NFSD: Implement FATTR4_CLONE_BLKSIZE attribute

RFC 7862 states that if an NFS server implements a CLONE operation,
it MUST also implement FATTR4_CLONE_BLKSIZE. NFSD implements CLONE,
but does not implement FATTR4_CLONE_BLKSIZE.

Note that in Section 12.2, RFC 7862 claims that
FATTR4_CLONE_BLKSIZE is RECOMMENDED, not REQUIRED. Likely this is
because a minor version is not permitted to add a REQUIRED
attribute. Confusing.

We assume this attribute reports a block size as a count of bytes,
as RFC 7862 does not specify a unit.

Reported-by: Roland Mainz <roland.mainz@nrubsig.org>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Roland Mainz <roland.mainz@nrubsig.org>
Cc: stable@vger.kernel.org # v6.7+
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index e67420729ecd609c46c3f5d411dea73aa0047ffc..9eb8e570462251fd857e43478448574264e7a0a0 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3391,6 +3391,23 @@ static __be32 nfsd4_encode_fattr4_suppattr_exclcreat(struct xdr_stream *xdr,
        return nfsd4_encode_bitmap4(xdr, supp[0], supp[1], supp[2]);
 }
 
+/*
+ * Copied from generic_remap_checks/generic_remap_file_range_prep.
+ *
+ * These generic functions use the file system's s_blocksize, but
+ * individual file systems aren't required to use
+ * generic_remap_file_range_prep. Until there is a mechanism for
+ * determining a particular file system's (or file's) clone block
+ * size, this is the best NFSD can do.
+ */
+static __be32 nfsd4_encode_fattr4_clone_blksize(struct xdr_stream *xdr,
+                                               const struct nfsd4_fattr_args *args)
+{
+       struct inode *inode = d_inode(args->dentry);
+
+       return nfsd4_encode_uint32_t(xdr, inode->i_sb->s_blocksize);
+}
+
 #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
 static __be32 nfsd4_encode_fattr4_sec_label(struct xdr_stream *xdr,
                                            const struct nfsd4_fattr_args *args)
@@ -3545,7 +3562,7 @@ static const nfsd4_enc_attr nfsd4_enc_fattr4_encode_ops[] = {
        [FATTR4_MODE_SET_MASKED]        = nfsd4_encode_fattr4__noop,
        [FATTR4_SUPPATTR_EXCLCREAT]     = nfsd4_encode_fattr4_suppattr_exclcreat,
        [FATTR4_FS_CHARSET_CAP]         = nfsd4_encode_fattr4__noop,
-       [FATTR4_CLONE_BLKSIZE]          = nfsd4_encode_fattr4__noop,
+       [FATTR4_CLONE_BLKSIZE]          = nfsd4_encode_fattr4_clone_blksize,
        [FATTR4_SPACE_FREED]            = nfsd4_encode_fattr4__noop,
        [FATTR4_CHANGE_ATTR_TYPE]       = nfsd4_encode_fattr4__noop,