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02bcd15774
Create the index dir on mount. The index dir will contain hardlinks to upper inodes, named after the hex representation of their origin lower inodes. The index dir is going to be used to prevent breaking lower hardlinks on copy up and to implement overlayfs NFS export. Because the feature is not fully backward compat, enabling the feature is opt-in by config/module/mount option. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
46 lines
1.9 KiB
Plaintext
46 lines
1.9 KiB
Plaintext
config OVERLAY_FS
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tristate "Overlay filesystem support"
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select EXPORTFS
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help
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An overlay filesystem combines two filesystems - an 'upper' filesystem
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and a 'lower' filesystem. When a name exists in both filesystems, the
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object in the 'upper' filesystem is visible while the object in the
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'lower' filesystem is either hidden or, in the case of directories,
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merged with the 'upper' object.
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For more information see Documentation/filesystems/overlayfs.txt
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config OVERLAY_FS_REDIRECT_DIR
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bool "Overlayfs: turn on redirect dir feature by default"
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depends on OVERLAY_FS
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help
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If this config option is enabled then overlay filesystems will use
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redirects when renaming directories by default. In this case it is
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still possible to turn off redirects globally with the
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"redirect_dir=off" module option or on a filesystem instance basis
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with the "redirect_dir=off" mount option.
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Note, that redirects are not backward compatible. That is, mounting
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an overlay which has redirects on a kernel that doesn't support this
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feature will have unexpected results.
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config OVERLAY_FS_INDEX
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bool "Overlayfs: turn on inodes index feature by default"
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depends on OVERLAY_FS
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help
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If this config option is enabled then overlay filesystems will use
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the inodes index dir to map lower inodes to upper inodes by default.
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In this case it is still possible to turn off index globally with the
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"index=off" module option or on a filesystem instance basis with the
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"index=off" mount option.
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The inodes index feature prevents breaking of lower hardlinks on copy
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up.
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Note, that the inodes index feature is read-only backward compatible.
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That is, mounting an overlay which has an index dir on a kernel that
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doesn't support this feature read-only, will not have any negative
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outcomes. However, mounting the same overlay with an old kernel
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read-write and then mounting it again with a new kernel, will have
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unexpected results.
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