[PATCH] scsi_debug: implement IMMED bit

[PATCH] scsi_debug: implement IMMED bit

[Douglas Gilbert]

The start stop unit command takes in the order of a second to complete
on some SAS SSDs and longer on hard disks. Synchronize cache can also
take some time. Both commands have an IMMED bit for those apps that don't
want to wait. This patch introduces a long delay for those commands
when the IMMED bit is clear.

Changes:
  - add the SYNCHRONIZE CACHE(16) command
  - together with the existing START STOP UNIT and SYNCHRONIZE CACHE(10)
    commands process the IMMED bit in their cdbs
  - if the IMMED bit is set, return immediately
  - if the IMMED bit is clear, treat the delay parameter as having
    a unit of one second
  - in the SYNCHRONIZE CACHE processing do a bounds check

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
---
 drivers/scsi/scsi_debug.c | 76 ++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 65 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index a5986dae9020..0996fcb8a8d2 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -6,7 +6,7 @@
  *  anything out of the ordinary is seen.
  * ^^^^^^^^^^^^^^^^^^^^^^^ Original ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  *
- * Copyright (C) 2001 - 2017 Douglas Gilbert
+ * Copyright (C) 2001 - 2018 Douglas Gilbert
  *
  * 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
@@ -61,8 +61,8 @@
 #include "scsi_logging.h"
 
 /* make sure inq_product_rev string corresponds to this version */
-#define SDEBUG_VERSION "0187"	/* format to fit INQUIRY revision field */
-static const char *sdebug_version_date = "20171202";
+#define SDEBUG_VERSION "0188"	/* format to fit INQUIRY revision field */
+static const char *sdebug_version_date = "20180128";
 
 #define MY_NAME "scsi_debug"
 
@@ -234,6 +234,7 @@ static const char *sdebug_version_date = "20171202";
 #define F_INV_OP		0x200
 #define F_FAKE_RW		0x400
 #define F_M_ACCESS		0x800	/* media access */
+#define F_LONG_DELAY		0x1000
 
 #define FF_RESPOND (F_RL_WLUN_OK | F_SKIP_UA | F_DELAY_OVERR)
 #define FF_MEDIA_IO (F_M_ACCESS | F_FAKE_RW)
@@ -349,7 +350,7 @@ enum sdeb_opcode_index {
 	SDEB_I_XDWRITEREAD = 25,	/* 10 only */
 	SDEB_I_WRITE_BUFFER = 26,
 	SDEB_I_WRITE_SAME = 27,		/* 10, 16 */
-	SDEB_I_SYNC_CACHE = 28,		/* 10 only */
+	SDEB_I_SYNC_CACHE = 28,		/* 10, 16 */
 	SDEB_I_COMP_WRITE = 29,
 	SDEB_I_LAST_ELEMENT = 30,	/* keep this last (previous + 1) */
 };
@@ -382,7 +383,7 @@ static const unsigned char opcode_ind_arr[256] = {
 /* 0x80; 0x80->0x9f: 16 byte cdbs */
 	0, 0, 0, 0, 0, SDEB_I_ATA_PT, 0, 0,
 	SDEB_I_READ, SDEB_I_COMP_WRITE, SDEB_I_WRITE, 0, 0, 0, 0, 0,
-	0, 0, 0, SDEB_I_WRITE_SAME, 0, 0, 0, 0,
+	0, SDEB_I_SYNC_CACHE, 0, SDEB_I_WRITE_SAME, 0, 0, 0, 0,
 	0, 0, 0, 0, 0, 0, SDEB_I_SERV_ACT_IN_16, SDEB_I_SERV_ACT_OUT_16,
 /* 0xa0; 0xa0->0xbf: 12 byte cdbs */
 	SDEB_I_REPORT_LUNS, SDEB_I_ATA_PT, 0, SDEB_I_MAINT_IN,
@@ -398,6 +399,14 @@ static const unsigned char opcode_ind_arr[256] = {
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 };
 
