ceph: add new field max_file_size in ceph_fs_client

In order to not bother to VFS and other specific filesystems,
we decided to do offset validation inside ceph kernel client,
so just simply set sb->s_maxbytes to MAX_LFS_FILESIZE so that
it can successfully pass VFS check. We add new field max_file_size
in ceph_fs_client to store real file size limit and doing proper
check based on it.
Signed-off-by: NChengguang Xu <cgxu519@gmx.com>
Reviewed-by: N"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>

fs/ceph/mds_client.c

@@ -4018,7 +4018,8 @@ void ceph_mdsc_handle_mdsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
 	} else {
 		mdsc->mdsmap = newmap;  /* first mds map */
 	}
-	mdsc->fsc->sb->s_maxbytes = mdsc->mdsmap->m_max_file_size;
+	mdsc->fsc->max_file_size = min((loff_t)mdsc->mdsmap->m_max_file_size,
+					MAX_LFS_FILESIZE);
 
 	__wake_requests(mdsc, &mdsc->waiting_for_map);
 	ceph_monc_got_map(&mdsc->fsc->client->monc, CEPH_SUB_MDSMAP,

fs/ceph/super.c

@@ -940,11 +940,12 @@ static int ceph_set_super(struct super_block *s, void *data)
 	dout("set_super %p data %p\n", s, data);
 
 	s->s_flags = fsc->mount_options->sb_flags;
-	s->s_maxbytes = 1ULL << 40;  /* temp value until we get mdsmap */
+	s->s_maxbytes = MAX_LFS_FILESIZE;
 
 	s->s_xattr = ceph_xattr_handlers;
 	s->s_fs_info = fsc;
 	fsc->sb = s;
+	fsc->max_file_size = 1ULL << 40; /* temp value until we get mdsmap */
 
 	s->s_op = &ceph_super_ops;
 	s->s_d_op = &ceph_dentry_ops;

fs/ceph/super.h

@@ -98,6 +98,7 @@ struct ceph_fs_client {
 
 	unsigned long mount_state;
 	int min_caps;                  /* min caps i added */
+	loff_t max_file_size;
 
 	struct ceph_mds_client *mdsc;