Patch "firewire: fw-sbp2: fix NULL pointer deref. in scsi_remove_device"
had the unintended effect that firewire-sbp2 could not be unloaded
anymore until all SBP-2 devices were unplugged.

We now fix the NULL pointer bug by reacquiring a reference to the sdev
instead of holding a reference to the sdev (and to the module) all the
time.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Tested-by: NJarod Wilson <jwilson@redhat.com>

Fix a kernel bug when unplugging an SBP-2 device after having its
scsi_device already removed via the "delete" sysfs attribute.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Fix a kernel bug when running rescan-scsi-bus while a FireWire disk is
connected:  http://bugzilla.kernel.org/show_bug.cgi?id=10008Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

While fw-sbp2 takes the necessary time to reconnect to a logical unit
after bus reset, the SCSI core keeps sending new commands.  They are all
immediately completed with host busy status, and application clients or
filesystems will break quickly.  The SCSI device might even be taken
offline:  http://bugzilla.kernel.org/show_bug.cgi?id=9734

The only remedy seems to be to block the SCSI device until reconnect.
Alas the SCSI core has no useful API to block only one logical unit i.e.
the scsi_device, therefore we block the entire Scsi_Host.  This
currently corresponds to an SBP-2 target.  In case of targets with
multiple logical units, we need to satisfy the dependencies between
logical units by carefully tracking the blocking state of the target and
its units.  We block all logical units of a target as soon as one of
them needs to be blocked, and keep them blocked until all of them are
ready to be unblocked.

Furthermore, as the history of the old sbp2 driver has shown, the
scsi_block_requests() API is a minefield with high potential of
deadlocks.  We therefore take extra measures to keep logical units
unblocked during __scsi_add_device() and during shutdown.

This avoids I/O errors during reconnect in many but alas not in all
cases.  There may still be errors after a re-login had to be performed.
Also, some bridges have been seen to cease fetching management ORBs if
I/O went on up until a bus reset.  In these cases, all management ORBs
time out after mgt_orb_timeout.  The old sbp2 driver is less vulnerable
or maybe not vulnerable to this, for as yet unknown reasons.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

fw-sbp2 is unable to reconnect while performing __scsi_add_device
because there is only a single workqueue thread context available for
both at the moment.  This should be fixed eventually.

An actual failure of __scsi_add_device is easy to handle, but an
incomplete execution of __scsi_add_device with an sdev returned would
remain undetected and leave the SBP-2 target unusable.

Therefore we use a workaround:  If there was a bus reset during
__scsi_add_device (i.e. during the SCSI probe), we remove the new sdev
immediately, log out, and attempt login and SCSI probe again.

Tested-by: Jarod Wilson <jwilson@redhat.com> (earlier version)
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

If fw-sbp2 was too late with requesting the reconnect, the target would
reject this.  In this case, log out before attempting the reconnect.
Else several firmwares will deny the re-login because they somehow
didn't invalidate the old login.

Also, don't retry reconnects in this situation.  The retries won't
succeed either.

These changes improve chances for successful re-login and shorten the
period during which the logical unit is inaccessible.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NJarod Wilson <jwilson@redhat.com>

When a reconnect failed but re-login succeeded, __scsi_add_device was
called again.

In those cases, __scsi_add_device succeeded and returned the pointer to
the existing scsi_device.  fw-sbp2 then continued orderly, except that
it missed to call sbp2_cancel_orbs.  SCSI core would call fw-sbp2's
eh_abort_handler eventually if there had been an outstanding command.

This patch avoids the needless lookups and temporary allocations in SCSI
core and I/O stall and timeout until eh_abort_handler hits.

Also, __scsi_add_device tolerating calls for devices which already exist
is undocumented behavior on which we shouldn't rely.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NJarod Wilson <jwilson@redhat.com>

for easier readable logs if more than one SBP-2 device is present.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NJarod Wilson <jwilson@redhat.com>

Like the old sbp2 driver, wait for the write transaction to the
AGENT_RESET to complete before proceeding (after login, after reconnect,
or in SCSI error handling).

