scsi: scsi_debug: Update documentation url and bump version

This driver maintains a version number which is cross-referenced in the
documentation (e.g. to indicate when features are added or changed

scsi: scsi_debug: Update documentation url and bump version

This driver maintains a version number which is cross-referenced in the
documentation (e.g. to indicate when features are added or changed) and
exposed through the responses to various SCSI commands. For example the
version number is use as the Product Revision number in standard SCSI
INQUIRY responses issued by this driver. The version date string is placed
in a vendor specific area in each standard SCSI INQUIRY response. This
patch bumps both.

Update the driver documentation URL that appears at the top of the driver
source file.

Link: https://lore.kernel.org/r/20200712182927.72044-3-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: every_nth triggered error injection

This patch simplifies, or at least makes more consistent, the way setting
the every_nth parameter injects errors. Here is a list of 'opts' flags

scsi: scsi_debug: every_nth triggered error injection

This patch simplifies, or at least makes more consistent, the way setting
the every_nth parameter injects errors. Here is a list of 'opts' flags and
in which cases they inject errors when abs(every_nth)%command_count == 0 is
reached:

- OPT_RECOVERED_ERR: issued on READ(*)s, WRITE(*)s and
WRITE_SCATTEREDs
- OPT_DIF_ERR: issued on READ(*)s, WRITE(*)s and
WRITE_SCATTEREDs
- OPT_DIX_ERR: issued on READ(*)s, WRITE(*)s and
WRITE_SCATTEREDs
- OPT_SHORT_TRANSFER: issued on READ(*)s
- OPT_TRANSPORT_ERR: issued on all commands
- OPT_CMD_ABORT: issued on all commands

The other uses of every_nth were not modified.

Previously if, for example, OPT_SHORT_TRANSFER was armed then if
(abs(every_nth) % command_count == 0) occurred during a command that was
_not_ a READ, then no error injection occurred. This behaviour puzzled
several testers. Now a global "inject_pending" flag is set and the _next_
READ will get hit and that flag is cleared. OPT_RECOVERED_ERR, OPT_DIF_ERR
and OPT_DIX_ERR have similar behaviour. A downside of this is that there
might be a hang-over pending injection that gets triggered by a following
test.

Also expand the every_nth runtime parameter so that it can take hex value
(i.e. with a leading '0x') as well as a decimal value. Now both the 'opts'
and the 'every_nth' runtime parameters can take hexadecimal values.

Link: https://lore.kernel.org/r/20200712182927.72044-2-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Support hostwide tags

Many SCSI HBAs support a hostwide tagset, whereby each command submitted to
the HW from all submission queues must have a unique tag identifier.

Normally thi

scsi: scsi_debug: Support hostwide tags

Many SCSI HBAs support a hostwide tagset, whereby each command submitted to
the HW from all submission queues must have a unique tag identifier.

Normally this unique tag will be in the range [0, max queue], where "max
queue" is the depth of each of the submission queues.

Add support for this hostwide tag feature, via module parameter
"host_max_queue". A non-zero value means that the feature is enabled. In
this case, the submission queues are not exposed to upper layer, i.e. from
blk-mq prespective, the device has a single hw queue. There are 2 reasons
for this:

a. It is assumed that the host can support nr_hw_queues * can_queue
commands, but this is not true for hostwide tags

b. For nr_hw_queues != 0, the request tag is not unique over all HW
queues, and some HBA drivers want to use this tag for the hostwide tag

However, like many SCSI HBA drivers today - megaraid sas being an example -
the full set of HW submission queues are still used in the LLDD driver. So
instead of using a complicated "reply_map" to create a per-CPU submission
queue mapping like megaraid_sas (as it depends on a PCI device + MSIs) -
use a simple algorithm:

hwq = cpu % queue count

If the host_max_queue param is set non-zero, then the max queue depth is
fixed at this value also.

