ceph: specify max_bytes on readdir replies

Specify max bytes in request to bound size of reply.  Add associated
mount option with default value of 512 KB.
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/ceph_fs.h

@@ -361,6 +361,7 @@ union ceph_mds_request_args {
 	struct {
 		__le32 frag;                 /* which dir fragment */
 		__le32 max_entries;          /* how many dentries to grab */
+		__le32 max_bytes;
 	} __attribute__ ((packed)) readdir;
 	struct {
 		__le32 mode;

fs/ceph/dir.c

@@ -233,6 +233,7 @@ static int ceph_readdir(struct file *filp, void *dirent, filldir_t filldir)
 	u32 ftype;
 	struct ceph_mds_reply_info_parsed *rinfo;
 	const int max_entries = client->mount_args->max_readdir;
+	const int max_bytes = client->mount_args->max_readdir_bytes;
 
 	dout("readdir %p filp %p frag %u off %u\n", inode, filp, frag, off);
 	if (fi->at_end)
@@ -316,6 +317,7 @@ static int ceph_readdir(struct file *filp, void *dirent, filldir_t filldir)
 		req->r_readdir_offset = fi->next_offset;
 		req->r_args.readdir.frag = cpu_to_le32(frag);
 		req->r_args.readdir.max_entries = cpu_to_le32(max_entries);
+		req->r_args.readdir.max_bytes = cpu_to_le32(max_bytes);
 		req->r_num_caps = max_entries + 1;
 		err = ceph_mdsc_do_request(mdsc, NULL, req);
 		if (err < 0) {

fs/ceph/super.c

@@ -190,6 +190,8 @@ static int ceph_show_options(struct seq_file *m, struct vfsmount *mnt)
 			   args->cap_release_safety);
 	if (args->max_readdir != CEPH_MAX_READDIR_DEFAULT)
 		seq_printf(m, ",readdir_max_entries=%d", args->max_readdir);
+	if (args->max_readdir_bytes != CEPH_MAX_READDIR_BYTES_DEFAULT)
+		seq_printf(m, ",readdir_max_bytes=%d", args->max_readdir_bytes);
 	if (strcmp(args->snapdir_name, CEPH_SNAPDIRNAME_DEFAULT))
 		seq_printf(m, ",snapdirname=%s", args->snapdir_name);
 	if (args->name)
@@ -333,6 +335,7 @@ enum {
 	Opt_caps_wanted_delay_max,
 	Opt_cap_release_safety,
 	Opt_readdir_max_entries,
+	Opt_readdir_max_bytes,
 	Opt_congestion_kb,
 	Opt_last_int,
 	/* int args above */
@@ -365,6 +368,7 @@ static match_table_t arg_tokens = {
 	{Opt_caps_wanted_delay_max, "caps_wanted_delay_max=%d"},
 	{Opt_cap_release_safety, "cap_release_safety=%d"},
 	{Opt_readdir_max_entries, "readdir_max_entries=%d"},
+	{Opt_readdir_max_bytes, "readdir_max_bytes=%d"},
 	{Opt_congestion_kb, "write_congestion_kb=%d"},
 	/* int args above */
 	{Opt_snapdirname, "snapdirname=%s"},
@@ -415,6 +419,7 @@ static struct ceph_mount_args *parse_mount_args(int flags, char *options,
 	args->snapdir_name = kstrdup(CEPH_SNAPDIRNAME_DEFAULT, GFP_KERNEL);
 	args->cap_release_safety = CEPH_CAP_RELEASE_SAFETY_DEFAULT;
 	args->max_readdir = CEPH_MAX_READDIR_DEFAULT;
+	args->max_readdir_bytes = CEPH_MAX_READDIR_BYTES_DEFAULT;
 	args->congestion_kb = default_congestion_kb();
 
 	/* ip1[:port1][,ip2[:port2]...]:/subdir/in/fs */
@@ -522,6 +527,9 @@ static struct ceph_mount_args *parse_mount_args(int flags, char *options,
 		case Opt_readdir_max_entries:
 			args->max_readdir = intval;
 			break;
+		case Opt_readdir_max_bytes:
+			args->max_readdir_bytes = intval;
+			break;
 		case Opt_congestion_kb:
 			args->congestion_kb = intval;
 			break;

fs/ceph/super.h

@@ -66,7 +66,8 @@ struct ceph_mount_args {
 	int congestion_kb;    /* max writeback in flight */
 	int caps_wanted_delay_min, caps_wanted_delay_max;
 	int cap_release_safety;
-	int max_readdir;      /* max readdir size */
+	int max_readdir;       /* max readdir result (entires) */
+	int max_readdir_bytes; /* max readdir result (bytes) */
 	char *snapdir_name;   /* default ".snap" */
 	char *name;
 	char *secret;
@@ -81,6 +82,7 @@ struct ceph_mount_args {
 #define CEPH_OSD_IDLE_TTL_DEFAULT    60
 #define CEPH_MOUNT_RSIZE_DEFAULT    (512*1024) /* readahead */
 #define CEPH_MAX_READDIR_DEFAULT    1024
+#define CEPH_MAX_READDIR_BYTES_DEFAULT    (512*1024)
 
 #define CEPH_MSG_MAX_FRONT_LEN	(16*1024*1024)
 #define CEPH_MSG_MAX_DATA_LEN	(16*1024*1024)