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authorPeter Xu <peterx@redhat.com>2021-03-12 21:07:33 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-03-13 11:27:30 -0800
commit4eae4efa2c299f85b7ebfbeeda56c19c5eba2768 (patch)
treea69d7671b767a4a5a05ff3d7088a6a05218be7ff /mm/hugetlb.c
parentca6eb14d6453bea85ac66fa4c6ab75dfe93eaf45 (diff)
downloadlinux-4eae4efa2c299f85b7ebfbeeda56c19c5eba2768.tar.bz2
hugetlb: do early cow when page pinned on src mm
This is the last missing piece of the COW-during-fork effort when there're pinned pages found. One can reference 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes", 2020-09-27) for more information, since we do similar things here rather than pte this time, but just for hugetlb. Note that after Jason's recent work on 57efa1fe5957 ("mm/gup: prevent gup_fast from racing with COW during fork", 2020-12-15) which is safer and easier to understand, we're safe now within the whole copy_page_range() against gup-fast, we don't need the wr-protect trick that proposed in 70e806e4e645 anymore. Link: https://lkml.kernel.org/r/20210217233547.93892-6-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: Jason Gunthorpe <jgg@ziepe.ca> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: David Airlie <airlied@linux.ie> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: Gal Pressman <galpress@amazon.com> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Kirill Shutemov <kirill@shutemov.name> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Roland Scheidegger <sroland@vmware.com> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com> Cc: Wei Zhang <wzam@amazon.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c66
1 files changed, 62 insertions, 4 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7786267da2fe..5b1ab1f427c5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3728,6 +3728,18 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
return false;
}
+static void
+hugetlb_install_page(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr,
+ struct page *new_page)
+{
+ __SetPageUptodate(new_page);
+ set_huge_pte_at(vma->vm_mm, addr, ptep, make_huge_pte(vma, new_page, 1));
+ hugepage_add_new_anon_rmap(new_page, vma, addr);
+ hugetlb_count_add(pages_per_huge_page(hstate_vma(vma)), vma->vm_mm);
+ ClearHPageRestoreReserve(new_page);
+ SetHPageMigratable(new_page);
+}
+
int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
struct vm_area_struct *vma)
{
@@ -3737,6 +3749,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
bool cow = is_cow_mapping(vma->vm_flags);
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);
+ unsigned long npages = pages_per_huge_page(h);
struct address_space *mapping = vma->vm_file->f_mapping;
struct mmu_notifier_range range;
int ret = 0;
@@ -3785,6 +3798,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
entry = huge_ptep_get(src_pte);
dst_entry = huge_ptep_get(dst_pte);
+again:
if (huge_pte_none(entry) || !huge_pte_none(dst_entry)) {
/*
* Skip if src entry none. Also, skip in the
@@ -3808,6 +3822,52 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
}
set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz);
} else {
+ entry = huge_ptep_get(src_pte);
+ ptepage = pte_page(entry);
+ get_page(ptepage);
+
+ /*
+ * This is a rare case where we see pinned hugetlb
+ * pages while they're prone to COW. We need to do the
+ * COW earlier during fork.
+ *
+ * When pre-allocating the page or copying data, we
+ * need to be without the pgtable locks since we could
+ * sleep during the process.
+ */
+ if (unlikely(page_needs_cow_for_dma(vma, ptepage))) {
+ pte_t src_pte_old = entry;
+ struct page *new;
+
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+ /* Do not use reserve as it's private owned */
+ new = alloc_huge_page(vma, addr, 1);
+ if (IS_ERR(new)) {
+ put_page(ptepage);
+ ret = PTR_ERR(new);
+ break;
+ }
+ copy_user_huge_page(new, ptepage, addr, vma,
+ npages);
+ put_page(ptepage);
+
+ /* Install the new huge page if src pte stable */
+ dst_ptl = huge_pte_lock(h, dst, dst_pte);
+ src_ptl = huge_pte_lockptr(h, src, src_pte);
+ spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
+ entry = huge_ptep_get(src_pte);
+ if (!pte_same(src_pte_old, entry)) {
+ put_page(new);
+ /* dst_entry won't change as in child */
+ goto again;
+ }
+ hugetlb_install_page(vma, dst_pte, addr, new);
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+ continue;
+ }
+
if (cow) {
/*
* No need to notify as we are downgrading page
@@ -3818,12 +3878,10 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
*/
huge_ptep_set_wrprotect(src, addr, src_pte);
}
- entry = huge_ptep_get(src_pte);
- ptepage = pte_page(entry);
- get_page(ptepage);
+
page_dup_rmap(ptepage, true);
set_huge_pte_at(dst, addr, dst_pte, entry);
- hugetlb_count_add(pages_per_huge_page(h), dst);
+ hugetlb_count_add(npages, dst);
}
spin_unlock(src_ptl);
spin_unlock(dst_ptl);