If and when hostwide shared tags are supported in blk-mq/scsi mid-layer,
then the policy to set nr_hw_queues = 0 for hostwide tags can be revised.

Link: https://lore.kernel.org/r/1594297400-24756-3-git-send-email-john.garry@huawei.com
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add check for sdebug_max_queue during module init

sdebug_max_queue should not exceed SDEBUG_CANQUEUE, otherwise crashes like
this can be triggered by passing an out-of-range value:

scsi: scsi_debug: Add check for sdebug_max_queue during module init

sdebug_max_queue should not exceed SDEBUG_CANQUEUE, otherwise crashes like
this can be triggered by passing an out-of-range value:

Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI RC0 - V1.16.01 03/15/2019
pstate: 20400009 (nzCv daif +PAN -UAO BTYPE=--)
pc : schedule_resp+0x2a4/0xa70 [scsi_debug]
lr : schedule_resp+0x52c/0xa70 [scsi_debug]
sp : ffff800022ab36f0
x29: ffff800022ab36f0 x28: ffff0023a935a610
x27: ffff800008e0a648 x26: 0000000000000003
x25: ffff0023e84f3200 x24: 00000000003d0900
x23: 0000000000000000 x22: 0000000000000000
x21: ffff0023be60a320 x20: ffff0023be60b538
x19: ffff800008e13000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000
x15: 0000000000000000 x14: 0000000000000000
x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000000 x10: 0000000000000000
x9 : 0000000000000001 x8 : 0000000000000000
x7 : 0000000000000000 x6 : 00000000000000c1
x5 : 0000020000200000 x4 : dead0000000000ff
x3 : 0000000000000200 x2 : 0000000000000200
x1 : ffff800008e13d88 x0 : 0000000000000000
Call trace:
schedule_resp+0x2a4/0xa70 [scsi_debug]
scsi_debug_queuecommand+0x2c4/0x9e0 [scsi_debug]
scsi_queue_rq+0x698/0x840
__blk_mq_try_issue_directly+0x108/0x228
blk_mq_request_issue_directly+0x58/0x98
blk_mq_try_issue_list_directly+0x5c/0xf0
blk_mq_sched_insert_requests+0x18c/0x200
blk_mq_flush_plug_list+0x11c/0x190
blk_flush_plug_list+0xdc/0x110
blk_finish_plug+0x38/0x210
blkdev_direct_IO+0x450/0x4d8
generic_file_read_iter+0x84/0x180
blkdev_read_iter+0x3c/0x50
aio_read+0xc0/0x170
io_submit_one+0x5c8/0xc98
__arm64_sys_io_submit+0x1b0/0x258
el0_svc_common.constprop.3+0x68/0x170
do_el0_svc+0x24/0x90
el0_sync_handler+0x13c/0x1a8
el0_sync+0x158/0x180
Code: 528847e0 72a001e0 6b00003f 540018cd (3941c340)

In addition, it should not be less than 1.

So add checks for these, and fail the module init for those cases.

[mkp: changed if condition to match error message]

Link: https://lore.kernel.org/r/1594297400-24756-2-git-send-email-john.garry@huawei.com
Fixes: c483739430f1 ("scsi_debug: add multiple queue support")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Fix in_use bitmap corruption

Heavy testing indicates the irqsave() spinlock around the __set_bit() is
insufficient to stop following clear_bit() calls being rarely applied
out-of-o

scsi: scsi_debug: Fix in_use bitmap corruption

Heavy testing indicates the irqsave() spinlock around the __set_bit() is
insufficient to stop following clear_bit() calls being rarely applied
out-of-order. Also the nearby failed kzalloc() path leading to
SCSI_MLQUEUE_HOST_BUSY does not properly undo the in_use bitmap and
num_in_q, fix.

