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mm: Turn page_maybe_dma_pinned() into folio_maybe_dma_pinned()

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Replace three calls to compound_head() with one.  This removes the last
user of compound_pincount(), so remove that helper too.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
This commit is contained in:
Matthew Wilcox (Oracle) 2021-12-27 18:40:41 -05:00
parent 3d11b225ae
commit 0b90ddae13
1 changed files with 63 additions and 66 deletions
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129
include/linux/mm.h
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@ -892,13 +892,6 @@ static inline int head_compound_pincount(struct page *head)
return atomic_read(compound_pincount_ptr(head));
}
static inline int compound_pincount(struct page *page)
{
VM_BUG_ON_PAGE(!PageCompound(page), page);
page = compound_head(page);
return head_compound_pincount(page);
}
static inline void set_compound_order(struct page *page, unsigned int order)
{
page[1].compound_order = order;
@ -1236,70 +1229,11 @@ void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
bool make_dirty);
void unpin_user_pages(struct page **pages, unsigned long npages);
/**
* page_maybe_dma_pinned - Report if a page is pinned for DMA.
* @page: The page.
*
* This function checks if a page has been pinned via a call to
* a function in the pin_user_pages() family.
*
* For non-huge pages, the return value is partially fuzzy: false is not fuzzy,
* because it means "definitely not pinned for DMA", but true means "probably
* pinned for DMA, but possibly a false positive due to having at least
* GUP_PIN_COUNTING_BIAS worth of normal page references".
*
* False positives are OK, because: a) it's unlikely for a page to get that many
* refcounts, and b) all the callers of this routine are expected to be able to
* deal gracefully with a false positive.
*
* For huge pages, the result will be exactly correct. That's because we have
* more tracking data available: the 3rd struct page in the compound page is
* used to track the pincount (instead using of the GUP_PIN_COUNTING_BIAS
* scheme).
*
* For more information, please see Documentation/core-api/pin_user_pages.rst.
*
* Return: True, if it is likely that the page has been "dma-pinned".
* False, if the page is definitely not dma-pinned.
*/
static inline bool page_maybe_dma_pinned(struct page *page)
{
if (PageCompound(page))
return compound_pincount(page) > 0;
/*
* page_ref_count() is signed. If that refcount overflows, then
* page_ref_count() returns a negative value, and callers will avoid
* further incrementing the refcount.
*
* Here, for that overflow case, use the signed bit to count a little
* bit higher via unsigned math, and thus still get an accurate result.
*/
return ((unsigned int)page_ref_count(compound_head(page))) >=
GUP_PIN_COUNTING_BIAS;
}
static inline bool is_cow_mapping(vm_flags_t flags)
{
return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
}
/*
* This should most likely only be called during fork() to see whether we
* should break the cow immediately for a page on the src mm.
*/
static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
struct page *page)
{
if (!is_cow_mapping(vma->vm_flags))
return false;
if (!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags))
return false;
return page_maybe_dma_pinned(page);
}
#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
#define SECTION_IN_PAGE_FLAGS
#endif
@ -1549,6 +1483,69 @@ static inline atomic_t *folio_pincount_ptr(struct folio *folio)
return &folio_page(folio, 1)->compound_pincount;
}
/**
* folio_maybe_dma_pinned - Report if a folio may be pinned for DMA.
* @folio: The folio.
*
* This function checks if a folio has been pinned via a call to
* a function in the pin_user_pages() family.
*
* For small folios, the return value is partially fuzzy: false is not fuzzy,
* because it means "definitely not pinned for DMA", but true means "probably
* pinned for DMA, but possibly a false positive due to having at least
* GUP_PIN_COUNTING_BIAS worth of normal folio references".
*
* False positives are OK, because: a) it's unlikely for a folio to
* get that many refcounts, and b) all the callers of this routine are
* expected to be able to deal gracefully with a false positive.
*
* For large folios, the result will be exactly correct. That's because
* we have more tracking data available: the compound_pincount is used
* instead of the GUP_PIN_COUNTING_BIAS scheme.
*
* For more information, please see Documentation/core-api/pin_user_pages.rst.
*
* Return: True, if it is likely that the page has been "dma-pinned".
* False, if the page is definitely not dma-pinned.
*/
static inline bool folio_maybe_dma_pinned(struct folio *folio)
{
if (folio_test_large(folio))
return atomic_read(folio_pincount_ptr(folio)) > 0;
/*
* folio_ref_count() is signed. If that refcount overflows, then
* folio_ref_count() returns a negative value, and callers will avoid
* further incrementing the refcount.
*
* Here, for that overflow case, use the sign bit to count a little
* bit higher via unsigned math, and thus still get an accurate result.
*/
return ((unsigned int)folio_ref_count(folio)) >=
GUP_PIN_COUNTING_BIAS;
}
static inline bool page_maybe_dma_pinned(struct page *page)
{
return folio_maybe_dma_pinned(page_folio(page));
}
/*
* This should most likely only be called during fork() to see whether we
* should break the cow immediately for a page on the src mm.
*/
static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
struct page *page)
{
if (!is_cow_mapping(vma->vm_flags))
return false;
if (!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags))
return false;
return page_maybe_dma_pinned(page);
}
/* MIGRATE_CMA and ZONE_MOVABLE do not allow pin pages */
#ifdef CONFIG_MIGRATION
static inline bool is_pinnable_page(struct page *page)