Commit Graph

350 Commits

Author SHA1 Message Date
Vasily Tarasov
c2dea2d1fd cfq: async queue allocation per priority
If we have two processes with different ioprio_class, but the same
ioprio_data, their async requests will fall into the same queue. I guess
such behavior is not expected, because it's not right to put real-time
requests and best-effort requests in the same queue.

The attached patch fixes the problem by introducing additional *cfqq
fields on cfqd, pointing to per-(class,priority) async queues.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-20 10:06:38 +02:00
Paul Mundt
20c2df83d2 mm: Remove slab destructors from kmem_cache_create().
Slab destructors were no longer supported after Christoph's
c59def9f22 change. They've been
BUGs for both slab and slub, and slob never supported them
either.

This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2007-07-20 10:11:58 +09:00
Yoann Padioleau
dd00cc486a some kmalloc/memset ->kzalloc (tree wide)
Transform some calls to kmalloc/memset to a single kzalloc (or kcalloc).

Here is a short excerpt of the semantic patch performing
this transformation:

@@
type T2;
expression x;
identifier f,fld;
expression E;
expression E1,E2;
expression e1,e2,e3,y;
statement S;
@@

 x =
- kmalloc
+ kzalloc
  (E1,E2)
  ...  when != \(x->fld=E;\|y=f(...,x,...);\|f(...,x,...);\|x=E;\|while(...) S\|for(e1;e2;e3) S\)
- memset((T2)x,0,E1);

@@
expression E1,E2,E3;
@@

- kzalloc(E1 * E2,E3)
+ kcalloc(E1,E2,E3)

[akpm@linux-foundation.org: get kcalloc args the right way around]
Signed-off-by: Yoann Padioleau <padator@wanadoo.fr>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Acked-by: Russell King <rmk@arm.linux.org.uk>
Cc: Bryan Wu <bryan.wu@analog.com>
Acked-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Dave Airlie <airlied@linux.ie>
Acked-by: Roland Dreier <rolandd@cisco.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Acked-by: Pierre Ossman <drzeus-list@drzeus.cx>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: "David S. Miller" <davem@davemloft.net>
Acked-by: Greg KH <greg@kroah.com>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-19 10:04:50 -07:00
Linus Torvalds
f3d9071667 Merge branch 'bsg' of git://git.kernel.dk/data/git/linux-2.6-block
* 'bsg' of git://git.kernel.dk/data/git/linux-2.6-block:
  bsg: fix missing space in version print
  Don't define empty struct bsg_class_device if !CONFIG_BLK_DEV_BSG
  bsg: Kconfig updates
  bsg: minor cleanup
  bsg: device hash table cleanup
  bsg: fix initialization error handling bugs
  bsg: mark FUJITA Tomonori as bsg maintainer
  bsg: convert to dynamic major
  bsg: address various review comments
2007-07-17 15:26:31 -07:00
Akinobu Mita
f4480240f7 unregister_blkdev(): return void
Put WARN_ON and fixed all callers of unregister_blkdev().  Now we can make
unregister_blkdev return void.

Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 10:23:03 -07:00
Akinobu Mita
294462a5c6 unregister_blkdev(): do WARN_ON on failure
When unregister_blkdev() has failed, something wrong happened.  This patch
adds WARN_ON to notify of such badness.

Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 10:23:03 -07:00
Christoph Lameter
94f6030ca7 Slab allocators: Replace explicit zeroing with __GFP_ZERO
kmalloc_node() and kmem_cache_alloc_node() were not available in a zeroing
variant in the past.  But with __GFP_ZERO it is possible now to do zeroing
while allocating.

