There are two sites where the flag is being changed: ide_retry_pc
and idetape_do_request. Both codepaths are protected by hwif->busy
(ide_lock_port) and therefore we shouldn't need the atomic accesses.
Spotted-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
The driver's resetproc() method resets both channels at once -- most probably
by driving RESET- on them. Not only such reset can severely disturb concurrent
operations on another channel, it also ensues 2-second delay, while there's no
apparent reason why SRST reset being performed prior to resetproc() call needs
to be followed up by another reset.
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
The driver's dma_lost_irq() and dma_clear() methods call pdc202xx_reset()
which resets both channels at once -- most probably by driving RESET- on them.
Not only such reset can severely disturb concurrent operations on another
channel, it is also a clear overkill (especially in the first case) and is
completely unexpected and thus not properly handled by the IDE core in this
context (in the second case the usual SRST reset would most probably ensue
anyway though); it also causes quite arbitrary 2-second delay. Hence, use the
standard ide_dma_lost_irq() method and don't install the optional dma_clear()
method at all -- the driver should do well without this age-old cruft...
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
The driver's dma_test_irq() method, although tests some chip specific interrupt
bits, finally always relies on the SFF-8038i standard interrupt bit. I see no
point in testing the bits that are not trusted anyway -- the driver should be
fully able to use the standard method implemetation, ide_dma_test_irq().
With this change 'pdc202xx_dma_ops' finally becomes identical to 'sff_dma_ops',
and we can get rid of it...
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
From the perspective of most users of recent systems, disabling Host
Protected Area (HPA) can break vendor RAID formats, GPT partitions and
risks corrupting firmware or overwriting vendor system recovery tools.
Unfortunately the original (kernels < 2.6.30) behavior (unconditionally
disabling HPA and using full disk capacity) was introduced at the time
when the main use of HPA was to make the drive look small enough for the
BIOS to allow the system to boot with large capacity drives.
Thus to allow the maximum compatibility with the existing setups (using
HPA and partitioned with HPA disabled) we automically disable HPA if
any partitions overlapping HPA are detected. Additionally HPA can also
be disabled using the "nohpa" module parameter (i.e. "ide_core.nohpa=0.0"
to disable HPA on /dev/hda).
v2:
Fix ->resume HPA support.
While at it:
- remove stale "idebus=" entry from Documentation/kernel-parameters.txt
Cc: Robert Hancock <hancockrwd@gmail.com>
Cc: Frans Pop <elendil@planet.nl>
Cc: "Andries E. Brouwer" <Andries.Brouwer@cwi.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
[patch description was based on input from Alan Cox and Frans Pop]
Emphatically-Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
* Use ->probed_capacity to store native device capacity for ATA disks.
* Add ->set_capacity method to struct ide_disk_ops.
* Implement disk device ->set_capacity method for ATA disks.
* Implement block device ->set_capacity method.
v2:
* Check if LBA and HPA are supported in ide_disk_set_capacity().
* According to the spec the SET MAX ADDRESS command shall be
immediately preceded by a READ NATIVE MAX ADDRESS command.
* Add ide_disk_hpa_{get_native,set}_capacity() helpers.
Together with the previous patch adding ->set_capacity block device
method this allows automatic disabling of Host Protected Area (HPA)
if any partitions overlapping HPA are detected.
Cc: Robert Hancock <hancockrwd@gmail.com>
Cc: Frans Pop <elendil@planet.nl>
Cc: "Andries E. Brouwer" <Andries.Brouwer@cwi.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Emphatically-Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
pdc202xx_reset() calls pdc202xx_reset_host() twice, for both channels, while
that function actually twiddles the single, shared software reset bit -- the
net effect is a duplicated reset and horrendous 4 second delay happening not
only on a channel reset but also when dma_lost_irq() and dma_clear() methods
are called. Fold pdc202xx_reset_host() into pdc202xx_reset(), fix printk(),
and move it before the actual reset...
