linux-kernel - [PATCH 08/10] mm: introduce commit_merge(), abstracting merge operation

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Message-ID: <3b04eb13b499df3ebf50ae3cde9a7ed5e76237fd.1722849860.git.lorenzo.stoakes@oracle.com>
Date: Mon,  5 Aug 2024 13:13:55 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc: "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 08/10] mm: introduce commit_merge(), abstracting merge operation

Pull this operation into its own function and have vma_expand() call
commit_merge() instead.

This lays the groundwork for a subsequent patch which replaces vma_merge()
with a simpler function which can share the same code.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 mm/vma.c | 57 ++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 45 insertions(+), 12 deletions(-)

diff --git a/mm/vma.c b/mm/vma.c
index a404cf718f9e..b7e3c64d5d68 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -564,6 +564,49 @@ void validate_mm(struct mm_struct *mm)
 }
 #endif /* CONFIG_DEBUG_VM_MAPLE_TREE */
 
+/* Actually perform the VMA merge operation. */
+static int commit_merge(struct vma_merge_struct *vmg,
+			struct vm_area_struct *adjust,
+			struct vm_area_struct *remove,
+			struct vm_area_struct *remove2,
+			long adj_start,
+			bool expanded)
+{
+	struct vma_prepare vp;
+
+	init_multi_vma_prep(&vp, vmg->vma, adjust, remove, remove2);
+
+	if (expanded) {
+		vma_iter_config(vmg->vmi, vmg->start, vmg->end);
+	} else {
+		vma_iter_config(vmg->vmi, adjust->vm_start + adj_start,
+				adjust->vm_end);
+	}
+
+	if (vma_iter_prealloc(vmg->vmi, vmg->vma))
+		return -ENOMEM;
+
+	vma_prepare(&vp);
+	vma_adjust_trans_huge(vmg->vma, vmg->start, vmg->end, adj_start);
+	vma_set_range(vmg->vma, vmg->start, vmg->end, vmg->pgoff);
+
+	if (expanded)
+		vma_iter_store(vmg->vmi, vmg->vma);
+
+	if (adj_start) {
+		adjust->vm_start += adj_start;
+		adjust->vm_pgoff += PHYS_PFN(adj_start);
+		if (adj_start < 0) {
+			WARN_ON(expanded);
+			vma_iter_store(vmg->vmi, adjust);
+		}
+	}
+
+	vma_complete(&vp, vmg->vmi, vmg->vma->vm_mm);
+
+	return 0;
+}
+
 /*
  * vma_merge_new_vma - Attempt to merge a new VMA into address space
  *
@@ -700,7 +743,6 @@ int vma_expand(struct vma_merge_struct *vmg)
 	bool remove_next = false;
 	struct vm_area_struct *vma = vmg->vma;
 	struct vm_area_struct *next = vmg->next;
-	struct vma_prepare vp;
 
 	vma_start_write(vma);
 	if (next && (vma != next) && (vmg->end == next->vm_end)) {
@@ -713,24 +755,15 @@ int vma_expand(struct vma_merge_struct *vmg)
 			return ret;
 	}
 
-	init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL);
 	/* Not merging but overwriting any part of next is not handled. */
-	VM_WARN_ON(next && !vp.remove &&
+	VM_WARN_ON(next && !remove_next &&
 		  next != vma && vmg->end > next->vm_start);
 	/* Only handles expanding */
 	VM_WARN_ON(vma->vm_start < vmg->start || vma->vm_end > vmg->end);
 
-	/* Note: vma iterator must be pointing to 'start' */
-	vma_iter_config(vmg->vmi, vmg->start, vmg->end);
-	if (vma_iter_prealloc(vmg->vmi, vma))
+	if (commit_merge(vmg, NULL, remove_next ? next : NULL, NULL, 0, true))
 		goto nomem;
 
-	vma_prepare(&vp);
-	vma_adjust_trans_huge(vma, vmg->start, vmg->end, 0);
-	vma_set_range(vma, vmg->start, vmg->end, vmg->pgoff);
-	vma_iter_store(vmg->vmi, vma);
-
-	vma_complete(&vp, vmg->vmi, vma->vm_mm);
 	return 0;
 
 nomem:
-- 
2.45.2