Use __GFP_ZERO to remove the explicit clearing of memory via memset whereever
we can.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 10:23:02 -07:00
Jens Axboe
5d3a8cd34b bsg: fix missing space in version print
Tomo introduced a bug in his commit, removing the space between
"driver" and "version" in the init printk.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-17 15:10:09 +02:00
FUJITA Tomonori
319a7b7fb9 bsg: Kconfig updates
- add the detailed explanation.
- remove 'default y'.
- make 'EXPERIMENTAL' keyword visible to the user in menu.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-17 12:22:09 +02:00
FUJITA Tomonori
0ed081ce20 bsg: minor cleanup
- fix MODULE_DESCRIPTION typo.
- unify MODULE_DESCRIPTION and bsg_version.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-17 12:21:35 +02:00
FUJITA Tomonori
1c1133e1ff bsg: device hash table cleanup
- kill unused bsg_list_idx macro.
- add bsg_dev_idx_hash() that returns an appropriate hlist_head.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-17 12:21:15 +02:00
FUJITA Tomonori
9b9f770cef bsg: fix initialization error handling bugs
This fixes the following bugs and cleans up the initialization code:

- cdev_del is missing.
- unregister_chrdev_region should be used instead of unregister_chrdev.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-17 12:20:46 +02:00
Jens Axboe
46f6ef4afc bsg: convert to dynamic major
240 was hardcoded, that was clearly a dumb mistake. Convert bsg
to use alloc_chrdev_region() to retrieve a dynamic major.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-17 08:56:10 +02:00
Jens Axboe
25fd164303 bsg: address various review comments
This address most of the comments made by Andrew. The two remaining
are conversion to idr, and dynamic major.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-17 08:52:29 +02:00
Linus Torvalds
29417b899a Make BLK_DEV_BSG depend strictly on SCSI=y
The SCSI code can be compiled modular, but BLK_DEV_BSG currently cannot,
and depends on the SCSI layer.  So make sure that it depends on the SCSI
layer being compiled in, not just available as a module.

Noticed by Jeff Garzik and S.Çağlar Onur.

Cc: Jeff Garzik <jeff@garzik.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: S.Çağlar Onur <caglar@pardus.org.tr>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-16 16:53:22 -07:00
Linus Torvalds
abce891a10 Fix new generic block device SG compile
We had a merge issue with the "dentry" field going away from the
kobject, and being replaced by a sysfs_dirent field (named "sd")
instead.  That broke the BSG compile.

Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@SteelEye.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-16 11:18:23 -07:00
FUJITA Tomonori
58ff411e0d bsg: Kconfig updates
This updates bsg entry in Kconfig:

- bsg supports sg v4
- bsg depends on SCSI
- it might be better to mark it experimental for a while

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:47 +02:00
FUJITA Tomonori
15d10b611f bsg: add SCSI transport-level request support
This enables bsg to handle SCSI transport-level request like SAS
management protocol (SMP).

- add BSG_SUB_PROTOCOL_{SCSI_CMD, SCSI_TMF, SCSI_TRANSPORT} definitions.
- SCSI transport-level requests skip blk_verify_command().

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:47 +02:00
FUJITA Tomonori
2c9ecdf40a bsg: add bidi support
bsg uses the rq->next_rq pointer for a bidi request.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:47 +02:00
FUJITA Tomonori
abae1fde63 add a struct request pointer to the request structure
This adds a struct request pointer to the request structure for the
second data phase (bidi for now). A request queue supporting bidi
requests sets QUEUE_FLAG_BIDI. This prevents sending bidi requests to
a non-bidi queue.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:46 +02:00
FUJITA Tomonori
efba1a31f3 bsg: fix the deadlock on discarding done commands
The previous commit introduced a deadlock in discarding commands,
because we forget to unlock the bd spinlock.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:46 +02:00
FUJITA Tomonori
e7d7217324 bsg: fix a blocking read bug
This patch fixes a bug that read() returns ENODATA even with a
blocking file descriptor when there are no commands pending.

This also includes some cleanups.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:46 +02:00
FUJITA Tomonori
4cf0723ac8 bsg: minor bug fixes
This fixes the following minor issues:

- add EXPORT_SYMBOL_GPL for bsg_register_queue and
bsg_unregister_queue.

- shut up gcc warnings

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <axboe@nelson.home.kernel.dk>
2007-07-16 08:52:46 +02:00
FUJITA Tomonori
292b7f2712 improve bsg device allocation
This patch addresses on two issues on bsg device allocation.

