linux-toradex.git/drivers/md/dm-raid1.c, branch v2.6.27.25

dm raid1: fix error count

2009-01-18T18:35:26+00:00

commit d460c65a6a9ec9e0d284864ec3a9a2d1b73f0e43 upstream.

Always increase the error count when I/O on a leg of a mirror fails.

The error count is used to decide whether to select an alternative
mirror leg.  If the target doesn't use the "handle_errors" feature, the
error count is not updated and the bio can get requeued forever by the
read callback.

Fix it by increasing error_count before the handle_errors feature
checking.

Signed-off-by: Milan Broz 
Signed-off-by: Jonathan Brassow 
Signed-off-by: Alasdair G Kergon 
Signed-off-by: Greg Kroah-Hartman

dm raid1: flush workqueue before destruction

2008-11-20T22:54:51+00:00

commit 18776c7316545482a02bfaa2629a2aa1afc48357 upstream.

We queue work on keventd queue --- so this queue must be flushed in the
destructor. Otherwise, keventd could access mirror_set after it was freed.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon 
Signed-off-by: Greg Kroah-Hartman

dm: unplug queues in threads

2008-04-25T12:26:57+00:00

Remove an avoidable 3ms delay on some dm-raid1 and kcopyd I/O.

It is specified that any submitted bio without BIO_RW_SYNC flag may plug the
queue (i.e. block the requests from being dispatched to the physical device).

The queue is unplugged when the caller calls blk_unplug() function. Usually, the
sequence is that someone calls submit_bh to submit IO on a buffer. The IO plugs
the queue and waits (to be possibly joined with other adjacent bios). Then, when
the caller calls wait_on_buffer(), it unplugs the queue and submits the IOs to
the disk.

This was happenning:

When doing O_SYNC writes, function fsync_buffers_list() submits a list of
bios to dm_raid1, the bios are added to dm_raid1 write queue and kmirrord is
woken up.

fsync_buffers_list() calls wait_on_buffer().  That unplugs the queue, but
there are no bios on the device queue as they are still in the dm_raid1 queue.

wait_on_buffer() starts waiting until the IO is finished.

kmirrord is scheduled, kmirrord takes bios and submits them to the devices.

The submitted bio plugs the harddisk queue but there is no one to unplug it.
(The process that called wait_on_buffer() is already sleeping.)

So there is a 3ms timeout, after which the queues on the harddisks are
unplugged and requests are processed.

This 3ms timeout meant that in certain workloads (e.g. O_SYNC, 8kb writes),
dm-raid1 is 10 times slower than md raid1.

Every time we submit something asynchronously via dm_io, we must unplug the
queue actually to send the request to the device.

This patch adds an unplug call to kmirrord - while processing requests, it keeps
the queue plugged (so that adjacent bios can be merged); when it finishes
processing all the bios, it unplugs the queue to submit the bios.

It also fixes kcopyd which has the same potential problem. All kcopyd requests
are submitted with BIO_RW_SYNC.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon 
Acked-by: Jens Axboe

dm raid1: use timer

2008-04-25T12:26:56+00:00

This patch replaces the schedule() in the main kmirrord thread with a timer.
The schedule() could introduce an unwanted delay when work is ready to be
processed.

The code instead calls wake() when there's work to be done immediately, and
delayed_wake() after a failure to give a short delay before retrying.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon

dm: move include files

2008-04-25T12:26:55+00:00

Publish the dm-io, dm-log and dm-kcopyd headers in include/linux.

Signed-off-by: Alasdair G Kergon

dm log: clean interface

2008-04-25T12:26:46+00:00

Clean up the dm-log interface to prepare for publishing it in include/linux.

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Alasdair G Kergon

dm kcopyd: clean interface

2008-04-25T12:26:44+00:00

Clean up the kcopyd interface to prepare for publishing it in include/linux.

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Alasdair G Kergon

dm io: clean interface

2008-04-25T12:26:43+00:00

Clean up the dm-io interface to prepare for publishing it in include/linux.

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Alasdair G Kergon

dm log: move dirty region log code into separate module

2008-04-25T12:26:39+00:00

Move the dirty region log code into a separate module so
other targets can share the code.

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Alasdair G Kergon

dm raid1: use list_split_init

2008-04-25T12:26:36+00:00

Use shorter list_splice_init() for brevity.

Signed-off-by: Robert P. J. Day 
Signed-off-by: Alasdair G Kergon