[linux.git] / fs / overlayfs / Kconfig

config OVERLAY_FS
	tristate "Overlay filesystem support"
	select EXPORTFS
	help
	  An overlay filesystem combines two filesystems - an 'upper' filesystem
	  and a 'lower' filesystem.  When a name exists in both filesystems, the
	  object in the 'upper' filesystem is visible while the object in the
	  'lower' filesystem is either hidden or, in the case of directories,
	  merged with the 'upper' object.

	  For more information see Documentation/filesystems/overlayfs.txt

config OVERLAY_FS_REDIRECT_DIR
	bool "Overlayfs: turn on redirect directory feature by default"
	depends on OVERLAY_FS
	help
	  If this config option is enabled then overlay filesystems will use
	  redirects when renaming directories by default.  In this case it is
	  still possible to turn off redirects globally with the
	  "redirect_dir=off" module option or on a filesystem instance basis
	  with the "redirect_dir=off" mount option.

	  Note, that redirects are not backward compatible.  That is, mounting
	  an overlay which has redirects on a kernel that doesn't support this
	  feature will have unexpected results.

	  If unsure, say N.

config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
	bool "Overlayfs: follow redirects even if redirects are turned off"
	default y
	depends on OVERLAY_FS
	help
	  Disable this to get a possibly more secure configuration, but that
	  might not be backward compatible with previous kernels.

	  If backward compatibility is not an issue, then it is safe and
	  recommended to say N here.

	  For more information, see Documentation/filesystems/overlayfs.txt

	  If unsure, say Y.

config OVERLAY_FS_INDEX
	bool "Overlayfs: turn on inodes index feature by default"
	depends on OVERLAY_FS
	help
	  If this config option is enabled then overlay filesystems will use
	  the index directory to map lower inodes to upper inodes by default.
	  In this case it is still possible to turn off index globally with the
	  "index=off" module option or on a filesystem instance basis with the
	  "index=off" mount option.

	  The inodes index feature prevents breaking of lower hardlinks on copy
	  up.

	  Note, that the inodes index feature is not backward compatible.
	  That is, mounting an overlay which has an inodes index on a kernel
	  that doesn't support this feature will have unexpected results.

	  If unsure, say N.

config OVERLAY_FS_NFS_EXPORT
	bool "Overlayfs: turn on NFS export feature by default"
	depends on OVERLAY_FS
	depends on OVERLAY_FS_INDEX
	depends on !OVERLAY_FS_METACOPY
	help
	  If this config option is enabled then overlay filesystems will use
	  the index directory to decode overlay NFS file handles by default.
	  In this case, it is still possible to turn off NFS export support
	  globally with the "nfs_export=off" module option or on a filesystem
	  instance basis with the "nfs_export=off" mount option.

	  The NFS export feature creates an index on copy up of every file and
	  directory.  This full index is used to detect overlay filesystems
	  inconsistencies on lookup, like redirect from multiple upper dirs to
	  the same lower dir.  The full index may incur some overhead on mount
	  time, especially when verifying that directory file handles are not
	  stale.

	  Note, that the NFS export feature is not backward compatible.
	  That is, mounting an overlay which has a full index on a kernel
	  that doesn't support this feature will have unexpected results.

	  Most users should say N here and enable this feature on a case-by-
	  case basis with the "nfs_export=on" mount option.

	  Say N unless you fully understand the consequences.

config OVERLAY_FS_XINO_AUTO
	bool "Overlayfs: auto enable inode number mapping"
	default n
	depends on OVERLAY_FS
	help
	  If this config option is enabled then overlay filesystems will use
	  unused high bits in undelying filesystem inode numbers to map all
	  inodes to a unified address space.  The mapped 64bit inode numbers
	  might not be compatible with applications that expect 32bit inodes.

	  If compatibility with applications that expect 32bit inodes is not an
	  issue, then it is safe and recommended to say Y here.

	  For more information, see Documentation/filesystems/overlayfs.txt

	  If unsure, say N.

config OVERLAY_FS_METACOPY
	bool "Overlayfs: turn on metadata only copy up feature by default"
	depends on OVERLAY_FS
	select OVERLAY_FS_REDIRECT_DIR
	help
	  If this config option is enabled then overlay filesystems will
	  copy up only metadata where appropriate and data copy up will
	  happen when a file is opened for WRITE operation. It is still
	  possible to turn off this feature globally with the "metacopy=off"
	  module option or on a filesystem instance basis with the
	  "metacopy=off" mount option.

	  Note, that this feature is not backward compatible.  That is,
	  mounting an overlay which has metacopy only inodes on a kernel
	  that doesn't support this feature will have unexpected results.

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