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| author | Mike Kravetz <mike.kravetz@oracle.com> | 2020-10-14 02:56:42 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-10-14 04:38:34 +0300 |
| commit | 0bf7b64e6e51eb69cf6fce7c9f7ff44840393e64 (patch) | |
| tree | c3abf285b8d4c709ef66fdc71bafc42be135d67b /mm/hugetlb.c | |
| parent | 6664bfc8e934dd008565510a41d86a552bd0bb00 (diff) | |
| download | linux-0bf7b64e6e51eb69cf6fce7c9f7ff44840393e64.tar.xz | |
hugetlb: add lockdep check for i_mmap_rwsem held in huge_pmd_share
As a debugging aid, huge_pmd_share should make sure i_mmap_rwsem is held
if necessary. To clarify the 'if necessary', expand the comment block at
the beginning of huge_pmd_share.
No functional change. The added i_mmap_assert_locked() call is only
enabled if CONFIG_LOCKDEP.
Ideally, this should have been included with commit 34ae204f1851
("hugetlbfs: remove call to huge_pte_alloc without i_mmap_rwsem").
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lkml.kernel.org/r/20200911201248.88537-1-mike.kravetz@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
| -rw-r--r-- | mm/hugetlb.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index cc70e541c9bf..2fb9a4c7a161 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5337,10 +5337,16 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, * !shared pmd case because we can allocate the pmd later as well, it makes the * code much cleaner. * - * This routine must be called with i_mmap_rwsem held in at least read mode. - * For hugetlbfs, this prevents removal of any page table entries associated - * with the address space. This is important as we are setting up sharing - * based on existing page table entries (mappings). + * This routine must be called with i_mmap_rwsem held in at least read mode if + * sharing is possible. For hugetlbfs, this prevents removal of any page + * table entries associated with the address space. This is important as we + * are setting up sharing based on existing page table entries (mappings). + * + * NOTE: This routine is only called from huge_pte_alloc. Some callers of + * huge_pte_alloc know that sharing is not possible and do not take + * i_mmap_rwsem as a performance optimization. This is handled by the + * if !vma_shareable check at the beginning of the routine. i_mmap_rwsem is + * only required for subsequent processing. */ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) { @@ -5357,6 +5363,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) if (!vma_shareable(vma, addr)) return (pte_t *)pmd_alloc(mm, pud, addr); + i_mmap_assert_locked(mapping); vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) { if (svma == vma) continue; |