Linux Virtualization - May 2018 - [PATCH 0/2] Use sbitmap instead of percpu_ida

From: Matthew Wilcox <mawilcox at microsoft.com>

This is a pretty rough-and-ready conversion of the target drivers
from using percpu_ida to sbitmap.  It compiles; I don't have a target
setup, so it's completely untested.  I haven't tried to do anything
particularly clever here, so it's possible that, for example, the wait
queue in iscsi_target_util could be more clever, like the block layer
uses multiple wait queues to avoid pingpongs.  Or maybe we could figure
out a way to not store the CPU that the ID was allocated on, or perhaps
the options I specified to sbitmap_queue_init() are suboptimal.

Patch 2 isn't interesting; it just deletes the implementation.  Patch 1
will be where all the action is.

Matthew Wilcox (2):
  Convert target drivers to use sbitmap
  Remove percpu_ida

 drivers/scsi/qla2xxx/qla_target.c        |  16 +-
 drivers/target/iscsi/iscsi_target_util.c |  34 +-
 drivers/target/sbp/sbp_target.c          |   8 +-
 drivers/target/target_core_transport.c   |   5 +-
 drivers/target/tcm_fc/tfc_cmd.c          |  11 +-
 drivers/usb/gadget/function/f_tcm.c      |   8 +-
 drivers/vhost/scsi.c                     |   9 +-
 drivers/xen/xen-scsiback.c               |   8 +-
 include/linux/percpu_ida.h               |  83 -----
 include/target/iscsi/iscsi_target_core.h |   1 +
 include/target/target_core_base.h        |   5 +-
 lib/Makefile                             |   2 +-
 lib/percpu_ida.c                         | 391 -----------------------
 13 files changed, 74 insertions(+), 507 deletions(-)
 delete mode 100644 include/linux/percpu_ida.h
 delete mode 100644 lib/percpu_ida.c

-- 
2.17.0

From: Matthew Wilcox <mawilcox at microsoft.com>

The sbitmap and the percpu_ida perform essentially the same task,
allocating tags for commands.  Since the sbitmap is more used than
the percpu_ida, convert the percpu_ida users to the sbitmap API.

Signed-off-by: Matthew Wilcox <mawilcox at microsoft.com>
---
 drivers/scsi/qla2xxx/qla_target.c        | 16 ++++++-----
 drivers/target/iscsi/iscsi_target_util.c | 34 +++++++++++++++++++++---
 drivers/target/sbp/sbp_target.c          |  8 +++---
 drivers/target/target_core_transport.c   |  5 ++--
 drivers/target/tcm_fc/tfc_cmd.c          | 11 ++++----
 drivers/usb/gadget/function/f_tcm.c      |  8 +++---
 drivers/vhost/scsi.c                     |  9 ++++---
 drivers/xen/xen-scsiback.c               |  8 +++---
 include/target/iscsi/iscsi_target_core.h |  1 +
 include/target/target_core_base.h        |  5 ++--
 10 files changed, 73 insertions(+), 32 deletions(-)

diff --git a/drivers/scsi/qla2xxx/qla_target.c
b/drivers/scsi/qla2xxx/qla_target.c
index 025dc2d3f3de..cdf671c2af61 100644
--- a/drivers/scsi/qla2xxx/qla_target.c
+++ b/drivers/scsi/qla2xxx/qla_target.c
@@ -3719,7 +3719,8 @@ void qlt_free_cmd(struct qla_tgt_cmd *cmd)
 		return;
 	}
 	cmd->jiffies_at_free = get_jiffies_64();
-	percpu_ida_free(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag);
+	sbitmap_queue_clear(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag,
+			cmd->se_cmd.map_cpu);
 }
 EXPORT_SYMBOL(qlt_free_cmd);
 
@@ -4084,7 +4085,8 @@ static void __qlt_do_work(struct qla_tgt_cmd *cmd)
 	qlt_send_term_exchange(qpair, NULL, &cmd->atio, 1, 0);
 
 	qlt_decr_num_pend_cmds(vha);
-	percpu_ida_free(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag);
+	sbitmap_queue_clear(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag,
+			cmd->se_cmd.map_cpu);
 	spin_unlock_irqrestore(qpair->qp_lock_ptr, flags);
 
 	spin_lock_irqsave(&ha->tgt.sess_lock, flags);
@@ -4215,9 +4217,9 @@ static struct qla_tgt_cmd *qlt_get_tag(scsi_qla_host_t
*vha,
 {
 	struct se_session *se_sess = sess->se_sess;
 	struct qla_tgt_cmd *cmd;
-	int tag;
+	int tag, cpu;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
 	if (tag < 0)
 		return NULL;
 
@@ -4230,6 +4232,7 @@ static struct qla_tgt_cmd *qlt_get_tag(scsi_qla_host_t
*vha,
 	qlt_incr_num_pend_cmds(vha);
 	cmd->vha = vha;
 	cmd->se_cmd.map_tag = tag;
+	cmd->se_cmd.map_cpu = cpu;
 	cmd->sess = sess;
 	cmd->loop_id = sess->loop_id;
 	cmd->conf_compl_supported = sess->conf_compl_supported;
@@ -5212,7 +5215,7 @@ qlt_alloc_qfull_cmd(struct scsi_qla_host *vha,
 	struct fc_port *sess;
 	struct se_session *se_sess;
 	struct qla_tgt_cmd *cmd;
-	int tag;
+	int tag, cpu;
 	unsigned long flags;
 
 	if (unlikely(tgt->tgt_stop)) {
@@ -5244,7 +5247,7 @@ qlt_alloc_qfull_cmd(struct scsi_qla_host *vha,
 
 	se_sess = sess->se_sess;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
 	if (tag < 0)
 		return;
 
