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| author | Lorenzo Stoakes <ljs@kernel.org> | 2026-07-10 21:16:55 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-08-04 19:18:59 -0700 |
| commit | dfe2b9abf65d4e046ef9ca53523776d5f3f97532 (patch) | |
| tree | 08644895927215c732f776b34649944b080ffc88 | |
| parent | 8802c4069ee98f064b41d047cfa96475852e57f8 (diff) | |
| download | linux-dfe2b9abf65d4e046ef9ca53523776d5f3f97532.tar.gz linux-dfe2b9abf65d4e046ef9ca53523776d5f3f97532.zip | |
mm/vma: clean up anon_vma_compatible()
Break up the existing very large conditional, add comments and use
vma_[start/end]_pgoff() to make clearer what we're doing here.
No functional change intended.
Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-14-2a5aa403d977@kernel.org
Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Ackerley Tng <ackerleytng@google.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Kai Huang <kai.huang@intel.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: SJ Park <sj@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Liam R. Howlett (Oracle) <liam@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/vma.c | 21 |
1 files changed, 16 insertions, 5 deletions
@@ -1967,14 +1967,25 @@ static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct * { vma_flags_t diff = vma_flags_diff_pair(&a->flags, &b->flags); + /* Ignore flags that mprotect() can change. */ vma_flags_clear_mask(&diff, VMA_ACCESS_FLAGS); + /* Ignore flags that do not impact merging. */ vma_flags_clear_mask(&diff, VMA_IGNORE_MERGE_FLAGS); - return a->vm_end == b->vm_start && - mpol_equal(vma_policy(a), vma_policy(b)) && - a->vm_file == b->vm_file && - vma_flags_empty(&diff) && - b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT); + /* Must be adjacent. */ + if (a->vm_end != b->vm_start) + return false; + /* Must have matching policy. */ + if (!mpol_equal(vma_policy(a), vma_policy(b))) + return false; + /* Must both be anon or map the same file (MAP_PRIVATE case). */ + if (a->vm_file != b->vm_file) + return false; + /* Flags must be equivalent modulo mprotect(). */ + if (!vma_flags_empty(&diff)) + return false; + /* Page offset must align. */ + return vma_end_pgoff(a) == vma_start_pgoff(b); } /* |