Link: https://lore.kernel.org/r/20200702145355.522283-1-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Parser tables and code interaction

This patch is in response to a static analyser report from Dan Carpenter
titled: "[bug report] scsi: scsi_debug: Add per_host_store option". Thi

scsi: scsi_debug: Parser tables and code interaction

This patch is in response to a static analyser report from Dan Carpenter
titled: "[bug report] scsi: scsi_debug: Add per_host_store option". This
code may not clear the static analyzer reports, but may shed light on why
they occur. Amongst other things this driver has a table driven SCSI
command parser which also involves some C code. There are some invariants
between the table entries and the corresponding C code (i.e. the resp_*()
functions) that, if broken, may lead to a NULL dereference. And the report
is valid, at least in the case of the PRE-FETCH command. Alas, that is not
one of the cases that the static analyzer reported.

In this particular corner case: when the fake_rw flag is set and the table
entry for a "store"-accessing command does not have the required F_FAKE_RW
flag set, do the following. Call BUG_ON() in the devip2sip() very close to
a comment block explaining why it was called and how to fix it.
checkpatch.pl complains about the BUG_ON() but there is no reasonable
remedial action that can be taken at run time.

This change allows the code reported by the static analyzer to be
simplified. Comments were also added to the table flags (e.g. F_FAKE_RW)
so developers who add commands might be more inclined to use them
(properly).

Link: https://lore.kernel.org/r/20200513013943.25285-1-dgilbert@interlog.com
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Fix an error handling bug in sdeb_zbc_model_str()

This test is checking the wrong variable. It should be testing "res".
The "sdeb_zbc_model" variable is an enum (unsigned in this

scsi: scsi_debug: Fix an error handling bug in sdeb_zbc_model_str()

This test is checking the wrong variable. It should be testing "res".
The "sdeb_zbc_model" variable is an enum (unsigned in this situation)
and we never assign negative values to it.

[mkp: fixed commit desc issue reported by Doug]

Link: https://lore.kernel.org/r/20200509100408.GA5555@mwanda
Fixes: 9267e0eb41fe ("scsi: scsi_debug: Add ZBC module parameter")
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Disallow zone sizes that are not powers of 2

Allowing a non-power-of-2 zone size forces the use of direct division
operations of 64-bit sector values to obtain a zone number or num

scsi: scsi_debug: Disallow zone sizes that are not powers of 2

Allowing a non-power-of-2 zone size forces the use of direct division
operations of 64-bit sector values to obtain a zone number or number of
zones. Doing so without using do_div() leads to compilation errors on
32-bit architectures.

Devices with a zone size that is not a power of 2 do not exist today so
allowing their emulation is of limited interest as the sd driver will not
support them anyway. To fix this compilation error, instead of using
do_div() for sector values divisions, simply disallow zone size values that
are not a power of 2.

[mkp: commit desc]

Link: https://lore.kernel.org/r/20200507023526.221574-1-damien.lemoal@wdc.com
Fixes: 98e0a689868c ("scsi: scsi_debug: Add zone_size_mb module parameter")
Fixes: f0d1cf9378bd ("scsi: scsi_debug: Add ZBC zone commands")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Implement ZBC host-aware emulation

Implement ZBC host-aware device model emulation. The main changes from the
host-managed emulation are the device type (TYPE_DISK is used), relaxa

scsi: scsi_debug: Implement ZBC host-aware emulation

Implement ZBC host-aware device model emulation. The main changes from the
host-managed emulation are the device type (TYPE_DISK is used), relaxation
of access checks for read and write operations and different handling of a
sequential write preferred zone write pointer as mandated by the ZBC r05
specifications.

To facilitate the implementation and avoid a lot of "if" statement, the
zmodel field is added to the device information and the z_type field to the
zone state data structure.

Link: https://lore.kernel.org/r/20200422104221.378203-8-damien.lemoal@wdc.com
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add zone_size_mb module parameter

Add the zone_size_mb module parameters to control the zone size of a ZBC
device. If the zone size specified is not a divisor of the device capacit

scsi: scsi_debug: Add zone_size_mb module parameter

Add the zone_size_mb module parameters to control the zone size of a ZBC
device. If the zone size specified is not a divisor of the device capacity,
the last zone of the device will be created as a smaller "runt" zone. This
parameter is ignored for device types other than 0x14 (zbc=2 case).