@@ -5275,6 +5278,7 @@ qlt_alloc_qfull_cmd(struct scsi_qla_host *vha,
 	cmd->reset_count = ha->base_qpair->chip_reset;
 	cmd->q_full = 1;
 	cmd->qpair = ha->base_qpair;
+	cmd->se_cmd.map_cpu = cpu;
 
 	if (qfull) {
 		cmd->q_full = 1;
diff --git a/drivers/target/iscsi/iscsi_target_util.c
b/drivers/target/iscsi/iscsi_target_util.c
index 4435bf374d2d..28bcffae609f 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -17,7 +17,7 @@
 
******************************************************************************/
 
 #include <linux/list.h>
-#include <linux/percpu_ida.h>
+#include <linux/sched/signal.h>
 #include <net/ipv6.h>         /* ipv6_addr_equal() */
 #include <scsi/scsi_tcq.h>
 #include <scsi/iscsi_proto.h>
@@ -147,6 +147,28 @@ void iscsit_free_r2ts_from_list(struct iscsi_cmd *cmd)
 	spin_unlock_bh(&cmd->r2t_lock);
 }
 
+int iscsit_wait_for_tag(struct se_session *se_sess, int state, int *cpup)
+{
+	int tag = -1;
+	DEFINE_WAIT(wait);
+	struct sbq_wait_state *ws;
+
+	if (state == TASK_RUNNING)
+		return tag;
+
+	ws = &se_sess->sess_tag_pool.ws[0];
+	for (;;) {
+		prepare_to_wait_exclusive(&ws->wait, &wait, state);
+		if (signal_pending_state(state, current))
+			break;
+		schedule();
+		tag = sbitmap_queue_get(&se_sess->sess_tag_pool, cpup);
+	}
+
+	finish_wait(&ws->wait, &wait);
+	return tag;
+}
+
 /*
  * May be called from software interrupt (timer) context for allocating
  * iSCSI NopINs.
@@ -155,9 +177,11 @@ struct iscsi_cmd *iscsit_allocate_cmd(struct iscsi_conn
*conn, int state)
 {
 	struct iscsi_cmd *cmd;
 	struct se_session *se_sess = conn->sess->se_sess;
-	int size, tag;
+	int size, tag, cpu;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, state);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
+	if (tag < 0)
+		tag = iscsit_wait_for_tag(se_sess, state, &cpu);
 	if (tag < 0)
 		return NULL;
 
@@ -166,6 +190,7 @@ struct iscsi_cmd *iscsit_allocate_cmd(struct iscsi_conn
*conn, int state)
 	memset(cmd, 0, size);
 
 	cmd->se_cmd.map_tag = tag;
+	cmd->se_cmd.map_cpu = cpu;
 	cmd->conn = conn;
 	cmd->data_direction = DMA_NONE;
 	INIT_LIST_HEAD(&cmd->i_conn_node);
@@ -711,7 +736,8 @@ void iscsit_release_cmd(struct iscsi_cmd *cmd)
 	kfree(cmd->iov_data);
 	kfree(cmd->text_in_ptr);
 
-	percpu_ida_free(&sess->se_sess->sess_tag_pool, se_cmd->map_tag);
+	sbitmap_queue_clear(&sess->se_sess->sess_tag_pool,
se_cmd->map_tag,
+			se_cmd->map_cpu);
 }
 EXPORT_SYMBOL(iscsit_release_cmd);
 
diff --git a/drivers/target/sbp/sbp_target.c b/drivers/target/sbp/sbp_target.c
index fb1003921d85..c58f9f04c6be 100644
--- a/drivers/target/sbp/sbp_target.c
+++ b/drivers/target/sbp/sbp_target.c
@@ -926,15 +926,16 @@ static struct sbp_target_request *sbp_mgt_get_req(struct
sbp_session *sess,
 {
 	struct se_session *se_sess = sess->se_sess;
 	struct sbp_target_request *req;
-	int tag;
+	int tag, cpu;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
 	if (tag < 0)
 		return ERR_PTR(-ENOMEM);
 
 	req = &((struct sbp_target_request *)se_sess->sess_cmd_map)[tag];
 	memset(req, 0, sizeof(*req));
 	req->se_cmd.map_tag = tag;
+	req->se_cmd.map_cpu = cpu;
 	req->se_cmd.tag = next_orb;
 
 	return req;
@@ -1460,7 +1461,8 @@ static void sbp_free_request(struct sbp_target_request
*req)
 	kfree(req->pg_tbl);
 	kfree(req->cmd_buf);
 
-	percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
+	sbitmap_queue_clear(&se_sess->sess_tag_pool, se_cmd->map_tag,
+			se_cmd->map_cpu);
 }
 
 static void sbp_mgt_agent_process(struct work_struct *work)
diff --git a/drivers/target/target_core_transport.c
b/drivers/target/target_core_transport.c
index 4558f2e1fe1b..3103890ed109 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -260,7 +260,8 @@ int transport_alloc_session_tags(struct se_session *se_sess,
 		}
 	}
 
