[stgt] RFC [PATCH] Implement PERSISTENT RESERVE IN/OUT

[Arne Redlich]

[dropping stgt-devel at berlios]

Am Mittwoch, den 20.08.2008, 15:01 +1000 schrieb Mark Harvey:
> Apologies for sending as an attachment... gmail and all.
> 
> This is an initial attempt to implement PERSISTENT RESERVE IN and
> PERSISTENT RESERVE OUT.
> 
> Currently only READ KEY service action will actually return anything.
> It returns a hard-coded 'ABC1234'.
> 
> This post is a request for comment before I get too far into coding effort.
> 
> # lsscsi -g
> [3:0:0:0]    disk    USB-HS   HTS726060M9AT00  0.01  /dev/sda  /dev/sg0
> [7:0:0:0]    storage IET      Controller       0001  -         /dev/sg1
> [7:0:0:1]    disk    QUANTUM  HD100            0010  /dev/sdb  /dev/sg2
> [7:0:0:2]    tape    QUANTUM  DLT6000          0010  /dev/st0  /dev/sg3
> [7:0:0:3]    tape    QUANTUM  DLT6000          0010  /dev/st1  /dev/sg4
> [7:0:0:4]    tape    QUANTUM  DLT6000          0010  /dev/st2  /dev/sg5
> [7:0:0:5]    mediumx STK      L700             0010  -         /dev/sg6
> 
> # sg_persist -i /dev/sg3
> >> No service action given; assume Persistent Reservations In command
> >> with Read Keys service action
>   QUANTUM  DLT6000  0010
>   Peripheral device type: tape
>   PR generation=0x0, 4 registered reservation keys follow:
>     0x4142433132333400
>     0x0
>     0x0
>     0x0
> 
> 
> I'll include in-line for viewing pleasure :)
> 
> [PATCH 1/2]
> From 11ad9ee209708f51bd2884598d309b1e7079cdce Mon Sep 17 00:00:00 2001
> From: Mark Harvey <markh794 at gmail.com>
> Date: Wed, 20 Aug 2008 14:42:27 +1000
> Subject: RFC - Implement PERSISTENT RESERVE IN/OUT
> 
> Implement service action 'READ KEY' which returns
> a hard-coded string 'ABC1234'
> 
> Signed-off-by: Mark Harvey <markh794 at gmail.com>
> ---
>  usr/scsi.h |    5 ++
>  usr/spc.c  |  231 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  usr/spc.h  |    2 +
>  usr/tgtd.h |   13 ++++
>  4 files changed, 251 insertions(+), 0 deletions(-)
> 
> diff --git a/usr/scsi.h b/usr/scsi.h
> index 84fadff..a9481a1 100644
> --- a/usr/scsi.h
> +++ b/usr/scsi.h
> @@ -208,6 +208,11 @@
>  #define ASC_POSITION_PAST_BOM			0x3b0c
>  #define ASC_MEDIUM_REMOVAL_PREVENTED		0x5302
>  #define ASC_BAD_MICROCODE_DETECTED		0x8283
> +#define ASC_INSUFFICENT_RESERVE_RESOURCE	0x5502
> +#define ASC_INSUFFICENT_RESOURCE		0x5503
> +#define ASC_INSUFFICENT_REGISTRAT_RESOURCE	0x5504
> +#define ASC_INSUFFICENT_AC_RESOURCE		0x5505
> +#define ASC_AUX_MEMORY_OUT_OF_SPACE		0x5506
> 
>  /* Key 6: Unit Attention */
>  #define ASC_NOT_READY_TO_TRANSITION		0x2800
> diff --git a/usr/spc.c b/usr/spc.c
> index bd2c975..cc088bf 100644
> --- a/usr/spc.c
> +++ b/usr/spc.c
> @@ -880,6 +880,237 @@ void dump_cdb(struct scsi_cmd *cmd)
>  	}
>  }
> 
> +/**
> + * SCSI Persistent Reservation
> + *
> + * Reference: spc4r16 Ch 5.7

Though I'm not sure it will differ at all in this area, but SPC-3 should
be used as reference when implementing it - cf. spc_inquiry().

[snip]

> +struct scsi_pr {
> +	/* Persistent Reservation Generation */
> +	uint32_t PRgeneration;
> +	uint8_t pr_key[PR_RESERVATION_SZ][PR_KEY_SZ];
> +};
> +

Too bad the most interesting part is missing - an efficient way to
lookup the registered keys. I could imagine using a hashtable, but then
again finding a good hash function is not easy - (u64)key % tablesize
possibly? So:

struct scsi_pr_key {
	struct list_head entry;
	uint8_t key[8];
	struct it_nexus *itn;
};

>  struct scsi_lu {
>  	int fd;
>  	uint64_t addr; /* persistent mapped address */
> @@ -150,6 +161,8 @@ struct scsi_lu {
>  	uint8_t	mode_block_descriptor[BLOCK_DESCRIPTOR_LEN];
>  	struct mode_pg *mode_pgs[0x3f];
> 
> +	struct scsi_pr pr;
> +
	struct list_head pr_keys[PR_HT_SIZE];


>  	struct lu_phy_attr attrs;
> 
>  	/* A pointer for each modules private use.

Cheers,
Arne

--
To unsubscribe from this list: send the line "unsubscribe stgt" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html