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Commit ac95beedf8 (ide: add struct ide_port_ops
(take 2)) erroneously converted the driver's dma_timeout() and dma_lost_irq()
methods to call the driver's resetproc() method regardless of whether it was
defined for this specific controller while it hadn't been defined and hence
called for PDC20246. So the dma_clear() method, the successor of dma_timeout(),
shouldn't exist and the dma_lost_irq() method should be standard for PDC20246.
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
We need to explicitly mark words 85-87 as valid ones since
firmware doesn't do it.
This should fix support for LBA48 and FLUSH CACHE [EXT] command
which stopped working after we applied more strict checking of
identify words in:
commit 942dcd85bf
("ide: idedisk_supports_lba48() -> ata_id_lba48_enabled()")
and
commit 4b58f17d7c
("ide: ide_id_has_flush_cache() -> ata_id_flush_enabled()")
Reported-and-tested-by: "Trevor Hemsley" <trevor.hemsley@ntlworld.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
This patch adds the PCI Device ID 0xc409 to the PCI ID table of via82cxxx.c,
as well as the 0x8409 south bridge ID.
This is required to make the IDE driver work on the VX855/VX875 integrated
chipset.
Signed-off-by: Harald Welte <HaraldWelte@viatech.com>
Cc: Joseph Chan <JosephChan@via.com.tw>
Cc: Bruce Chang <BruceChang@via.com.tw>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Nowadays we (almost) always store the currently executing command
in hwif->cmd so we can use it for the failed opcode reporting.
Cc: Martin Lottermoser <Martin.Lottermoser@t-online.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
On Tuesday 19 May 2009 20:29:28 Martin Lottermoser wrote:
> hdc: cdrom_decode_status: error=0x40 <3>{ LastFailedSense=0x04 }
> ide: failed opcode was: unknown
> hdc: DMA disabled
> ------------[ cut here ]------------
> kernel BUG at drivers/ide/ide-io.c:872!
It is possible for ide-cd to ignore ide_error()'s return value under
some circumstances. Workaround it in ide_intr() and ide_timer_expiry()
by checking if there is a device/port reset pending currently.
Fixes bug #13345:
http://bugzilla.kernel.org/show_bug.cgi?id=13345
Reported-by: Martin Lottermoser <Martin.Lottermoser@t-online.de>
Reported-and-tested-by: Modestas Vainius <modestas@vainius.eu>
Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Since 2.6.26 we support UDMA66 on ATAPI devices requiring IVB quirk:
commit 8588a2b732
("ide: add SH-S202J to ivb_list[]")
We also later added support for more such devices in:
commit e97564f362
("ide: More TSST drives with broken cable detection")
and in:
commit 3ced5c49bd
("ide: add TSSTcorp CDDVDW SH-S202H to ivb_list[]")
It turns out that such devices lack cable detection altogether
(which in turn results in incorrect detection of 40-wire cables
by our current cable detection strategy) so always handle them
by trusting host-side cable detection only.
v2:
Model detection fixup from Martin.
Reported-and-tested-by: Martin Lottermoser <Martin.Lottermoser@t-online.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Remove hw_regs_t typedef and rename struct hw_regs_s to struct ide_hw.
There should be no functional changes caused by this patch.
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Pass number of ports to ide_host_{alloc,add}() and then update
all users accordingly.
v2:
- drop no longer needed NULL initializers in buddha.c, cmd640.c and gayle.c
(noticed by Sergei)
There should be no functional changes caused by this patch.
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
* Convert host drivers that still use hw_regs_t's chipset field to use
the one in struct ide_port_info instead.
* Move special handling of ide_pci chipset type from ide_hw_configure()
to ide_init_port().
* Remove chipset field from hw_regs_t.
While at it:
- remove stale comment in delkin_cb.c
There should be no functional changes caused by this patch.
