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[86.146.209.214]) by smtp.googlemail.com with ESMTPSA id a4-20020adffb84000000b002d322b9a7f5sm12142491wrr.88.2023.03.21.13.46.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Mar 2023 13:46:21 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Cc: David Hildenbrand , Matthew Wilcox , Vlastimil Babka , "Liam R . Howlett" , maple-tree@lists.infradead.org, Vernon Yang , Lorenzo Stoakes Subject: [PATCH v2 2/4] mm/mmap/vma_merge: set next to NULL if not applicable Date: Tue, 21 Mar 2023 20:45:56 +0000 Message-Id: <3506997a8146a287ec13ee7a53cf916707537bf8.1679431180.git.lstoakes@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We are only interested in next if end == next->vm_start (in which case we check to see if we can set merge_next), so perform this check alongside checking whether curr should be set. This groups all of the simple range checks together and establishes the invariant that, if prev, curr or next are non-NULL then their positions are as expected. This has no functional impact. Signed-off-by: Lorenzo Stoakes --- mm/mmap.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index c9834364ac98..6361baf75601 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -930,15 +930,15 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, if (vm_flags & VM_SPECIAL) return NULL; - curr = find_vma(mm, prev ? prev->vm_end : 0); - if (curr && curr->vm_end == end) /* cases 6, 7, 8 */ - next = find_vma(mm, curr->vm_end); - else - next = curr; + /* Does the input range span an existing VMA? (cases 5 - 8) */ + curr = find_vma_intersection(mm, prev ? prev->vm_end : 0, end); - /* In cases 1 - 4 there's no CCCC vma */ - if (curr && end <= curr->vm_start) - curr = NULL; + if (curr && end == curr->vm_end) + /* Is there is a VMA immediately adjacent (cases 6 - 8)? */ + next = vma_lookup(mm, curr->vm_end); + else if (!curr) + /* Is there a VMA next to a hole (case 1 - 3) or prev (4)? */ + next = vma_lookup(mm, end); /* verify some invariant that must be enforced by the caller */ VM_WARN_ON(prev && addr <= prev->vm_start); @@ -959,11 +959,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, } } /* Can we merge the successor? */ - if (next && end == next->vm_start && - mpol_equal(policy, vma_policy(next)) && - can_vma_merge_before(next, vm_flags, - anon_vma, file, pgoff+pglen, - vm_userfaultfd_ctx, anon_name)) { + if (next && mpol_equal(policy, vma_policy(next)) && + can_vma_merge_before(next, vm_flags, + anon_vma, file, pgoff+pglen, + vm_userfaultfd_ctx, anon_name)) { merge_next = true; } -- 2.39.2