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mm/gup: move __get_user_pages_fast() down a few lines in gup.c

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Patch series "mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages()", v2.

In order to convert the drm/i915 driver from get_user_pages() to
pin_user_pages(), a FOLL_PIN equivalent of __get_user_pages_fast() was
required.  That led to refactoring __get_user_pages_fast(), with the
following goals:

1) As above: provide a pin_user_pages*() routine for drm/i915 to call,
   in place of __get_user_pages_fast(),

2) Get rid of the gup.c duplicate code for walking page tables with
   interrupts disabled. This duplicate code is a minor maintenance
   problem anyway.

3) Make it easy for an upcoming patch from Souptick, which aims to
   convert __get_user_pages_fast() to use a gup_flags argument, instead
   of a bool writeable arg.  Also, if this series looks good, we can
   ask Souptick to change the name as well, to whatever the consensus
   is. My initial recommendation is: get_user_pages_fast_only(), to
   match the new pin_user_pages_only().

This patch (of 4):

This is in order to avoid a forward declaration of
internal_get_user_pages_fast(), in the next patch.

This is code movement only--all generated code should be identical.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: "Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://lkml.kernel.org/r/20200522051931.54191-1-jhubbard@nvidia.com
Link: http://lkml.kernel.org/r/20200519002124.2025955-1-jhubbard@nvidia.com
Link: http://lkml.kernel.org/r/20200519002124.2025955-2-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
John Hubbard 2020-06-03 15:56:27 -07:00 committed by Linus Torvalds
parent dd8657b6c1
commit 9e1f0580d3
1 changed files with 66 additions and 66 deletions
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132
mm/gup.c
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@ -2703,72 +2703,6 @@ static bool gup_fast_permitted(unsigned long start, unsigned long end)
}
#endif
/*
* Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
* the regular GUP.
* Note a difference with get_user_pages_fast: this always returns the
* number of pages pinned, 0 if no pages were pinned.
*
* If the architecture does not support this function, simply return with no
* pages pinned.
*
* Careful, careful! COW breaking can go either way, so a non-write
* access can get ambiguous page results. If you call this function without
* 'write' set, you'd better be sure that you're ok with that ambiguity.
*/
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages)
{
unsigned long len, end;
unsigned long flags;
int nr_pinned = 0;
/*
* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
* because gup fast is always a "pin with a +1 page refcount" request.
*/
unsigned int gup_flags = FOLL_GET;
if (write)
gup_flags |= FOLL_WRITE;
start = untagged_addr(start) & PAGE_MASK;
len = (unsigned long) nr_pages << PAGE_SHIFT;
end = start + len;
if (end <= start)
return 0;
if (unlikely(!access_ok((void __user *)start, len)))
return 0;
/*
* Disable interrupts. We use the nested form as we can already have
* interrupts disabled by get_futex_key.
*
* With interrupts disabled, we block page table pages from being
* freed from under us. See struct mmu_table_batch comments in
* include/asm-generic/tlb.h for more details.
*
* We do not adopt an rcu_read_lock(.) here as we also want to
* block IPIs that come from THPs splitting.
*
* NOTE! We allow read-only gup_fast() here, but you'd better be
* careful about possible COW pages. You'll get _a_ COW page, but
* not necessarily the one you intended to get depending on what
* COW event happens after this. COW may break the page copy in a
* random direction.
*/
if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
gup_fast_permitted(start, end)) {
local_irq_save(flags);
gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
local_irq_restore(flags);
}
return nr_pinned;
}
EXPORT_SYMBOL_GPL(__get_user_pages_fast);
static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)
{
@ -2848,6 +2782,72 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
return ret;
}
/*
* Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
* the regular GUP.
* Note a difference with get_user_pages_fast: this always returns the
* number of pages pinned, 0 if no pages were pinned.
*
* If the architecture does not support this function, simply return with no
* pages pinned.
*
* Careful, careful! COW breaking can go either way, so a non-write
* access can get ambiguous page results. If you call this function without
* 'write' set, you'd better be sure that you're ok with that ambiguity.
*/
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages)
{
unsigned long len, end;
unsigned long flags;
int nr_pinned = 0;
/*
* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
* because gup fast is always a "pin with a +1 page refcount" request.
*/
unsigned int gup_flags = FOLL_GET;
if (write)
gup_flags |= FOLL_WRITE;
start = untagged_addr(start) & PAGE_MASK;
len = (unsigned long) nr_pages << PAGE_SHIFT;
end = start + len;
if (end <= start)
return 0;
if (unlikely(!access_ok((void __user *)start, len)))
return 0;
/*
* Disable interrupts. We use the nested form as we can already have
* interrupts disabled by get_futex_key.
*
* With interrupts disabled, we block page table pages from being
* freed from under us. See struct mmu_table_batch comments in
* include/asm-generic/tlb.h for more details.
*
* We do not adopt an rcu_read_lock(.) here as we also want to
* block IPIs that come from THPs splitting.
*
* NOTE! We allow read-only gup_fast() here, but you'd better be
* careful about possible COW pages. You'll get _a_ COW page, but
* not necessarily the one you intended to get depending on what
* COW event happens after this. COW may break the page copy in a
* random direction.
*/
if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
gup_fast_permitted(start, end)) {
local_irq_save(flags);
gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
local_irq_restore(flags);
}
return nr_pinned;
}
EXPORT_SYMBOL_GPL(__get_user_pages_fast);
/**
* get_user_pages_fast() - pin user pages in memory
* @start: starting user address