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da4458bd DH |
1 | /* NOMMU mmap support for RomFS on MTD devices |
2 | * | |
3 | * Copyright © 2007 Red Hat, Inc. All Rights Reserved. | |
4 | * Written by David Howells (dhowells@redhat.com) | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public License | |
8 | * as published by the Free Software Foundation; either version | |
9 | * 2 of the License, or (at your option) any later version. | |
10 | */ | |
11 | ||
12 | #include <linux/mm.h> | |
13 | #include <linux/mtd/super.h> | |
14 | #include "internal.h" | |
15 | ||
16 | /* | |
17 | * try to determine where a shared mapping can be made | |
18 | * - only supported for NOMMU at the moment (MMU can't doesn't copy private | |
19 | * mappings) | |
20 | * - attempts to map through to the underlying MTD device | |
21 | */ | |
22 | static unsigned long romfs_get_unmapped_area(struct file *file, | |
23 | unsigned long addr, | |
24 | unsigned long len, | |
25 | unsigned long pgoff, | |
26 | unsigned long flags) | |
27 | { | |
28 | struct inode *inode = file->f_mapping->host; | |
29 | struct mtd_info *mtd = inode->i_sb->s_mtd; | |
2b4b2482 | 30 | unsigned long isize, offset, maxpages, lpages; |
4991e725 | 31 | int ret; |
da4458bd DH |
32 | |
33 | if (!mtd) | |
4991e725 | 34 | return (unsigned long) -ENOSYS; |
da4458bd | 35 | |
2b4b2482 BL |
36 | /* the mapping mustn't extend beyond the EOF */ |
37 | lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
da4458bd DH |
38 | isize = i_size_read(inode); |
39 | offset = pgoff << PAGE_SHIFT; | |
2b4b2482 BL |
40 | |
41 | maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
42 | if ((pgoff >= maxpages) || (maxpages - pgoff < lpages)) | |
da4458bd DH |
43 | return (unsigned long) -EINVAL; |
44 | ||
4991e725 AB |
45 | if (addr != 0) |
46 | return (unsigned long) -EINVAL; | |
da4458bd | 47 | |
4991e725 AB |
48 | if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT)) |
49 | return (unsigned long) -EINVAL; | |
da4458bd | 50 | |
4991e725 AB |
51 | offset += ROMFS_I(inode)->i_dataoffset; |
52 | if (offset > mtd->size - len) | |
53 | return (unsigned long) -EINVAL; | |
da4458bd | 54 | |
4991e725 AB |
55 | ret = mtd_get_unmapped_area(mtd, len, offset, flags); |
56 | if (ret == -EOPNOTSUPP) | |
57 | ret = -ENOSYS; | |
58 | return (unsigned long) ret; | |
da4458bd DH |
59 | } |
60 | ||
61 | /* | |
62 | * permit a R/O mapping to be made directly through onto an MTD device if | |
63 | * possible | |
64 | */ | |
65 | static int romfs_mmap(struct file *file, struct vm_area_struct *vma) | |
66 | { | |
67 | return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS; | |
68 | } | |
69 | ||
70 | const struct file_operations romfs_ro_fops = { | |
71 | .llseek = generic_file_llseek, | |
72 | .read = do_sync_read, | |
73 | .aio_read = generic_file_aio_read, | |
74 | .splice_read = generic_file_splice_read, | |
75 | .mmap = romfs_mmap, | |
76 | .get_unmapped_area = romfs_get_unmapped_area, | |
77 | }; |