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| author |   Qi Zheng <zhengqi.arch@bytedance.com> | 2024-09-26 14:46:22 +0800 |
|---|---|---|
| committer |   Andrew Morton <akpm@linux-foundation.org> | 2024-11-05 16:56:28 -0800 |
| commit | 838d02354464c301fcddf4f524365846608ac296 (patch) | |
| tree | 2149e05497d4e1ea4b2377351f6ea884690ca7f4 | |
| parent | mm: copy_pte_range() use pte_offset_map_rw_nolock() (diff) | |
| download | wireguard-linux-838d02354464c301fcddf4f524365846608ac296.tar.xz wireguard-linux-838d02354464c301fcddf4f524365846608ac296.zip | |
mm: mremap: move_ptes() use pte_offset_map_rw_nolock()
In move_ptes(), we may modify the new_pte after acquiring the new_ptl, so
convert it to using pte_offset_map_rw_nolock(). Now new_pte is none, so
hpage_collapse_scan_file() path can not find this by traversing
file->f_mapping, so there is no concurrency with retract_page_tables().
In addition, we already hold the exclusive mmap_lock, so this new_pte page
is stable, so there is no need to get pmdval and do pmd_same() check.
Link: https://lkml.kernel.org/r/9d582a09dbcf12e562ac5fe0ba05e9248a58f5e0.1727332572.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/mremap.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/mremap.c b/mm/mremap.c index dda09e957a5d..5917feafe8cc 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -140,6 +140,7 @@ static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, { struct mm_struct *mm = vma->vm_mm; pte_t *old_pte, *new_pte, pte; + pmd_t dummy_pmdval; spinlock_t *old_ptl, *new_ptl; bool force_flush = false; unsigned long len = old_end - old_addr; @@ -175,7 +176,15 @@ static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, err = -EAGAIN; goto out; } - new_pte = pte_offset_map_nolock(mm, new_pmd, new_addr, &new_ptl); + /* + * Now new_pte is none, so hpage_collapse_scan_file() path can not find + * this by traversing file->f_mapping, so there is no concurrency with + * retract_page_tables(). In addition, we already hold the exclusive + * mmap_lock, so this new_pte page is stable, so there is no need to get + * pmdval and do pmd_same() check. + */ + new_pte = pte_offset_map_rw_nolock(mm, new_pmd, new_addr, &dummy_pmdval, + &new_ptl); if (!new_pte) { pte_unmap_unlock(old_pte, old_ptl); err = -EAGAIN; |