linux-toradex.git/drivers/block/nbd.c, branch v2.6.27.20

nbd: fix I/O hang on disconnected nbds

2009-02-17T17:46:15+00:00

commit 4d48a542b42747c36a5937447d9c3de7c897ea50 upstream.

Fix a problem that causes I/O to a disconnected (or partially initialized)
nbd device to hang indefinitely.  To reproduce:

# ioctl NBD_SET_SIZE_BLOCKS /dev/nbd23 514048
# dd if=/dev/nbd23 of=/dev/null bs=4096 count=1

...hangs...

This can also occur when an nbd device loses its nbd-client/server
connection.  Although we clear the queue of any outstanding I/Os after the
client/server connection fails, any additional I/Os that get queued later
will hang.

This bug may also be the problem reported in this bug report:
http://bugzilla.kernel.org/show_bug.cgi?id=12277

Testing would need to be performed to determine if the two issues are the
same.

This problem was introduced by the new request handling thread code ("NBD:
allow nbd to be used locally", 3/2008), which entered into mainline around
2.6.25.

The fix, which is fairly simple, is to restore the check for lo->sock
being NULL in do_nbd_request.  This causes I/O to an uninitialized nbd to
immediately fail with an I/O error, as it did prior to the introduction of
this bug.

Signed-off-by: Paul Clements 
Reported-by: Jon Nelson 
Acked-by: Pavel Machek 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

nbd: fix memory leak of nbd_dev array

2008-08-20T22:40:30+00:00

We leak the memory allocated for the nbd_dev array at multiple places.
Fix them by either adding a kfree() or by rearranging code to return
before we allocate the memory.

Signed-off-by: Sven Wegener 
Cc: Paul Clements 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block

2008-04-29T15:18:03+00:00

* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  block: Skip I/O merges when disabled
  block: add large command support
  block: replace sizeof(rq->cmd) with BLK_MAX_CDB
  ide: use blk_rq_init() to initialize the request
  block: use blk_rq_init() to initialize the request
  block: rename and export rq_init()
  block: no need to initialize rq->cmd with blk_get_request
  block: no need to initialize rq->cmd in prepare_flush_fn hook
  block/blk-barrier.c:blk_ordered_cur_seq() mustn't be inline
  block/elevator.c:elv_rq_merge_ok() mustn't be inline
  block: make queue flags non-atomic
  block: add dma alignment and padding support to blk_rq_map_kern
  unexport blk_max_pfn
  ps3disk: Remove superfluous cast
  block: make rq_init() do a full memset()
  relay: fix splice problem

Remove duplicated unlikely() in IS_ERR()

2008-04-29T15:06:25+00:00

Some drivers have duplicated unlikely() macros.  IS_ERR() already has
unlikely() in itself.

This patch cleans up such pointless code.

Signed-off-by: Hirofumi Nakagawa 
Acked-by: David S. Miller 
Acked-by: Jeff Garzik 
Cc: Paul Clements 
Cc: Richard Purdie 
Cc: Alessandro Zummo 
Cc: David Brownell 
Cc: James Bottomley 
Cc: Michael Halcrow 
Cc: Anton Altaparmakov 
Cc: Al Viro 
Cc: Carsten Otte 
Cc: Patrick McHardy 
Cc: Paul Mundt 
Cc: Jaroslav Kysela 
Cc: Takashi Iwai 
Acked-by: Mike Frysinger 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

NBD: add partition support

2008-04-29T15:06:23+00:00

Permit the use of partitions with network block devices (NBD).

A new parameter is introduced to define how many partition we want to be able
to manage per network block device.  This parameter is "max_part".

For instance, to manage 63 partitions / loop device, we will do:

   [on the server side]
# nbd-server 1234 /dev/sdb
   [on the client side]
# modprobe nbd max_part=63
# ls -l /dev/nbd*
brw-rw---- 1 root disk 43,   0 2008-03-25 11:14 /dev/nbd0
brw-rw---- 1 root disk 43,  64 2008-03-25 11:11 /dev/nbd1
brw-rw---- 1 root disk 43, 640 2008-03-25 11:11 /dev/nbd10
brw-rw---- 1 root disk 43, 704 2008-03-25 11:11 /dev/nbd11
brw-rw---- 1 root disk 43, 768 2008-03-25 11:11 /dev/nbd12
brw-rw---- 1 root disk 43, 832 2008-03-25 11:11 /dev/nbd13
brw-rw---- 1 root disk 43, 896 2008-03-25 11:11 /dev/nbd14
brw-rw---- 1 root disk 43, 960 2008-03-25 11:11 /dev/nbd15
brw-rw---- 1 root disk 43, 128 2008-03-25 11:11 /dev/nbd2
brw-rw---- 1 root disk 43, 192 2008-03-25 11:11 /dev/nbd3
brw-rw---- 1 root disk 43, 256 2008-03-25 11:11 /dev/nbd4
brw-rw---- 1 root disk 43, 320 2008-03-25 11:11 /dev/nbd5
brw-rw---- 1 root disk 43, 384 2008-03-25 11:11 /dev/nbd6
brw-rw---- 1 root disk 43, 448 2008-03-25 11:11 /dev/nbd7
brw-rw---- 1 root disk 43, 512 2008-03-25 11:11 /dev/nbd8
brw-rw---- 1 root disk 43, 576 2008-03-25 11:11 /dev/nbd9
# nbd-client localhost 1234 /dev/nbd0
Negotiation: ..size = 80418240KB
bs=1024, sz=80418240

