mirrors/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2025-11-01 00:58:39 +02:00
Code Issues Projects Releases Packages Wiki Activity Actions

hugetlb: do early cow when page pinned on src mm

Browse source 
This is the last missing piece of the COW-during-fork effort when there're
pinned pages found.  One can reference 70e806e4e6 ("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 57efa1fe59 ("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
70e806e4e6 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>
This commit is contained in:
Peter Xu 2021-03-12 21:07:33 -08:00 committed by Linus Torvalds
parent ca6eb14d64
commit 4eae4efa2c
1 changed files with 62 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

66
mm/hugetlb.c
View file

@ -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);