On Tue, 10 Mar 2020 18:46:40 -0700
John Hubbard <jhubbard@xxxxxxxxxx> wrote:
> On 3/7/20 3:25 PM, Andrew Morton wrote:
> >
> > The patch titled
> > Subject: mm/gup: fixup for 9947ea2c1e608e32 "mm/gup: track
> > FOLL_PIN pages" has been added to the -mm tree. Its filename is
> > mm-gup-track-foll_pin-pages-fix-2.patch
> >
>
> This appears to be causing a build failure in mm/gup.c, in mmotm, as
> of today anyway:
>
> commit 5d9ee416b570 ("pci: test for unexpectedly disabled
> bridges")
>
>
> I vaguely recall reviewing an earlier version that moved
> put_compound_head() up higher in gup.c, in order to avoid this. In
yes, that is what I had sent
> any case, that's what this needs in order to build. Sorry for missing
> it in the review.
I don't think you missed it, because the patch I sent out to be
squashed did move it up
> Claudio, did you compile-test the patch? I'm not sure how this made
not only compile tested, I even actually tested-tested it.
> it all the way to mmotm without it triggering something, either, but
> I can't see anything obviously wrong with my tree, which has no local
> changes applied.
>
> Here's what I'm seeing, and it makes sense because
> put_compound_head() is actually at line 2323:
the patch I had sent out did move put_compound_head to around line 116
> mm/gup.c: In function ‘gup_pte_range’:
> mm/gup.c:2177:4: error: implicit declaration of function
> ‘put_compound_head’; did you mean ‘set_compound_head’?
> [-Werror=implicit-function-declaration] 2177 |
> put_compound_head(head, 1, flags); | ^~~~~~~~~~~~~~~~~ |
> set_compound_head mm/gup.c: At top level:
> mm/gup.c:2323:13: warning: conflicting types for ‘put_compound_head’
> 2323 | static void put_compound_head(struct page *page, int refs,
> unsigned int flags) | ^~~~~~~~~~~~~~~~~
> mm/gup.c:2323:13: error: static declaration of ‘put_compound_head’
> follows non-static declaration mm/gup.c:2177:4: note: previous
> implicit declaration of ‘put_compound_head’ was here 2177 |
> put_compound_head(head, 1, flags); | ^~~~~~~~~~~~~~~~~
>
> And here's a compile-tested (only) proposed fix:
I think the most appropriate place would be right after
try_grab_compound_head, which is where I had put it.
> diff --git a/mm/gup.c b/mm/gup.c
> index 722fcdd32ab8..6344252f0632 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2116,6 +2116,28 @@ static inline pte_t gup_get_pte(pte_t *ptep)
> }
> #endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
>
> +static void put_compound_head(struct page *page, int refs, unsigned
> int flags) +{
> + if (flags & FOLL_PIN) {
> + mod_node_page_state(page_pgdat(page),
> NR_FOLL_PIN_RELEASED,
> + refs);
> +
> + if (hpage_pincount_available(page))
> + hpage_pincount_sub(page, refs);
> + else
> + refs *= GUP_PIN_COUNTING_BIAS;
> + }
> +
> + VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
> + /*
> + * Calling put_page() for each ref is unnecessarily slow.
> Only the last
> + * ref needs a put_page().
> + */
> + if (refs > 1)
> + page_ref_sub(page, refs - 1);
> + put_page(page);
> +}
> +
> static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
> unsigned int flags,
> struct page **pages)
> @@ -2320,28 +2342,6 @@ static int record_subpages(struct page *page,
> unsigned long addr, return nr;
> }
>
> -static void put_compound_head(struct page *page, int refs, unsigned
> int flags) -{
> - if (flags & FOLL_PIN) {
> - mod_node_page_state(page_pgdat(page),
> NR_FOLL_PIN_RELEASED,
> - refs);
> -
> - if (hpage_pincount_available(page))
> - hpage_pincount_sub(page, refs);
> - else
> - refs *= GUP_PIN_COUNTING_BIAS;
> - }
> -
> - VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
> - /*
> - * Calling put_page() for each ref is unnecessarily slow.
> Only the last
> - * ref needs a put_page().
> - */
> - if (refs > 1)
> - page_ref_sub(page, refs - 1);
> - put_page(page);
> -}
> -
> #ifdef CONFIG_ARCH_HAS_HUGEPD
> static unsigned long hugepte_addr_end(unsigned long addr, unsigned
> long end, unsigned long sz)
>
>
>
> thanks,