- the current maxium number of bsg devices is 256. It's too small if
we allocate bsg devices to all SCSI devices, transport entities, etc.
This increses the maxium number to 32768 (taken from the sg driver).

- SCSI devices are dynamically added and removed. Currently, bsg can't
handle it well since bsd_device->minor is simply increased.

This is dependent on the patchset that I posted yesterday:

http://marc.info/?l=linux-scsi&m=117440208726755&w=2

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:46 +02:00
FUJITA Tomonori
4e2872d6b0 bind bsg to all SCSI devices
This patch binds bsg to all SCSI devices (their request queues) like
the current sg driver does. We can send SCSI commands to non disk and
cdrom scsi devices like OSD via bsg.

This patch removes bsg_register_queue from blk_register_queue so bsg
devices aren't bound to non SCSI block devices. If they want bsg, I'll
send a patch to do that.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:46 +02:00
FUJITA Tomonori
d351af01b9 bsg: bind bsg to request_queue instead of gendisk
This patch binds bsg devices to request_queue instead of gendisk. Any
objects (like transport entities) can define own request_handler and
create own bsg device.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:46 +02:00
FUJITA Tomonori
45e79a3acd bsg: add a request_queue argument to scsi_cmd_ioctl()
bsg uses scsi_cmd_ioctl() for some SCSI/sg ioctl
commands. scsi_cmd_ioctl() gets a request queue from a gendisk
arguement. This prevents bsg being bound to SCSI devices that don't
have a gendisk (like OSD). This adds a request_queue argument to
scsi_cmd_ioctl(). The SCSI/sg ioctl commands doesn't use a gendisk so
it's safe for any SCSI devices to use scsi_cmd_ioctl().

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:45 +02:00
FUJITA Tomonori
7e75d73080 bsg: simplify __bsg_alloc_command failpath
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:45 +02:00
Jens Axboe
264a047218 bsg: add cheasy error checks for sysfs stuff
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:45 +02:00
Jens Axboe
5309cb38de Add queue resizing support
Just get rid of the preallocated command map, use the slab cache
to get/free commands instead.

Original patch from FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
changed by me to not use a mempool.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:45 +02:00
Jens Axboe
2ef7086a20 bsg: silence a bogus gcc warning
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:45 +02:00
Jens Axboe
b711afa695 bsg: style cleanup
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:45 +02:00
FUJITA Tomonori
10e8855b94 bsg: add SG_IO to SG v4
This adds SG_IO support to SG v4.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:44 +02:00
FUJITA Tomonori
70e36eceaf bsg: replace SG v3 with SG v4
This patch replaces SG v3 in bsg with SG v4 (except for SG_IO).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:44 +02:00
FUJITA Tomonori
337ad41dea block: export blk_verify_command for SG v4
blk_fill_sghdr_rq doesn't work for SG v4 so verify_command needed to
be exported.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:44 +02:00
FUJITA Tomonori
9e69fbb537 bsg: minor cleanups
This just kills linux/config.h and dprintk warnings.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:44 +02:00
FUJITA Tomonori
ac6b91b803 block: changes for blk_rq_unmap_user new API
This converts block/scsi_ioctl.c use blk_rq_unmap_user new
API. blk_unmap_sghdr_rq is too simple and it might be better to remove
it.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:44 +02:00
Jens Axboe
3d6392cfbd bsg: support for full generic block layer SG v3
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-16 08:52:44 +02:00
Matthias Kaehlcke
70cee26e02 Use list_for_each_entry() instead of list_for_each() in the block device
elevator

Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-10 13:43:32 +02:00
Jan Engelhardt
16ed002f22 Use menuconfigs instead of menus, so the whole menu can be disabled at once
instead of going through all options.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-10 13:43:27 +02:00
Jens Axboe
15c31be4d5 cfq-iosched: fix async queue behaviour
With the cfq_queue hash removal, we inadvertently got rid of the
async queue sharing. This was not intentional, in fact CFQ purposely
shares the async queue per priority level to get good merging for
async writes.

