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| author | Miklos Szeredi <mszeredi@redhat.com> | 2016-12-16 13:02:56 +0300 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2016-12-16 13:02:56 +0300 |
| commit | a6c6065511411c57167a6cdae0c33263fb662b51 (patch) | |
| tree | cd2c7904884c557a0d7d26a88efc737a8885407a /Documentation/filesystems | |
| parent | 02b69b284cd7815239fabfe895bfef9a9eb5a3ce (diff) | |
| download | linux-a6c6065511411c57167a6cdae0c33263fb662b51.tar.xz | |
ovl: redirect on rename-dir
Current code returns EXDEV when a directory would need to be copied up to
move. We could copy up the directory tree in this case, but there's
another, simpler solution: point to old lower directory from moved upper
directory.
This is achieved with a "trusted.overlay.redirect" xattr storing the path
relative to the root of the overlay. After such attribute has been set,
the directory can be moved without further actions required.
This is a backward incompatible feature, old kernels won't be able to
correctly mount an overlay containing redirected directories.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/overlayfs.txt | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt index 7aeb8e8d80cf..fb6f3070c6fe 100644 --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.txt @@ -130,6 +130,23 @@ directory. Readdir on directories that are not merged is simply handled by the underlying directory (upper or lower). +renaming directories +-------------------- + +When renaming a directory that is on the lower layer or merged (i.e. the +directory was not created on the upper layer to start with) overlayfs can +handle it in two different ways: + +1) return EXDEV error: this error is returned by rename(2) when trying to + move a file or directory across filesystem boundaries. Hence + applications are usually prepared to hande this error (mv(1) for example + recursively copies the directory tree). This is the default behavior. + +2) If the "redirect_dir" feature is enabled, then the directory will be + copied up (but not the contents). Then the "trusted.overlay.redirect" + extended attribute is set to the path of the original location from the + root of the overlay. Finally the directory is moved to the new + location. Non-directories --------------- @@ -189,8 +206,8 @@ If a file with multiple hard links is copied up, then this will "break" the link. Changes will not be propagated to other names referring to the same inode. -Directory trees are not copied up. If rename(2) is performed on a directory -which is on the lower layer or is merged, then -EXDEV will be returned. +Unless "redirect_dir" feature is enabled, rename(2) on a lower or merged +directory will fail with EXDEV. Changes to underlying filesystems --------------------------------- |