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| author | Amir Goldstein <amir73il@gmail.com> | 2018-01-19 10:26:53 +0100 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2018-01-24 11:25:37 +0100 |
| commit | f168f1098dd9038daaf9f7be5f81cdea4985886a (patch) | |
| tree | bd8e8a9a2afcf548a6e96922ca3d81e2ef518f2c /fs/overlayfs/Kconfig | |
| parent | ovl: update documentation of inodes index feature (diff) | |
| download | linux-f168f1098dd9038daaf9f7be5f81cdea4985886a.tar.xz linux-f168f1098dd9038daaf9f7be5f81cdea4985886a.zip | |
ovl: add support for "nfs_export" configuration
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>
Diffstat (limited to 'fs/overlayfs/Kconfig')
| -rw-r--r-- | fs/overlayfs/Kconfig | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig index 9eac01c3e21e..406e72de88f6 100644 --- a/fs/overlayfs/Kconfig +++ b/fs/overlayfs/Kconfig @@ -50,3 +50,25 @@ config OVERLAY_FS_INDEX 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. |