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[86.146.209.214]) by smtp.googlemail.com with ESMTPSA id n23-20020a1c7217000000b003eb68bb61c8sm4849965wmc.3.2023.03.18.04.15.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Mar 2023 04:15:28 -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, Lorenzo Stoakes Subject: [PATCH 2/4] mm/mmap/vma_merge: set next to NULL if not applicable Date: Sat, 18 Mar 2023 11:13:19 +0000 Message-Id: <4d717269303d8a6fe1d837968c252eeb6ff1d7e5.1679137163.git.lstoakes@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: jqiwpwgdyhz47ta9i7bnu11f3w79busu X-Rspam-User: X-Rspamd-Queue-Id: B4CF280011 X-Rspamd-Server: rspam06 X-HE-Tag: 1679138131-680972 X-HE-Meta: U2FsdGVkX1+omQTGPnhBTnA6rqyELIXRykVRa0VYG2m9zCYdykSbGLSnjty5mCoMg/3Mk5RFj/M5Z9W8MLsn7esb68FWXWf1TLYokIT2fTJa5/7ObgzuCfBBd6KgaX9A7vJz+Scw4DUyR+exFDSJuwUrOc98t8InknpKbph650O914xlP0VsY2JBo0O25LDGcgI7NZsXpecABQsphRBG7i48iGAuORInJ8Cv6CwWEHZb/vt5SvzkaamhRErbTvD7maO+lI0jY+5+OT2+Z1xKubhK+JTfMe3IZ0R4YTtCeV2aLpSGn7viAWTFoT+KgjKvhkqZZM1zHLQUfznD3rFJwmU1hDt6mZ7f5t3ME+eNGHA7hD0QQcX0WLI8//GKavxdW9+hpPHH4mjGLvoay7fVYqfM55HIdbVULFsc7fsRNOL1Gte1Z+vjn3NzlYVyJCVvUlknYyKYhthkds7gry5rn4EKrqX1L0n01q9srcHH22XhlmHhl1StnMi9bsGohRdxvSmD33c7V++vK2Shg0vnu4Br8Xp1Z7vOmOcB2wDmH4uc7IOVqS2csa6tjEfpSVIoNHiuiEjh7hCXYwDST+JB45S6abZk1YhfA/RMdQDAzMVEBIdxguD9SYlvLmtKotb7JyTHXpF5rCKALNJH6BxwYtzWhV/RNwDJkCLgj3jkJVghZtUBKiRiorodZUAObWTOf6hrEq+yCy/D9uhUTXDehZ5r3B5P9wJPIOXkSm4I4JGywmr63eorW7uFJln17o1q0X5EugN/J/YBw1AppuSLkvg5NLTXSzk4hmMMmNSH7jKsa629lxtgQVCImPNpMc44SiWAyQZuYOz02Nq4Aepc2RA2a8qPVN6Kvq/Nw3nhZEAOMrI1YtaDj7SyoT9AaB1S9g5PWN/ps7HNPpNDFDOndzgBK95dmfrKipuQlqYFcW78Ja/cmNCUS0NWtLionrhuZ4oVCgW6ddnwwEpvELW W8P2UyE6 DiTPFW+Gx5scsDmRUMgFom9y20F63lR0bWYKvf3YuGn6m3i7JUcEJ51mO6uSQewxprBYRHirtfalkU84oHWJgo5Bm8uMTnNGedH+w6HRZs2GDJ1O0DENnseP6mveMnJ9J1ITFjHZx0FKt7/ipSlDGA5fbIyuo4EtAc632/CF6YDTbs9xdCTCRkVjr0MvvW8MxJmydMgYfea/QTU0n5QxVxRmUlqT4IUx3U4qv7W/oRpZOwBFZXVJRboFh0cxSj97vqkGq0SAt2g6faFhB2q6M8qKR5f7dCf4RRzDP6jm/Y2kZpmar64Wz8Ub7ndMBWpg8digZkd2mHRsNy/eKMosEkQIOsY2Nc4H4jnNH4NXhdOoRfYX5yxjpu5lRHQn4nAViS9dr3o6W9ZredxBH+NOHN12CbAC0oh6ZLmTZbLLpwX5WCxOLwOs78gyGVW2WH1Bf9Pzsbp0heHnRmNZNuD6Edjq2OzGlvORm2EiUDHFJx0Vs9sk8WYjWa0TYtRBoi//NYy+i X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. Additionally, use the abstract 'vma' object to look up the possible curr or next VMA in order to avoid any confusion as to what these variables represent - now curr and next are assigned once and only once. This has no functional impact. Signed-off-by: Lorenzo Stoakes --- mm/mmap.c | 61 ++++++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 49 insertions(+), 12 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index c9834364ac98..66893fc72e03 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -930,15 +930,53 @@ 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; + /* + * If there is a previous VMA specified, find the next, otherwise find + * the first. + */ + vma = find_vma(mm, prev ? prev->vm_end : 0); + + /* + * Does the input range span an existing VMA? If so, we designate this + * VMA 'curr'. The caller will have ensured that curr->vm_start == addr. + * + * Cases 5 - 8. + */ + if (vma && end > vma->vm_start) { + curr = vma; - /* In cases 1 - 4 there's no CCCC vma */ - if (curr && end <= curr->vm_start) + /* + * If the addr - end range spans this VMA entirely, then we + * check to see if another VMA follows it. + * + * If it is _immediately_ adjacent (checked below), then we + * designate it 'next' (cases 6 - 8). + */ + if (curr->vm_end == end) + vma = find_vma(mm, curr->vm_end); + else + /* Case 5. */ + vma = NULL; + } else { + /* + * The addr - end range either spans the end of prev or spans no + * VMA at all - in either case we dispense with 'curr' and + * maintain only 'prev' and (possibly) 'next'. + * + * Cases 1 - 4. + */ curr = NULL; + } + + /* + * We only actually examine the next VMA if it is immediately adjacent + * to end which sits either at the end of a hole (cases 1 - 3), PPPP + * (case 4) or CCCC (cases 6 - 8). + */ + if (vma && end == vma->vm_start) + next = vma; + else + next = NULL; /* verify some invariant that must be enforced by the caller */ VM_WARN_ON(prev && addr <= prev->vm_start); @@ -959,11 +997,10 @@ 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