Commit 01293a62 authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

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: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@Oracle.com>
Tested-by: default avatarYu 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 69dbe6da

ipc/shm.c

+10 −11
Original line number Diff line number Diff line
@@ -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

	 */