There is one occasion where AGENT_RESET is written to from atomic
context when getting DEAD status for a command ORB.  There we still
continue without waiting for the transaction to complete because this
is more difficult to fix...
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Several different SBP-2 bridges accept a login early while the IDE
device is still powering up.  They are therefore unable to respond to
SCSI INQUIRY immediately, and the SCSI core has to retry the INQUIRY.
One of these retries is typically successful, and all is well.

But in case of Momobay FX-3A, the INQUIRY retries tend to fail entirely.
This can usually be avoided by waiting a little while after login before
letting the SCSI core send the INQUIRY.  The old sbp2 driver handles
this more gracefully for as yet unknown reasons (perhaps because it
waits for fetch agent resets to complete, unlike fw-sbp2 which quickly
proceeds after requesting the agent reset).  Therefore the workaround is
not as much necessary for sbp2.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NJarod Wilson <jwilson@redhat.com>

If a device is being unplugged while fw-sbp2 had a login or reconnect on
schedule, it would take about half a minute to shut the fw_unit down:

    Jan 27 18:34:54 stein firewire_sbp2: logged in to fw2.0 LUN 0000 (0 retries)
    <unplug>
    Jan 27 18:34:59 stein firewire_sbp2: sbp2_scsi_abort
    Jan 27 18:34:59 stein scsi 25:0:0:0: Device offlined - not ready after error recovery
    Jan 27 18:35:01 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:06 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:12 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:17 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:22 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:27 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:32 stein firewire_sbp2: orb reply timed out, rcode=0x11
    Jan 27 18:35:32 stein firewire_sbp2: failed to login to fw2.0 LUN 0000
    Jan 27 18:35:32 stein firewire_sbp2: released fw2.0

After this patch, typically only a few seconds spent in __scsi_add_device
remain:

    Jan 27 19:05:50 stein firewire_sbp2: logged in to fw2.0 LUN 0000 (0 retries)
    <unplug>
    Jan 27 19:05:56 stein firewire_sbp2: sbp2_scsi_abort
    Jan 27 19:05:56 stein scsi 33:0:0:0: Device offlined - not ready after error recovery
    Jan 27 19:05:56 stein firewire_sbp2: released fw2.0

The benefit of this is less noise in the syslog.  It furthermore avoids
a few wasted CPU cycles and needlessly prolonged lifetime of a few
driver objects.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NJarod Wilson <jwilson@redhat.com>

This fixes a "can't recognize device" kind of bug.

If the SCSI INQUIRY failed and hence __scsi_add_device failed due to a
bus reset, we tried a logout and then waited for the already scheduled
login work to happen.  So far so good, but the generation used for the
logout was outdated, hence the logout never reached the target.  The
target might therefore deny the subsequent relogin attempt, which would
also leave the target inaccessible.

Therefore fetch a fresh device->generation for the logout.  Use memory
barriers to prevent our plan being foiled by compiler or hardware
optimizations.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Standardize on "unsigned int" style.
Sort some struct members thematically.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

To be more compliant with section 7.4.8 of the SBP-2 specification,
use the mgt_ORB_timeout specified in the SBP-2 device's config rom
for login ORB attempts (though with some sanity checks). A happy
side-effect is that certain device and controller combinations that
sometimes take more than 20 seconds to get synced up (like my laptop
with just about any SBP-2 device) now function more reliably.
Signed-off-by: NJarod Wilson <jwilson@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (silenced sparse)

Increase (and rename) the login orb reply timeout value to 20s
to match that of the old firewire stack. 2s simply didn't give
many devices enough time to spin up and reply.

Fixes inability to recognize some devices.
Failure mode was "orb reply timed out"/"failed to login".
Signed-off-by: NJarod Wilson <jwilson@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (style, comments, changelog)

fw_device.node_id and fw_device.generation are accessed without mutexes.
We have to ensure that all readers will get to see node_id updates
before generation updates.

