diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index c6fcbf428317..e773be07f767 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1254,6 +1254,22 @@ int __ceph_setxattr(struct inode *inode, const char *name,
 	      ceph_vinop(inode), name, ceph_cap_string(issued));
 	__build_xattrs(inode);
 
+	/*
+	 * __build_xattrs() may have released and reacquired i_ceph_lock,
+	 * during which handle_cap_grant() could have replaced i_xattrs.blob
+	 * with a newer MDS-provided blob and bumped i_xattrs.version. If that
+	 * caused __build_xattrs() to rebuild the rb-tree from the new blob,
+	 * count/names_size/vals_size may now be larger than when
+	 * required_blob_size was computed above. Recompute it here so the
+	 * prealloc_blob size check below reflects the current tree state.
+	 */
+	required_blob_size = __get_required_blob_size(ci, name_len, val_len);
+	if (required_blob_size > mdsc->mdsmap->m_max_xattr_size) {
+		doutc(cl, "sync (size too large): %d > %llu\n",
+		      required_blob_size, mdsc->mdsmap->m_max_xattr_size);
+		goto do_sync;
+	}
+
 	if (!ci->i_xattrs.prealloc_blob ||
 	    required_blob_size > ci->i_xattrs.prealloc_blob->alloc_len) {
 		struct ceph_buffer *blob;