linux.git/drivers/block/drbd/drbd_bitmap.c, branch v2.6.39

drbd: fix up merge error

2011-03-28T14:42:58+00:00

In commit 95a0f10cddbf ("drbd: store in-core bitmap little endian,
regardless of architecture") drbd had made the sane choice to use
little-endian bitmap functions everywhere.  However, it used the
horrible old functions names from , that were
never really meant to be exported.

In the meantime, things got cleaned up, and in commit c4945b9ed472
("asm-generic: rename generic little-endian bitops functions") we
renamed the LE bitops to something sane, exactly so that they could be
used in random code without people gouging their eyes out when seeing
the crazy jumble of letters that were the old internal names.

As a result the drbd thing merged cleanly (commit 8d49a77568d1: "Merge
branch 'for-2.6.39/drivers' of git://git.kernel.dk/linux-2.6-block"),
since there was no data conflict - but the end result obviously doesn't
actually compile.

Reported-and-tested-by: Ingo Molnar 
Cc: Jens Axboe 
Cc: Stephen Rothwell 
Signed-off-by: Linus Torvalds

drbd: need include for bitops functions declarations

2011-03-17T14:02:51+00:00

Signed-off-by: Stephen Rothwell 
Signed-off-by: Jens Axboe

drbd: describe bitmap locking for bulk operation in finer detail

2011-03-10T10:48:02+00:00

Now that we do no longer in-place endian-swap the bitmap, we allow
selected bitmap operations (testing bits, sometimes even settting bits)
during some bulk operations.

This caused us to hit a lot of FIXME asserts similar to
	FIXME asender in drbd_bm_count_bits,
	bitmap locked for 'write from resync_finished' by worker
Which now is nonsense: looking at the bitmap is perfectly legal
as long as it is not being resized.

This cosmetic patch defines some flags to describe expectations in finer
detail, so the asserts in e.g. bm_change_bits_to() can be skipped if
appropriate.

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

drbd: fix potential access of on-stack wait_queue_head_t after return

2011-03-10T10:45:08+00:00

I run into something declaring itself as "spinlock deadlock",
 BUG: spinlock lockup on CPU#1, kjournald/27816, ffff88000ad6bca0
 Pid: 27816, comm: kjournald Tainted: G        W 2.6.34.6 #2
 Call Trace:
    [] do_raw_spin_lock+0x11e/0x14d
  [] _raw_spin_lock_irqsave+0x6a/0x81
  [] ? __wake_up+0x22/0x50
  [] __wake_up+0x22/0x50
  [] bm_async_io_complete+0x258/0x299 [drbd]
but the call traces do not fit at all,
all other cpus are cpu_idle.

I think it may be this race:

drbd_bm_write_page
 wait_queue_head_t io_wait;
 atomic_t in_flight;
 bm_async_io
  submit_bio
					bm_async_io_complete
					  if (atomic_dec_and_test(in_flight))
 wait_event(io_wait,
	atomic_read(in_flight) == 0)
 return
					    wake_up(io_wait)

The wake_up now accesses the wait_queue_head_t spinlock, which is no
longer valid, since the stack frame of drbd_bm_write_page has been
clobbered now.

Fix this by using struct completion, which does both the condition test
as well as the wake_up inside its spinlock, so this race cannot happen.

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

drbd: be less noisy with some log messages

2011-03-10T10:43:37+00:00

We expect changes to a bitmap page in drbd_bm_write_page,
that's why we submit a copy page.

If a page changes during global writeout, that would be unexpected,
and reason to warn, though.

Also, often page writeout can be skipped (on activity log transactions
during normal operation, for example), no need to log that everytime.

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

drbd: Removed a reference to debug macros removed long time ago

2011-03-10T10:43:27+00:00

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

drbd: get rid of unused debug code

2011-03-10T10:43:26+00:00

Long time ago, we had paranoia code in the bitmap that allocated one
extra word, assigned a magic value, and checked on every occasion that
the magic value was still unchanged.

That debug code is unused, the extra long word complicates code a bit.
Get rid of it.

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

drbd: allow petabyte storage on 64bit arch

2011-03-10T10:43:24+00:00

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

drbd: bitmap keep track of changes vs on-disk bitmap

2011-03-10T10:43:19+00:00

When we set or clear bits in a bitmap page,
also set a flag in the page->private pointer.

This allows us to skip writes of unchanged pages.

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

drbd: store in-core bitmap little endian, regardless of architecture

2011-03-10T10:36:40+00:00

Our on-disk bitmap is a little endian bitstream.
Up to now, we have stored the in-core copy of that in
native endian, applying byte order conversion when necessary.

Instead, keep the bitmap pages little endian, as they are read from disk,
and use the generic_*_le_bit family of functions.

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