-------NOTE, RFC: partition table is not automatically read.
The driver sets bdev->bd_invalidated to 1 to force the read of the partition
table of the device, but this is done only on an open of the device.
So we have to do a "touch /dev/nbdX" or something like that.
It can't be done from the nbd-client or nbd driver because at this
level we can't ask to read the partition table and to serve the request
at the same time (-> deadlock)

If someone has a better idea, I'm open to any suggestion.
-------NOTE, RFC

# fdisk -l /dev/nbd0

Disk /dev/nbd0: 82.3 GB, 82348277760 bytes
255 heads, 63 sectors/track, 10011 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

     Device Boot      Start         End      Blocks   Id  System
/dev/nbd0p1   *           1        9965    80043831   83  Linux
/dev/nbd0p2            9966       10011      369495    5  Extended
/dev/nbd0p5            9966       10011      369463+  82  Linux swap / Solaris

# ls -l /dev/nbd0*
brw-rw---- 1 root disk 43,   0 2008-03-25 11:16 /dev/nbd0
brw-rw---- 1 root disk 43,   1 2008-03-25 11:16 /dev/nbd0p1
brw-rw---- 1 root disk 43,   2 2008-03-25 11:16 /dev/nbd0p2
brw-rw---- 1 root disk 43,   5 2008-03-25 11:16 /dev/nbd0p5
# mount /dev/nbd0p1 /mnt
# ls /mnt
bin    dev   initrd      lost+found  opt   sbin     sys  var
boot   etc   initrd.img  media       proc  selinux  tmp  vmlinuz
cdrom  home  lib         mnt         root  srv      usr
# umount /mnt
# nbd-client -d /dev/nbd0
# ls -l /dev/nbd0*
brw-rw---- 1 root disk 43, 0 2008-03-25 11:16 /dev/nbd0
-------NOTE
On "nbd-client -d", we can do an iocl(BLKRRPART) to update partition table:
as the size of the device is 0, we don't have to serve the partition manager
request (-> no deadlock).
-------NOTE

Signed-off-by: Paul Clements 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

NBD: allow nbd to be used locally

2008-04-29T15:06:23+00:00

This patch allows Network Block Device to be mounted locally (nbd-client to
nbd-server over 127.0.0.1).

It creates a kthread to avoid the deadlock described in NBD tools
documentation.  So, if nbd-client hangs waiting for pages, the kblockd thread
can continue its work and free pages.

I have tested the patch to verify that it avoids the hang that always occurs
when writing to a localhost nbd connection.  I have also tested to verify that
no performance degradation results from the additional thread and queue.

Patch originally from Laurent Vivier.

Signed-off-by: Paul Clements 
Signed-off-by: Laurent Vivier 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

block: use blk_rq_init() to initialize the request

2008-04-29T12:48:55+00:00

Any path needs to call it to initialize the request.

This is a preparation for large command support, which needs to
initialize the request in a proper way (that is, just doing a memset()
will not work).

Signed-off-by: FUJITA Tomonori 
Cc: Jens Axboe 
Signed-off-by: Jens Axboe

nbd: prevent sock_xmit from attempting to use a NULL socket

2008-04-02T22:28:19+00:00

NBD does not protect the nbd_device's socket from becoming NULL during
receives.

This closes a race with the NBD_CLEAR_SOCK ioctl (nbd-client -d) setting
the nbd_device's socket to NULL right before NBD calls sock_xmit.

Signed-off-by: Mike Snitzer 
Cc: Paul Clements 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

NBD: make nbd default to deadline I/O scheduler

2008-02-24T01:12:15+00:00

NBD doesn't work well with CFQ (or AS) schedulers, so let's default to
something else.

The two problems I have experienced with nbd and cfq are:

1) nbd hangs with cfq on RHEL 5 (2.6.18) -- this may well have been
   fixed

   There's a similar debian bug that has been filed as well:

   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=447638

   There have been posts to nbd-general mailing list about problems with
   cfq and nbd also.

2) nbd performs about 10% better (the last time I tested) with deadline
   vs.  cfq (the overhead of cfq doesn't provide much advantage to nbd [not
   being a real disk], and you end up going through the I/O scheduler on
   the nbd server anyway, so it makes sense that deadline is better with
   nbd)

Signed-off-by: Paul Clements 
Cc: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

NBD: remove limit on max number of nbd devices

2008-02-08T17:22:41+00:00

Remove the arbitrary 128 device limit for NBD.  nbds_max can now be set to
any number.  In certain scenarios where devices are used sparsely we have
run into the 128 device limit.

Signed-off-by: Paul Clements 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds