsemem with NUMA on a 32 bit platform. In that case we need to use additional bits from the remaining 25 which does not allow the use of all 5 extended page flags. We could deal with that case by only allowing sparsemem vmemmap (if sparsemem is selected as a model) on 32 bit NUMA platforms. Signed-off-by: Christoph Lameter --- include/linux/page-flags.h | 32 +++++++++++++++++++++++++++++--- mm/Kconfig | 11 +++++++++++ 2 files changed, 40 insertions(+), 3 deletions(-) Index: linux-2.6/include/linux/page-flags.h =================================================================== --- linux-2.6.orig/include/linux/page-flags.h 2008-02-29 19:33:01.000000000 -0800 +++ linux-2.6/include/linux/page-flags.h 2008-02-29 19:37:31.000000000 -0800 @@ -81,11 +81,24 @@ enum pageflags { PG_reserved, PG_private, /* If pagecache, has fs-private data */ PG_writeback, /* Page is under writeback */ - PG_compound, /* A compound page */ PG_swapcache, /* Swap page: swp_entry_t in private */ PG_mappedtodisk, /* Has blocks allocated on-disk */ PG_reclaim, /* To be reclaimed asap */ PG_buddy, /* Page is free, on buddy lists */ +#ifdef CONFIG_EXTENDED_PAGEFLAGS + /* + * Page flags that are only available without sparsemem on 32 bit + * (sparsemem vmemmap is ok. Flags are always available on 64 bit. + */ + PG_mlock, /* Page cannot be swapped out */ + PG_pin, /* Page cannot be moved in memory */ + PG_tail, /* Tail of a compound page */ + PG_head, /* Head of a compound page */ + PG_vcompound, /* Compound page is virtually mapped */ + PG_filebacked, /* Page is backed by an actual disk (not RAM) */ +#else + PG_compound, /* A compound page */ +#endif #if (BITS_PER_LONG > 32) /* @@ -245,8 +258,20 @@ static inline void set_page_writeback(st test_set_page_writeback(page); } -TESTPAGEFLAG(Compound, compound) -__PAGEFLAG(Head, compound) +#ifdef CONFIG_EXTENDED_PAGEFLAGS +__PAGEFLAG(Head, head) +__PAGEFLAG(Tail, tail) +__PAGEFLAG(Vcompound, vcompound) +__PAGEFLAG(Mlock, mlock) +__PAGEFLAG(Pin, pin) +__PAGEFLAG(FileBacked, filebacked) + +static inline int PageCompound(struct page *page) +{ + return (page->flags & ((1 << PG_tail) | (1 << PG_head))) != 0; +} + +#else /* * PG_reclaim is used in combination with PG_compound to mark the @@ -274,5 +299,6 @@ static inline void __ClearPageTail(struc { page->flags &= ~PG_head_tail_mask; } +#endif #endif /* PAGE_FLAGS_H */ Index: linux-2.6/mm/Kconfig =================================================================== --- linux-2.6.orig/mm/Kconfig 2008-02-29 19:13:55.000000000 -0800 +++ linux-2.6/mm/Kconfig 2008-02-29 19:37:31.000000000 -0800 @@ -193,3 +193,14 @@ config NR_QUICK config VIRT_TO_BUS def_bool y depends on !ARCH_NO_VIRT_TO_BUS + +# +# I wish we could get rid of this...... The main problem is the page +# flag use on 32 bit system with NUMA and SPARSEMEM (no sparsemem_vmemmap). +# Does not really make any sense to use sparsemem there since 32 bit spaces +# will typically be backed by contiguous RAM these days. So there is nothing +# sparse there anymore. +# +config EXTENDED_PAGEFLAGS + def_bool y + depends on 64BIT || !SPARSEMEM || !NUMA || SPARSEMEM_VMEMMAP -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/