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Replace:
- special_t typedef by IDE_SFLAG_* flags
- 'special_t special' ide_drive_t's field by 'u8 special_flags' one
There should be no functional changes caused by this patch.
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
While at it:
- change debug printk() level to KERN_DEBUG and use __func__
- update documentation
v2:
- fix DEBUG build (noticed by Sergei)
There should be no functional changes caused by this patch.
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Initially set PIO Mode 0 for all host drivers that have a 'set_pio_mode'
method before the IDE core figures out the most suited PIO mode for the
attached device.
Signed-off-by: Joao Ramos <joao.ramos@inov.pt>
Cc: Sergei Shtylyov <sshtylyov@ru.montavista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
This error only occurs when IDETAPE_DEBUG_LOG is enabled.
Signed-off-by: Mark de Wever <koraq@xs4all.nl>
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
The Sony TZ90 needs the cable type hardcoding. See bug #12734
Signed-off-by: Alan Cox <alan@linux.intel.com>
Reported-by: Jonathan E. Snow <jesnow@uh.edu>
[bart: port it from ata_piix to piix and give reporter the proper credit]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
The second IDE channel of version 6 PCB is not being registered anymore since
the commit 48c3c10726 (ide: add struct ide_host
(take 3)).
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Impact: fix an oops which always triggers
ide_tape_issue_pc() assumed drive->pc isn't NULL on invocation when
checking for back-to-back request sense issues but drive->pc can be
NULL and even when it's not NULL, it's not safe to dereference it once
the previous command is complete because pc could have been freed or
was on stack. Kill back-to-back REQUEST_SENSE detection.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Some time ago we had to disable init_hwif callback for PowerPC builds.
That was because of a historical IRQ overwrite in the driver, which
was causing IDE malfunction on the MPC8610HPCD PowerPC boards.
It's unclear whether this overwrite is still useful, but it is proven
to cause a bit of harm, and today some PowerPC targets (Xilinx ML510,
as reported by Roderick Colenbrander) need the init_hwif, so we have
to re-enable it and remove the overwrite.
Reported-by: Roderick Colenbrander <thunderbird2k@gmail.com>
Suggested-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Original patch (dfa4411cc3) was buggy.
This is a more proper fix which introduces blk_rq_quiet() macro
alleviating the need for dumb, too short caching variables.
Thanks to Helge Deller and Bart for debugging this.
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Reported-and-tested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Bugfixes noted by checking the code against the controller
documentation (TI document number SPRUE21):
- Remove declarations for eight non-existent registers (!);
and remove accesses to two of them.
- Remove access to various non-existent bitfields in some of
the registers which *do* exist (those fields must-be-zero).
- Provide comment to replace bogus reset logic (removed above,
it relied on non-existent bitfields). Resets require GPIO
help; this driver doesn't currently know about that.
With some minor cleanup: relocate a comment, avoid an extra
lookup of the PIO timings.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
On Tuesday 14 April 2009 20:31:21 Subrata Modak wrote:
> Observed the following build error:
> ---
> CC drivers/macintosh/mediabay.o
> In file included from drivers/macintosh/mediabay.c:21:
> include/linux/ide.h:605: error: field ‘request_sense_rq’ has incomplete
> type
> make[2]: *** [drivers/macintosh/mediabay.o] Error 1
> make[1]: *** [drivers/macintosh] Error 2
> make: *** [drivers] Error 2
> ---
mediabay shouldn't include <linux/ide.h> unconditionally so
remove the superfluous include from mediabay.c (<asm/mediabay.h>
will pull <linux/ide.h> in for CONFIG_BLK_DEV_IDE_PMAC=y).
Reported-by: Subrata Modak <subrata@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
My laptop (Acer Travelmate 660) always cuts the power when rebooting
which causes the disk to emergency-park it's head.
Add a dmi check to stop disk as for shutdown on this laptop.
Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
With 2.6.30-rc2 I face a kernel crash on the 32bit hppa architecture
due to ide-cd when udev creates the device nodes at startup:
Kernel Fault: Code=26 regs=8ed34c40 (Addr=00000024)
IASQ: 00000000 00000000 IAOQ: 1034b5ac 1034b5b0
IIR: 4ab30048 ISR: 00000000 IOR: 00000024
CPU: 0 CR30: 8ed34000 CR31: ffff55ff
ORIG_R28: 00000000
IAOQ[0]: ide_complete_rq+0x2c/0x70
IAOQ[1]: ide_complete_rq+0x30/0x70
RP(r2): cdrom_newpc_intr+0x178/0x46c
Backtrace:
[<1035c608>] cdrom_newpc_intr+0x178/0x46c
[<1034c494>] ide_intr+0x1b0/0x214
[<1016d284>] handle_IRQ_event+0x70/0x150
[<1016d4b0>] __do_IRQ+0x14c/0x1cc
[<102f7864>] superio_interrupt+0x88/0xbc
[<1016d284>] handle_IRQ_event+0x70/0x150
[<1016d4b0>] __do_IRQ+0x14c/0x1cc
[<10112efc>] do_cpu_irq_mask+0x9c/0xd0
[<10116068>] intr_return+0x0/0x4
This crash seems to happen due to an uninitialized variable "rc".
The compiler even warns about that:
CC drivers/ide/ide-cd.o
/mnt/sda4/home/cvs/parisc/git-kernel/linus-linux-2.6/drivers/ide/ide-cd.c: In function `cdrom_newpc_intr':
/mnt/sda4/home/cvs/parisc/git-kernel/linus-linux-2.6/drivers/ide/ide-cd.c:612: warning: `rc' might be used uninitialized in this function
After applying the trivial patch below, which just initializes
the variable to zero, the kernel doesn't crash any longer:
Starting the hotplug events dispatcher: udevd.
Synthesizing the initial hotplug events...
hda: command error: status=0x51 { DriveReady SeekComplete Error }
hda: command error: error=0x54 <3>{ AbortedCommand LastFailedSense=0x05 }
ide: failed opcode was: unknown
done.
Signed-off-by: Helge Deller <deller@gmx.de>
Acked-by: Borislav Petkov <petkovbb@gmail.com>
Cc: Linus <torvalds@linux-foundation.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Fix UDMA throughput bug: tCYC averages t2CYCTYP/2, but the code
previously assumed it was the same as t2CYCTYP. (That is, it was
using just one clock edge, not both.) Move the table's type
declaration so it's adjacent to the table, making it more clear
what those numbers mean.
On one system this change increased throughput by almost 4x: UDMA/66
sometimes topped 23 MB/sec (on a drive known to do much better). On
another system it was around a 10% win (UDMA/66 up to 7+ MB/sec).
The difference might be caused by the ratio between memory and IDE
clocks. In the system with large speedup, this was exactly 2 (as a
workaround for a rev 1.1 silicon bug). The other system used a more
standard ratio of 1.63 (and rev 2.1 silicon) ... clock domain synch
might have some issues, they're not unheard-of.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Impact: drop unnecessary code
Now that everything uses bio and block operations, there is no need to
reset request fields manually when retrying a request. Every field is
guaranteed to be always valid. Drop unnecessary request field
resetting from ide_dma_timeout_retry().
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: remove code path which is no longer necessary
All IDE data transfers now use rq->bio. Simplify ide_map_sg()
accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Impact: remove fields and code paths which are no longer necessary
Now that ide-tape uses standard mechanisms to transfer data, special
case handling for bh handling can be dropped from ide-atapi. Drop the
followings.
* pc->cur_pos, b_count, bh and b_data
* drive->pc_update_buffers() and pc_io_buffers().
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: cleanup
idetape_chrdev_read/write() functions are unnecessarily complex when
everything can be handled in a single loop. Collapse
idetape_add_chrdev_read/write_request() into the rw functions and
simplify the implementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: cleanup
Byte size is what most issue functions deal with, make
idetape_queue_rw_tail() and its wrappers take byte size instead of
sector counts. idetape_chrdev_read() and write() functions are
converted to use tape->buffer_size instead of ctl from tape->cap.
