Re: [PATCH 04/16] MIPS: use the generic get_user_pages_fast code
From: Jason Gunthorpe <jgg@ziepe.ca>
Date: 2019-06-21 14:05:46
Also in:
linux-mips, linux-sh, linuxppc-dev, lkml, sparclinux
On Tue, Jun 11, 2019 at 04:40:50PM +0200, Christoph Hellwig wrote:
quoted hunk ↗ jump to hunk
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 <redacted>
However, looks to me like this patch is also a bug fix for this:
commit 5b167c123b3c3582f62cf1896465019bc40fe526
Author: Kamal Dasu [off-list ref]
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