# 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.rst

  
  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.rst

  	  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

  	depends on 64BIT

  	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.rst

  
  	  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.