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NFS: Default change_attr_type to NFS4_CHANGE_TYPE_IS_UNDEFINED 

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: 7b24dacf08 ("NFS: Another inode revalidation improvement")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Trond Myklebust 2021-09-26 14:05:04 -04:00
parent a1e7f30a86
commit eea413308f
3 changed files with 5 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/nfs/inode.c
View File

@ -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)

2
fs/nfs/nfs3xdr.c
View File

@ -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;
}

2
fs/nfs/proc.c
View File

@ -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;
}