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[86.146.209.214]) by smtp.googlemail.com with ESMTPSA id u4-20020a5d4344000000b002c5526234d2sm13290279wrr.8.2023.03.22.00.13.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 00:13:13 -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 v3 4/4] mm/mmap/vma_merge: init cleanup, be explicit about the non-mergeable case Date: Wed, 22 Mar 2023 07:13:04 +0000 Message-Id: X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: A61CA120013 X-Rspam-User: X-Stat-Signature: ywmdtdiddckco3zkfxhfx7nprkwnnh3w X-HE-Tag: 1679469195-582152 X-HE-Meta: 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 jNCTQwCE 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 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: 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 and reorder initial variables so they are more logically grouped. This has no functional impact. Signed-off-by: Lorenzo Stoakes --- mm/mmap.c | 57 ++++++++++++++++++++++++++++--------------------------- 1 file changed, 29 insertions(+), 28 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 2a4f63716231..642f3d063be1 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; + pgoff_t vma_pgoff; + int err = 0; bool merge_prev = false; bool merge_next = false; bool vma_expanded = false; - struct vma_prepare vp; + unsigned long vma_start = addr; unsigned long vma_end = end; + pgoff_t pglen = (end - addr) >> PAGE_SHIFT; long adj_start = 0; - unsigned long vma_start = addr; validate_mm(mm); /* @@ -939,36 +939,38 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, else next = NULL; /* case 5 */ - /* - * 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. - */ - res = vma = prev; - - /* Verify some invariant that must be enforced by the caller. */ - VM_WARN_ON(prev && addr <= prev->vm_start); - 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) + if (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)) { + 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; - } + 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. + */ + res = vma = prev; + + /* Verify some invariant that must be enforced by the caller. */ + VM_WARN_ON(prev && addr <= prev->vm_start); + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); + VM_WARN_ON(addr >= end); remove = remove2 = adjust = NULL; /* Can we merge both the predecessor and the successor? */ @@ -984,7 +986,7 @@ 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 */ @@ -994,7 +996,7 @@ 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; @@ -1010,7 +1012,6 @@ 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; @@ -1019,7 +1020,7 @@ 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