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  1. 05 May, 2020 2 commits
    • Douglas Gilbert's avatar
      scsi: scsi_debug: Add per_host_store option · 87c715dc
      Douglas Gilbert authored 
      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.comSigned-off-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
      87c715dc
    • Douglas Gilbert's avatar
      scsi: scsi_debug: Randomize command completion time · 0c4bc91d
      Douglas Gilbert authored 
      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.comReviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
      0c4bc91d
  3. 30 Apr, 2020 4 commits
  5. 27 Apr, 2020 7 commits
  7. 24 Apr, 2020 25 commits
  9. 22 Apr, 2020 2 commits
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