config AUFS_FS tristate "Aufs (Advanced multi layered unification filesystem) support" depends on EXPERIMENTAL help Aufs is a stackable unification filesystem such as Unionfs, which unifies several directories and provides a merged single directory. In the early days, aufs was entirely re-designed and re-implemented Unionfs Version 1.x series. Introducing many original ideas, approaches and improvements, it becomes totally different from Unionfs while keeping the basic features. if AUFS_FS choice prompt "Maximum number of branches" default AUFS_BRANCH_MAX_127 help Specifies the maximum number of branches (or member directories) in a single aufs. The larger value consumes more system resources and has a minor impact to performance. config AUFS_BRANCH_MAX_127 bool "127" help Specifies the maximum number of branches (or member directories) in a single aufs. The larger value consumes more system resources and has a minor impact to performance. config AUFS_BRANCH_MAX_511 bool "511" help Specifies the maximum number of branches (or member directories) in a single aufs. The larger value consumes more system resources and has a minor impact to performance. config AUFS_BRANCH_MAX_1023 bool "1023" help Specifies the maximum number of branches (or member directories) in a single aufs. The larger value consumes more system resources and has a minor impact to performance. config AUFS_BRANCH_MAX_32767 bool "32767" help Specifies the maximum number of branches (or member directories) in a single aufs. The larger value consumes more system resources and has a minor impact to performance. endchoice config AUFS_SBILIST bool depends on AUFS_MAGIC_SYSRQ || PROC_FS default y help Automatic configuration for internal use. When aufs supports Magic SysRq or /proc, enabled automatically. config AUFS_HNOTIFY bool "Detect direct branch access (bypassing aufs)" help If you want to modify files on branches directly, eg. bypassing aufs, and want aufs to detect the changes of them fully, then enable this option and use 'udba=notify' mount option. Currently there is only one available configuration, "fsnotify". It will have a negative impact to the performance. See detail in aufs.5. choice prompt "method" if AUFS_HNOTIFY default AUFS_HFSNOTIFY config AUFS_HFSNOTIFY bool "fsnotify" select FSNOTIFY endchoice config AUFS_EXPORT bool "NFS-exportable aufs" depends on EXPORTFS help If you want to export your mounted aufs via NFS, then enable this option. There are several requirements for this configuration. See detail in aufs.5. config AUFS_INO_T_64 bool depends on AUFS_EXPORT depends on 64BIT && !(ALPHA || S390) default y help Automatic configuration for internal use. /* typedef unsigned long/int __kernel_ino_t */ /* alpha and s390x are int */ config AUFS_RDU bool "Readdir in userspace" help Aufs has two methods to provide a merged view for a directory, by a user-space library and by kernel-space natively. The latter is always enabled but sometimes large and slow. If you enable this option, install the library in aufs2-util package, and set some environment variables for your readdir(3), then the work will be handled in user-space which generally shows better performance in most cases. See detail in aufs.5. config AUFS_PROC_MAP bool "support for /proc/maps and lsof(1)" depends on PROC_FS help When you issue mmap(2) in aufs, it is actually a direct mmap(2) call to the file on the branch fs since the file in aufs is purely virtual. And the file path printed in /proc/maps (and others) will be the path on the branch fs. In most cases, it does no harm. But some utilities like lsof(1) may confuse since the utility or user may expect the file path in aufs to be printed. To address this issue, aufs provides a patch which introduces a new member called vm_prfile into struct vm_are_struct. The patch is meaningless without enabling this configuration since nobody sets the new vm_prfile member. If you don't apply the patch, then enabling this configuration will cause a compile error. This approach is fragile since if someone else make some changes around vm_file, then vm_prfile may not work anymore. As a workaround such case, aufs provides this configuration. If you disable it, then lsof(1) may produce incorrect result but the problem will be gone even if the aufs patch is applied (I hope). config AUFS_SP_IATTR bool "Respect the attributes (mtime/ctime mainly) of special files" help When you write something to a special file, some attributes of it (mtime/ctime mainly) may be updated. Generally such updates are less important (actually some device drivers and NFS ignore it). But some applications (such like test program) requires such updates. If you need these updates, then enable this configuration which introduces some overhead. Currently this configuration handles FIFO only. config AUFS_SHWH bool "Show whiteouts" help If you want to make the whiteouts in aufs visible, then enable this option and specify 'shwh' mount option. Although it may sounds like philosophy or something, but in technically it simply shows the name of whiteout with keeping its behaviour. config AUFS_BR_RAMFS bool "Ramfs (initramfs/rootfs) as an aufs branch" help If you want to use ramfs as an aufs branch fs, then enable this option. Generally tmpfs is recommended. Aufs prohibited them to be a branch fs by default, because initramfs becomes unusable after switch_root or something generally. If you sets initramfs as an aufs branch and boot your system by switch_root, you will meet a problem easily since the files in initramfs may be inaccessible. Unless you are going to use ramfs as an aufs branch fs without switch_root or something, leave it N. config AUFS_BR_FUSE bool "Fuse fs as an aufs branch" depends on FUSE_FS select AUFS_POLL help If you want to use fuse-based userspace filesystem as an aufs branch fs, then enable this option. It implements the internal poll(2) operation which is implemented by fuse only (curretnly). config AUFS_POLL bool help Automatic configuration for internal use. config AUFS_BR_HFSPLUS bool "Hfsplus as an aufs branch" depends on HFSPLUS_FS default y help If you want to use hfsplus fs as an aufs branch fs, then enable this option. This option introduces a small overhead at copying-up a file on hfsplus. config AUFS_BDEV_LOOP bool depends on BLK_DEV_LOOP default y help Automatic configuration for internal use. Convert =[ym] into =y. config AUFS_DEBUG bool "Debug aufs" help Enable this to compile aufs internal debug code. It will have a negative impact to the performance. config AUFS_MAGIC_SYSRQ bool depends on AUFS_DEBUG && MAGIC_SYSRQ default y help Automatic configuration for internal use. When aufs supports Magic SysRq, enabled automatically. endif