Note: for testing purposes, zone sizes that are not a power of 2 are
accepted but will result in the drive being rejected by the sd driver.

Link: https://lore.kernel.org/r/20200422104221.378203-7-damien.lemoal@wdc.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add zone_nr_conv module parameter

Allow controlling the number of conventional zones of a ZBC device with the
new zone_nr_conv module parameter. The default value is 1 and the spec

scsi: scsi_debug: Add zone_nr_conv module parameter

Allow controlling the number of conventional zones of a ZBC device with the
new zone_nr_conv module parameter. The default value is 1 and the specified
value must be less than the total number of zones of the device. This
parameter is ignored for device types other than 0x14 (zbc=2 case).

Link: https://lore.kernel.org/r/20200422104221.378203-6-damien.lemoal@wdc.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add zone_max_open module parameter

Add the zone_max_open module parameters to control the maximum number of
open zones of a ZBC device. This parameter is ignored for device types
o

scsi: scsi_debug: Add zone_max_open module parameter

Add the zone_max_open module parameters to control the maximum number of
open zones of a ZBC device. This parameter is ignored for device types
other than 0x14 (zbc=2 case).

Link: https://lore.kernel.org/r/20200422104221.378203-5-damien.lemoal@wdc.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add ZBC module parameter

Add the zbc module parameter to take either:
0: none (probably a conventional disk)
1: host-aware
2: host-managed

These values are cho

scsi: scsi_debug: Add ZBC module parameter

Add the zbc module parameter to take either:
0: none (probably a conventional disk)
1: host-aware
2: host-managed

These values are chosen to match 'enum blk_zoned_model' found in
include/linux/blkdev.h . Instead of "none", "no" or "0" can be given.
Instead of "host-aware", "aware or "1" can be given. Instead of
"host-managed", "managed" or "2" can be given.

Note: the zbc parameter can only be given at driver/module load time; it
cannot be changed via sysfs thereafter.

At this time there is no ZBC "host-aware" implementation so that string (or
the value '1') results in a modprobe error.

Link: https://lore.kernel.org/r/20200422104221.378203-4-damien.lemoal@wdc.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add ZBC zone commands

Add support for the 5 ZBC commands and enough functionality to emulate a
host-managed device with one conventional zone and a set of sequential
write-required

scsi: scsi_debug: Add ZBC zone commands

Add support for the 5 ZBC commands and enough functionality to emulate a
host-managed device with one conventional zone and a set of sequential
write-required zones up to the disk capacity.

Link: https://lore.kernel.org/r/20200422104221.378203-3-damien.lemoal@wdc.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add ZBC mode and VPD pages

The ZBC standard "piggy-backs" on many, but not all, of the facilities in
SBC. Add those ZBC mode pages (plus mode parameter block descriptors
(e.g. "WP"

scsi: scsi_debug: Add ZBC mode and VPD pages

The ZBC standard "piggy-backs" on many, but not all, of the facilities in
SBC. Add those ZBC mode pages (plus mode parameter block descriptors
(e.g. "WP")) and VPD pages in common with SBC. Add ZBC specific VPD page
for the host-managed ZBC device type (ptype=0x14).

Link: https://lore.kernel.org/r/20200422104221.378203-2-damien.lemoal@wdc.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Bump to version 1.89

The scsi_debug driver version is visible in:

/sys/modules/scsi_debug/version

and can thus be used by user space programs to alter the features they try
to

scsi: scsi_debug: Bump to version 1.89

The scsi_debug driver version is visible in:

/sys/modules/scsi_debug/version

and can thus be used by user space programs to alter the features they try
to use. Since the per_host_store and zbc/zone options are significant
additions, bump the version number to 1.89 .