-	rc = percpu_ida_init(&se_sess->sess_tag_pool, tag_num);
+	rc = sbitmap_queue_init_node(&se_sess->sess_tag_pool, tag_num, -1,
+			false, GFP_KERNEL, NUMA_NO_NODE);
 	if (rc < 0) {
 		pr_err("Unable to init se_sess->sess_tag_pool,"
 			" tag_num: %u\n", tag_num);
@@ -547,7 +548,7 @@ void transport_free_session(struct se_session *se_sess)
 		target_put_nacl(se_nacl);
 	}
 	if (se_sess->sess_cmd_map) {
-		percpu_ida_destroy(&se_sess->sess_tag_pool);
+		sbitmap_queue_free(&se_sess->sess_tag_pool);
 		kvfree(se_sess->sess_cmd_map);
 	}
 	kmem_cache_free(se_sess_cache, se_sess);
diff --git a/drivers/target/tcm_fc/tfc_cmd.c b/drivers/target/tcm_fc/tfc_cmd.c
index ec372860106f..b3e3364b7147 100644
--- a/drivers/target/tcm_fc/tfc_cmd.c
+++ b/drivers/target/tcm_fc/tfc_cmd.c
@@ -28,7 +28,6 @@
 #include <linux/configfs.h>
 #include <linux/ctype.h>
 #include <linux/hash.h>
-#include <linux/percpu_ida.h>
 #include <asm/unaligned.h>
 #include <scsi/scsi_tcq.h>
 #include <scsi/libfc.h>
@@ -92,7 +91,8 @@ static void ft_free_cmd(struct ft_cmd *cmd)
 	if (fr_seq(fp))
 		fc_seq_release(fr_seq(fp));
 	fc_frame_free(fp);
-	percpu_ida_free(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag);
+	sbitmap_queue_clear(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag,
+			cmd->se_cmd.map_cpu);
 	ft_sess_put(sess);	/* undo get from lookup at recv */
 }
 
@@ -448,9 +448,9 @@ 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;
+	int tag, cpu;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
 	if (tag < 0)
 		goto busy;
 
@@ -458,10 +458,11 @@ static void ft_recv_cmd(struct ft_sess *sess, struct
fc_frame *fp)
 	memset(cmd, 0, sizeof(struct ft_cmd));
 
 	cmd->se_cmd.map_tag = tag;
+	cmd->se_cmd.map_cpu = cpu;
 	cmd->sess = sess;
 	cmd->seq = fc_seq_assign(lport, fp);
 	if (!cmd->seq) {
-		percpu_ida_free(&se_sess->sess_tag_pool, tag);
+		sbitmap_queue_clear(&se_sess->sess_tag_pool, tag, cpu);
 		goto busy;
 	}
 	cmd->req_frame = fp;		/* hold frame during cmd */
diff --git a/drivers/usb/gadget/function/f_tcm.c
b/drivers/usb/gadget/function/f_tcm.c
index d78dbb73bde8..b335f4f33bc3 100644
--- a/drivers/usb/gadget/function/f_tcm.c
+++ b/drivers/usb/gadget/function/f_tcm.c
@@ -1071,15 +1071,16 @@ static struct usbg_cmd *usbg_get_cmd(struct f_uas *fu,
 {
 	struct se_session *se_sess = tv_nexus->tvn_se_sess;
 	struct usbg_cmd *cmd;
-	int tag;
+	int tag, cpu;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
 	if (tag < 0)
 		return ERR_PTR(-ENOMEM);
 
 	cmd = &((struct usbg_cmd *)se_sess->sess_cmd_map)[tag];
 	memset(cmd, 0, sizeof(*cmd));
 	cmd->se_cmd.map_tag = tag;
+	cmd->se_cmd.map_cpu = cpu;
 	cmd->se_cmd.tag = cmd->tag = scsi_tag;
 	cmd->fu = fu;
 
@@ -1288,7 +1289,8 @@ static void usbg_release_cmd(struct se_cmd *se_cmd)
 	struct se_session *se_sess = se_cmd->se_sess;
 
 	kfree(cmd->data_buf);
-	percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
+	sbitmap_queue_clear(&se_sess->sess_tag_pool, se_cmd->map_tag,
+			se_cmd->map_cpu);
 }
 
 static u32 usbg_sess_get_index(struct se_session *se_sess)
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 7ad57094d736..1fadaa39f322 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -46,7 +46,6 @@
 #include <linux/virtio_scsi.h>
 #include <linux/llist.h>
 #include <linux/bitmap.h>
-#include <linux/percpu_ida.h>
 
 #include "vhost.h"
 
@@ -324,7 +323,8 @@ static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
 	}
 
 	vhost_scsi_put_inflight(tv_cmd->inflight);
-	percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
+	sbitmap_queue_clear(&se_sess->sess_tag_pool, se_cmd->map_tag,
+			se_cmd->map_cpu);
 }
 
 static u32 vhost_scsi_sess_get_index(struct se_session *se_sess)
@@ -567,7 +567,7 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct
vhost_scsi_tpg *tpg,
 	struct se_session *se_sess;
 	struct scatterlist *sg, *prot_sg;
 	struct page **pages;
-	int tag;
+	int tag, cpu;
 
