linux.git/drivers/block/aoe, branch v2.6.25

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

2008-02-08T17:42:46+00:00

* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  Enhanced partition statistics: documentation update
  Enhanced partition statistics: remove old partition statistics
  Enhanced partition statistics: procfs
  Enhanced partition statistics: sysfs
  Enhanced partition statistics: aoe fix
  Enhanced partition statistics: update partition statitics
  Enhanced partition statistics: core statistics
  block: fixup rq_init() a bit

Manually fixed conflict in drivers/block/aoe/aoecmd.c due to statistics
support.

aoe: statically initialise devlist_lock

2008-02-08T17:22:32+00:00

I guess aoedev_init() can go away now.

Cc: Greg KH 
Cc: "Ed L. Cashin" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: update copyright date

2008-02-08T17:22:32+00:00

Update the year in the copyright notices.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: make error messages more specific

2008-02-08T17:22:32+00:00

Andrew Morton pointed out that the "too many targets" message in patch 2 could
be printed for failing GFP_ATOMIC allocations.  This patch makes the messages
more specific.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: the aoeminor doesn't need a long format

2008-02-08T17:22:32+00:00

The aoedev aoeminor member doesn't need a long format.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: add module parameter for users who need more outstanding I/O

2008-02-08T17:22:32+00:00

An AoE target provides an estimate of the number of outstanding commands that
the AoE initiator can send before getting a response.  The aoe_maxout
parameter provides a way to set an even lower limit.  It will not allow a user
to use more outstanding commands than the target permits.  If a user discovers
a problem with a large setting, this parameter provides a way for us to work
with them to debug the problem.  We expect to improve the dynamic window
sizing algorithm and drop this parameter.  For the time being, it is a
debugging aid.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: only install new AoE device once

2008-02-08T17:22:32+00:00

An aoe driver user who had about 70 AoE targets found that he was hitting a
BUG in sysfs_create_file because the aoe driver was trying to tell the kernel
about an AoE device more than once.  Each AoE device was reachable by several
local network interfaces, and multiple ATA device indentify responses were
returning from that single device.

This patch eliminates a race condition so that aoe always informs the block
layer of a new AoE device once in the presence of multiple incoming ATA device
identify responses.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: dynamically allocate a capped number of skbs when necessary

2008-02-08T17:22:32+00:00

What this Patch Does

  Even before this recent series of 12 patches to 2.6.22-rc4, the aoe
  driver was reusing a small set of skbs that were allocated once and
  were only used for outbound AoE commands.

  The network layer cannot be allowed to put_page on the data that is
  still associated with a bio we haven't returned to the block layer,
  so the aoe driver (even before the patch under discussion) is still
  the owner of skbs that have been handed to the network layer for
  transmission.  We need to keep track of these skbs so that we can
  free them, but by tracking them, we can also easily re-use them.

  The new patch was a response to the behavior of certain network
  drivers.  We cannot reuse an skb that the network driver still has
  in its transmit ring.  Network drivers can defer transmit ring
  cleanup and then use the state in the skb to determine how many data
  segments to clean up in its transmit ring.  The tg3 driver is one
  driver that behaves in this way.

  When the network driver defers cleanup of its transmit ring, the aoe
  driver can find itself in a situation where it would like to send an
  AoE command, and the AoE target is ready for more work, but the
  network driver still has all of the pre-allocated skbs.  In that
  case, the new patch just calls alloc_skb, as you'd expect.

  We don't want to get carried away, though.  We try not to do
  excessive allocation in the write path, so we cap the number of skbs
  we dynamically allocate.

  Probably calling it a "dynamic pool" is misleading.  We were already
  trying to use a small fixed-size set of pre-allocated skbs before
  this patch, and this patch just provides a little headroom (with a
  ceiling, though) to accomodate network drivers that hang onto skbs,
  by allocating when needed.  The d->skbpool_hd list of allocated skbs
  is necessary so that we can free them later.

  We didn't notice the need for this headroom until AoE targets got
  fast enough.

Alternatives

  If the network layer never did a put_page on the pages in the bio's
  we get from the block layer, then it would be possible for us to
  hand skbs to the network layer and forget about them, allowing the
  network layer to free skbs itself (and thereby calling our own
  skb->destructor callback function if we needed that).  In that case
  we could get rid of the pre-allocated skbs and also the
  d->skbpool_hd, instead just calling alloc_skb every time we wanted
  to transmit a packet.  The slab allocator would effectively maintain
  the list of skbs.

  Besides a loss of CPU cache locality, the main concern with that
  approach the danger that it would increase the likelihood of
  deadlock when VM is trying to free pages by writing dirty data from
  the page cache through the aoe driver out to persistent storage on
  an AoE device.  Right now we have a situation where we have
  pre-allocation that corresponds to how much we use, which seems
  ideal.

  Of course, there's still the separate issue of receiving the packets
  that tell us that a write has successfully completed on the AoE
  target.  When memory is low and VM is using AoE to flush dirty data
  to free up pages, it would be perfect if there were a way for us to
  register a fast callback that could recognize write command
  completion responses.  But I don't think the current problems with
  the receive side of the situation are a justification for
  exacerbating the problem on the transmit side.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: user can ask driver to forget previously detected devices

2008-02-08T17:22:31+00:00

When an AoE device is detected, the kernel is informed, and a new block device
is created.  If the device is unused, the block device corresponding to remote
device that is no longer available may be removed from the system by telling
the aoe driver to "flush" its list of devices.

Without this patch, software like GPFS and LVM may attempt to read from AoE
devices that were discovered earlier but are no longer present, blocking until
the I/O attempt times out.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aoe: eliminate goto and improve readability

2008-02-08T17:22:31+00:00

Adam Richter suggested eliminating this goto.

Signed-off-by: Ed L. Cashin 
Cc: Greg KH 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds