diff mbox series

[v4,44/66] ipc/shm: Use VMA iterator instead of linked list

Message ID 20211201142918.921493-45-Liam.Howlett@oracle.com (mailing list archive)
State New
Headers show
Series Introducing the Maple Tree | expand

Commit Message

Liam R. Howlett Dec. 1, 2021, 2:30 p.m. UTC 
From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>

The VMA iterator is faster than the linked llist, and it can be walked
even when VMAs are being removed from the address space, so there's no
need to keep track of 'next'.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 ipc/shm.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

Comments

Vlastimil Babka Jan. 21, 2022, 12:25 p.m. UTC | #1 
On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
> 
> The VMA iterator is faster than the linked llist, and it can be walked
> even when VMAs are being removed from the address space, so there's no
> need to keep track of 'next'.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>
diff mbox series

Patch

diff --git a/ipc/shm.c b/ipc/shm.c
index b3048ebd5c31..7d86f058fb86 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1721,7 +1721,7 @@  long ksys_shmdt(char __user *shmaddr)
 #ifdef CONFIG_MMU
 	loff_t size = 0;
 	struct file *file;
-	struct vm_area_struct *next;
+	VMA_ITERATOR(vmi, mm, addr);
 #endif
 
 	if (addr & ~PAGE_MASK)
@@ -1751,12 +1751,9 @@  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
-	while (vma) {
-		next = vma->vm_next;
-
+	for_each_vma(vmi, vma) {
 		/*
 		 * Check if the starting address would match, i.e. it's
 		 * a fragment created by mprotect() and/or munmap(), or it
@@ -1774,6 +1771,7 @@  long ksys_shmdt(char __user *shmaddr)
 			file = vma->vm_file;
 			size = i_size_read(file_inode(vma->vm_file));
 			do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
+			mas_pause(&vmi.mas);
 			/*
 			 * We discovered the size of the shm segment, so
 			 * break out of here and fall through to the next
@@ -1781,10 +1779,9 @@  long ksys_shmdt(char __user *shmaddr)
 			 * searching for matching vma's.
 			 */
 			retval = 0;
-			vma = next;
+			vma = vma_next(&vmi);
 			break;
 		}
-		vma = next;
 	}
 
 	/*
@@ -1794,17 +1791,19 @@  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))
+		    (vma->vm_file == file)) {
 			do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
-		vma = next;
+			mas_pause(&vmi.mas);
+		}
+
+		vma = vma_next(&vmi);
 	}
 
 #else	/* CONFIG_MMU */
+	vma = vma_lookup(mm, addr);
 	/* under NOMMU conditions, the exact address to be destroyed must be
 	 * given
 	 */