Message ID | 20230302012610.17055-1-ying.huang@intel.com |
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State | New |
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Series |
migrate_pages: silence gcc notes for mis-casting
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Commit Message
Huang, Ying
March 2, 2023, 1:26 a.m. UTC
The following GCC notes was reported for commit 64c8902ed441
("migrate_pages: split unmap_and_move() to _unmap() and _move()").
mm/migrate.c: In function ‘__migrate_folio_extract’:
mm/migrate.c:1050:20: note: randstruct: casting between randomized
structure pointer types (ssa): ‘struct anon_vma’ and ‘struct
address_space’
1050 | *anon_vmap = (void *)dst->mapping;
| ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
The casting itself is safe. Because we only use dst->mapping to store
the pointer itself temporarily and dst is a newly allocated folio and
not used by anyone else during that. But the notes should be silenced
and some comments are deserved. So, we do that in this patch.
Fixes: 64c8902ed441 ("migrate_pages: split unmap_and_move() to _unmap() and _move()")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Bharata B Rao <bharata@amd.com>
Cc: Alistair Popple <apopple@nvidia.com>
---
mm/migrate.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/mm/migrate.c b/mm/migrate.c index c17ce5ee8d92..53fcc23025c7 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1047,7 +1047,16 @@ static void __migrate_folio_extract(struct folio *dst, int *page_was_mappedp, struct anon_vma **anon_vmap) { - *anon_vmap = (void *)dst->mapping; + struct anon_vma *anon_vma; + + /* + * 2 steps assignment to silence gcc notes for mis-casting. The + * casting is safe. Because we only use dst->mapping to store + * the pointer itself temporarily and dst is a newly allocated + * folio and not used by anyone else during that. + */ + anon_vma = (void *)dst->mapping; + *anon_vmap = anon_vma; *page_was_mappedp = (unsigned long)dst->private; dst->mapping = NULL; dst->private = NULL;