 	tv_nexus = tpg->tpg_nexus;
 	if (!tv_nexus) {
@@ -576,7 +576,7 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct
vhost_scsi_tpg *tpg,
 	}
 	se_sess = tv_nexus->tvn_se_sess;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
 	if (tag < 0) {
 		pr_err("Unable to obtain tag for vhost_scsi_cmd\n");
 		return ERR_PTR(-ENOMEM);
@@ -591,6 +591,7 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct
vhost_scsi_tpg *tpg,
 	cmd->tvc_prot_sgl = prot_sg;
 	cmd->tvc_upages = pages;
 	cmd->tvc_se_cmd.map_tag = tag;
+	cmd->tvc_se_cmd.map_cpu = cpu;
 	cmd->tvc_tag = scsi_tag;
 	cmd->tvc_lun = lun;
 	cmd->tvc_task_attr = task_attr;
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 7bc88fd43cfc..d2c71b8608f0 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -654,9 +654,9 @@ static struct vscsibk_pend *scsiback_get_pend_req(struct
vscsiif_back_ring *ring
 	struct scsiback_nexus *nexus = tpg->tpg_nexus;
 	struct se_session *se_sess = nexus->tvn_se_sess;
 	struct vscsibk_pend *req;
-	int tag, i;
+	int tag, cpu, i;
 
-	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
 	if (tag < 0) {
 		pr_err("Unable to obtain tag for vscsiif_request\n");
 		return ERR_PTR(-ENOMEM);
@@ -665,6 +665,7 @@ static struct vscsibk_pend *scsiback_get_pend_req(struct
vscsiif_back_ring *ring
 	req = &((struct vscsibk_pend *)se_sess->sess_cmd_map)[tag];
 	memset(req, 0, sizeof(*req));
 	req->se_cmd.map_tag = tag;
+	req->se_cmd.map_cpu = cpu;
 
 	for (i = 0; i < VSCSI_MAX_GRANTS; i++)
 		req->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
@@ -1379,7 +1380,8 @@ static void scsiback_release_cmd(struct se_cmd *se_cmd)
 {
 	struct se_session *se_sess = se_cmd->se_sess;
 
-	percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
+	sbitmap_queue_clear(&se_sess->sess_tag_pool, se_cmd->map_tag,
+			se_cmd->map_cpu);
 }
 
 static u32 scsiback_sess_get_index(struct se_session *se_sess)
diff --git a/include/target/iscsi/iscsi_target_core.h
b/include/target/iscsi/iscsi_target_core.h
index cf5f3fff1f1a..f2e6abea8490 100644
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/include/target/iscsi/iscsi_target_core.h
@@ -4,6 +4,7 @@
 
 #include <linux/dma-direction.h>     /* enum dma_data_direction */
 #include <linux/list.h>              /* struct list_head */
+#include <linux/sched.h>
 #include <linux/socket.h>            /* struct sockaddr_storage */
 #include <linux/types.h>             /* u8 */
 #include <scsi/iscsi_proto.h>        /* itt_t */
diff --git a/include/target/target_core_base.h
b/include/target/target_core_base.h
index 9f9f5902af38..cd417b17fee6 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -4,7 +4,7 @@
 
 #include <linux/configfs.h>      /* struct config_group */
 #include <linux/dma-direction.h> /* enum dma_data_direction */
-#include <linux/percpu_ida.h>    /* struct percpu_ida */
+#include <linux/sbitmap.h>
 #include <linux/percpu-refcount.h>
 #include <linux/semaphore.h>     /* struct semaphore */
 #include <linux/completion.h>
@@ -454,6 +454,7 @@ struct se_cmd {
 	int			sam_task_attr;
 	/* Used for se_sess->sess_tag_pool */
 	unsigned int		map_tag;
+	int			map_cpu;
 	/* Transport protocol dependent state, see transport_state_table */
 	enum transport_state_table t_state;
 	/* See se_cmd_flags_table */
@@ -607,7 +608,7 @@ struct se_session {
 	struct list_head	sess_wait_list;
 	spinlock_t		sess_cmd_lock;
 	void			*sess_cmd_map;
-	struct percpu_ida	sess_tag_pool;
+	struct sbitmap_queue	sess_tag_pool;
 };
 
 struct se_device;
-- 
2.17.0

From: Matthew Wilcox <mawilcox at microsoft.com>

With its one user gone, remove the library code.

Signed-off-by: Matthew Wilcox <mawilcox at microsoft.com>
---
 include/linux/percpu_ida.h |  83 --------
 lib/Makefile               |   2 +-
 lib/percpu_ida.c           | 391 -------------------------------------
 3 files changed, 1 insertion(+), 475 deletions(-)
 delete mode 100644 include/linux/percpu_ida.h
 delete mode 100644 lib/percpu_ida.c

