linux-toradex.git/include/linux/iocontext.h, branch tegra-9.12.15

io context: fix ref counting

2009-07-31T06:55:48+00:00

Commit d9c7d394a8ebacb60097b192939ae9f15235225e
("block: prevent possible io_context->refcount overflow") mistakenly
changed atomic_inc(&ioc->nr_tasks) to atomic_long_inc(&ioc->refcount).

Signed-off-by: Li Zefan 
Acked-by: Nikanth Karthikesan 
Signed-off-by: Jens Axboe

block: prevent possible io_context->refcount overflow

2009-06-10T21:07:15+00:00

Currently io_context has an atomic_t(32-bit) as refcount.  In the case of
cfq, for each device against whcih a task does I/O, a reference to the
io_context would be taken.  And when there are multiple process sharing
io_contexts(CLONE_IO) would also have a reference to the same io_context.

Theoretically the possible maximum number of processes sharing the same
io_context + the number of disks/cfq_data referring to the same io_context
can overflow the 32-bit counter on a very high-end machine.

Even though it is an improbable case, let us make it atomic_long_t.

Signed-off-by: Nikanth Karthikesan 
Signed-off-by: Andrew Morton 
Signed-off-by: Jens Axboe

block: blkdev.h cleanup, move iocontext stuff to iocontext.h

2008-07-03T11:21:14+00:00

Signed-off-by: Jens Axboe

io context: increment task attachment count in ioc_task_link()

2008-04-15T07:25:33+00:00

Thanks to Nikanth Karthikesan  for reporting this.

Signed-off-by: Jens Axboe

cfq-iosched: fix rcu freeing of cfq io contexts

2008-04-02T13:42:20+00:00

SLAB_DESTROY_BY_RCU is not a direct substitute for normal call_rcu()
freeing, since it'll page freeing but NOT object freeing. So change
cfq to do the freeing on its own.

Signed-off-by: Fabio Checconi 
Acked-by: Paul E. McKenney 
Signed-off-by: Jens Axboe

cfq-iosched: add hlist for browsing parallel to the radix tree

2008-02-19T09:04:00+00:00

It's cumbersome to browse a radix tree from start to finish, especially
since we modify keys when a process exits. So add a hlist for the single
purpose of browsing over all known cfq_io_contexts, used for exit,
io prio change, etc.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=9948

Signed-off-by: Jens Axboe

block: cfq: make the io contect sharing lockless

2008-01-28T09:50:33+00:00

The io context sharing introduced a per-ioc spinlock, that would protect
the cfq io context lookup. That is a regression from the original, since
we never needed any locking there because the ioc/cic were process private.

The cic lookup is changed from an rbtree construct to a radix tree, which
we can then use RCU to make the reader side lockless. That is the performance
critical path, modifying the radix tree is only done on process creation
(when that process first does IO, actually) and on process exit (if that
process has done IO).

As it so happens, radix trees are also much faster for this type of
lookup where the key is a pointer. It's a very sparse tree.

Signed-off-by: Jens Axboe

io context sharing: preliminary support

2008-01-28T09:50:31+00:00

Detach task state from ioc, instead keep track of how many processes
are accessing the ioc.

Signed-off-by: Jens Axboe

ioprio: move io priority from task_struct to io_context

2008-01-28T09:50:29+00:00

This is where it belongs and then it doesn't take up space for a
process that doesn't do IO.

Signed-off-by: Jens Axboe