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authorMiklos Szeredi <mszeredi@redhat.com>2019-05-31 11:27:25 +0200
committerMiklos Szeredi <mszeredi@redhat.com>2019-05-31 11:27:25 +0200
commit5d3211b651a012bc77410ebf097b7271a7ce5c95 (patch)
treedaeb13ad09e563e8cfda372dd64a4813aa174d0e /Documentation
parent146d62e5a5867fbf84490d82455718bfb10fe824 (diff)
ovl: doc: add non-standard corner cases
While most corner cases have already been dealt with, some remain and should be documented. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/overlayfs.txt16
1 files changed, 14 insertions, 2 deletions
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
index eef7d9d259e8..1da2f1668f08 100644
--- a/Documentation/filesystems/overlayfs.txt
+++ b/Documentation/filesystems/overlayfs.txt
@@ -336,8 +336,20 @@ the copied layers will fail the verification of the lower root file handle.
Non-standard behavior
---------------------
-Overlayfs can now act as a POSIX compliant filesystem with the following
-features turned on:
+Current version of overlayfs can act as a mostly POSIX compliant
+filesystem.
+
+This is the list of cases that overlayfs doesn't currently handle:
+
+a) POSIX mandates updating st_atime for reads. This is currently not
+done in the case when the file resides on a lower layer.
+
+b) If a file residing on a lower layer is opened for read-only and then
+memory mapped with MAP_SHARED, then subsequent changes to the file are not
+reflected in the memory mapping.
+
+The following options allow overlayfs to act more like a standards
+compliant filesystem:
1) "redirect_dir"