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authorNikanth Karthikesan <knikanth@novell.com>2009-06-10 12:57:06 -0700
committerJens Axboe <jens.axboe@oracle.com>2009-06-10 23:07:15 +0200
commitd9c7d394a8ebacb60097b192939ae9f15235225e (patch)
tree4fbf9c7677acb03c23d05faba1a4b0bcfb6702b4 /include/linux/iocontext.h
parent1d589bb16b825b3a7b4edd34d997f1f1f953033d (diff)
block: prevent possible io_context->refcount overflow
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>
Diffstat (limited to 'include/linux/iocontext.h')
-rw-r--r--include/linux/iocontext.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 08b987bccf89..dd05434fa45f 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -64,7 +64,7 @@ struct cfq_io_context {
* and kmalloc'ed. These could be shared between processes.
*/
struct io_context {
- atomic_t refcount;
+ atomic_long_t refcount;
atomic_t nr_tasks;
/* all the fields below are protected by this lock */
@@ -91,8 +91,8 @@ static inline struct io_context *ioc_task_link(struct io_context *ioc)
* if ref count is zero, don't allow sharing (ioc is going away, it's
* a race).
*/
- if (ioc && atomic_inc_not_zero(&ioc->refcount)) {
- atomic_inc(&ioc->nr_tasks);
+ if (ioc && atomic_long_inc_not_zero(&ioc->refcount)) {
+ atomic_long_inc(&ioc->refcount);
return ioc;
}