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| author | Nikanth Karthikesan <knikanth@novell.com> | 2009-06-10 12:57:06 -0700 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2009-06-10 23:07:15 +0200 |
| commit | d9c7d394a8ebacb60097b192939ae9f15235225e (patch) | |
| tree | 4fbf9c7677acb03c23d05faba1a4b0bcfb6702b4 /include/linux/iocontext.h | |
| parent | 1d589bb16b825b3a7b4edd34d997f1f1f953033d (diff) | |
| download | linux-d9c7d394a8ebacb60097b192939ae9f15235225e.tar.gz linux-d9c7d394a8ebacb60097b192939ae9f15235225e.tar.bz2 linux-d9c7d394a8ebacb60097b192939ae9f15235225e.zip | |
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.h | 6 |
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; } |