mg_disk implements its own partial completion.  Convert to standard
block layer partial completion.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: unsik Kim <donari75@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

include/linux/mg_disk.h is used only by drivers/block/mg_disk.c.  No
reason to put it in a separate header.  Fold it into mg_disk.c.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: unsik Kim <donari75@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

swim curiously tries to update request parameters before calling
__blk_end_request() when __blk_end_request() will do it anyway and
unnecessarily checks whether current_nr_sectors is zero right after
fetching.

Drop unnecessary stuff and use standard block layer mechanisms.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Laurent Vivier <Laurent@lvivier.info>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

swim3 curiously tries to update request parameters before calling
__blk_end_request() when __blk_end_request() will do it anyway, and it
updates request for partial completion manually instead of using
blk_update_request().  Also, it does some spurious checks on rq such
as testing whether rq->sector is negative or current_nr_sectors is
zero right after fetching.

Drop unnecessary stuff and use standard block layer mechanisms.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

hd read/write_intr() functions manually manipulate request to
incrementally complete it, which block layer already supports.  Simply
use block layer completion routines instead of manual partial
completion.

While at it, clear unnecessary elv_next_request() check at the tail of
read_intr().  This also makes read and write_intr() more consistent.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

ubd curiously updates rq->sector while issuing the request in multiple
pieces.  Don't do it and simply use local copy of sector.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

ubd had its own block request partial completion mechanism, which is
unnecessary as block layer already does it.  Kill ubd_end_request()
and ubd_finish() and replace them with direct call to
blk_end_request().

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

vdc_end_request() is a thin silly wrapper on top of
__blk_end_request().  Kill it.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

ps3disk_interrupt() always completes requests fully but it uses
rq->hard_cur_sectors for FLUSH requests for some reason.  Drop them
and simply use __blk_end_request_all().

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

rq_data_dir() can only be READ or WRITE and rq->sector and nr_sectors
are always automatically updated after partial request completion.
Don't worry about rq_data_dir() not being either READ or WRITE or
manually update sector and nr_sectors.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jörg Dorchain <joerg@dorchain.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: unsik Kim <donari75@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

blk_get_request() always returns properly zeroed requests.  Don't set
fields to zero/NULL unnecessarily.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

In the process of mindlessly copying [__]blk_end_request_all(),
[__]blk_end_request_cur() ended up returning void even though they're
partial completion functions.  Fix it.

[ Impact: fix braindead API ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

We currently don't do merging on discard requests, but we potentially
could. If we do, then we need to include discard requests in the IO
accounting, or merging would end up decrementing in_flight IO counters
for an IO which never incremented them.

So enable accounting for discard requests.

Problem found by Nikanth Karthikesan <knikanth@suse.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

We currently check for file system requests outside of blk_do_io_stat(rq),
but we may as well just include it.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Now that all block request data transfer is done via bio, rq->data
isn't used.  Kill it.

While at it, make the roles of rq->special and buffer clear.

[ Impact: drop now unncessary field from struct request ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Boaz Harrosh <bharrosh@panasas.com>

omap mailbox uses rq->data as the second opaque pointer to carry
mbox_msg_t and rq->special message argument which is needed only for
tx.  Add and use omap_msg_tx_data struct for tx and use rq->special
for mbox_msg_t for rx such that only rq->special is used as opaque
pointer.

[ Impact: cleanup rq->data usage, extra kmalloc in msg_send ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Russell King <rmk@arm.linux.org.uk>

end_request() has been kept around for backward compatibility;
however, it's about time for it to go away.

* There aren't too many users left.

* Its use of @updtodate is pretty confusing.

* In some cases, newer code ends up using mixture of end_request() and
  [__]blk_end_request[_all](), which is way too confusing.

So, add [__]blk_end_request_cur() and replace end_request() with it.
Most conversions are straightforward.  Noteworthy ones are...

* paride/pcd: next_request() updated to take 0/-errno instead of 1/0.

* paride/pf: pf_end_request() and next_request() updated to take
  0/-errno instead of 1/0.