So put some logic in cfq_get_queue() to track the shared queues.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-10 13:43:25 +02:00
Tejun Heo
f4b09303d0 [BLOCK] drop unnecessary bvec rewinding from flush_dry_bio_endio
Barrier bios are completed twice - once after the barrier write itself
is done and again after the whole sequence is complete.
flush_dry_bio_endio() is for the first completion.  It doesn't really
complete the bio.  It rewinds bvec and resets bio so that it can be
completed again when the whole barrier sequence is complete.

The bvec rewinding code has the following problems.

1. The rewinding code is wrong because filesystems may pass bvec with
   non zero bv_offset.

2. The block layer doesn't guarantee anything about the state of
   bvec array on request completion.  bv_offset and len are updated
   iff __end_that_request_first() completes the bvec partially.

Because of #2, #1 doesn't really matter (nobody cares whether bvec is
re-wound correctly or not) but then again by not doing unwinding at
all, we'll always give back the same bvec to the caller as full bvec
completion doesn't alter bvecs and the final completion is always full
completion.

Drop unnecessary rewinding code.

This is spotted by Neil Brown.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-10 08:03:33 +02:00
Jens Axboe
32eef96411 blk_hw_contig_segment(): bad segment size checks
Two bugs in there:

- The virt oversize check should use the current bio hardware back
  size and the next bio front size, not the same bio. Spotted by
  Neil Brown.

- The segment size check should add hw front sizes, not total bio
  sizes. Spotted by James Bottomley

Acked-by: James Bottomley <James.Bottomley@SteelEye.com>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-10 08:03:32 +02:00
Tejun Heo
bc90ba093a block: always requeue !fs requests at the front
SCSI marks internal commands with REQ_PREEMPT and push it at the front
of the request queue using blk_execute_rq().  When entering suspended
or frozen state, SCSI devices are quiesced using
scsi_device_quiesce().  In quiesced state, only REQ_PREEMPT requests
are processed.  This is how SCSI blocks other requests out while
suspending and resuming.  As all internal commands are pushed at the
front of the queue, this usually works.

Unfortunately, this interacts badly with ordered requeueing.  To
preserve request order on requeueing (due to busy device, active EH or
other failures), requests are sorted according to ordered sequence on
requeue if IO barrier is in progress.

The following sequence deadlocks.

1. IO barrier sequence issues.

2. Suspend requested.  Queue is quiesced with part or all of IO
   barrier sequence at the front.

3. During suspending or resuming, SCSI issues internal command which
   gets deferred and requeued for some reason.  As the command is
   issued after the IO barrier in #1, ordered requeueing code puts the
   request after IO barrier sequence.

4. The device is ready to process requests again but still is in
   quiesced state and the first request of the queue isn't
   REQ_PREEMPT, so command processing is deadlocked -
   suspending/resuming waits for the issued request to complete while
   the request can't be processed till device is put back into
   running state by resuming.

This can be fixed by always putting !fs requests at the front when
requeueing.

The following thread reports this deadlock.

  http://thread.gmane.org/gmane.linux.kernel/537473

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: David Greaves <david@dgreaves.com>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-06-15 16:12:20 -07:00
Kristen Carlson Accardi
8ce7ad7b2d genhd: send async notification on media change
Send an uevent to user space to indicate that a media change event has
occurred.

Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-23 20:14:12 -07:00
Kristen Carlson Accardi
86ce18d7b7 genhd: expose AN to user space
Allow user space to determine if a disk supports Asynchronous Notification of
media changes.  This is done by adding a new sysfs file "capability_flags",
which is documented in (insert file name).  This sysfs file will export all
disk capabilities flags to user space.  We also define a new flag to define
the media change notification capability.

Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-23 20:14:11 -07:00
Jens Axboe
f653c34dd3 ll_rw_blk: fix gcc 4.2 warning on current_io_context()
current_io_context() is both static and exported with EXPORT_SYMBOL().
As there are no users outside of ll_rw_blk.c itself, just kill the
export.

Problem reported by Martin Michlmayr <tbm@cyrius.com>

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-15 10:44:15 -07:00
Neil Brown
d89d87965d When stacked block devices are in-use (e.g. md or dm), the recursive calls
to generic_make_request can use up a lot of space, and we would rather they
didn't.

