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scsi: target: Convert target drivers to use sbitmap

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The sbitmap and the percpu_ida perform essentially the same task,
allocating tags for commands.  The sbitmap outperforms the percpu_ida as
documented here: https://lkml.org/lkml/2014/4/22/553

The sbitmap interface is a little harder to use, but being able to remove
the percpu_ida code and getting better performance justifies the additional
complexity.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>	# f_tcm
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Matthew Wilcox
2018-06-12 12:05:44 -07:00
committed by Martin K. Petersen
parent 83c2b54b92
commit 10e9cbb6b5
10 changed files with 59 additions and 24 deletions
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33
drivers/target/iscsi/iscsi_target_util.c
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@@ -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 +147,30 @@ void iscsit_free_r2ts_from_list(struct iscsi_cmd *cmd)
spin_unlock_bh(&cmd->r2t_lock);
}
static 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;
tag = sbitmap_queue_get(&se_sess->sess_tag_pool, cpup);
if (tag >= 0)
break;
schedule();
}
finish_wait(&ws->wait, &wait);
return tag;
}
/*
* May be called from software interrupt (timer) context for allocating
* iSCSI NopINs.
@@ -155,9 +179,11 @@ 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 +192,7 @@ 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);