Link: https://lore.kernel.org/r/20200421151424.32668-9-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Re-arrange parameters alphabetically

This module has a lot of parameters and when searching for one, the author
prefers them in alphabetical order. This can lead to somewhat illogi

scsi: scsi_debug: Re-arrange parameters alphabetically

This module has a lot of parameters and when searching for one, the author
prefers them in alphabetical order. This can lead to somewhat illogical
ordering (e.g. inq_product before inq_vendor). However it is not clear what
another sensible total logical ordering would be.

Link: https://lore.kernel.org/r/20200421151424.32668-8-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Implement PRE-FETCH commands

Many disks implement the SCSI PRE-FETCH commands. One use case might be a
disk-to-disk compare, say between disks A and B. Then this sequence of
comman

scsi: scsi_debug: Implement PRE-FETCH commands

Many disks implement the SCSI PRE-FETCH commands. One use case might be a
disk-to-disk compare, say between disks A and B. Then this sequence of
commands might be used: PRE-FETCH(from B, IMMED), READ(from A), VERIFY
(BYTCHK=1 on B with data returned from READ). The PRE-FETCH (which returns
quickly due to the IMMED) fetches the data from the media into B's cache
which should speed the trailing VERIFY command. The next chunk of the
compare might be done in parallel, with A and B reversed.

The implementation tries to bring the specified range in main memory into
the cache(s) associated with this machine's CPU(s) using the
prefetch_range() function.

Link: https://lore.kernel.org/r/20200421151424.32668-7-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Improve command duration calculation

Previously the code did the work implied by the given SCSI command and
after that it waited for a timer based on the user specified command
dur

scsi: scsi_debug: Improve command duration calculation

Previously the code did the work implied by the given SCSI command and
after that it waited for a timer based on the user specified command
duration to be exhausted before informing the mid-level that the command
was complete. For short command durations, the time to complete the work
implied by the SCSI command could be significant compared to the user
specified command duration.

For example a WRITE of 128 blocks (say 512 bytes each) on a machine that
can copy from main memory to main memory at a rate of 10 GB/sec will take
around 6.4 microseconds to do that copy. If the user specified a command
duration of 5 microseconds (ndelay=5000), should the driver do a further
delay of 5 microseconds after the copy or return immediately because 6.4 >
5 ?

The action prior to this patch was to always do the timer based
delay. After this patch, for ndelay values less than 1 millisecond, this
driver will complete the command immediately. And in the case where the
user specified delay was 7 microseconds, a timer delay of 600 nanoseconds
will be set ((7 - 6.4) * 1000).

Link: https://lore.kernel.org/r/20200421151424.32668-6-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Weaken rwlock around ramdisk access

The design of this driver is to do any ramdisk access on the same thread
that invoked the queuecommand() call. That is assumed to be user space

scsi: scsi_debug: Weaken rwlock around ramdisk access

The design of this driver is to do any ramdisk access on the same thread
that invoked the queuecommand() call. That is assumed to be user space
context. The command duration is implemented by setting the delay with a
high resolution timer. The hr timer's callback may well be in interrupt
context, but it doesn't touch the ramdisk. So try removing the
_irqsave()/_irqrestore() portion on the read-write lock that protects
ramdisk access.

Link: https://lore.kernel.org/r/20200421151424.32668-5-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Implement VERIFY(10), add VERIFY(16)

With the addition of the per_host_store option, the ability to check
whether two different ramdisk images are the same or not becomes
practical

scsi: scsi_debug: Implement VERIFY(10), add VERIFY(16)

With the addition of the per_host_store option, the ability to check
whether two different ramdisk images are the same or not becomes
practical. Prior to this patch VERIFY(10) always returned true (i.e. the
SCSI GOOD status) without checking. This option adds support for BYTCHK
equal to 0, 1 and 3. If the comparison fails, then a sense key of
MISCOMPARE is returned as per the T10 standards. Also add support for the
VERIFY(16) command.

