linux.git/drivers/block/drbd/drbd_actlog.c, branch v3.13

drbd: Allow online change of al-stripes and al-stripe-size

2013-06-28T14:04:36+00:00

Allow to change the AL layout with an resize operation. For that
the reisze command gets two new fields: al_stripes and al_stripe_size.

In order to make the operation crash save:
1) Lock out all IO and MD-IO
2) Write the super block with MDF_PRIMARY_IND clear
3) write the bitmap to the new location (all zeros, since
   we allow only while connected)
4) Initialize the new AL-area
5) Write the super block with the restored MDF_PRIMARY_IND.
6) Unfreeze all IO

Since the AL-layout has no influence on the protocol, this operation
needs to be beforemed on both sides of a resource (if intended).

Signed-off-by: Andreas Gruenbacher 
Signed-off-by: Philipp Reisner 
Signed-off-by: Jens Axboe

drbd: fix if(); found by kbuild test robot

2013-03-28T16:10:26+00:00

Recently introduced al_begin_io_nonblock() was returning -EBUSY,
even when it should return -EWOULDBLOCK.

Impact:
A few spurious wake_up() calls in prepare_al_transaction_nonblock().

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: consolidate as many updates as possible into one AL transaction

2013-03-23T04:18:09+00:00

Depending on current IO depth, try to consolidate as many updates
as possible into one activity log transaction.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: split out some helper functions to drbd_al_begin_io

2013-03-23T00:15:17+00:00

To make the code easier to follow,
use an explicit find_active_resync_extent(),
and add a "nonblock" parameter to _al_get().

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: split drbd_al_begin_io into fastpath, prepare, and commit

2013-03-23T00:15:17+00:00

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: drbd_al_being_io: short circuit to reduce latency

2013-03-23T00:14:00+00:00

A request hitting an already "hot" extent should proceed right away,
even if some other requests need to wait for pending transactions.

Without that short-circuit, several simultaneous make_request contexts
race for committing the transaction, possibly penalizing the innocent.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: Clarify when activity log I/O is delegated to the worker thread

2013-03-23T00:14:00+00:00

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: read meta data early, base on-disk offsets on super block

2013-03-23T00:13:59+00:00

We used to calculate all on-disk meta data offsets, and then compare
the stored offsets, basically treating them as magic numbers.

Now with the activity log striping, the activity log size is no longer
fixed.  We need to first read the super block, then base the activity
log and bitmap offsets on the stored offsets/al stripe settings.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: prepare for new striped layout of activity log

2013-03-23T00:13:59+00:00

Introduce two new on-disk meta data fields: al_stripes and al_stripe_size_4k
The intended use case is activity log on RAID 0 or similar.
Logically consecutive transactions will advance their on-disk position
by al_stripe_size_4k 4kB (transaction sized) blocks.

Right now, these are still asserted to be the backward compatible
values al_stripes = 1, al_stripe_size_4k = 8 (which amounts to 32kB).

Also introduce a caching member for meta_dev_idx in the in-core
structure: even though it is initially passed in in the rcu-protected
disk_conf structure, it cannot change without a detach/attach cycle.

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe

drbd: cleanup ondisk meta data layout calculations and defines

2013-03-23T00:13:59+00:00

Add a comment about our meta data layout variants,
and rename a few defines (e.g. MD_RESERVED_SECT -> MD_128MB_SECT)
to make it clear that they are short hand for fixed constants,
and not arbitrarily to be redefined as one may see fit.

Properly pad struct meta_data_on_disk to 4kB,
and initialize to zero not only the first 512 Byte,
but all of it in drbd_md_sync().

Signed-off-by: Philipp Reisner 
Signed-off-by: Lars Ellenberg 
Signed-off-by: Jens Axboe