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[86.146.209.214]) by smtp.googlemail.com with ESMTPSA id a4-20020adffb84000000b002d322b9a7f5sm12142491wrr.88.2023.03.21.13.46.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Mar 2023 13:46:24 -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 4/4] mm/mmap/vma_merge: init cleanup, be explicit about the non-mergeable case Date: Tue, 21 Mar 2023 20:45:58 +0000 Message-Id: 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 Reorder the initial variables sensibly and set vma_start and vm_pgoff there rather than later so all initial values are set at the same time meaning we don't have to set these later. Rather than setting err = -1 and only resetting if we hit merge cases, explicitly check the non-mergeable case to make it abundantly clear that we only proceed with the rest if something is mergeable, default err to 0 and only update if an error might occur. Move the merge_prev, merge_next cases closer to the logic determining curr, next. This has no functional impact. Signed-off-by: Lorenzo Stoakes --- mm/mmap.c | 55 ++++++++++++++++++++++++++----------------------------- 1 file changed, 26 insertions(+), 29 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 7aec49c3bc74..d60cb0b7ae15 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -909,18 +909,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, struct vm_userfaultfd_ctx vm_userfaultfd_ctx, struct anon_vma_name *anon_name) { - pgoff_t pglen = (end - addr) >> PAGE_SHIFT; - pgoff_t vma_pgoff; struct vm_area_struct *curr, *next, *res; struct vm_area_struct *vma, *adjust, *remove, *remove2; - int err = -1; + struct vma_prepare vp; + int err = 0; bool merge_prev = false; bool merge_next = false; bool vma_expanded = false; - struct vma_prepare vp; + unsigned long vma_start = prev ? prev->vm_start : addr; unsigned long vma_end = end; + pgoff_t vma_pgoff = prev ? prev->vm_pgoff : 0; + pgoff_t pglen = (end - addr) >> PAGE_SHIFT; long adj_start = 0; - unsigned long vma_start = addr; validate_mm(mm); /* @@ -940,6 +940,23 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, /* Is there a VMA next to a hole (case 1 - 3) or prev (4)? */ next = vma_lookup(mm, end); + /* Can we merge the predecessor? */ + if (prev && addr == prev->vm_end && mpol_equal(vma_policy(prev), policy) + && can_vma_merge_after(prev, vm_flags, anon_vma, file, + pgoff, vm_userfaultfd_ctx, anon_name)) { + merge_prev = true; + vma_prev(vmi); + } + + /* Can we merge the successor? */ + merge_next = next && mpol_equal(policy, vma_policy(next)) && + can_vma_merge_before(next, vm_flags, + anon_vma, file, pgoff+pglen, + vm_userfaultfd_ctx, anon_name); + + if (!merge_prev && !merge_next) + return NULL; /* Not mergeable. */ + /* * By default, we return prev. Cases 3, 4, 8 will instead return next * and cases 3, 8 will also update vma to point at next. @@ -951,26 +968,6 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); VM_WARN_ON(addr >= end); - if (prev) { - vma_start = prev->vm_start; - vma_pgoff = prev->vm_pgoff; - /* Can we merge the predecessor? */ - if (prev->vm_end == addr && mpol_equal(vma_policy(prev), policy) - && can_vma_merge_after(prev, vm_flags, anon_vma, file, - pgoff, vm_userfaultfd_ctx, anon_name)) { - merge_prev = true; - vma_prev(vmi); - } - } - - /* Can we merge the successor? */ - 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; - } - remove = remove2 = adjust = NULL; /* Can we merge both the predecessor and the successor? */ if (merge_prev && merge_next && @@ -985,7 +982,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, err = dup_anon_vma(prev, curr); } } else if (merge_prev) { - err = 0; /* case 2 */ + /* case 2 */ if (curr) { err = dup_anon_vma(prev, curr); if (end == curr->vm_end) { /* case 7 */ @@ -995,7 +992,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, adj_start = (end - curr->vm_start); } } - } else if (merge_next) { + } else { /* merge_next */ res = next; if (prev && addr < prev->vm_end) { /* case 4 */ vma_end = addr; @@ -1011,7 +1008,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, vma_start = addr; vma_end = next->vm_end; vma_pgoff = next->vm_pgoff; - err = 0; + if (curr) { /* case 8 */ vma_pgoff = curr->vm_pgoff; remove = curr; @@ -1020,7 +1017,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, } } - /* Cannot merge or error in anon_vma clone */ + /* Error in anon_vma clone. */ if (err) return NULL; -- 2.39.2