diff --git a/include/linux/percpu_ida.h b/include/linux/percpu_ida.h
deleted file mode 100644
index 07d78e4653bc..000000000000
--- a/include/linux/percpu_ida.h
+++ /dev/null
@@ -1,83 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __PERCPU_IDA_H__
-#define __PERCPU_IDA_H__
-
-#include <linux/types.h>
-#include <linux/bitops.h>
-#include <linux/init.h>
-#include <linux/sched.h>
-#include <linux/spinlock_types.h>
-#include <linux/wait.h>
-#include <linux/cpumask.h>
-
-struct percpu_ida_cpu;
-
-struct percpu_ida {
-	/*
-	 * number of tags available to be allocated, as passed to
-	 * percpu_ida_init()
-	 */
-	unsigned			nr_tags;
-	unsigned			percpu_max_size;
-	unsigned			percpu_batch_size;
-
-	struct percpu_ida_cpu __percpu	*tag_cpu;
-
-	/*
-	 * Bitmap of cpus that (may) have tags on their percpu freelists:
-	 * steal_tags() uses this to decide when to steal tags, and which cpus
-	 * to try stealing from.
-	 *
-	 * It's ok for a freelist to be empty when its bit is set - steal_tags()
-	 * will just keep looking - but the bitmap _must_ be set whenever a
-	 * percpu freelist does have tags.
-	 */
-	cpumask_t			cpus_have_tags;
-
-	struct {
-		spinlock_t		lock;
-		/*
-		 * When we go to steal tags from another cpu (see steal_tags()),
-		 * we want to pick a cpu at random. Cycling through them every
-		 * time we steal is a bit easier and more or less equivalent:
-		 */
-		unsigned		cpu_last_stolen;
-
-		/* For sleeping on allocation failure */
-		wait_queue_head_t	wait;
-
-		/*
-		 * Global freelist - it's a stack where nr_free points to the
-		 * top
-		 */
-		unsigned		nr_free;
-		unsigned		*freelist;
-	} ____cacheline_aligned_in_smp;
-};
-
-/*
- * Number of tags we move between the percpu freelist and the global freelist
at
- * a time
- */
-#define IDA_DEFAULT_PCPU_BATCH_MOVE	32U
-/* Max size of percpu freelist, */
-#define IDA_DEFAULT_PCPU_SIZE	((IDA_DEFAULT_PCPU_BATCH_MOVE * 3) / 2)
-
-int percpu_ida_alloc(struct percpu_ida *pool, int state);
-void percpu_ida_free(struct percpu_ida *pool, unsigned tag);
-
-void percpu_ida_destroy(struct percpu_ida *pool);
-int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
-	unsigned long max_size, unsigned long batch_size);
-static inline int percpu_ida_init(struct percpu_ida *pool, unsigned long
nr_tags)
-{
-	return __percpu_ida_init(pool, nr_tags, IDA_DEFAULT_PCPU_SIZE,
-		IDA_DEFAULT_PCPU_BATCH_MOVE);
-}
-
-typedef int (*percpu_ida_cb)(unsigned, void *);
-int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
-	void *data);
-
-unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu);
-#endif /* __PERCPU_IDA_H__ */
diff --git a/lib/Makefile b/lib/Makefile
index ce20696d5a92..7626dece1d27 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -39,7 +39,7 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o
random32.o \
 	 bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
 	 gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
 	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
-	 percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \
+	 percpu-refcount.o rhashtable.o reciprocal_div.o \
 	 once.o refcount.o usercopy.o errseq.o bucket_locks.o
 obj-$(CONFIG_STRING_SELFTEST) += test_string.o
 obj-y += string_helpers.o
diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c
deleted file mode 100644
index 6016f1deb1f5..000000000000
--- a/lib/percpu_ida.c
+++ /dev/null
@@ -1,391 +0,0 @@
-/*
- * Percpu IDA library
- *
- * Copyright (C) 2013 Datera, Inc. Kent Overstreet
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2, or (at
- * your option) any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- */
-
-#include <linux/mm.h>
-#include <linux/bitmap.h>
-#include <linux/bitops.h>
-#include <linux/bug.h>
-#include <linux/err.h>
-#include <linux/export.h>
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/percpu.h>
-#include <linux/sched/signal.h>
-#include <linux/string.h>
-#include <linux/spinlock.h>
-#include <linux/percpu_ida.h>
-
-struct percpu_ida_cpu {
-	/*
-	 * Even though this is percpu, we need a lock for tag stealing by remote
-	 * CPUs:
-	 */
-	spinlock_t			lock;
-
-	/* nr_free/freelist form a stack of free IDs */
-	unsigned			nr_free;
-	unsigned			freelist[];
-};
-
-static inline void move_tags(unsigned *dst, unsigned *dst_nr,
-			     unsigned *src, unsigned *src_nr,
-			     unsigned nr)
-{
-	*src_nr -= nr;
-	memcpy(dst + *dst_nr, src + *src_nr, sizeof(unsigned) * nr);
-	*dst_nr += nr;
-}
-
-/*
- * Try to steal tags from a remote cpu's percpu freelist.
- *
- * We first check how many percpu freelists have tags
- *
- * Then we iterate through the cpus until we find some tags - we don't
attempt
- * to find the "best" cpu to steal from, to keep cacheline bouncing
to a
- * minimum.
- */
-static inline void steal_tags(struct percpu_ida *pool,
-			      struct percpu_ida_cpu *tags)
-{
-	unsigned cpus_have_tags, cpu = pool->cpu_last_stolen;
-	struct percpu_ida_cpu *remote;
-
-	for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags);
-	     cpus_have_tags; cpus_have_tags--) {
-		cpu = cpumask_next(cpu, &pool->cpus_have_tags);
-
-		if (cpu >= nr_cpu_ids) {
-			cpu = cpumask_first(&pool->cpus_have_tags);
-			if (cpu >= nr_cpu_ids)
-				BUG();
-		}
-
-		pool->cpu_last_stolen = cpu;
-		remote = per_cpu_ptr(pool->tag_cpu, cpu);
-
-		cpumask_clear_cpu(cpu, &pool->cpus_have_tags);
-
-		if (remote == tags)
-			continue;
-
-		spin_lock(&remote->lock);
-
-		if (remote->nr_free) {
-			memcpy(tags->freelist,
-			       remote->freelist,
-			       sizeof(unsigned) * remote->nr_free);
-
-			tags->nr_free = remote->nr_free;
-			remote->nr_free = 0;
-		}
-
-		spin_unlock(&remote->lock);
-
-		if (tags->nr_free)
-			break;
-	}
-}
-
-/*
- * Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them
onto
- * our percpu freelist:
- */
-static inline void alloc_global_tags(struct percpu_ida *pool,
-				     struct percpu_ida_cpu *tags)
-{
-	move_tags(tags->freelist, &tags->nr_free,
-		  pool->freelist, &pool->nr_free,
-		  min(pool->nr_free, pool->percpu_batch_size));
-}
-
-static inline unsigned alloc_local_tag(struct percpu_ida_cpu *tags)
-{
-	int tag = -ENOSPC;
-
-	spin_lock(&tags->lock);
-	if (tags->nr_free)
-		tag = tags->freelist[--tags->nr_free];
-	spin_unlock(&tags->lock);
-
-	return tag;
-}
-
-/**
- * percpu_ida_alloc - allocate a tag
- * @pool: pool to allocate from
- * @state: task state for prepare_to_wait
- *
- * Returns a tag - an integer in the range [0..nr_tags) (passed to
- * tag_pool_init()), or otherwise -ENOSPC on allocation failure.
- *
- * Safe to be called from interrupt context (assuming it isn't passed
- * TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, of course).
- *
- * @gfp indicates whether or not to wait until a free id is available (it's
not
- * used for internal memory allocations); thus if passed __GFP_RECLAIM we may
sleep
- * however long it takes until another thread frees an id (same semantics as a
- * mempool).
- *
- * Will not fail if passed TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE.
- */
-int percpu_ida_alloc(struct percpu_ida *pool, int state)
-{
-	DEFINE_WAIT(wait);
-	struct percpu_ida_cpu *tags;
-	unsigned long flags;
-	int tag;
-
-	local_irq_save(flags);
-	tags = this_cpu_ptr(pool->tag_cpu);
-
-	/* Fastpath */
-	tag = alloc_local_tag(tags);
-	if (likely(tag >= 0)) {
-		local_irq_restore(flags);
-		return tag;
-	}
-
-	while (1) {
-		spin_lock(&pool->lock);
-
-		/*
-		 * prepare_to_wait() must come before steal_tags(), in case
-		 * percpu_ida_free() on another cpu flips a bit in
-		 * cpus_have_tags
-		 *
-		 * global lock held and irqs disabled, don't need percpu lock
-		 */
-		if (state != TASK_RUNNING)
-			prepare_to_wait(&pool->wait, &wait, state);
-
-		if (!tags->nr_free)
-			alloc_global_tags(pool, tags);
-		if (!tags->nr_free)
-			steal_tags(pool, tags);
-
-		if (tags->nr_free) {
-			tag = tags->freelist[--tags->nr_free];
-			if (tags->nr_free)
-				cpumask_set_cpu(smp_processor_id(),
-						&pool->cpus_have_tags);
-		}
-
-		spin_unlock(&pool->lock);
-		local_irq_restore(flags);
-
-		if (tag >= 0 || state == TASK_RUNNING)
-			break;
-
-		if (signal_pending_state(state, current)) {
-			tag = -ERESTARTSYS;
-			break;
-		}
-
-		schedule();
-
-		local_irq_save(flags);
-		tags = this_cpu_ptr(pool->tag_cpu);
-	}
-	if (state != TASK_RUNNING)
-		finish_wait(&pool->wait, &wait);
-
-	return tag;
-}
-EXPORT_SYMBOL_GPL(percpu_ida_alloc);
-
-/**
- * percpu_ida_free - free a tag
- * @pool: pool @tag was allocated from
- * @tag: a tag previously allocated with percpu_ida_alloc()
- *
- * Safe to be called from interrupt context.
- */
-void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
-{
-	struct percpu_ida_cpu *tags;
-	unsigned long flags;
-	unsigned nr_free;
-
-	BUG_ON(tag >= pool->nr_tags);
-
-	local_irq_save(flags);
-	tags = this_cpu_ptr(pool->tag_cpu);
-
-	spin_lock(&tags->lock);
-	tags->freelist[tags->nr_free++] = tag;
-
-	nr_free = tags->nr_free;
-	spin_unlock(&tags->lock);
-
-	if (nr_free == 1) {
-		cpumask_set_cpu(smp_processor_id(),
-				&pool->cpus_have_tags);
-		wake_up(&pool->wait);
-	}
-
-	if (nr_free == pool->percpu_max_size) {
-		spin_lock(&pool->lock);
-
-		/*
-		 * Global lock held and irqs disabled, don't need percpu
-		 * lock
-		 */
-		if (tags->nr_free == pool->percpu_max_size) {
-			move_tags(pool->freelist, &pool->nr_free,
-				  tags->freelist, &tags->nr_free,
-				  pool->percpu_batch_size);
-
-			wake_up(&pool->wait);
-		}
-		spin_unlock(&pool->lock);
-	}
-
-	local_irq_restore(flags);
-}
-EXPORT_SYMBOL_GPL(percpu_ida_free);
-
-/**
- * percpu_ida_destroy - release a tag pool's resources
- * @pool: pool to free
- *
- * Frees the resources allocated by percpu_ida_init().
- */
-void percpu_ida_destroy(struct percpu_ida *pool)
-{
-	free_percpu(pool->tag_cpu);
-	free_pages((unsigned long) pool->freelist,
-		   get_order(pool->nr_tags * sizeof(unsigned)));
-}
-EXPORT_SYMBOL_GPL(percpu_ida_destroy);
-
-/**
- * percpu_ida_init - initialize a percpu tag pool
- * @pool: pool to initialize
- * @nr_tags: number of tags that will be available for allocation
- *
- * Initializes @pool so that it can be used to allocate tags - integers in the
- * range [0, nr_tags). Typically, they'll be used by driver code to refer
to a
- * preallocated array of tag structures.
- *
- * Allocation is percpu, but sharding is limited by nr_tags - for best
- * performance, the workload should not span more cpus than nr_tags / 128.
- */
-int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
-	unsigned long max_size, unsigned long batch_size)
-{
-	unsigned i, cpu, order;
-
-	memset(pool, 0, sizeof(*pool));
-
-	init_waitqueue_head(&pool->wait);
-	spin_lock_init(&pool->lock);
-	pool->nr_tags = nr_tags;
-	pool->percpu_max_size = max_size;
-	pool->percpu_batch_size = batch_size;
-
-	/* Guard against overflow */
-	if (nr_tags > (unsigned) INT_MAX + 1) {
-		pr_err("percpu_ida_init(): nr_tags too large\n");
-		return -EINVAL;
-	}
-
-	order = get_order(nr_tags * sizeof(unsigned));
-	pool->freelist = (void *) __get_free_pages(GFP_KERNEL, order);
-	if (!pool->freelist)
-		return -ENOMEM;
-
-	for (i = 0; i < nr_tags; i++)
-		pool->freelist[i] = i;
-
-	pool->nr_free = nr_tags;
-
-	pool->tag_cpu = __alloc_percpu(sizeof(struct percpu_ida_cpu) +
-				       pool->percpu_max_size * sizeof(unsigned),
-				       sizeof(unsigned));
-	if (!pool->tag_cpu)
-		goto err;
-
-	for_each_possible_cpu(cpu)
-		spin_lock_init(&per_cpu_ptr(pool->tag_cpu, cpu)->lock);
-
-	return 0;
-err:
-	percpu_ida_destroy(pool);
-	return -ENOMEM;
-}
-EXPORT_SYMBOL_GPL(__percpu_ida_init);
-
-/**
- * percpu_ida_for_each_free - iterate free ids of a pool
- * @pool: pool to iterate
- * @fn: interate callback function
- * @data: parameter for @fn
- *
- * Note, this doesn't guarantee to iterate all free ids restrictly. Some
free
- * ids might be missed, some might be iterated duplicated, and some might
- * be iterated and not free soon.
- */
-int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
-	void *data)
-{
-	unsigned long flags;
-	struct percpu_ida_cpu *remote;
-	unsigned cpu, i, err = 0;
-
-	local_irq_save(flags);
-	for_each_possible_cpu(cpu) {
-		remote = per_cpu_ptr(pool->tag_cpu, cpu);
-		spin_lock(&remote->lock);
-		for (i = 0; i < remote->nr_free; i++) {
-			err = fn(remote->freelist[i], data);
-			if (err)
-				break;
-		}
-		spin_unlock(&remote->lock);
-		if (err)
-			goto out;
-	}
-
-	spin_lock(&pool->lock);
-	for (i = 0; i < pool->nr_free; i++) {
-		err = fn(pool->freelist[i], data);
-		if (err)
-			break;
-	}
-	spin_unlock(&pool->lock);
-out:
-	local_irq_restore(flags);
-	return err;
-}
-EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);
-
-/**
- * percpu_ida_free_tags - return free tags number of a specific cpu or global
pool
- * @pool: pool related
- * @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
- *
- * Note: this just returns a snapshot of free tags number.
- */
-unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu)
-{
-	struct percpu_ida_cpu *remote;
-	if (cpu == nr_cpu_ids)
-		return pool->nr_free;
-	remote = per_cpu_ptr(pool->tag_cpu, cpu);
-	return remote->nr_free;
-}
-EXPORT_SYMBOL_GPL(percpu_ida_free_tags);
-- 
2.17.0