* xd: xd_readwrite() updated to return 0/-errno instead of 1/0.

* mtd/mtd_blkdevs: blktrans_discard_request() updated to return
  0/-errno instead of 1/0.  Unnecessary local variable res
  initialization removed from mtd_blktrans_thread().

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NJoerg Dorchain <joerg@dorchain.net>
Acked-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NLaurent Vivier <Laurent@lvivier.info>
Cc: Tim Waugh <tim@cyberelk.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Markus Lidel <Markus.Lidel@shadowconnect.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Cc: unsik Kim <donari75@gmail.com>

There are many [__]blk_end_request() call sites which call it with
full request length and expect full completion.  Many of them ensure
that the request actually completes by doing BUG_ON() the return
value, which is awkward and error-prone.

This patch adds [__]blk_end_request_all() which takes @rq and @error
and fully completes the request.  BUG_ON() is added to to ensure that
this actually happens.

Most conversions are simple but there are a few noteworthy ones.

* cdrom/viocd: viocd_end_request() replaced with direct calls to
  __blk_end_request_all().

* s390/block/dasd: dasd_end_request() replaced with direct calls to
  __blk_end_request_all().

* s390/char/tape_block: tapeblock_end_request() replaced with direct
  calls to blk_end_request_all().

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mike Miller <mike.miller@hp.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Alex Dubov <oakad@yahoo.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>

rq->start_time was initialized in init_request_from_bio() so special
requests didn't have start_time set.  This has been okay as start_time
has been used only for fs requests; however, there is no indication of
this actually is the case or not.  Set rq->start_time in blk_rq_init()
and guarantee that all initialized rq's have its start_time set.  This
improves consistency at virtually no cost and future changes will make
use of the timestamp for !bio requests.

[ Impact: rq->start_time is valid for all requests ]
Signed-off-by: NTejun Heo <tj@kernel.org>

Request completion has gone through several changes and became a bit
messy over the time.  Clean it up.

1. end_that_request_data() is a thin wrapper around
   end_that_request_data_first() which checks whether bio is NULL
   before doing anything and handles bidi completion.
   blk_update_request() is a thin wrapper around
   end_that_request_data() which clears nr_sectors on the last
   iteration but doesn't use the bidi completion.

   Clean it up by moving the initial bio NULL check and nr_sectors
   clearing on the last iteration into end_that_request_data() and
   renaming it to blk_update_request(), which makes blk_end_io() the
   only user of end_that_request_data().  Collapse
   end_that_request_data() into blk_end_io().

2. There are four visible completion variants - blk_end_request(),
   __blk_end_request(), blk_end_bidi_request() and end_request().
   blk_end_request() and blk_end_bidi_request() uses blk_end_request()
   as the backend but __blk_end_request() and end_request() use
   separate implementation in __blk_end_request() due to different
   locking rules.

   blk_end_bidi_request() is identical to blk_end_io().  Collapse
   blk_end_io() into blk_end_bidi_request(), separate out request
   update into internal helper blk_update_bidi_request() and add
   __blk_end_bidi_request().  Redefine [__]blk_end_request() as thin
   inline wrappers around [__]blk_end_bidi_request().

3. As the whole request issue/completion usages are about to be
   modified and audited, it's a good chance to convert completion
   functions return bool which better indicates the intended meaning
   of return values.

4. The function name end_that_request_last() is from the days when it
   was a public interface and slighly confusing.  Give it a proper
   internal name - blk_finish_request().

5. Add description explaning that blk_end_bidi_request() can be safely
   used for uni requests as suggested by Boaz Harrosh.

The only visible behavior change is from #1.  nr_sectors counts are
cleared after the final iteration no matter which function is used to
complete the request.  I couldn't find any place where the code
assumes those nr_sectors counters contain the values for the last
segment and this change is good as it makes the API much more
consistent as the end result is now same whether a request is
completed using [__]blk_end_request() alone or in combination with
blk_update_request().

API further cleaned up per Christoph's suggestion.

