diff options
Diffstat (limited to 'Documentation/filesystems/overlayfs.txt')
| -rw-r--r-- | Documentation/filesystems/overlayfs.txt | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt index bcbf9710e4af..634d03e20c2d 100644 --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.txt @@ -66,7 +66,7 @@ At mount time, the two directories given as mount options "lowerdir" and "upperdir" are combined into a merged directory: mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,\ -workdir=/work /merged + workdir=/work /merged The "workdir" needs to be an empty directory on the same filesystem as upperdir. @@ -118,6 +118,7 @@ programs. seek offsets are assigned sequentially when the directories are read. Thus if + - read part of a directory - remember an offset, and close the directory - re-open the directory some time later @@ -130,6 +131,23 @@ 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 --------------- @@ -185,13 +203,13 @@ filesystem, so both st_dev and st_ino of the file may change. Any open files referring to this inode will access the old data. -Any file locks (and leases) obtained before copy_up will not apply -to the copied up file. - 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. +Unless "redirect_dir" feature is enabled, rename(2) on a lower or merged +directory will fail with EXDEV. + Changes to underlying filesystems --------------------------------- |