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authorKevin Locke <kevin@kevinlocke.name>2020-08-22 20:22:57 -0600
committerMiklos Szeredi <mszeredi@redhat.com>2020-11-12 11:31:55 +0100
commit13c6ad0f45fd0382e77829a6c738f3e18739c15b (patch)
tree7c926f0614d1efdcebabbb6893ae0acedffbc93d /Documentation/filesystems/overlayfs.rst
parent0a8d0b64dd6acfbc9e9b79022654bbe1ade4a29a (diff)
ovl: document lower modification caveats
Some overlayfs optional features are incompatible with offline changes to the lower tree and may result in -EXDEV, -EIO, or other errors. Such modification is not supported and the error behavior is intentionally not specified. Update the "Changes to underlying filesystems" section to note this restriction. Move the paragraph describing the offline behavior below the online behavior so it is adjacent to the following 3 paragraphs describing the NFS export offline modification behavior. Link: https://lore.kernel.org/linux-unionfs/20200708142353.GA103536@redhat.com/ Link: https://lore.kernel.org/linux-unionfs/CAOQ4uxi23Zsmfb4rCed1n=On0NNA5KZD74jjjeyz+et32sk-gg@mail.gmail.com/ Link: https://lore.kernel.org/linux-unionfs/20200817135651.GA637139@redhat.com/ Link: https://lore.kernel.org/linux-unionfs/20200709153616.GE150543@redhat.com/ Link: https://lore.kernel.org/linux-unionfs/20200812135529.GA122370@kevinolos/ Signed-off-by: Kevin Locke <kevin@kevinlocke.name> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'Documentation/filesystems/overlayfs.rst')
-rw-r--r--Documentation/filesystems/overlayfs.rst10
1 files changed, 7 insertions, 3 deletions
diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst
index 1ef4ef38b542..b86be7c6a952 100644
--- a/Documentation/filesystems/overlayfs.rst
+++ b/Documentation/filesystems/overlayfs.rst
@@ -469,14 +469,18 @@ summarized in the `Inode properties`_ table above.
Changes to underlying filesystems
---------------------------------
-Offline changes, when the overlay is not mounted, are allowed to either
-the upper or the lower trees.
-
Changes to the underlying filesystems while part of a mounted overlay
filesystem are not allowed. If the underlying filesystem is changed,
the behavior of the overlay is undefined, though it will not result in
a crash or deadlock.
+Offline changes, when the overlay is not mounted, are allowed to the
+upper tree. Offline changes to the lower tree are only allowed if the
+"metadata only copy up", "inode index", and "redirect_dir" features
+have not been used. If the lower tree is modified and any of these
+features has been used, the behavior of the overlay is undefined,
+though it will not result in a crash or deadlock.
+
When the overlay NFS export feature is enabled, overlay filesystems
behavior on offline changes of the underlying lower layer is different
than the behavior when NFS export is disabled.