Link: https://lore.kernel.org/r/20200421151424.32668-4-dgilbert@interlog.com
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Add per_host_store option

The scsi_debug driver has always been restricted to using one ramdisk image
(or none) for its storage. This means that thousands of scsi_debug devices
can

scsi: scsi_debug: Add per_host_store option

The scsi_debug driver has always been restricted to using one ramdisk image
(or none) for its storage. This means that thousands of scsi_debug devices
can be created without exhausting the host machine's RAM. The downside is
that all scsi_debug devices share the same ramdisk image. This option
changes the way a following write to the add_host parameter (or an add_host
in the module/driver invocation) operates. For each new host that is
created while per_host_store is true, a new store (of dev-size_mb MiB) is
created and associated with all the LUs that belong to that new host. The
user (who will need root permissions) needs to take care not to exhaust all
the machine's available RAM.

One reason for doing this is to check that (partial) disk to disk copies
based on scsi_debug devices have actually copied accurately. To test this
the add_host=<n> parameter where <n> is 2 or greater can be used when the
scsi_debug module is loaded. Let us assume that /dev/sdb and /dev/sg1 are
the same scsi_debug device, while /dev/sdc and /dev/sg2 are the same
scsi_debug device. With per_host_store=1 add_host=2 they will have
different ramdisk images. Then the following pseudocode could be executed
to check if the sgh_dd copy worked:

dd if=/dev/urandom of=/dev/sdb
sgh_dd if=/dev/sg1 of=/dev/sg2 [plus option(s) to test]
cmp /dev/sdb /dev/sdc

If the cmp fails then the copy has failed (or some other mechanism wrote to
/dev/sdb or /dev/sdc in the interim).

[mkp: use kstrtobool()]

Link: https://lore.kernel.org/r/20200421151424.32668-3-dgilbert@interlog.com
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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scsi: scsi_debug: Randomize command completion time

Add a new command line option (e.g. random=1) and sysfs attribute that
causes subsequent command completion times to be between the current
comman

scsi: scsi_debug: Randomize command completion time

Add a new command line option (e.g. random=1) and sysfs attribute that
causes subsequent command completion times to be between the current
command delay setting and 0. A uniformly distributed 32 bit, kernel
provided integer is used for this purpose.

Since the existing 'delay' whose units are jiffies (typically milliseconds)
and 'ndelay' (units: nanoseconds) options (and sysfs attributes) span a
range greater than 32 bits, some scaling is required.

The purpose of this patch is to widen the range of testing cases that are
visited in long running tests. Put simply: rarely struct race conditions
are more likely to be found when this facility is used.

The default is the previous case in which all command completions were
roughly equal to (if not, slightly longer) than the value given by the
'delay' or 'ndelay' settings (or their defaults). This option's default is
equivalent to setting 'random=0' .

[mkp: use kstrtobool()]

Link: https://lore.kernel.org/r/20200421151424.32668-2-dgilbert@interlog.com
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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block: move struct partition out of genhd.h

struct partition is the on-disk format of a MSDOS partition table entry.
Move it out of genhd.h into a new msdos_partition.h header and give it
a msdos_ p

block: move struct partition out of genhd.h

struct partition is the on-disk format of a MSDOS partition table entry.
Move it out of genhd.h into a new msdos_partition.h header and give it
a msdos_ prefix to avoid confusion.
Also move the magic number from block/partitions/msdos.h to the new
header so that it can be used by the SCSI drivers looking at the DOS
partition tables.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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scsi: scsi_debug: num_tgts must be >= 0

Passing the parameter "num_tgts=-1" will start an infinite loop that
exhausts the system memory

Link: https://lore.kernel.org/r/20191115163727.24626-1-mlomba

scsi: scsi_debug: num_tgts must be >= 0

Passing the parameter "num_tgts=-1" will start an infinite loop that
exhausts the system memory

Link: https://lore.kernel.org/r/20191115163727.24626-1-mlombard@redhat.com
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

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