Commit 5f544cfa authored by Nicholas Bellinger's avatar Nicholas Bellinger Committed by Nicholas Bellinger
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tcm_fc: Convert to per-cpu command map pre-allocation of ft_cmd

This patch converts tcm_fc to use transport_init_session_tags()
pre-allocation logic for struct ft_cmd descriptors using per-cpu
session tag pooling in order to effectively avoid memory allocation
+ release for each received I/O.

It adds percpu_ida_alloc() in ft_recv_cmd() to obtain an tag and
locate ft_cmd from se_sess->sess_cmd_map[], and percpu_ida_free()
in ft_free_cmd() to release the tag based upon se_cmd->map_tag id.

It also uses a TCM_FC_DEFAULT_TAGS value of 512, that puts the
per se_sess->sess_cmd_map allocation at ~360K on 64-bit.

v2 changes:

  - Handle possible tag < 0 failure with GFP_ATOMIC

Cc: Mark Rustad <>
Cc: Robert Love <>
Cc: Kent Overstreet <>
Signed-off-by: default avatarNicholas Bellinger <>
parent 15c03dd4
......@@ -22,6 +22,7 @@
#define FT_NAMELEN 32 /* length of ASCII WWPNs including pad */
#define FT_TPG_NAMELEN 32 /* max length of TPG name */
#define FT_LUN_NAMELEN 32 /* max length of LUN name */
#define TCM_FC_DEFAULT_TAGS 512 /* tags used for per-session preallocation */
struct ft_transport_id {
__u8 format;
......@@ -28,6 +28,7 @@
#include <linux/configfs.h>
#include <linux/ctype.h>
#include <linux/hash.h>
#include <linux/percpu_ida.h>
#include <asm/unaligned.h>
#include <scsi/scsi.h>
#include <scsi/scsi_host.h>
......@@ -89,16 +90,18 @@ static void ft_free_cmd(struct ft_cmd *cmd)
struct fc_frame *fp;
struct fc_lport *lport;
struct se_session *se_sess;
if (!cmd)
se_sess = cmd->sess->se_sess;
fp = cmd->req_frame;
lport = fr_dev(fp);
if (fr_seq(fp))
percpu_ida_free(&se_sess->sess_tag_pool, cmd->se_cmd.map_tag);
ft_sess_put(cmd->sess); /* undo get from lookup at recv */
void ft_release_cmd(struct se_cmd *se_cmd)
......@@ -432,14 +435,21 @@ static void ft_recv_cmd(struct ft_sess *sess, struct fc_frame *fp)
struct ft_cmd *cmd;
struct fc_lport *lport = sess->tport->lport;
struct se_session *se_sess = sess->se_sess;
int tag;
cmd = kzalloc(sizeof(*cmd), GFP_ATOMIC);
if (!cmd)
tag = percpu_ida_alloc(&se_sess->sess_tag_pool, GFP_ATOMIC);
if (tag < 0)
goto busy;
cmd = &((struct ft_cmd *)se_sess->sess_cmd_map)[tag];
memset(cmd, 0, sizeof(struct ft_cmd));
cmd->se_cmd.map_tag = tag;
cmd->sess = sess;
cmd->seq = lport->tt.seq_assign(lport, fp);
if (!cmd->seq) {
percpu_ida_free(&se_sess->sess_tag_pool, tag);
goto busy;
cmd->req_frame = fp; /* hold frame during cmd */
......@@ -210,7 +210,8 @@ static struct ft_sess *ft_sess_create(struct ft_tport *tport, u32 port_id,
if (!sess)
return NULL;
sess->se_sess = transport_init_session();
sess->se_sess = transport_init_session_tags(TCM_FC_DEFAULT_TAGS,
sizeof(struct ft_cmd));
if (IS_ERR(sess->se_sess)) {
return NULL;
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