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mm/rmap: introduce folio_try_dup_anon_rmap_[pte|ptes|pmd]() 

The last user of page_needs_cow_for_dma() and __page_dup_rmap() are gone,
remove them.

Add folio_try_dup_anon_rmap_ptes() right away, we want to perform rmap
baching during fork() soon.

Link: https://lkml.kernel.org/r/20231220224504.646757-35-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2023-12-20 23:44:58 +01:00 committed by Andrew Morton
parent d8ef5e311d
commit 61d90309b7
2 changed files with 106 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/mm.h
View File

@ -1975,12 +1975,6 @@ static inline bool folio_needs_cow_for_dma(struct vm_area_struct *vma,
return folio_maybe_dma_pinned(folio);
}
static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
struct page *page)
{
return folio_needs_cow_for_dma(vma, page_folio(page));
}
/**
* is_zero_page - Query if a page is a zero page
* @page: The page to query

150
include/linux/rmap.h
View File

@ -362,68 +362,130 @@ static inline void folio_dup_file_rmap_pmd(struct folio *folio,
#endif
}
static inline void __page_dup_rmap(struct page *page, bool compound)
static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *src_vma,
enum rmap_level level)
{
VM_WARN_ON(folio_test_hugetlb(page_folio(page)));
bool maybe_pinned;
int i;
if (compound) {
struct folio *folio = (struct folio *)page;
VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
__folio_rmap_sanity_checks(folio, page, nr_pages, level);
VM_BUG_ON_PAGE(compound && !PageHead(page), page);
/*
* If this folio may have been pinned by the parent process,
* don't allow to duplicate the mappings but instead require to e.g.,
* copy the subpage immediately for the child so that we'll always
* guarantee the pinned folio won't be randomly replaced in the
* future on write faults.
*/
maybe_pinned = likely(!folio_is_device_private(folio)) &&
unlikely(folio_needs_cow_for_dma(src_vma, folio));
/*
* No need to check+clear for already shared PTEs/PMDs of the
* folio. But if any page is PageAnonExclusive, we must fallback to
* copying if the folio maybe pinned.
*/
switch (level) {
case RMAP_LEVEL_PTE:
if (unlikely(maybe_pinned)) {
for (i = 0; i < nr_pages; i++)
if (PageAnonExclusive(page + i))
return -EBUSY;
}
do {
if (PageAnonExclusive(page))
ClearPageAnonExclusive(page);
atomic_inc(&page->_mapcount);
} while (page++, --nr_pages > 0);
break;
case RMAP_LEVEL_PMD:
if (PageAnonExclusive(page)) {
if (unlikely(maybe_pinned))
return -EBUSY;
ClearPageAnonExclusive(page);
}
atomic_inc(&folio->_entire_mapcount);
} else {
atomic_inc(&page->_mapcount);
break;
}
return 0;
}
/**
* page_try_dup_anon_rmap - try duplicating a mapping of an already mapped
* anonymous page
* @page: the page to duplicate the mapping for
* @compound: the page is mapped as compound or as a small page
* @vma: the source vma
* folio_try_dup_anon_rmap_ptes - try duplicating PTE mappings of a page range
* of a folio
* @folio: The folio to duplicate the mappings of
* @page: The first page to duplicate the mappings of
* @nr_pages: The number of pages of which the mapping will be duplicated
* @src_vma: The vm area from which the mappings are duplicated
*
* The caller needs to hold the PT lock and the vma->vma_mm->write_protect_seq.
* The page range of the folio is defined by [page, page + nr_pages)
*
* Duplicating the mapping can only fail if the page may be pinned; device
* private pages cannot get pinned and consequently this function cannot fail.
* The caller needs to hold the page table lock and the
* vma->vma_mm->write_protect_seq.
*
* If duplicating the mapping succeeds, the page has to be mapped R/O into
* the parent and the child. It must *not* get mapped writable after this call.
* Duplicating the mappings can only fail if the folio may be pinned; device
* private folios cannot get pinned and consequently this function cannot fail
* for them.
*
* If duplicating the mappings succeeded, the duplicated PTEs have to be R/O in
* the parent and the child. They must *not* be writable after this call
* succeeded.
*
* Returns 0 if duplicating the mappings succeeded. Returns -EBUSY otherwise.
*/
static inline int folio_try_dup_anon_rmap_ptes(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *src_vma)
{
return __folio_try_dup_anon_rmap(folio, page, nr_pages, src_vma,
RMAP_LEVEL_PTE);
}
#define folio_try_dup_anon_rmap_pte(folio, page, vma) \
folio_try_dup_anon_rmap_ptes(folio, page, 1, vma)
/**
* folio_try_dup_anon_rmap_pmd - try duplicating a PMD mapping of a page range
* of a folio
* @folio: The folio to duplicate the mapping of
* @page: The first page to duplicate the mapping of
* @src_vma: The vm area from which the mapping is duplicated
*
* The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
*
* The caller needs to hold the page table lock and the
* vma->vma_mm->write_protect_seq.
*
* Duplicating the mapping can only fail if the folio may be pinned; device
* private folios cannot get pinned and consequently this function cannot fail
* for them.
*
* If duplicating the mapping succeeds, the duplicated PMD has to be R/O in
* the parent and the child. They must *not* be writable after this call
* succeeded.
*
* Returns 0 if duplicating the mapping succeeded. Returns -EBUSY otherwise.
*/
static inline int folio_try_dup_anon_rmap_pmd(struct folio *folio,
struct page *page, struct vm_area_struct *src_vma)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
return __folio_try_dup_anon_rmap(folio, page, HPAGE_PMD_NR, src_vma,
RMAP_LEVEL_PMD);
#else
WARN_ON_ONCE(true);
return -EBUSY;
#endif
}
static inline int page_try_dup_anon_rmap(struct page *page, bool compound,
struct vm_area_struct *vma)
{
VM_BUG_ON_PAGE(!PageAnon(page), page);
struct folio *folio = page_folio(page);
/*
* No need to check+clear for already shared pages, including KSM
* pages.
*/
if (!PageAnonExclusive(page))
goto dup;
/*
* If this page may have been pinned by the parent process,
* don't allow to duplicate the mapping but instead require to e.g.,
* copy the page immediately for the child so that we'll always
* guarantee the pinned page won't be randomly replaced in the
* future on write faults.
*/
if (likely(!is_device_private_page(page)) &&
unlikely(page_needs_cow_for_dma(vma, page)))
return -EBUSY;
ClearPageAnonExclusive(page);
/*
* It's okay to share the anon page between both processes, mapping
* the page R/O into both processes.
*/
dup:
__page_dup_rmap(page, compound);
return 0;
if (likely(!compound))
return folio_try_dup_anon_rmap_pte(folio, page, vma);
return folio_try_dup_anon_rmap_pmd(folio, page, vma);
}
/**