From 01293a62bae2fa55c09cebf5a771eab7219171c3 Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
Date: Tue, 6 Sep 2022 19:48:58 +0000
Subject: [PATCH] ipc/shm: use VMA iterator instead of linked list
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'.
Link: https://lkml.kernel.org/r/20220906194824.2110408-46-Liam.Howlett@oracle.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
ipc/shm.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
diff --git a/ipc/shm.c b/ipc/shm.c
index b3048ebd5c315..7d86f058fb861 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
*/
--
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