From 01293a62bae2fa55c09cebf5a771eab7219171c3 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" 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) Signed-off-by: Liam R. Howlett Tested-by: Yu Zhao Cc: Catalin Marinas Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: SeongJae Park Cc: Sven Schnelle Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton --- ipc/shm.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) 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 */