Messages in this thread | | | Date | Thu, 22 Dec 2016 11:55:28 -0800 (PST) | From | Hugh Dickins <> | Subject | Re: [PATCH 1/2] mm: Use owner_priv bit for PageSwapCache, valid when PageSwapBacked |
| |
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@google.com>
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
| |