litmus-rt.git/block, branch wip-mc

cfq-iosched: make code consistent

2011-06-27T07:36:06+00:00

ioc->ioc_data is rcu protectd, so uses correct API to access it.
This doesn't change any behavior, but just make code consistent.

Signed-off-by: Shaohua Li 
Cc: stable@kernel.org # after ab4bd22d
Signed-off-by: Jens Axboe

cfq-iosched: fix a rcu warning

2011-06-27T07:36:06+00:00

I got a rcu warnning at boot. the ioc->ioc_data is rcu_deferenced, but
doesn't hold rcu_read_lock.

Signed-off-by: Shaohua Li 
Cc: stable@kernel.org # after ab4bd22d
Signed-off-by: Jens Axboe

block: Add attribute((format(printf...) and fix fallout

2011-06-13T08:42:49+00:00

Use the compiler to verify format strings and arguments.

Fix fallout.

Signed-off-by: Joe Perches 
Signed-off-by: Jens Axboe

block: make disk_block_events() properly wait for work cancellation

2011-06-09T18:43:59+00:00

disk_block_events() should guarantee that the event work is not in
flight on return and once blocked it shouldn't issue further
cancellations.

Because there was no synchronization between the first blocker doing
cancel_delayed_work_sync() and the following blockers, the following
blockers could finish before cancellation was complete, which broke
both guarantees - event work could be in flight and cancellation could
happen after return.

This bug triggered WARN_ON_ONCE() in disk_clear_events() reported in
bug#34662.

  https://bugzilla.kernel.org/show_bug.cgi?id=34662

Fix it by adding an outer mutex which protects both block count
manipulation and work cancellation.

-v2: Use outer mutex instead of bit waitqueue per Linus.

Signed-off-by: Tejun Heo 
Tested-by: Sitsofe Wheeler 
Reported-by: Sitsofe Wheeler 
Reported-by: Borislav Petkov 
Reported-by: Meelis Roos 
Reported-by: Linus Torvalds 
Cc: Andrew Morton 
Cc: Jens Axboe 
Cc: Kay Sievers 
Signed-off-by: Jens Axboe

block: remove non-syncing __disk_block_events() and fold it into disk_block_events()

2011-06-09T18:43:55+00:00

After the previous update to disk_check_events(), nobody is using
non-syncing __disk_block_events().  Remove @sync and, as this makes
__disk_block_events() virtually identical to disk_block_events(),
remove the underscore prefixed version.

Signed-off-by: Tejun Heo 
Cc: Jens Axboe 
Signed-off-by: Jens Axboe

block: don't use non-syncing event blocking in disk_check_events()

2011-06-09T18:43:54+00:00

This patch is part of fix for triggering of WARN_ON_ONCE() in
disk_clear_events() reported in bug#34662.

  https://bugzilla.kernel.org/show_bug.cgi?id=34662

disk_clear_events() blocks events, schedules and flushes the event
work.  It expects the work to have started execution on schedule and
finished on return from flush.  WARN_ON_ONCE() triggers if the event
work hasn't executed as expected.  This problem happens because
__disk_block_events() fails to guarantee that the event work item is
not in flight on return from the function in race-free manner.  The
problem is two-fold and this patch addresses one of them.

When __disk_block_events() is called with @sync == %false, it bumps
event block count, calls cancel_delayed_work() and return.  This makes
it impossible to guarantee that event polling is not in flight on
return from syncing __disk_block_events() - if the first blocker was
non-syncing, polling could still be in progress and later syncing ones
would assume that the first blocker already canceled it.

Making __disk_block_events() cancel_sync regardless of block count
isn't feasible either as it may race with forced event checking in
disk_clear_events().

As disk_check_events() is the only user of non-syncing
__disk_block_events(), updating it to directly cancel and schedule
event work is the easiest way to solve the issue.

Note that there's another bug in __disk_block_events() and this patch
doesn't fix the issue completely.  Later patch will fix the other bug.

Signed-off-by: Tejun Heo 
Tested-by: Sitsofe Wheeler 
Reported-by: Sitsofe Wheeler 
Reported-by: Borislav Petkov 
Reported-by: Meelis Roos 
Reported-by: Linus Torvalds 
Cc: Andrew Morton 
Cc: Jens Axboe 
Cc: Kay Sievers 
Signed-off-by: Jens Axboe

cfq-iosched: fix locking around ioc->ioc_data assignment

2011-06-06T03:56:49+00:00

Since we are modifying this RCU pointer, we need to hold
the lock protecting it around it.

This fixes a potential reuse and double free of a cfq
io_context structure. The bug has been in CFQ for a long
time, it hit very few people but those it did hit seemed
to see it a lot.

Tracked in RH bugzilla here:

https://bugzilla.redhat.com/show_bug.cgi?id=577968

Credit goes to Paul Bolle for figuring out that the issue
was around the one-hit ioc->ioc_data cache. Thanks to his
hard work the issue is now fixed.

Cc: stable@kernel.org
Signed-off-by: Jens Axboe

block: Use hlist_entry() for io_context.cic_list.first

2011-06-02T11:05:02+00:00

list_entry() and hlist_entry() are both simply aliases for
container_of(), but since io_context.cic_list.first is an hlist_node one
should at least use the correct alias.

Signed-off-by: Paul Bolle 
Signed-off-by: Jens Axboe

cfq-iosched: Remove bogus check in queue_fail path