| rjw | 1f88458 | 2022-01-06 17:20:42 +0800 | [diff] [blame^] | 1 | config OVERLAY_FS |
| 2 | tristate "Overlay filesystem support" |
| 3 | select EXPORTFS |
| 4 | help |
| 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. |
| 10 | |
| 11 | For more information see Documentation/filesystems/overlayfs.txt |
| 12 | |
| 13 | config OVERLAY_FS_REDIRECT_DIR |
| 14 | bool "Overlayfs: turn on redirect dir feature by default" |
| 15 | depends on OVERLAY_FS |
| 16 | help |
| 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. |
| 22 | |
| 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. |
| 26 | |
| 27 | config OVERLAY_FS_INDEX |
| 28 | bool "Overlayfs: turn on inodes index feature by default" |
| 29 | depends on OVERLAY_FS |
| 30 | help |
| 31 | If this config option is enabled then overlay filesystems will use |
| 32 | the inodes index dir to map lower inodes to upper inodes by default. |
| 33 | In this case it is still possible to turn off index globally with the |
| 34 | "index=off" module option or on a filesystem instance basis with the |
| 35 | "index=off" mount option. |
| 36 | |
| 37 | The inodes index feature prevents breaking of lower hardlinks on copy |
| 38 | up. |
| 39 | |
| 40 | Note, that the inodes index feature is read-only backward compatible. |
| 41 | That is, mounting an overlay which has an index dir on a kernel that |
| 42 | doesn't support this feature read-only, will not have any negative |
| 43 | outcomes. However, mounting the same overlay with an old kernel |
| 44 | read-write and then mounting it again with a new kernel, will have |
| 45 | unexpected results. |