[PATCH v2 14/33] mm/vma: clean up anon_vma_compatible()
Lorenzo Stoakes <[email protected]>
| Newsgroups | dev.linux.lists.nvdimm,dev.linux.lists.damon,dev.linux.lists.iommu,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-parisc,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 |
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| Message-ID | <[email protected]> |
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. Reviewed-by: Gregory Price <[email protected]> Reviewed-by: Pedro Falcato <[email protected]> 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 995de8198fbb..084afdf37385 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); } /* -- 2.55.0