659743b02c
Replace the session lock with two locks, a forward lock and a backwards lock named frwd_lock and back_lock respectively. The forward lock protects resources that change while sending a request to the target, such as cmdsn, queued_cmdsn, and allocating task from the commands' pool with kfifo_out. The backward lock protects resources that change while processing a response or in error path, such as cmdsn_exp, cmdsn_max, and returning tasks to the commands' pool with kfifo_in. Under a steady state fast-path situation, that is when one or more processes/threads submit IO to an iscsi device and a single kernel upcall (e.g softirq) is dealing with processing of responses without errors, this patch eliminates the contention between the queuecommand()/request response/scsi_done() flows associated with iscsi sessions. Between the forward and the backward locks exists a strict locking hierarchy. The mutual exclusion zone protected by the forward lock can enclose the mutual exclusion zone protected by the backward lock but not vice versa. For example, in iscsi_conn_teardown or in iscsi_xmit_data when there is a failure and __iscsi_put_task is called, the backward lock is taken while the forward lock is still taken. On the other hand, if in the RX path a nop is to be sent, for example in iscsi_handle_reject or __iscsi_complete_pdu than the forward lock is released and the backward lock is taken for the duration of iscsi_send_nopout, later the backward lock is released and the forward lock is retaken. libiscsi_tcp uses two kernel fifos the r2t pool and the r2t queue. The insertion and deletion from these queues didn't corespond to the assumption taken by the new forward/backwards session locking paradigm. That is, in iscsi_tcp_clenup_task which belongs to the RX (backwards) path, r2t is taken out from r2t queue and inserted to the r2t pool. In iscsi_tcp_get_curr_r2t which belong to the TX (forward) path, r2t is also inserted to the r2t pool and another r2t is pulled from r2t queue. Only in iscsi_tcp_r2t_rsp which is called in the RX path but can requeue to the TX path, r2t is taken from the r2t pool and inserted to the r2t queue. In order to cope with this situation, two spin locks were added, pool2queue and queue2pool. The former protects extracting from the r2t pool and inserting to the r2t queue, and the later protects the extracing from the r2t queue and inserting to the r2t pool. Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com> Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com> [minor fix up to apply cleanly and compile fix] Signed-off-by: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: James Bottomley <JBottomley@Parallels.com>
136 lines
4.3 KiB
C
136 lines
4.3 KiB
C
/*
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* iSCSI over TCP/IP Data-Path lib
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*
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* Copyright (C) 2008 Mike Christie
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* Copyright (C) 2008 Red Hat, Inc. All rights reserved.
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* maintained by open-iscsi@googlegroups.com
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* See the file COPYING included with this distribution for more details.
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*/
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#ifndef LIBISCSI_TCP_H
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#define LIBISCSI_TCP_H
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#include <scsi/libiscsi.h>
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struct iscsi_tcp_conn;
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struct iscsi_segment;
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struct sk_buff;
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struct hash_desc;
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typedef int iscsi_segment_done_fn_t(struct iscsi_tcp_conn *,
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struct iscsi_segment *);
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struct iscsi_segment {
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unsigned char *data;
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unsigned int size;
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unsigned int copied;
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unsigned int total_size;
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unsigned int total_copied;
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struct hash_desc *hash;
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unsigned char padbuf[ISCSI_PAD_LEN];
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unsigned char recv_digest[ISCSI_DIGEST_SIZE];
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unsigned char digest[ISCSI_DIGEST_SIZE];
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unsigned int digest_len;
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struct scatterlist *sg;
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void *sg_mapped;
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unsigned int sg_offset;
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bool atomic_mapped;
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iscsi_segment_done_fn_t *done;
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};
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/* Socket connection receive helper */
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struct iscsi_tcp_recv {
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struct iscsi_hdr *hdr;
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struct iscsi_segment segment;
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/* Allocate buffer for BHS + AHS */
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uint32_t hdr_buf[64];
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/* copied and flipped values */
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int datalen;
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};
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struct iscsi_tcp_conn {
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struct iscsi_conn *iscsi_conn;
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void *dd_data;
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int stop_stage; /* conn_stop() flag: *
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* stop to recover, *
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* stop to terminate */
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/* control data */
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struct iscsi_tcp_recv in; /* TCP receive context */
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/* CRC32C (Rx) LLD should set this is they do not offload */
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struct hash_desc *rx_hash;
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};
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struct iscsi_tcp_task {
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uint32_t exp_datasn; /* expected target's R2TSN/DataSN */
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int data_offset;
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struct iscsi_r2t_info *r2t; /* in progress solict R2T */
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struct iscsi_pool r2tpool;
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struct kfifo r2tqueue;
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void *dd_data;
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spinlock_t pool2queue;
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spinlock_t queue2pool;
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};
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enum {
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ISCSI_TCP_SEGMENT_DONE, /* curr seg has been processed */
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ISCSI_TCP_SKB_DONE, /* skb is out of data */
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ISCSI_TCP_CONN_ERR, /* iscsi layer has fired a conn err */
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ISCSI_TCP_SUSPENDED, /* conn is suspended */
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};
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extern void iscsi_tcp_hdr_recv_prep(struct iscsi_tcp_conn *tcp_conn);
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extern int iscsi_tcp_recv_skb(struct iscsi_conn *conn, struct sk_buff *skb,
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unsigned int offset, bool offloaded, int *status);
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extern void iscsi_tcp_cleanup_task(struct iscsi_task *task);
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extern int iscsi_tcp_task_init(struct iscsi_task *task);
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extern int iscsi_tcp_task_xmit(struct iscsi_task *task);
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/* segment helpers */
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extern int iscsi_tcp_recv_segment_is_hdr(struct iscsi_tcp_conn *tcp_conn);
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extern int iscsi_tcp_segment_done(struct iscsi_tcp_conn *tcp_conn,
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struct iscsi_segment *segment, int recv,
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unsigned copied);
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extern void iscsi_tcp_segment_unmap(struct iscsi_segment *segment);
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extern void iscsi_segment_init_linear(struct iscsi_segment *segment,
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void *data, size_t size,
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iscsi_segment_done_fn_t *done,
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struct hash_desc *hash);
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extern int
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iscsi_segment_seek_sg(struct iscsi_segment *segment,
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struct scatterlist *sg_list, unsigned int sg_count,
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unsigned int offset, size_t size,
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iscsi_segment_done_fn_t *done, struct hash_desc *hash);
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/* digest helpers */
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extern void iscsi_tcp_dgst_header(struct hash_desc *hash, const void *hdr,
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size_t hdrlen,
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unsigned char digest[ISCSI_DIGEST_SIZE]);
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extern struct iscsi_cls_conn *
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iscsi_tcp_conn_setup(struct iscsi_cls_session *cls_session, int dd_data_size,
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uint32_t conn_idx);
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extern void iscsi_tcp_conn_teardown(struct iscsi_cls_conn *cls_conn);
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/* misc helpers */
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extern int iscsi_tcp_r2tpool_alloc(struct iscsi_session *session);
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extern void iscsi_tcp_r2tpool_free(struct iscsi_session *session);
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extern int iscsi_tcp_set_max_r2t(struct iscsi_conn *conn, char *buf);
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extern void iscsi_tcp_conn_get_stats(struct iscsi_cls_conn *cls_conn,
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struct iscsi_stats *stats);
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#endif /* LIBISCSI_TCP_H */
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