On Thu, 22 Dec 2016, Nicholas Piggin wrote:
I agree with every word of that changelog ;)
And I'll stamp this with
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
The thing that Peter remembers I commented on (which 0day caught too),
was to remove PG_swapcache from PAGE_FLAGS_CHECK_AT_FREE: you've done
that now, so this is good. (Note in passing: wouldn't it be good to
add PG_waiters to PAGE_FLAGS_CHECK_AT_FREE in the 2/2?)
Though I did yesterday notice a few more problematic uses of
PG_swapcache, which you'll probably need to refine to exclude
other uses of PG_owner_priv_1; though no great hurry for those,
so not necessarily in this same patch. Do your own grep, but
fs/proc/page.c derives its KPF_SWAPCACHE from PG_swapcache,
needs refining.
kernel/kexec_core.c says VMCOREINFO_NUMBER(PG_swapcache):
I haven't looked into what that's about, it will probably just
have to be commented as now including other uses of the same bit.
mm/memory-failure.c has an error_states[] table that involves
testing PG_swapcache as "sc", but looks as if it can be changed
to factor in "swapbacked" too.
Hugh
> ---
> include/linux/page-flags.h | 24 ++++++++++++++++--------
> include/trace/events/mmflags.h | 1 -
> 2 files changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 74e4dda91238..a57c909a15e4 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -87,7 +87,6 @@ enum pageflags {
> PG_private_2, /* If pagecache, has fs aux data */
> PG_writeback, /* Page is under writeback */
> PG_head, /* A head page */
> - PG_swapcache, /* Swap page: swp_entry_t in private */
> PG_mappedtodisk, /* Has blocks allocated on-disk */
> PG_reclaim, /* To be reclaimed asap */
> PG_swapbacked, /* Page is backed by RAM/swap */
> @@ -110,6 +109,9 @@ enum pageflags {
> /* Filesystems */
> PG_checked = PG_owner_priv_1,
>
> + /* SwapBacked */
> + PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */
> +
> /* Two page bits are conscripted by FS-Cache to maintain local caching
> * state. These bits are set on pages belonging to the netfs's inodes
> * when those inodes are being locally cached.
> @@ -314,7 +316,13 @@ PAGEFLAG_FALSE(HighMem)
> #endif
>
> #ifdef CONFIG_SWAP
> -PAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
> +static __always_inline int PageSwapCache(struct page *page)
> +{
> + return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);
> +
> +}
> +SETPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
> +CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND)
> #else
> PAGEFLAG_FALSE(SwapCache)
> #endif
> @@ -701,12 +709,12 @@ static inline void ClearPageSlabPfmemalloc(struct page *page)
> * Flags checked when a page is freed. Pages being freed should not have
> * these flags set. It they are, there is a problem.
> */
> -#define PAGE_FLAGS_CHECK_AT_FREE \
> - (1UL << PG_lru | 1UL << PG_locked | \
> - 1UL << PG_private | 1UL << PG_private_2 | \
> - 1UL << PG_writeback | 1UL << PG_reserved | \
> - 1UL << PG_slab | 1UL << PG_swapcache | 1UL << PG_active | \
> - 1UL << PG_unevictable | __PG_MLOCKED)
> +#define PAGE_FLAGS_CHECK_AT_FREE \
> + (1UL << PG_lru | 1UL << PG_locked | \
> + 1UL << PG_private | 1UL << PG_private_2 | \
> + 1UL << PG_writeback | 1UL << PG_reserved | \
> + 1UL << PG_slab | 1UL << PG_active | \
> + 1UL << PG_unevictable | __PG_MLOCKED)
>
> /*
> * Flags checked when a page is prepped for return by the page allocator.
> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index 5a81ab48a2fb..30c2adbdebe8 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -95,7 +95,6 @@
> {1UL << PG_private_2, "private_2" }, \
> {1UL << PG_writeback, "writeback" }, \
> {1UL << PG_head, "head" }, \
> - {1UL << PG_swapcache, "swapcache" }, \
> {1UL << PG_mappedtodisk, "mappedtodisk" }, \
> {1UL << PG_reclaim, "reclaim" }, \
> {1UL << PG_swapbacked, "swapbacked" }, \
> --
> 2.11.0
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