[linux-2.6-block.git] / fs / overlayfs / Kconfig

# SPDX-License-Identifier: GPL-2.0-only
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
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
688ea0e5 MS	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.
36cd95df MS	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
438c84c2 MS	42
36cd95df MS	43	If unsure, say Y.
36cd95df MS	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.
36cd95df MS	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
f168f109 AG	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.