As generic_make_request is a void function, and as it is generally not
expected that it will have any effect immediately, it is safe to delay any
call to generic_make_request until there is sufficient stack space
available.

As ->bi_next is reserved for the driver to use, it can have no valid value
when generic_make_request is called, and as __make_request implicitly
assumes it will be NULL (ELEVATOR_BACK_MERGE fork of switch) we can be
certain that all callers set it to NULL.  We can therefore safely use
bi_next to link pending requests together, providing we clear it before
making the real call.

So, we choose to allow each thread to only be active in one
generic_make_request at a time.  If a subsequent (recursive) call is made,
the bio is linked into a per-thread list, and is handled when the active
call completes.

As the list of pending bios is per-thread, there are no locking issues to
worry about.

I say above that it is "safe to delay any call...".  There are, however,
some behaviours of a make_request_fn which would make it unsafe.  These
include any behaviour that assumes anything will have changed after a
recursive call to generic_make_request.

These could include:
 - waiting for that call to finish and call it's bi_end_io function.
   md use to sometimes do this (marking the superblock dirty before
   completing a write) but doesn't any more
 - inspecting the bio for fields that generic_make_request might
   change, such as bi_sector or bi_bdev.  It is hard to see a good
   reason for this, and I don't think anyone actually does it.
 - inspecing the queue to see if, e.g. it is 'full' yet.  Again, I
   think this is very unlikely to be useful, or to be done.

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <dm-devel@redhat.com>

Alasdair G Kergon <agk@redhat.com> said:

 I can see nothing wrong with this in principle.

 For device-mapper at the moment though it's essential that, while the bio
 mappings may now get delayed, they still get processed in exactly
 the same order as they were passed to generic_make_request().

 My main concern is whether the timing changes implicit in this patch
 will make the rare data-corrupting races in the existing snapshot code
 more likely. (I'm working on a fix for these races, but the unfinished
 patch is already several hundred lines long.)

 It would be helpful if some people on this mailing list would test
 this patch in various scenarios and report back.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-05-11 13:28:37 +02:00
Linus Torvalds
9a9136e270 Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial
* git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial: (25 commits)
  sound: convert "sound" subdirectory to UTF-8
  MAINTAINERS: Add cxacru website/mailing list
  include files: convert "include" subdirectory to UTF-8
  general: convert "kernel" subdirectory to UTF-8
  documentation: convert the Documentation directory to UTF-8
  Convert the toplevel files CREDITS and MAINTAINERS to UTF-8.
  remove broken URLs from net drivers' output
  Magic number prefix consistency change to Documentation/magic-number.txt
  trivial: s/i_sem /i_mutex/
  fix file specification in comments
  drivers/base/platform.c: fix small typo in doc
  misc doc and kconfig typos
  Remove obsolete fat_cvf help text
  Fix occurrences of "the the "
  Fix minor typoes in kernel/module.c
  Kconfig: Remove reference to external mqueue library
  Kconfig: A couple of grammatical fixes in arch/i386/Kconfig
  Correct comments in genrtc.c to refer to correct /proc file.
  Fix more "deprecated" spellos.
  Fix "deprecated" typoes.
  ...

Fix trivial comment conflict in kernel/relay.c.
2007-05-09 12:54:17 -07:00
Rafael J. Wysocki
8bb7844286 Add suspend-related notifications for CPU hotplug
Since nonboot CPUs are now disabled after tasks and devices have been
frozen and the CPU hotplug infrastructure is used for this purpose, we need
special CPU hotplug notifications that will help the CPU-hotplug-aware
subsystems distinguish normal CPU hotplug events from CPU hotplug events
related to a system-wide suspend or resume operation in progress.  This
patch introduces such notifications and causes them to be used during
suspend and resume transitions.  It also changes all of the
CPU-hotplug-aware subsystems to take these notifications into consideration
(for now they are handled in the same way as the corresponding "normal"
ones).

[oleg@tv-sign.ru: cleanups]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-09 12:30:56 -07:00