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path: root/include/linux/iocontext.h
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2009-06-10block: prevent possible io_context->refcount overflowNikanth Karthikesan
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 <knikanth@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-07-03block: blkdev.h cleanup, move iocontext stuff to iocontext.hJens Axboe
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-15io context: increment task attachment count in ioc_task_link()Jens Axboe
Thanks to Nikanth Karthikesan <knikanth@suse.de> for reporting this. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-02cfq-iosched: fix rcu freeing of cfq io contextsFabio Checconi
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 <fabio@gandalf.sssup.it> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-02-19cfq-iosched: add hlist for browsing parallel to the radix treeJens Axboe
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 <jens.axboe@oracle.com>
2008-01-28block: cfq: make the io contect sharing locklessJens Axboe
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 <jens.axboe@oracle.com>
2008-01-28io context sharing: preliminary supportJens Axboe
Detach task state from ioc, instead keep track of how many processes are accessing the ioc. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28ioprio: move io priority from task_struct to io_contextJens Axboe
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 <jens.axboe@oracle.com>