lkml.org 
[lkml]   [2019]   [Jun]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 04/16] MIPS: use the generic get_user_pages_fast code
On Tue, Jun 11, 2019 at 04:40:50PM +0200, Christoph Hellwig wrote:
> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> index 4ccb465ef3f2..7d27194e3b45 100644
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -20,6 +20,7 @@
> #include <asm/cmpxchg.h>
> #include <asm/io.h>
> #include <asm/pgtable-bits.h>
> +#include <asm/cpu-features.h>
>
> struct mm_struct;
> struct vm_area_struct;
> @@ -626,6 +627,8 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
>
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> +#define gup_fast_permitted(start, end) (!cpu_has_dc_aliases)
> +

Today this check is only being done on the get_user_pages_fast() -
after this patch it is also done for __get_user_pages_fast().

Which means __get_user_pages_fast is now non-functional on a range of
MIPS CPUs, but that seems OK as far as I can tell, so:

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

However, looks to me like this patch is also a bug fix for this:

commit 5b167c123b3c3582f62cf1896465019bc40fe526
Author: Kamal Dasu <kdasu.kdev@gmail.com>
Date: Fri Jun 14 17:10:03 2013 +0000

MIPS: Fix get_user_page_fast() for mips with cache alias

get_user_pages_fast() is missing cache flushes for MIPS platforms with
cache aliases. Filesystem failures observed with DirectIO operations due
to missing flush_anon_page() that use page coloring logic to work with
cache aliases. This fix falls through to take slow_irqon path that calls
get_user_pages() that has required logic for platforms where
cpu_has_dc_aliases is true.

> - pgdp = pgd_offset(mm, addr);
> - do {
> - pgd_t pgd = *pgdp;
> -
> - next = pgd_addr_end(addr, end);
> - if (pgd_none(pgd))
> - goto slow;
> - if (!gup_pud_range(pgd, addr, next, gup_flags & FOLL_WRITE,
> - pages, &nr))

This is different too, the core code has a p4d layer, but I see that
whole thing gets NOP'd by the compiler as mips uses pgtable-nop4d.h -
right?

Jason

\
 
 \ /
  Last update: 2019-06-21 16:06    [W:0.173 / U:35.252 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site