Unionfs: Documentation update

Be little gentler & updated the URLs

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Josef 'Jeff' Sipek <jsipek@cs.sunysb.edu>

diff --git a/Documentation/filesystems/unionfs/00-INDEX b/Documentation/filesystems/unionfs/00-INDEX
index 32e96f29a860884bbaa30b8dbbb935b98d83c202..96fdf67501f5abefc414dfe71bd68693d3a442af 100644 (file)
--- a/Documentation/filesystems/unionfs/00-INDEX
+++ b/Documentation/filesystems/unionfs/00-INDEX
@@ -1,8 +1,10 @@
 00-INDEX
        - this file.
 concepts.txt
-       - A brief introduction of concepts
+       - A brief introduction of concepts.
+issues.txt
+       - A summary of known issues with unionfs.
 rename.txt
-       - Information regarding rename operations
+       - Information regarding rename operations.
 usage.txt
-       - Usage and known limitations
+       - Usage information and examples.

diff --git a/Documentation/filesystems/unionfs/issues.txt b/Documentation/filesystems/unionfs/issues.txt
new file mode 100644 (file)
index 0000000..b070175
--- /dev/null
+++ b/Documentation/filesystems/unionfs/issues.txt
@@ -0,0 +1,23 @@
+KNOWN Unionfs ISSUES:
+=====================
+
+1. The NFS server returns -EACCES for read-only exports, instead of -EROFS.
+   This means we can't reliably detect a read-only NFS export.
+
+2. Modifying a Unionfs branch directly, while the union is mounted, is
+   currently unsupported.  We have tested Unionfs under such conditions, and
+   fixed any bugs we found (Unionfs comes with an extensive regression test
+   suite).  However, it may still be possible that changes made to lower
+   branches directly could cause cache incoherency which, in the worst case,
+   may case an oops.  We are currently addressing this problem for Unionfs
+   and also generically for all stackable file systems, by handing mmap and
+   introducing small VFS/MM changes that would allow a file system to handle
+   cache coherency correctly.
+
+3. Unionfs should not use lookup_one_len() on the underlying f/s as it
+   confuses NFS.  Currently, unionfs_lookup() passes lookup intents to the
+   lower file-system, this eliminates part of the problem.  The remaining
+   calls to lookup_one_len may need to be changed to pass an intent.
+
+
+For more information, see <unionfs.filesystems.org>.

diff --git a/Documentation/filesystems/unionfs/usage.txt b/Documentation/filesystems/unionfs/usage.txt
index 3968c9e22334c43e3e6b7608e811c4c89a84a4d8..14e0856a93d81b2d411cef75abca43f0db38fb44 100644 (file)
--- a/Documentation/filesystems/unionfs/usage.txt
+++ b/Documentation/filesystems/unionfs/usage.txt
@@ -1,17 +1,18 @@
 Unionfs is a stackable unification file system, which can appear to merge
 the contents of several directories (branches), while keeping their physical
-content separate. Unionfs is useful for unified source tree management,
+content separate.  Unionfs is useful for unified source tree management,
 merged contents of split CD-ROM, merged separate software package
-directories, data grids, and more. Unionfs allows any mix of read-only and
+directories, data grids, and more.  Unionfs allows any mix of read-only and
 read-write branches, as well as insertion and deletion of branches anywhere
-in the fan-out. To maintain unix semantics, Unionfs handles elimination of
+in the fan-out.  To maintain Unix semantics, Unionfs handles elimination of
 duplicates, partial-error conditions, and more.
 
-mount -t unionfs -o branch-option[,union-options[,...]] none MOUNTPOINT
+# mount -t unionfs -o branch-option[,union-options[,...]] none MOUNTPOINT
 
 The available branch-option for the mount command is:
 
-dirs=branch[=ro|=rw][:...]
+       dirs=branch[=ro|=rw][:...]
+
 specifies a separated list of which directories compose the union.
 Directories that come earlier in the list have a higher precedence than
 those which come later. Additionally, read-only or read-write permissions of
@@ -19,24 +20,12 @@ the branch can be specified by appending =ro or =rw (default) to each
 directory.
 
 Syntax:
-dirs=/branch1[=ro|=rw]:/branch2[=ro|=rw]:...:/branchN[=ro|=rw]
-
-Example:
-dirs=/writable_branch=rw:/read-only_branch=ro
 
+       dirs=/branch1[=ro|=rw]:/branch2[=ro|=rw]:...:/branchN[=ro|=rw]
 
-KNOWN ISSUES:
-=============
-
-The NFS server returns -EACCES for read-only exports, instead of -EROFS.
-This means we can't reliably detect a read-only NFS export.
+Example:
 
-Modifying a Unionfs branch directly, while the union is mounted, is
-currently unsupported.  Any such change can cause Unionfs to oops, or stay
-silent and even RESULT IN DATA LOSS.
+       dirs=/writable_branch=rw:/read-only_branch=ro
 
-Unionfs should not use lookup_one_len() on the underlying fs as it confuses
-NFS. Currently, unionfs_lookup() passes lookup intents to the lower
-filesystem, this eliminates part of the problem. The remaining calls to
-lookup_one_len may need to be changed to pass an intent.
 
+For more information, see unionfs.filesystems.org.

diff --git a/fs/Kconfig b/fs/Kconfig
index 27aad69b3bf7d6ffa8c71ebae511b1d21128616c..883c1e9a8612e66d954e167e389a7ec06e6df366 100644 (file)
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -175,7 +175,7 @@ config UNION_FS
          merge the contents of several directories (branches), while keeping
          their physical content separate.
 
-         See <http://unionfs.filesystems.org> for details
+         See <http://unionfs.filesystems.org/> for details.
 
 config UNION_FS_XATTR
        bool "Unionfs extended attributes"

diff --git a/fs/unionfs/main.c b/fs/unionfs/main.c
index 36d30bc15e254615640355954a58969501fbe1b8..ca7ee26040cee98aef35582894c2854ffe765751 100644 (file)
--- a/fs/unionfs/main.c
+++ b/fs/unionfs/main.c
@@ -679,7 +679,7 @@ static void __exit exit_unionfs_fs(void)
 MODULE_AUTHOR("Erez Zadok, Filesystems and Storage Lab, Stony Brook University"
                " (http://www.fsl.cs.sunysb.edu)");
 MODULE_DESCRIPTION("Unionfs " UNIONFS_VERSION
-               " (http://www.unionfs.org)");
+               " (http://unionfs.filesystems.org)");
 MODULE_LICENSE("GPL");
 
 module_init(init_unionfs_fs);