mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-24 05:04:00 +08:00
f168f1098d
Introduce the "nfs_export" config, module and mount options. The NFS export feature depends on the "index" feature and enables two implicit overlayfs features: "index_all" and "verify_lower". The "index_all" feature creates an index on copy up of every file and directory. The "verify_lower" feature uses the full index to detect overlay filesystems inconsistencies on lookup, like redirect from multiple upper dirs to the same lower dir. NFS export can be enabled for non-upper mount with no index. However, because lower layer redirects cannot be verified with the index, enabling NFS export support on an overlay with no upper layer requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The full index may incur some overhead on mount time, especially when verifying that lower directory file handles are not stale. NFS export support, full index and consistency verification will be implemented by following patches. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
75 lines
3.1 KiB
Plaintext
75 lines
3.1 KiB
Plaintext
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_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.
|
|
|
|
For more information, see Documentation/filesystems/overlayfs.txt
|
|
|
|
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 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.
|
|
|
|
config OVERLAY_FS_NFS_EXPORT
|
|
bool "Overlayfs: turn on NFS export feature by default"
|
|
depends on OVERLAY_FS
|
|
depends on OVERLAY_FS_INDEX
|
|
help
|
|
If this config option is enabled then overlay filesystems will use
|
|
the inodes index dir 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.
|