linux-kernel - [PATCH v6 42/71] coredump: Remove vma linked list walk

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Message-ID: <20220215144241.3812052-42-Liam.Howlett@oracle.com>
Date:   Tue, 15 Feb 2022 14:43:18 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v6 42/71] coredump: Remove vma linked list walk

From: "Matthew Wilcox (Oracle)" <willy@...radead.org>

Use the Maple Tree iterator instead.  This is too complicated for the
VMA iterator to handle, so let's open-code it for now.  If this turns
out to be a common pattern, we can migrate it to common code.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 fs/coredump.c | 33 ++++++++++++---------------------
 1 file changed, 12 insertions(+), 21 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 1c060c0a2d72..127dffd0517e 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -1051,30 +1051,20 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
 	return vma->vm_end - vma->vm_start;
 }
 
-static struct vm_area_struct *first_vma(struct task_struct *tsk,
-					struct vm_area_struct *gate_vma)
-{
-	struct vm_area_struct *ret = tsk->mm->mmap;
-
-	if (ret)
-		return ret;
-	return gate_vma;
-}
-
 /*
  * Helper function for iterating across a vma list.  It ensures that the caller
  * will visit `gate_vma' prior to terminating the search.
  */
-static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
+static struct vm_area_struct *coredump_next_vma(struct ma_state *mas,
+				       struct vm_area_struct *vma,
 				       struct vm_area_struct *gate_vma)
 {
-	struct vm_area_struct *ret;
-
-	ret = this_vma->vm_next;
-	if (ret)
-		return ret;
-	if (this_vma == gate_vma)
+	if (vma == gate_vma)
 		return NULL;
+
+	vma = mas_next(mas, ULONG_MAX);
+	if (vma)
+		return vma;
 	return gate_vma;
 }
 
@@ -1086,9 +1076,10 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
 		      struct core_vma_metadata **vma_meta,
 		      size_t *vma_data_size_ptr)
 {
-	struct vm_area_struct *vma, *gate_vma;
+	struct vm_area_struct *gate_vma, *vma = NULL;
 	struct mm_struct *mm = current->mm;
-	int i;
+	MA_STATE(mas, &mm->mm_mt, 0, 0);
+	int i = 0;
 	size_t vma_data_size = 0;
 
 	/*
@@ -1108,8 +1099,7 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
 		return -ENOMEM;
 	}
 
-	for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
-			vma = next_vma(vma, gate_vma), i++) {
+	while ((vma = coredump_next_vma(&mas, vma, gate_vma)) != NULL) {
 		struct core_vma_metadata *m = (*vma_meta) + i;
 
 		m->start = vma->vm_start;
@@ -1118,6 +1108,7 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
 		m->dump_size = vma_dump_size(vma, cprm->mm_flags);
 
 		vma_data_size += m->dump_size;
+		i++;
 	}
 
 	mmap_write_unlock(mm);
-- 
2.34.1