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 if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) 41 goto out; 42 if (offset_in_page(start)) 43 goto out; 44 if ((flags & MS_ASYNC) && (flags & MS_SYNC)) 45 goto out; 46 error = -ENOMEM; 47 len = (len + ~PAGE_MASK) & PAGE_MASK; 48 end = start + len; 49 if (end < start) 50 goto out; 51 error = 0; 52 if (end == start) 53 goto out; 54 /* 55 * If the interval [start,end) covers some unmapped address ranges, 56 * just ignore them, but return -ENOMEM at the end. 57 */ 58 down_read(&mm->mmap_sem); 59 vma = find_vma(mm, start); 60 for (;;) { 61 struct file *file; 62 loff_t fstart, fend; 63 64 /* Still start < end. */ 65 error = -ENOMEM; 66 if (!vma) 67 goto out_unlock; 68 /* Here start < vma->vm_end. */ 69 if (start < vma->vm_start) { 70 start = vma->vm_start; 71 if (start >= end) 72 goto out_unlock; 73 unmapped_error = -ENOMEM; 74 } 75 /* Here vma->vm_start <= start < vma->vm_end. */ 76 if ((flags & MS_INVALIDATE) && 77 (vma->vm_flags & VM_LOCKED)) { 78 error = -EBUSY; 79 goto out_unlock; 80 } 81 file = vma->vm_file; 82 fstart = (start - vma->vm_start) + 83 ((loff_t)vma->vm_pgoff << PAGE_SHIFT); 84 fend = fstart + (min(end, vma->vm_end) - start) - 1; 85 start = vma->vm_end; 86 if ((flags & MS_SYNC) && file && 87 (vma->vm_flags & VM_SHARED)) { 88 get_file(file); 89 up_read(&mm->mmap_sem); 90 error = vfs_fsync_range(file, fstart, fend, 1); 91 fput(file); 92 if (error || start >= end) 93 goto out; 94 down_read(&mm->mmap_sem); 95 vma = find_vma(mm, start); 96 } else { 97 if (start >= end) { 98 error = 0; 99 goto out_unlock; 100 } 101 vma = vma->vm_next; 102 } 103 } 104 out_unlock: 105 up_read(&mm->mmap_sem); 106 out: 107 return error ? : unmapped_error; 108 } 109