+/*
+ * The following "response" functions return the SCSI mid-level's 4 byte
+ * tuple-in-an-int. To handle commands with an IMMED bit, for a faster
+ * command completion, they can mask their return value with
+ * SDEG_RES_IMMED_MASK .
+ */
+#define SDEG_RES_IMMED_MASK 0x40000000
+
 static int resp_inquiry(struct scsi_cmnd *, struct sdebug_dev_info *);
 static int resp_report_luns(struct scsi_cmnd *, struct sdebug_dev_info *);
 static int resp_requests(struct scsi_cmnd *, struct sdebug_dev_info *);
@@ -420,6 +429,7 @@ static int resp_write_same_16(struct scsi_cmnd *, struct sdebug_dev_info *);
 static int resp_xdwriteread_10(struct scsi_cmnd *, struct sdebug_dev_info *);
 static int resp_comp_write(struct scsi_cmnd *, struct sdebug_dev_info *);
 static int resp_write_buffer(struct scsi_cmnd *, struct sdebug_dev_info *);
+static int resp_sync_cache(struct scsi_cmnd *, struct sdebug_dev_info *);
 
 /*
  * The following are overflow arrays for cdbs that "hit" the same index in
@@ -499,6 +509,12 @@ static const struct opcode_info_t release_iarr[] = {
 	    {6,  0x1f, 0xff, 0, 0, 0xc7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0} },
 };
 
+static const struct opcode_info_t sync_cache_iarr[] = {
+	{0, 0x91, 0, F_LONG_DELAY | F_M_ACCESS, resp_sync_cache, NULL,
+	    {16,  0x7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	     0xff, 0xff, 0xff, 0xff, 0x3f, 0xc7} },	/* SYNC_CACHE (16) */
+};
+
 
 /* This array is accessed via SDEB_I_* values. Make sure all are mapped,
  * plus the terminating elements for logic that scans this table such as
@@ -536,8 +552,8 @@ static const struct opcode_info_t opcode_info_arr[SDEB_I_LAST_ELEMENT + 1] = {
 	{ARRAY_SIZE(write_iarr), 0x8a, 0, F_D_OUT | FF_MEDIA_IO,
 	    resp_write_dt0, write_iarr,			/* WRITE(16) */
 		{16,  0xfa, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-		 0xff, 0xff, 0xff, 0xff, 0xff, 0xc7} },		/* WRITE(16) */
-	{0, 0x1b, 0, 0, resp_start_stop, NULL,		/* START STOP UNIT */
+		 0xff, 0xff, 0xff, 0xff, 0xff, 0xc7} },
+	{0, 0x1b, 0, F_LONG_DELAY, resp_start_stop, NULL,/* START STOP UNIT */
 	    {6,  0x1, 0, 0xf, 0xf7, 0xc7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0} },
 	{ARRAY_SIZE(sa_in_16_iarr), 0x9e, 0x10, F_SA_LOW | F_D_IN,
 	    resp_readcap16, sa_in_16_iarr, /* SA_IN(16), READ CAPACITY(16) */
@@ -590,9 +606,10 @@ static const struct opcode_info_t opcode_info_arr[SDEB_I_LAST_ELEMENT + 1] = {
 	    resp_write_same_10, write_same_iarr,	/* WRITE SAME(10) */
 		{10,  0xff, 0xff, 0xff, 0xff, 0xff, 0x3f, 0xff, 0xff, 0xc7, 0,
 		 0, 0, 0, 0, 0} },
-	{0, 0x35, 0, F_DELAY_OVERR | FF_MEDIA_IO, NULL, NULL, /* SYNC_CACHE */
+	{ARRAY_SIZE(sync_cache_iarr), 0x35, 0, F_LONG_DELAY | F_M_ACCESS,
+	    resp_sync_cache, sync_cache_iarr,
 	    {10,  0x7, 0xff, 0xff, 0xff, 0xff, 0x3f, 0xff, 0xff, 0xc7, 0, 0,
-	     0, 0, 0, 0} },
+	     0, 0, 0, 0} },			/* SYNC_CACHE (10) */
 	{0, 0x89, 0, F_D_OUT | FF_MEDIA_IO, resp_comp_write, NULL,
 	    {16,  0xf8, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 0,
 	     0, 0xff, 0x3f, 0xc7} },		/* COMPARE AND WRITE */
@@ -1597,7 +1614,7 @@ static int resp_start_stop(struct scsi_cmnd * scp,
 	}
 	stop = !(cmd[4] & 1);
 	atomic_xchg(&devip->stopped, stop);
-	return 0;
+	return (cmd[1] & 0x1) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */
 }
 
 static sector_t get_sdebug_capacity(void)
@@ -3562,6 +3579,27 @@ static int resp_get_lba_status(struct scsi_cmnd *scp,
 	return fill_from_dev_buffer(scp, arr, SDEBUG_GET_LBA_STATUS_LEN);
 }
 
+static int resp_sync_cache(struct scsi_cmnd *scp,
+			   struct sdebug_dev_info *devip)
+{
+	u64 lba;
+	u32 num_blocks;
+	u8 *cmd = scp->cmnd;
+
+	if (cmd[0] == SYNCHRONIZE_CACHE) {	/* 10 byte cdb */
+		lba = get_unaligned_be32(cmd + 2);
+		num_blocks = get_unaligned_be16(cmd + 7);
+	} else {				/* SYNCHRONIZE_CACHE(16) */
+		lba = get_unaligned_be64(cmd + 2);
+		num_blocks = get_unaligned_be32(cmd + 10);
+	}
+	if (lba + num_blocks > sdebug_capacity) {
+		mk_sense_buffer(scp, ILLEGAL_REQUEST, LBA_OUT_OF_RANGE, 0);
+		return check_condition_result;
+	}
+	return (cmd[1] & 0x2) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */
+}
+
 #define RL_BUCKET_ELEMS 8
 
 /* Even though each pseudo target has a REPORT LUNS "well known logical unit"
@@ -5717,11 +5755,27 @@ static int scsi_debug_queuecommand(struct Scsi_Host *shost,
 		errsts = oip->pfp(scp, devip);	/* calls a resp_* function */
 	else if (r_pfp)	/* if leaf function ptr NULL, try the root's */
 		errsts = r_pfp(scp, devip);
+	if (errsts & SDEG_RES_IMMED_MASK) {
+		errsts &= ~SDEG_RES_IMMED_MASK;
+		flags |= F_DELAY_OVERR;
+		flags &= ~F_LONG_DELAY;
+	}
+
 
 fini:
 	if (F_DELAY_OVERR & flags)
 		return schedule_resp(scp, devip, errsts, 0, 0);
-	else
+	else if ((sdebug_jdelay || sdebug_ndelay) && (flags & F_LONG_DELAY)) {
+		/*
+		 * If any delay is active, want F_LONG_DELAY to be at least 1
+		 * second and if sdebug_jdelay>0 want a long delay of that
+		 * many seconds.
+		 */
+		int jdelay = (sdebug_jdelay < 2) ? 1 : sdebug_jdelay;
+
+		jdelay = mult_frac(USER_HZ * jdelay, HZ, USER_HZ);
+		return schedule_resp(scp, devip, errsts, jdelay, 0);
+	} else
 		return schedule_resp(scp, devip, errsts, sdebug_jdelay,
 				     sdebug_ndelay);
 check_cond:
-- 
2.14.1

Re: [PATCH] scsi_debug: implement IMMED bit

[Bart Van Assche]

On 01/29/18 21:54, Douglas Gilbert wrote:
> +static const struct opcode_info_t sync_cache_iarr[] = {
> +	{0, 0x91, 0, F_LONG_DELAY | F_M_ACCESS, resp_sync_cache, NULL,
> +	    {16,  0x7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
                   ^^^
Can you clarify the choice of "0x7" in the above? After having had a 
look at SBC-4 I was expecting 0x2 (the mask for the IMMED bit) since all 
other bits in that command byte are either reserved or obsolete.

> -	return 0;
> +	return (cmd[1] & 0x1) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */

Shouldn't the mask 0x2 be used to check for the IMMED bit?

Thanks,

Bart.

Re: [PATCH] scsi_debug: implement IMMED bit

[Douglas Gilbert]

On 2018-01-31 12:06 PM, Bart Van Assche wrote:
> On 01/29/18 21:54, Douglas Gilbert wrote:
>> +static const struct opcode_info_t sync_cache_iarr[] = {
>> +    {0, 0x91, 0, F_LONG_DELAY | F_M_ACCESS, resp_sync_cache, NULL,
>> +        {16,  0x7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
>                    ^^^
> Can you clarify the choice of "0x7" in the above? After having had a look at 
> SBC-4 I was expecting 0x2 (the mask for the IMMED bit) since all other bits in 
> that command byte are either reserved or obsolete.

As a general rule when you see "obsolete" that means that field was used
in an earlier standard (bit 0 was RELADDR and bit 2 was SYNC_NV). So
application clients complying with earlier versions of SBC might set those
bits. If they are set and the mask is being enforced I choose to not fail
the command as an illegal request. Basically accept and ignore.

>> -    return 0;
>> +    return (cmd[1] & 0x1) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */
> 
> Shouldn't the mask 0x2 be used to check for the IMMED bit?

That comment needs a little more context:

@@ -1597,7 +1614,7 @@ static int resp_start_stop(struct scsi_cmnd * scp,
         }
         stop = !(cmd[4] & 1);
         atomic_xchg(&devip->stopped, stop);
-       return 0;
+       return (cmd[1] & 0x1) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */


For START STOP UNIT the IMMED flag is byte 1, bit 0. So that code
is correct IMO.


And for SYNCHRONIZE CACHE(10 and 16) the IMMED flag is byte 1 bit 1
so the corresponding return statement is:

+       return (cmd[1] & 0x2) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */


Doug Gilbert

Re: [PATCH] scsi_debug: implement IMMED bit

[Bart Van Assche]

On Wed, 2018-01-31 at 15:26 -0500, Douglas Gilbert wrote:
> On 2018-01-31 12:06 PM, Bart Van Assche wrote:
> > On 01/29/18 21:54, Douglas Gilbert wrote:
> > > +static const struct opcode_info_t sync_cache_iarr[] = {
> > > +    {0, 0x91, 0, F_LONG_DELAY | F_M_ACCESS, resp_sync_cache, NULL,
> > > +        {16,  0x7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
> > 
> >                    ^^^
> > Can you clarify the choice of "0x7" in the above? After having had a look at 
> > SBC-4 I was expecting 0x2 (the mask for the IMMED bit) since all other bits in 
> > that command byte are either reserved or obsolete.
> 
> As a general rule when you see "obsolete" that means that field was used
> in an earlier standard (bit 0 was RELADDR and bit 2 was SYNC_NV). So
> application clients complying with earlier versions of SBC might set those
> bits. If they are set and the mask is being enforced I choose to not fail
> the command as an illegal request. Basically accept and ignore.

I agree with setting bits for obsolete flags. The reason I was asking about that
mask is because I found the following in SBC-4 for byte 1 of SYNCHRONIZE CACHE(16):
* Bits 7..3: reserved.
* Bit 2: obsolete.
* Bit 1: IMMED.
* Bit 0: reserved.

> > > -    return 0;
> > > +    return (cmd[1] & 0x1) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */
> > 
> > Shouldn't the mask 0x2 be used to check for the IMMED bit?
> 
> That comment needs a little more context:

Sorry, I confused byte 1 of the START STOP command with that of the SYNCHRONIZE
CACHE command so please ignore the above comment.

Bart.

Re: [PATCH] scsi_debug: implement IMMED bit

[Douglas Gilbert]

On 2018-01-31 05:05 PM, Bart Van Assche wrote:
> On Wed, 2018-01-31 at 15:26 -0500, Douglas Gilbert wrote:
>> On 2018-01-31 12:06 PM, Bart Van Assche wrote:
>>> On 01/29/18 21:54, Douglas Gilbert wrote:
>>>> +static const struct opcode_info_t sync_cache_iarr[] = {
>>>> +    {0, 0x91, 0, F_LONG_DELAY | F_M_ACCESS, resp_sync_cache, NULL,
>>>> +        {16,  0x7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
>>>
>>>                     ^^^
>>> Can you clarify the choice of "0x7" in the above? After having had a look at
>>> SBC-4 I was expecting 0x2 (the mask for the IMMED bit) since all other bits in
>>> that command byte are either reserved or obsolete.
>>
>> As a general rule when you see "obsolete" that means that field was used
>> in an earlier standard (bit 0 was RELADDR and bit 2 was SYNC_NV). So
>> application clients complying with earlier versions of SBC might set those
>> bits. If they are set and the mask is being enforced I choose to not fail
>> the command as an illegal request. Basically accept and ignore.
> 
> I agree with setting bits for obsolete flags. The reason I was asking about that
> mask is because I found the following in SBC-4 for byte 1 of SYNCHRONIZE CACHE(16):
> * Bits 7..3: reserved.
> * Bit 2: obsolete.
> * Bit 1: IMMED.
> * Bit 0: reserved.

I did see the discrepancy between byte 1 bit 0 in SYNCHRONIZE CACHE(10)
where it is "obsolete" and SYNCHRONIZE CACHE(16) where it is "reserved"
initially thinking it might be a typo. So I went for the more permissive.
I'm now guessing (because I don't have the drafts between SBC(-1) and
SBC-2 and for some reason T10 wants you to be a member to download older
drafts) that RELADDR was removed before SYNCHRONIZE CACHE(16) was added
(as there was no 64 LBA support in SBC-1). So if there never was a
publicly available draft where SYNCHRONIZE CACHE(16) had a RELADDR bit
defined, then why mark it as obsolete? Reserved means a later
draft/standard may use that bit/field.

BTW There is no requirement for a device server to enforce the mask and
most don't (from my testing). The mask is provided as an aid to the
application client and is required by the implementation of REPORT
SUPPORTED OPERATION CODES which is why I have it in scsi_debug. By default
the scsi_debug driver does not enforce the mask (but does when strict=1).

Anyway, aren't we splitting hairs here? Does this really justify a new
patch being rolled?

Doug Gilbert

>>>> -    return 0;
>>>> +    return (cmd[1] & 0x1) ? SDEG_RES_IMMED_MASK : 0; /* check IMMED bit */
>>>
>>> Shouldn't the mask 0x2 be used to check for the IMMED bit?
>>
>> That comment needs a little more context:
> 
> Sorry, I confused byte 1 of the START STOP command with that of the SYNCHRONIZE
> CACHE command so please ignore the above comment.
> 
> Bart.
> 

Re: [PATCH] scsi_debug: implement IMMED bit

[Bart Van Assche]

On Wed, 2018-01-31 at 17:40 -0500, Douglas Gilbert wrote:
> On 2018-01-31 05:05 PM, Bart Van Assche wrote:
> > On Wed, 2018-01-31 at 15:26 -0500, Douglas Gilbert wrote:
> > > On 2018-01-31 12:06 PM, Bart Van Assche wrote:
> > > > On 01/29/18 21:54, Douglas Gilbert wrote:
> > > > > +static const struct opcode_info_t sync_cache_iarr[] = {
> > > > > +    {0, 0x91, 0, F_LONG_DELAY | F_M_ACCESS, resp_sync_cache, NULL,
> > > > > +        {16,  0x7, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
> > > > 
> > > >                     ^^^
> > > > Can you clarify the choice of "0x7" in the above? After having had a look at
> > > > SBC-4 I was expecting 0x2 (the mask for the IMMED bit) since all other bits in
> > > > that command byte are either reserved or obsolete.
> > > 
> > > As a general rule when you see "obsolete" that means that field was used
> > > in an earlier standard (bit 0 was RELADDR and bit 2 was SYNC_NV). So
> > > application clients complying with earlier versions of SBC might set those
> > > bits. If they are set and the mask is being enforced I choose to not fail
> > > the command as an illegal request. Basically accept and ignore.
> > 
> > I agree with setting bits for obsolete flags. The reason I was asking about that
> > mask is because I found the following in SBC-4 for byte 1 of SYNCHRONIZE CACHE(16):
> > * Bits 7..3: reserved.
> > * Bit 2: obsolete.
> > * Bit 1: IMMED.
> > * Bit 0: reserved.
> 
> I did see the discrepancy between byte 1 bit 0 in SYNCHRONIZE CACHE(10)
> where it is "obsolete" and SYNCHRONIZE CACHE(16) where it is "reserved"
> initially thinking it might be a typo. So I went for the more permissive.
> I'm now guessing (because I don't have the drafts between SBC(-1) and
> SBC-2 and for some reason T10 wants you to be a member to download older
> drafts) that RELADDR was removed before SYNCHRONIZE CACHE(16) was added
> (as there was no 64 LBA support in SBC-1). So if there never was a
> publicly available draft where SYNCHRONIZE CACHE(16) had a RELADDR bit
> defined, then why mark it as obsolete? Reserved means a later
> draft/standard may use that bit/field.
> 
> BTW There is no requirement for a device server to enforce the mask and
> most don't (from my testing). The mask is provided as an aid to the
> application client and is required by the implementation of REPORT
> SUPPORTED OPERATION CODES which is why I have it in scsi_debug. By default
> the scsi_debug driver does not enforce the mask (but does when strict=1).
> 
> Anyway, aren't we splitting hairs here? Does this really justify a new
> patch being rolled?

People trust you as a SCSI expert and may consider to copy code from the
scsi_debug.c driver in their own GPL drivers if they need similar functionality.
Do you think that is sufficient as a motivation to edit and repost this patch?

Thanks,

Bart.