This cleans up code a little bit and will ease the next r/w
reimplementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: kill now unnecessary idetape_bh
With everything using standard mechanisms, there is no need for
idetape_bh anymore. Kill it and use tape->buf, cur and valid to
describe data buffer instead.
Changes worth mentioning are...
* idetape_queue_rq_tail() now always queue tape->buf and and adjusts
buffer state properly before completion.
* idetape_pad_zeros() clears the buffer only once.
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: use standard way to transfer data
ide-tape uses rq in an interesting way. For r/w requests, rq->special
is used to carry a private buffer management structure idetape_bh and
rq->nr_sectors and current_nr_sectors are initialized to the number of
idetape blocks which isn't necessary 512 bytes. Also,
rq->current_nr_sectors is used to report back the residual count in
units of idetape blocks.
This peculiarity taxes both block layer and ide. ide-atapi has
different paths and hooks to accomodate it and what a rq means becomes
quite confusing and making changes at the block layer becomes quite
difficult and error-prone.
This patch makes ide-tape use bio instead. With the previous patch,
ide-tape currently is using single contiguos buffer so replacing it
isn't difficult. Data buffer is mapped into bio using
blk_rq_map_kern() in idetape_queue_rw_tail(). idetape_io_buffers()
and idetape_update_buffers() are dropped and pc->bh is set to null to
tell ide-atapi to use standard data transfer mechanism and idetape_bh
byte counts are updated by the issuer on completion using the residual
count.
This change also nicely removes the FIXME in ide_pc_intr() where
ide-tape rqs need to be completed using ide_rq_bytes() instead of
blk_rq_bytes() (although this didn't really matter as the request
didn't have bio).
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Impact: simpler buffer allocation and handling, kills OOM, fix DMA transfers
ide-tape has its own multiple buffer mechanism using struct
idetape_bh. It allocates buffer with decreasing order-of-two
allocations so that it results in minimum number of segments.
However, the implementation is quite complex and works in a way that
no other block or ide driver works necessitating a lot of special case
handling.
The benefit this complex allocation scheme brings is questionable as
PIO or DMA the number of segments (16 maximum) doesn't make any
noticeable difference and it also doesn't negate the need for multiple
order allocation which can fail under memory pressure or high
fragmentation although it does lower the highest order necessary by
one when the buffer size isn't power of two.
As the first step to remove the custom buffer management, this patch
makes ide-tape allocate single continous buffer. The maximum order is
four. I doubt the change would cause any trouble but if it ever
matters, it should be converted to regular sg mechanism like everyone
else and even in that case dropping custom buffer handling and moving
to standard mechanism first make sense as an intermediate step.
This patch makes the first bh to contain the whole buffer and drops
multi bh handling code. Following patches will make further changes.
This patch has the side effect of killing OOM triggered by allocation
path and fixing DMA transfers. Previously, bug in alloc path
triggered OOM on command issue and commands were passed to DMA engine
without DMA-mapping all the segments.
Signed-off-by: Tejun Heo <tj@kernel.org>
Impact: allow residual count implementation in ->pc_callback()
rq->data_len has two duties - carrying the number of input bytes on
issue and carrying residual count back to the issuer on completion.
ide-atapi completion callback ->pc_callback() is the right place to do
this but currently ide-atapi depends on rq->data_len carrying the
original request size after calling ->pc_callback() to complete the pc
request.
This patch makes ide_pc_intr(), ide_tape_issue_pc() and
ide_floppy_issue_pc() cache length to complete before calling
->pc_callback() so that it can modify rq->data_len as necessary.
Note: As using rq->data_len for two purposes can make cases like this
incorrect in subtle ways, future changes will introduce separate
field for residual count.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
