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. Besides, if the 59 * flag is MS_ASYNC (w/o MS_INVALIDATE) the result would be -ENOMEM 60 * anyway and there is nothing left to do, so return immediately. 61 */ 62 mmap_read_lock(mm); 63 vma = find_vma(mm, start); 64 for (;;) { 65 struct file *file; 66 loff_t fstart, fend; 67 68 /* Still start < end. */ 69 error = -ENOMEM; 70 if (!vma) 71 goto out_unlock; 72 /* Here start < vma->vm_end. */ 73 if (start < vma->vm_start) { 74 if (flags == MS_ASYNC) 75 goto out_unlock; 76 start = vma->vm_start; 77 if (start >= end) 78 goto out_unlock; 79 unmapped_error = -ENOMEM; 80 } 81 /* Here vma->vm_start <= start < vma->vm_end. */ 82 if ((flags & MS_INVALIDATE) && 83 (vma->vm_flags & VM_LOCKED)) { 84 error = -EBUSY; 85 goto out_unlock; 86 } 87 file = vma->vm_file; 88 fstart = (start - vma->vm_start) + 89 ((loff_t)vma->vm_pgoff << PAGE_SHIFT); 90 fend = fstart + (min(end, vma->vm_end) - start) - 1; 91 start = vma->vm_end; 92 if ((flags & MS_SYNC) && file && 93 (vma->vm_flags & VM_SHARED)) { 94 get_file(file); 95 mmap_read_unlock(mm); 96 error = vfs_fsync_range(file, fstart, fend, 1); 97 fput(file); 98 if (error || start >= end) 99 goto out; 100 mmap_read_lock(mm); 101 vma = find_vma(mm, start); 102 } else { 103 if (start >= end) { 104 error = 0; 105 goto out_unlock; 106 } 107 vma = vma->vm_next; 108 } 109 } 110 out_unlock: 111 mmap_read_unlock(mm); 112 out: 113 return error ? : unmapped_error; 114 } 115