linux-kernel - [PATCH v3 40/66] ipc/shm: Stop using the vma linked list

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Date:   Tue, 5 Oct 2021 01:30:59 +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>,
        David Hildenbrand <david@...hat.com>,
        Douglas Gilbert <dgilbert@...erlog.com>
CC:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        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>
Subject: [PATCH v3 40/66] ipc/shm: Stop using the vma linked list

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

When searching for a VMA, a maple state can be used instead of the linked list in
the mm_struct

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 ipc/shm.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index ab749be6d8b7..ed6628679679 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1631,6 +1631,7 @@ long ksys_shmdt(char __user *shmaddr)
 	loff_t size = 0;
 	struct file *file;
 	struct vm_area_struct *next;
+	MA_STATE(mas, &mm->mm_mt, addr, addr);
 #endif
 
 	if (addr & ~PAGE_MASK)
@@ -1660,11 +1661,11 @@ long ksys_shmdt(char __user *shmaddr)
 	 * match the usual checks anyway. So assume all vma's are
 	 * above the starting address given.
 	 */
-	vma = find_vma(mm, addr);
 
 #ifdef CONFIG_MMU
+	vma = mas_find(&mas, ULONG_MAX);
 	while (vma) {
-		next = vma->vm_next;
+		next = mas_find(&mas, ULONG_MAX);
 
 		/*
 		 * Check if the starting address would match, i.e. it's
@@ -1703,21 +1704,21 @@ long ksys_shmdt(char __user *shmaddr)
 	 */
 	size = PAGE_ALIGN(size);
 	while (vma && (loff_t)(vma->vm_end - addr) <= size) {
-		next = vma->vm_next;
-
 		/* finding a matching vma now does not alter retval */
 		if ((vma->vm_ops == &shm_vm_ops) &&
 		    ((vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) &&
 		    (vma->vm_file == file))
 			do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
-		vma = next;
+
+		vma = mas_find(&mas, addr + size - 1);
 	}
 
 #else	/* CONFIG_MMU */
+	vma = mas_walk(&mas);
 	/* under NOMMU conditions, the exact address to be destroyed must be
 	 * given
 	 */
-	if (vma && vma->vm_start == addr && vma->vm_ops == &shm_vm_ops) {
+	if (vma && vma->vm_ops == &shm_vm_ops) {
 		do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
 		retval = 0;
 	}
-- 
2.30.2