[ Impact: cleanup, rq->*nr_sectors always updated after req completion ]
Signed-off-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NBoaz Harrosh <bharrosh@panasas.com>
Cc: Christoph Hellwig <hch@infradead.org>

With recent IDE updates, blk_end_request_callback() doesn't have any
user now.  Kill it.

[ Impact: removal of unused convoluted interface ]
Signed-off-by: NTejun Heo <tj@kernel.org>

Impact: code reorganization

elv_next_request() and elv_dequeue_request() are public block layer
interface than actual elevator implementation.  They mostly deal with
how requests interact with block layer and low level drivers at the
beginning of rqeuest processing whereas __elv_next_request() is the
actual eleveator request fetching interface.

Move the two functions to blk-core.c.  This prepares for further
interface cleanup.
Signed-off-by: NTejun Heo <tj@kernel.org>

Reorder request completion functions such that

* All request completion functions are located together.

* Functions which are used by only one caller is put right above the
  caller.

* end_request() is put after other completion functions but before
  blk_update_request().

This change is for completion function cleanup which will follow.

[ Impact: cleanup, code reorganization ]
Signed-off-by: NTejun Heo <tj@kernel.org>

* In blk_rq_timed_out_timer(), else { if } to else if

* In blk_add_timer(), simplify if/else block

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>

blk_insert_request() doesn't need to worry about REQ_SOFTBARRIER.
Don't set it.  Combined with recent ide updates, REQ_SOFTBARRIER is
now only used in elevator proper and for discard requests.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>

RQ_NOMERGE_FLAGS already clears defines which REQ flags aren't
mergeable.  There is no reason to specify it superflously.  It only
adds to confusion.  Don't set REQ_NOMERGE for barriers and requests
with specific queueing directive.  REQ_NOMERGE is now exclusively used
by the merging code.

[ Impact: cleanup ]
Signed-off-by: NTejun Heo <tj@kernel.org>

blk_start_queueing() is identical to __blk_run_queue() except that it
doesn't check for recursion.  None of the current users depends on
blk_start_queueing() running request_fn directly.  Replace usages of
blk_start_queueing() with [__]blk_run_queue() and kill it.

[ Impact: removal of mostly duplicate interface function ]
Signed-off-by: NTejun Heo <tj@kernel.org>

__blk_run_queue wraps blk_invoke_request_fn() such that it
additionally removes plug and bails out early if the queue is empty.
Both extra operations have their own pending mechanisms and don't
cause any harm correctness-wise when they are done superflously.

The only user of blk_invoke_request_fn() being blk_start_queue(),
there isn't much reason to keep both functions around.  Merge
blk_invoke_request_fn() into __blk_run_queue() and make
blk_start_queue() use __blk_run_queue() instead.

[ Impact: merge two subtly different internal functions ]
Signed-off-by: NTejun Heo <tj@kernel.org>

Doing a proper block dev ->readpages() speeds up the crazy dump(8)
approach of using interleaved process IO.
Signed-off-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Enable by default support for large devices and files (CONFIG_LBD):

- With 1TB disks being a commodity hardware it is quite easy to hit 2TB
  limitation while building RAIDs etc. and many distros have been using
  CONFIG_LBD=y by default already (at least Fedora 10 and openSUSE 11.1).

- This should also prevent a subtle ext4 filesystem compatibility issue:
  mke2fs.ext4 defaults to creating filesystems with huge_files feature
  enabled and such filesystems cannot be later mounted read-write on
  machines with CONFIG_LBD=n (it should be quite easy to hit this issue
  when trying to use filesystem created using distro kernel on system
  running the self-build kernel, think about USB disk enclosures & co.).

While at it:

- Clarify config option help text w.r.t. mounting ext4 filesystems
  (they can be mounted with CONFIG_LBD=n but in the read-only mode).

Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.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: NTejun 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: NTejun 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: NTejun 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: NTejun 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: NTejun Heo <tj@kernel.org>

Impact: cleanup

Read and write init paths are almost identical.  Unify them into
idetape_init_rw().
Signed-off-by: NTejun 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: NTejun 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: NTejun 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: NTejun Heo <tj@kernel.org>