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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 dir 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.
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 inodes index dir 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 read-only backward compatible.
That is, mounting an overlay which has an index dir on a kernel that
doesn't support this feature read-only, will not have any negative
outcomes. However, mounting the same overlay with an old kernel
read-write and then mounting it again with a new kernel, will have
unexpected results.
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