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ec8f24b7 | 1 | # SPDX-License-Identifier: GPL-2.0-only |
ef94b186 | 2 | config OVERLAY_FS |
e9be9d5e | 3 | tristate "Overlay filesystem support" |
72d42504 | 4 | select EXPORTFS |
e9be9d5e MS |
5 | help |
6 | An overlay filesystem combines two filesystems - an 'upper' filesystem | |
7 | and a 'lower' filesystem. When a name exists in both filesystems, the | |
8 | object in the 'upper' filesystem is visible while the object in the | |
9 | 'lower' filesystem is either hidden or, in the case of directories, | |
10 | merged with the 'upper' object. | |
11 | ||
12 | For more information see Documentation/filesystems/overlayfs.txt | |
688ea0e5 MS |
13 | |
14 | config OVERLAY_FS_REDIRECT_DIR | |
4280f74a | 15 | bool "Overlayfs: turn on redirect directory feature by default" |
688ea0e5 MS |
16 | depends on OVERLAY_FS |
17 | help | |
18 | If this config option is enabled then overlay filesystems will use | |
19 | redirects when renaming directories by default. In this case it is | |
20 | still possible to turn off redirects globally with the | |
21 | "redirect_dir=off" module option or on a filesystem instance basis | |
22 | with the "redirect_dir=off" mount option. | |
23 | ||
24 | Note, that redirects are not backward compatible. That is, mounting | |
25 | an overlay which has redirects on a kernel that doesn't support this | |
26 | feature will have unexpected results. | |
02bcd157 | 27 | |
36cd95df MS |
28 | If unsure, say N. |
29 | ||
438c84c2 MS |
30 | config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW |
31 | bool "Overlayfs: follow redirects even if redirects are turned off" | |
32 | default y | |
33 | depends on OVERLAY_FS | |
34 | help | |
35 | Disable this to get a possibly more secure configuration, but that | |
36 | might not be backward compatible with previous kernels. | |
37 | ||
36cd95df MS |
38 | If backward compatibility is not an issue, then it is safe and |
39 | recommended to say N here. | |
40 | ||
438c84c2 MS |
41 | For more information, see Documentation/filesystems/overlayfs.txt |
42 | ||
36cd95df MS |
43 | If unsure, say Y. |
44 | ||
02bcd157 AG |
45 | config OVERLAY_FS_INDEX |
46 | bool "Overlayfs: turn on inodes index feature by default" | |
47 | depends on OVERLAY_FS | |
48 | help | |
49 | If this config option is enabled then overlay filesystems will use | |
4280f74a | 50 | the index directory to map lower inodes to upper inodes by default. |
02bcd157 AG |
51 | In this case it is still possible to turn off index globally with the |
52 | "index=off" module option or on a filesystem instance basis with the | |
53 | "index=off" mount option. | |
54 | ||
55 | The inodes index feature prevents breaking of lower hardlinks on copy | |
56 | up. | |
57 | ||
60b86642 AG |
58 | Note, that the inodes index feature is not backward compatible. |
59 | That is, mounting an overlay which has an inodes index on a kernel | |
60 | that doesn't support this feature will have unexpected results. | |
f168f109 | 61 | |
36cd95df MS |
62 | If unsure, say N. |
63 | ||
f168f109 AG |
64 | config OVERLAY_FS_NFS_EXPORT |
65 | bool "Overlayfs: turn on NFS export feature by default" | |
66 | depends on OVERLAY_FS | |
67 | depends on OVERLAY_FS_INDEX | |
d5791044 | 68 | depends on !OVERLAY_FS_METACOPY |
f168f109 AG |
69 | help |
70 | If this config option is enabled then overlay filesystems will use | |
4280f74a | 71 | the index directory to decode overlay NFS file handles by default. |
f168f109 AG |
72 | In this case, it is still possible to turn off NFS export support |
73 | globally with the "nfs_export=off" module option or on a filesystem | |
74 | instance basis with the "nfs_export=off" mount option. | |
75 | ||
76 | The NFS export feature creates an index on copy up of every file and | |
77 | directory. This full index is used to detect overlay filesystems | |
78 | inconsistencies on lookup, like redirect from multiple upper dirs to | |
79 | the same lower dir. The full index may incur some overhead on mount | |
80 | time, especially when verifying that directory file handles are not | |
81 | stale. | |
82 | ||
83 | Note, that the NFS export feature is not backward compatible. | |
84 | That is, mounting an overlay which has a full index on a kernel | |
85 | that doesn't support this feature will have unexpected results. | |
36cd95df MS |
86 | |
87 | Most users should say N here and enable this feature on a case-by- | |
88 | case basis with the "nfs_export=on" mount option. | |
89 | ||
90 | Say N unless you fully understand the consequences. | |
795939a9 AG |
91 | |
92 | config OVERLAY_FS_XINO_AUTO | |
93 | bool "Overlayfs: auto enable inode number mapping" | |
94 | default n | |
95 | depends on OVERLAY_FS | |
96 | help | |
97 | If this config option is enabled then overlay filesystems will use | |
98 | unused high bits in undelying filesystem inode numbers to map all | |
99 | inodes to a unified address space. The mapped 64bit inode numbers | |
100 | might not be compatible with applications that expect 32bit inodes. | |
101 | ||
102 | If compatibility with applications that expect 32bit inodes is not an | |
103 | issue, then it is safe and recommended to say Y here. | |
104 | ||
105 | For more information, see Documentation/filesystems/overlayfs.txt | |
106 | ||
107 | If unsure, say N. | |
d5791044 VG |
108 | |
109 | config OVERLAY_FS_METACOPY | |
110 | bool "Overlayfs: turn on metadata only copy up feature by default" | |
111 | depends on OVERLAY_FS | |
112 | select OVERLAY_FS_REDIRECT_DIR | |
113 | help | |
114 | If this config option is enabled then overlay filesystems will | |
115 | copy up only metadata where appropriate and data copy up will | |
116 | happen when a file is opened for WRITE operation. It is still | |
117 | possible to turn off this feature globally with the "metacopy=off" | |
118 | module option or on a filesystem instance basis with the | |
119 | "metacopy=off" mount option. | |
120 | ||
121 | Note, that this feature is not backward compatible. That is, | |
122 | mounting an overlay which has metacopy only inodes on a kernel | |
123 | that doesn't support this feature will have unexpected results. | |
124 | ||
125 | If unsure, say N. |