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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 /block | |
| parent | 1d589bb16b825b3a7b4edd34d997f1f1f953033d (diff) | |
| download | lwn-d9c7d394a8ebacb60097b192939ae9f15235225e.tar.gz lwn-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 'block')
| -rw-r--r-- | block/blk-ioc.c | 12 | ||||
| -rw-r--r-- | block/cfq-iosched.c | 2 |
2 files changed, 7 insertions, 7 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c index 012f065ac8e2..d4ed6000147d 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -35,9 +35,9 @@ int put_io_context(struct io_context *ioc) if (ioc == NULL) return 1; - BUG_ON(atomic_read(&ioc->refcount) == 0); + BUG_ON(atomic_long_read(&ioc->refcount) == 0); - if (atomic_dec_and_test(&ioc->refcount)) { + if (atomic_long_dec_and_test(&ioc->refcount)) { rcu_read_lock(); if (ioc->aic && ioc->aic->dtor) ioc->aic->dtor(ioc->aic); @@ -90,7 +90,7 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node) ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node); if (ret) { - atomic_set(&ret->refcount, 1); + atomic_long_set(&ret->refcount, 1); atomic_set(&ret->nr_tasks, 1); spin_lock_init(&ret->lock); ret->ioprio_changed = 0; @@ -151,7 +151,7 @@ struct io_context *get_io_context(gfp_t gfp_flags, int node) ret = current_io_context(gfp_flags, node); if (unlikely(!ret)) break; - } while (!atomic_inc_not_zero(&ret->refcount)); + } while (!atomic_long_inc_not_zero(&ret->refcount)); return ret; } @@ -163,8 +163,8 @@ void copy_io_context(struct io_context **pdst, struct io_context **psrc) struct io_context *dst = *pdst; if (src) { - BUG_ON(atomic_read(&src->refcount) == 0); - atomic_inc(&src->refcount); + BUG_ON(atomic_long_read(&src->refcount) == 0); + atomic_long_inc(&src->refcount); put_io_context(dst); *pdst = src; } diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 99ac4304d711..ef2f72d42434 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1282,7 +1282,7 @@ static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) if (!cfqd->active_cic) { struct cfq_io_context *cic = RQ_CIC(rq); - atomic_inc(&cic->ioc->refcount); + atomic_long_inc(&cic->ioc->refcount); cfqd->active_cic = cic; } } |