Fixes an inability to recognize devices after "giving up on config rom",
https://bugzilla.redhat.com/show_bug.cgi?id=429950Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Reviewed by Nick Piggin <nickpiggin@yahoo.com.au>.

Verified to fix 'giving up on config rom' issues on multiple system and
drive combinations that were previously affected.
Signed-off-by: NJarod Wilson <jwilson@redhat.com>
Signed-off-by: NKristian Høgsberg <krh@redhat.com>

There was a small window where a login or reconnect job could use an
already updated card generation with an outdated node ID.  We have to
use the fw_device.generation here, not the fw_card.generation, because
the generation must never be newer than the node ID when we emit a
transaction.  This cannot be guaranteed with fw_card.generation.

Furthermore, the target's and initiator's node IDs can be obtained from
fw_device and fw_card.  Dereferencing their underlying topology objects
is not necessary.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Verified in concert with subsequent memory barriers patch to fix 'giving
up on config rom' issues on multiple system and drive combinations that
were previously affected.
Signed-off-by: NJarod Wilson <jwilson@redhat.com>

Ask the target to grant 4 seconds instead of the standard and minimum of
1 second window after bus reset for reconnection.  This accelerates
reconnection if there are more than one targets on the bus:  If a login
and inquiry to one target blocks the fw-sbp2 workqueue for more than 1s
after bus reset, we now still can reconnect to the other target.

Before that, fw-sbp2's reconnect attempts would be rejected with "error
status: 0:9" (function rejected), and fw-sbp2 would finally re-login.
All those futile reconnect attemps cost extra time until the target
which needs re-login is ready for I/O again.

The reconnect timeout field in the login ORB doesn't have to be honored
by the target though.  I found that we could get up to
  - allegedly 32768s from an old OXFW911 firmware
  - 256s from LSI bridges
  - 4s from OXUF922 and OXFW912 bridges,
  - 2s from TI bridges,
  - only the standard 1s from Initio and Prolific bridges and from
    Apple OpenFirmware in target mode.

We just try to get 4 seconds which already covers the case of a few
HDDs on the same bus quite nicely.

A minor drawback occurs in the following (rare and impractical) border
case:
  - two initiators are there, initiator 1 holds an exclusive login to
    a target,
  - initiator 1 goes off the bus,
  - target refuses login attempts from initiator 2 until reconnect_hold
    seconds after bus reset.

An alternative approach to the issue at hand would be to parallelize
fw-sbp2's reconnect and login work.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NJarod Wilson <jwilson@redhat.com>

Don't attempt to send a logout ORB if the target was already unplugged
or had its link switched off.  If two targets are attached, this
enhances the chance to quickly reconnect to the remaining target when
one target is plugged out.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NJarod Wilson <jwilson@redhat.com>

SBP2_MAX_SECTORS is nowhere used in fw-sbp2.
It merely got copied over from sbp2 where it played a role in the past.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

This somewhat reduces the size of firewire-sbp2.ko.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

This patch relaxes the default SCSI DMA alignment from 512 bytes to 4
bytes.  I remember from previous discussions that usb and firewire have
sector size alignment requirements, so I upped their alignments in the
respective slave allocs.

The reason for doing this is so that we don't get such a huge amount of
copy overhead in bio_copy_user() for udev.  (basically all inquiries it
issues can now be directly mapped).
Acked-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

Since patch "fw-sbp2: use an own workqueue (fix system responsiveness)"
increased parallelism between fw-sbp2 and fw-core, it was possible that
fw-sbp2 didn't release the SCSI device when the FireWire device was
disconnected.

This happened if sbp2_update() ran during sbp2_login(), because a bus
reset occurred during sbp2_login().  The sbp2_login() work would [try
to] reschedule itself because it failed due to the bus reset, and it
would _not_ drop its reference on the target.  However, sbp2_update()
would schedule sbp2_login() too before sbp2_login() rescheduled itself
and hence sbp2_update() would take an additional reference.  And then
we would have one reference too many.

