linux-kernel - [PATCH v4 48/66] fork: Use VMA iterator

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Message-ID: <20211201142918.921493-49-Liam.Howlett@oracle.com>
Date:   Wed, 1 Dec 2021 14:30:12 +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>
CC:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Rom Lemarchand <romlem@...gle.com>,
        Liam Howlett <liam.howlett@...cle.com>
Subject: [PATCH v4 48/66] fork: Use VMA iterator

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

The VMA iterator is faster than the linked list and removing the linked
list will shrink the vm_area_struct.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 kernel/fork.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 3493117c8d35..6de302e93519 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1228,13 +1228,16 @@ int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 	/* Forbid mm->exe_file change if old file still mapped. */
 	old_exe_file = get_mm_exe_file(mm);
 	if (old_exe_file) {
+		VMA_ITERATOR(vmi, mm, 0);
 		mmap_read_lock(mm);
-		for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
+		for_each_vma(vmi, vma) {
 			if (!vma->vm_file)
 				continue;
 			if (path_equal(&vma->vm_file->f_path,
-				       &old_exe_file->f_path))
+				       &old_exe_file->f_path)) {
 				ret = -EBUSY;
+				break;
+			}
 		}
 		mmap_read_unlock(mm);
 		fput(old_exe_file);
-- 
2.30.2