2 tristate "Overlay filesystem support"
5 An overlay filesystem combines two filesystems - an 'upper' filesystem
6 and a 'lower' filesystem. When a name exists in both filesystems, the
7 object in the 'upper' filesystem is visible while the object in the
8 'lower' filesystem is either hidden or, in the case of directories,
9 merged with the 'upper' object.
11 For more information see Documentation/filesystems/overlayfs.txt
13 config OVERLAY_FS_REDIRECT_DIR
14 bool "Overlayfs: turn on redirect directory feature by default"
17 If this config option is enabled then overlay filesystems will use
18 redirects when renaming directories by default. In this case it is
19 still possible to turn off redirects globally with the
20 "redirect_dir=off" module option or on a filesystem instance basis
21 with the "redirect_dir=off" mount option.
23 Note, that redirects are not backward compatible. That is, mounting
24 an overlay which has redirects on a kernel that doesn't support this
25 feature will have unexpected results.
29 config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
30 bool "Overlayfs: follow redirects even if redirects are turned off"
34 Disable this to get a possibly more secure configuration, but that
35 might not be backward compatible with previous kernels.
37 If backward compatibility is not an issue, then it is safe and
38 recommended to say N here.
40 For more information, see Documentation/filesystems/overlayfs.txt
44 config OVERLAY_FS_INDEX
45 bool "Overlayfs: turn on inodes index feature by default"
48 If this config option is enabled then overlay filesystems will use
49 the index directory to map lower inodes to upper inodes by default.
50 In this case it is still possible to turn off index globally with the
51 "index=off" module option or on a filesystem instance basis with the
52 "index=off" mount option.
54 The inodes index feature prevents breaking of lower hardlinks on copy
57 Note, that the inodes index feature is not backward compatible.
58 That is, mounting an overlay which has an inodes index on a kernel
59 that doesn't support this feature will have unexpected results.
63 config OVERLAY_FS_NFS_EXPORT
64 bool "Overlayfs: turn on NFS export feature by default"
66 depends on OVERLAY_FS_INDEX
68 If this config option is enabled then overlay filesystems will use
69 the index directory to decode overlay NFS file handles by default.
70 In this case, it is still possible to turn off NFS export support
71 globally with the "nfs_export=off" module option or on a filesystem
72 instance basis with the "nfs_export=off" mount option.
74 The NFS export feature creates an index on copy up of every file and
75 directory. This full index is used to detect overlay filesystems
76 inconsistencies on lookup, like redirect from multiple upper dirs to
77 the same lower dir. The full index may incur some overhead on mount
78 time, especially when verifying that directory file handles are not
81 Note, that the NFS export feature is not backward compatible.
82 That is, mounting an overlay which has a full index on a kernel
83 that doesn't support this feature will have unexpected results.
85 Most users should say N here and enable this feature on a case-by-
86 case basis with the "nfs_export=on" mount option.
88 Say N unless you fully understand the consequences.
90 config OVERLAY_FS_XINO_AUTO
91 bool "Overlayfs: auto enable inode number mapping"
95 If this config option is enabled then overlay filesystems will use
96 unused high bits in undelying filesystem inode numbers to map all
97 inodes to a unified address space. The mapped 64bit inode numbers
98 might not be compatible with applications that expect 32bit inodes.
100 If compatibility with applications that expect 32bit inodes is not an
101 issue, then it is safe and recommended to say Y here.
103 For more information, see Documentation/filesystems/overlayfs.txt