The fix is to _always_ drop the reference when leaving the sbp2_login()
work.  If the sbp2_login() work reschedules itself, it takes a
reference, but only if it wasn't already rescheduled by sbp2_update().

Ditto in the sbp2_reconnect() work.

The resulting code is actually simpler than before:  We _always_ take
a reference when successfully scheduling work.  And we _always_ drop
a reference when leaving a workqueue job.  No exceptions.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Firewire-sbp2 did very uncooperative things in the kernel's shared
workqueue:  Sleeping until reception of management status from the
target for up to 2 seconds, and performing SCSI inquiry and all of the
setup of SCSI command set drivers via scsi_add_device.  If there were
transient or permanent error conditions, this caused long blockage of
the kernel's events process, noticeable e.g. by blocked keyboard input.

We now allocate a workqueue process exclusive to fw-sbp2.  As a side
effect, this also increases parallelism of fw-sbp2's login and reconnect
work versus fw-core's device discovery and device update work which is
performed in the shared workqueue.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NKristian Høgsberg <krh@redhat.com>

On rare occasions, the ability to set one of the workaround flags at
runtime may save the day.

People who experience I/O errors with firewire-sbp2 while the old sbp2
driver worked for them should try workarounds=1 and report to the devel
mailinglist whether that improves things.  Firewire-sbp2 defaults to the
SCSI stack's maximum transfer size per command, while sbp2 limits them
to 128 kBytes.  Flag 1 accomplishes just that.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

Fixes "New firewire stack only recognizing half of a chain of drives",
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=242254Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

On IOMMU-less noncoherent architectures, orb->callback will memcpy the
whole SCSI command buffer for READ-like SCSI commands.  It is therefore
friendlier to enable IRQs before the call, like before patch "Add
ref-counting for sbp2 orbs".
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NKristian Høgsberg <krh@redhat.com>

This handles the case where we get the status write before getting the
complete_transaction callback ("status write for unknown orb").  In
this case, we just assume that the initial orb pointer transaction
succeeded and finish the orb.  To prevent the transaction callback
from touching freed memory, we ref-count the orb structures.
Signed-off-by: NKristian Høgsberg <krh@redhat.com>
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

As far as I know, all CardBus FireWire 400 adapters have a maximum
payload of 1024 bytes which is less than the speed-dependent limit of
2048 bytes.  Fw-sbp2 has to take the host adapter's limit into account.

This apparently fixes Juju's incompatibility with my CardBus cards, a
NEC based card and a VIA based card.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NKristian Høgsberg <krh@redhat.com>

Signed-off-by: NKristian Høgsberg <krh@redhat.com>

collapsed with fw-sbp2 patch "Drop cast to non-const char * in host
template initialization." from Kristian Høgsberg
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>

Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

The CPU must not touch the buffer after it was DMA-mapped.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NKristian Høgsberg <krh@redhat.com>

The CPU must not touch the buffer after it was DMA-mapped.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NKristian Høgsberg <krh@redhat.com>

  - The CPU must not touch the buffer after it was DMA-mapped.
  - The size argument of dma_unmap_single(...page_table...) was bogus.
  - Move a comment closer to the code to which it refers to.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NKristian Høgsberg <krh@redhat.com>

Add rudimentary check for the case that the page table overflows due to
merging of s/g elements by the IOMMU.  This would have lead to
overwriting of arbitrary memory.

After this change I expect that an offending command will be
unsuccessfully retried until the scsi_device is taken offline by SCSI
core.  It's a border case and not worth to implement a recovery
strategy.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NKristian Høgsberg <krh@redhat.com>

This is required per SBP-2 clause 5.2.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NKristian Høgsberg <krh@redhat.com>

Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NKristian Høgsberg <krh@redhat.com>

noticed by Jay Fenlason
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: NKristian Høgsberg <krh@redhat.com>