Re: [PATCH 12/30] mm/vma: clean up anon_vma_compatible()
Pedro Falcato <[email protected]>
| Newsgroups | org.kernel.vger.linux-parisc,dev.linux.lists.damon,dev.linux.lists.iommu,dev.linux.lists.nvdimm,org.freedesktop.lists.dri-devel,org.kernel.vger.kvm,org.kernel.vger.linux-arm-msm,org.kernel.vger.linux-fsdevel,org.kernel.vger.linux-kernel,org.kernel.vger.linux-perf-users,org.kernel.vger.linux-sgx,org.kernel.vger.linux-tegra,org.kernel.vger.linux-trace-kernel,org.kvack.linux-mm |
|---|---|
| Message-ID | <[email protected]> |
On Mon, Jun 29, 2026 at 01:23:23PM +0100, Lorenzo Stoakes wrote: > 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. > > Signed-off-by: Lorenzo Stoakes <[email protected]> > --- > mm/vma.c | 21 ++++++++++++++++----- > 1 file changed, 16 insertions(+), 5 deletions(-) > > diff --git a/mm/vma.c b/mm/vma.c > index b60375c6c5c3..6296acecf3b7 100644 > --- a/mm/vma.c > +++ b/mm/vma.c > @@ -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); Very nice. Reviewed-by: Pedro Falcato <[email protected]> -- Pedro