1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/mm/msync.c 4 * 5 * Copyright (C) 1994-1999 Linus Torvalds 6 */ 7 8 /* 9 * The msync() system call. 10 */ 11 #include <linux/fs.h> 12 #include <linux/mm.h> 13 #include <linux/mman.h> 14 #include <linux/file.h> 15 #include <linux/syscalls.h> 16 #include <linux/sched.h> 17 18 /* 19 * MS_SYNC syncs the entire file - including mappings. 20 * 21 * MS_ASYNC does not start I/O (it used to, up to 2.5.67). 22 * Nor does it marks the relevant pages dirty (it used to up to 2.6.17). 23 * Now it doesn't do anything, since dirty pages are properly tracked. 24 * 25 * The application may now run fsync() to 26 * write out the dirty pages and wait on the writeout and check the result. 27 * Or the application may run fadvise(FADV_DONTNEED) against the fd to start 28 * async writeout immediately. 29 * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to 30 * applications. 31 */ 32 SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) 33 { 34 unsigned long end; 35 struct mm_struct *mm = current->mm; 36 struct vm_area_struct *vma; 37 int unmapped_error = 0; 38 int error = -EINVAL; 39 40 start = untagged_addr(start); 41 42 if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) 43 goto out; 44 if (offset_in_page(start)) 45 goto out; 46 if ((flags & MS_ASYNC) && (flags & MS_SYNC)) 47 goto out; 48 error = -ENOMEM; 49 len = (len + ~PAGE_MASK) & PAGE_MASK; 50 end = start + len; 51 if (end < start) 52 goto out; 53 error = 0; 54 if (end == start) 55 goto out; 56 /* 57 * If the interval [start,end) covers some unmapped address ranges, 58 * just ignore them, but return -ENOMEM at the end. 59 */ 60 mmap_read_lock(mm); 61 vma = find_vma(mm, start); 62 for (;;) { 63 struct file *file; 64 loff_t fstart, fend; 65 66 /* Still start < end. */ 67 error = -ENOMEM; 68 if (!vma) 69 goto out_unlock; 70 /* Here start < vma->vm_end. */ 71 if (start < vma->vm_start) { 72 start = vma->vm_start; 73 if (start >= end) 74 goto out_unlock; 75 unmapped_error = -ENOMEM; 76 } 77 /* Here vma->vm_start <= start < vma->vm_end. */ 78 if ((flags & MS_INVALIDATE) && 79 (vma->vm_flags & VM_LOCKED)) { 80 error = -EBUSY; 81 goto out_unlock; 82 } 83 file = vma->vm_file; 84 fstart = (start - vma->vm_start) + 85 ((loff_t)vma->vm_pgoff << PAGE_SHIFT); 86 fend = fstart + (min(end, vma->vm_end) - start) - 1; 87 start = vma->vm_end; 88 if ((flags & MS_SYNC) && file && 89 (vma->vm_flags & VM_SHARED)) { 90 get_file(file); 91 mmap_read_unlock(mm); 92 error = vfs_fsync_range(file, fstart, fend, 1); 93 fput(file); 94 if (error || start >= end) 95 goto out; 96 mmap_read_lock(mm); 97 vma = find_vma(mm, start); 98 } else { 99 if (start >= end) { 100 error = 0; 101 goto out_unlock; 102 } 103 vma = vma->vm_next; 104 } 105 } 106 out_unlock: 107 mmap_read_unlock(mm); 108 out: 109 return error ? : unmapped_error; 110 } 111