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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>
This commit is contained in:
Liam R. Howlett 2022-09-06 19:48:58 +00:00 committed by Andrew Morton
parent 69dbe6daf1
commit 01293a62ba
1 changed files with 10 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
ipc/shm.c
View File

@ -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
*/