On 5/15/18 10:00 AM, Matthew Wilcox wrote:
> From: Matthew Wilcox <mawilcox at microsoft.com>
> 
> The sbitmap and the percpu_ida perform essentially the same task,
> allocating tags for commands.  Since the sbitmap is more used than
> the percpu_ida, convert the percpu_ida users to the sbitmap API.
It should also be the same performance as percpu_ida in light use, and
performs much better at > 50% utilization of the tag space. I think
that's better justification than "more used than".
> diff --git a/drivers/target/iscsi/iscsi_target_util.c
b/drivers/target/iscsi/iscsi_target_util.c
> index 4435bf374d2d..28bcffae609f 100644
> --- a/drivers/target/iscsi/iscsi_target_util.c
> +++ b/drivers/target/iscsi/iscsi_target_util.c
> @@ -17,7 +17,7 @@
>  
******************************************************************************/
>  
>  #include <linux/list.h>
> -#include <linux/percpu_ida.h>
> +#include <linux/sched/signal.h>
>  #include <net/ipv6.h>         /* ipv6_addr_equal() */
>  #include <scsi/scsi_tcq.h>
>  #include <scsi/iscsi_proto.h>
> @@ -147,6 +147,28 @@ void iscsit_free_r2ts_from_list(struct iscsi_cmd *cmd)
>  	spin_unlock_bh(&cmd->r2t_lock);
>  }
>  
> +int iscsit_wait_for_tag(struct se_session *se_sess, int state, int *cpup)
> +{
> +	int tag = -1;
> +	DEFINE_WAIT(wait);
> +	struct sbq_wait_state *ws;
> +
> +	if (state == TASK_RUNNING)
> +		return tag;
> +
> +	ws = &se_sess->sess_tag_pool.ws[0];
> +	for (;;) {
> +		prepare_to_wait_exclusive(&ws->wait, &wait, state);
> +		if (signal_pending_state(state, current))
> +			break;
> +		schedule();
> +		tag = sbitmap_queue_get(&se_sess->sess_tag_pool, cpup);
> +	}
> +
> +	finish_wait(&ws->wait, &wait);
> +	return tag;
> +}
Seems like that should be:


	ws = &se_sess->sess_tag_pool.ws[0];
	for (;;) {
		prepare_to_wait_exclusive(&ws->wait, &wait, state);
		if (signal_pending_state(state, current))
			break;
		tag = sbitmap_queue_get(&se_sess->sess_tag_pool, cpup);
		if (tag != -1)
			break;
		schedule();
	}

	finish_wait(&ws->wait, &wait);
	return tag;
>  /*
>   * May be called from software interrupt (timer) context for allocating
>   * iSCSI NopINs.
> @@ -155,9 +177,11 @@ struct iscsi_cmd *iscsit_allocate_cmd(struct
iscsi_conn *conn, int state)
>  {
>  	struct iscsi_cmd *cmd;
>  	struct se_session *se_sess = conn->sess->se_sess;
> -	int size, tag;
> +	int size, tag, cpu;
>  
> -	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, state);
> +	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);
> +	if (tag < 0)
> +		tag = iscsit_wait_for_tag(se_sess, state, &cpu);
>  	if (tag < 0)
>  		return NULL;
Might make sense to just roll the whole thing into iscsi_get_tag(), that
would be cleaner.

sbitmap should provide a helper for that, but we can do that cleanup
later. That would encapsulate things like the per-cpu caching hint too,
for instance.

Rest looks fine to me.

-- 
Jens Axboe

Fixes: 5aff7a710f13 ("Convert target drivers to use sbitmap")
Signed-off-by: Fengguang Wu <fengguang.wu at intel.com>
---
 iscsi_target_util.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/target/iscsi/iscsi_target_util.c
b/drivers/target/iscsi/iscsi_target_util.c
index 28bcffa..e147aef 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -147,7 +147,7 @@ void iscsit_free_r2ts_from_list(struct iscsi_cmd *cmd)
 	spin_unlock_bh(&cmd->r2t_lock);
 }
 
-int iscsit_wait_for_tag(struct se_session *se_sess, int state, int *cpup)
+static int iscsit_wait_for_tag(struct se_session *se_sess, int state, int
*cpup)
 {
 	int tag = -1;
 	DEFINE_WAIT(wait);

Hi Matthew,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.17-rc5 next-20180516]
[cannot apply to target/master]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system]

url:   
https://github.com/0day-ci/linux/commits/Matthew-Wilcox/Use-sbitmap-instead-of-percpu_ida/20180516-143658
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)
>> drivers/target/iscsi/iscsi_target_util.c:150:5: sparse: symbol
'iscsit_wait_for_tag' was not declared. Should it be static?
   drivers/target/iscsi/iscsi_target_util.c:1174:31: sparse: expression using
sizeof(void)
   drivers/target/iscsi/iscsi_target_util.c:1174:31: sparse: expression using
sizeof(void)

Please review and possibly fold the followup patch.

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

On Tue, 2018-05-15 at 09:00 -0700, Matthew Wilcox wrote:
> diff --git a/drivers/scsi/qla2xxx/qla_target.c
b/drivers/scsi/qla2xxx/qla_target.c
> index 025dc2d3f3de..cdf671c2af61 100644
> --- a/drivers/scsi/qla2xxx/qla_target.c
> +++ b/drivers/scsi/qla2xxx/qla_target.c
> @@ -3719,7 +3719,8 @@ void qlt_free_cmd(struct qla_tgt_cmd *cmd)
>  		return;
>  	}
>  	cmd->jiffies_at_free = get_jiffies_64();
> -	percpu_ida_free(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag);
> +	sbitmap_queue_clear(&sess->se_sess->sess_tag_pool,
cmd->se_cmd.map_tag,
> +			cmd->se_cmd.map_cpu);
>  }
>  EXPORT_SYMBOL(qlt_free_cmd);
Please introduce functions in the target core for allocating and freeing a tag
instead of spreading the knowledge of how to allocate and free tags over all
target drivers.
 
> +int iscsit_wait_for_tag(struct se_session *se_sess, int state, int *cpup)
> +{
> +	int tag = -1;
> +	DEFINE_WAIT(wait);
> +	struct sbq_wait_state *ws;
> +
> +	if (state == TASK_RUNNING)
> +		return tag;
> +
> +	ws = &se_sess->sess_tag_pool.ws[0];
> +	for (;;) {
> +		prepare_to_wait_exclusive(&ws->wait, &wait, state);
> +		if (signal_pending_state(state, current))
> +			break;
This looks weird to me. Shouldn't target code ignore signals instead of
causing
tag allocation to fail if a signal is received?
> +		schedule();
> +		tag = sbitmap_queue_get(&se_sess->sess_tag_pool, cpup);
> +	}
> +
> +	finish_wait(&ws->wait, &wait);
> +	return tag;
> +}
Thanks,

Bart.