Tgtd illustration
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This document illustrates the general architecture and data flow of tgtd, the iSCSI target daemon. It shows how tgtd handles iSCSI requests from initiators and processes SCSI commands by communicating with low-level driver routines and backing storage devices like mmc, osd, and sbc. Management tasks like login, logout, and error handling are also depicted.
![SCSI Cmd Processing In target.c, scsi.c, & devs
cmd_perform ==
scsi_cmd_perfor
scsi_cmd_queued
Processed later
dev_type_template.ops[op]. cmd_perfor
sbc_rw, sbc_sync_cache BS
Others processed in sbc.c or spc.c
Tuesday, November 8, 11 7](https://image.slidesharecdn.com/tgtd-111107190646-phpapp01/85/Tgtd-illustration-7-320.jpg)
Tgtd illustration
- 1. tgtd illustration based on https://github.com/fujita/tgt Tuesday, November 8, 11 1
- 2. General Arch epoll iSCSI, iSER, bst: aio, rdwr, FCoE, etc. null, sg, ssc low level backing initiator drivers con stores n R &W target mmc, osd, Core sbc, scc, smc, ssc lu SC a sk SI mt spc & tgtadm mgmt devices utils, common Tuesday, November 8, 11 2
- 3. Mgmt Routine If req Len> tgtadm_req tgt_mgmt tgtadm send commands here mtask_handler HDR_RECV sys_mgmt PDU_RECV target_mgmt IPC: mgmt_task portal_mgmt device_mgmt mtask_handler RSP_SEND account_mgmt connection_mgmt Tuesday, November 8, 11 3
- 4. State Transition of Conn Security Security Security auth Done Free Security login Security Login Login full full Only for iSER Init Start Full Kernel Ready Network Error Proto Error Logout Exit Close Scsi Tuesday, November 8, 11 4
- 5. Cmd rx in iscsid 1 Immediate: OpXX iscsi_task_queue iscsi_task_ececute Other: OP_DATA_OUT expected SNs: iscsi_task_execute Others: iscsi_task_ececute Add to pending list NOOP_OUT/LOGOUT: Set EPOLLIN|EPOLLOUT queue: SCSI_CMD: target_cmd_queue ... target.c iscsi_scsi_cmd_execute all: SCSI_TMFUNC: Set EPOLLIN|EPOLLOUT iscsi_tm_execute target_mgmt_request ... target.c Tuesday, November 8, 11 5
- 6. Cmd rx in iscsid 2 OpXX OP_DATA_OUT iscsi_data_out_rx_done Do nothing FINAL && not pending: iscsi_scsi_cmd_execute ... as in prev page Tuesday, November 8, 11 6
- 7. SCSI Cmd Processing In target.c, scsi.c, & devs cmd_perform == scsi_cmd_perfor scsi_cmd_queued Processed later dev_type_template.ops[op]. cmd_perfor sbc_rw, sbc_sync_cache BS Others processed in sbc.c or spc.c Tuesday, November 8, 11 7
- 8. Backing Storage bs_init bs_thread_info follows lu Create LU bs_open pathname, fd, size Dev request bs_cmd_submit(cmd) Destroy LU bs_close, bs_exit Tuesday, November 8, 11 8
- 9. That's All. Thanks! Tuesday, November 8, 11 9