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Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/filesystems/overlayfs.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst index 580ab9a0fe31..137afeb3f581 100644 --- a/Documentation/filesystems/overlayfs.rst +++ b/Documentation/filesystems/overlayfs.rst @@ -575,6 +575,14 @@ without significant effort. The advantage of mounting with the "volatile" option is that all forms of sync calls to the upper filesystem are omitted. +In order to avoid a giving a false sense of safety, the syncfs (and fsync) +semantics of volatile mounts are slightly different than that of the rest of +VFS. If any writeback error occurs on the upperdir's filesystem after a +volatile mount takes place, all sync functions will return an error. Once this +condition is reached, the filesystem will not recover, and every subsequent sync +call will return an error, even if the upperdir has not experience a new error +since the last sync call. + When overlay is mounted with "volatile" option, the directory "$workdir/work/incompat/volatile" is created. During next mount, overlay checks for this directory and refuses to mount if present. This is a strong |