Patch "ovl: persistent inode numbers for upper hardlinks" has been added to the 4.9-stable tree

Patch "ovl: persistent inode numbers for upper hardlinks" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ovl: persistent inode numbers for upper hardlinks

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ovl-persistent-inode-numbers-for-upper-hardlinks.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Apr  9 17:09:24 CEST 2018
From: Amir Goldstein <amir73il@gmail.com>
Date: Mon, 24 Apr 2017 19:54:13 +0300
Subject: ovl: persistent inode numbers for upper hardlinks

From: Amir Goldstein <amir73il@gmail.com>


[ Upstream commit 5b6c9053fb38a66fd5c6177fcf5022b24767811a ]

An upper type non directory dentry that is a copy up target
should have a reference to its lower copy up origin.

There are three ways for an upper type dentry to be instantiated:
1. A lower type dentry that is being copied up
2. An entry that is found in upper dir by ovl_lookup()
3. A negative dentry is hardlinked to an upper type dentry

In the first case, the lower reference is set before copy up.
In the second case, the lower reference is found by ovl_lookup().
In the last case of hardlinked upper dentry, it is not easy to
update the lower reference of the negative dentry.  Instead,
drop the newly hardlinked negative dentry from dcache and let
the next access call ovl_lookup() to find its lower reference.

This makes sure that the inode number reported by stat(2) after
the hardlink is created is the same inode number that will be
reported by stat(2) after mount cycle, which is the inode number
of the lower copy up origin of the hardlink source.

NOTE that this does not fix breaking of lower hardlinks on copy
up, but only fixes the case of lower nlink == 1, whose upper copy
up inode is hardlinked in upper dir.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/overlayfs/dir.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -180,6 +180,9 @@ static void ovl_instantiate(struct dentr
 		inc_nlink(inode);
 	}
 	d_instantiate(dentry, inode);
+	/* Force lookup of new upper hardlink to find its lower */
+	if (hardlink)
+		d_drop(dentry);
 }
 
 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,


Patches currently in stable-queue which might be from amir73il@gmail.com are

queue-4.9/ovl-persistent-inode-numbers-for-upper-hardlinks.patch