Patch "NFS: Default change_attr_type to NFS4_CHANGE_TYPE_IS_UNDEFINED" has been added to the 5.14-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    NFS: Default change_attr_type to NFS4_CHANGE_TYPE_IS_UNDEFINED

to the 5.14-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:
     nfs-default-change_attr_type-to-nfs4_change_type_is_.patch
and it can be found in the queue-5.14 subdirectory.

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



commit 943f8f52597827e415eab45f5d0d211bd83d042a
Author: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Date:   Sun Sep 26 14:05:04 2021 -0400

    NFS: Default change_attr_type to NFS4_CHANGE_TYPE_IS_UNDEFINED
    
    [ Upstream commit eea413308f2e6deb00f061f18081a53f3ecc8cc6 ]
    
    Both NFSv3 and NFSv2 generate their change attribute from the ctime
    value that was supplied by the server. However the problem is that there
    are plenty of servers out there with ctime resolutions of 1ms or worse.
    In a modern performance system, this is insufficient when trying to
    decide which is the most recent set of attributes when, for instance, a
    READ or GETATTR call races with a WRITE or SETATTR.
    
    For this reason, let's revert to labelling the NFSv2/v3 change
    attributes as NFS4_CHANGE_TYPE_IS_UNDEFINED. This will ensure we protect
    against such races.
    
    Fixes: 7b24dacf0840 ("NFS: Another inode revalidation improvement")
    Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
    Tested-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 853213b3a2095..6ea1bde33cb62 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1777,8 +1777,10 @@ static int nfs_inode_finish_partial_attr_update(const struct nfs_fattr *fattr,
 		NFS_INO_INVALID_BLOCKS | NFS_INO_INVALID_OTHER |
 		NFS_INO_INVALID_NLINK;
 	unsigned long cache_validity = NFS_I(inode)->cache_validity;
+	enum nfs4_change_attr_type ctype = NFS_SERVER(inode)->change_attr_type;
 
-	if (!(cache_validity & NFS_INO_INVALID_CHANGE) &&
+	if (ctype != NFS4_CHANGE_TYPE_IS_UNDEFINED &&
+	    !(cache_validity & NFS_INO_INVALID_CHANGE) &&
 	    (cache_validity & check_valid) != 0 &&
 	    (fattr->valid & NFS_ATTR_FATTR_CHANGE) != 0 &&
 	    nfs_inode_attrs_cmp_monotonic(fattr, inode) == 0)
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index e6eca1d7481b8..9274c9c5efea6 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -2227,7 +2227,7 @@ static int decode_fsinfo3resok(struct xdr_stream *xdr,
 
 	/* ignore properties */
 	result->lease_time = 0;
-	result->change_attr_type = NFS4_CHANGE_TYPE_IS_TIME_METADATA;
+	result->change_attr_type = NFS4_CHANGE_TYPE_IS_UNDEFINED;
 	return 0;
 }
 
diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c
index ea19dbf123014..ecc4e717808c4 100644
--- a/fs/nfs/proc.c
+++ b/fs/nfs/proc.c
@@ -91,7 +91,7 @@ nfs_proc_get_root(struct nfs_server *server, struct nfs_fh *fhandle,
 	info->dtpref = fsinfo.tsize;
 	info->maxfilesize = 0x7FFFFFFF;
 	info->lease_time = 0;
-	info->change_attr_type = NFS4_CHANGE_TYPE_IS_TIME_METADATA;
+	info->change_attr_type = NFS4_CHANGE_TYPE_IS_UNDEFINED;
 	return 0;
 }