The patch titled
block: prevent possible io_context->refcount overflow
has been added to the -mm tree. Its filename is
block-prevent-possible-io_context-refcount-overflow.patch
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------------------------------------------------------
Subject: block: prevent possible io_context->refcount overflow
From: Nikanth Karthikesan <knikanth@xxxxxxxxxx>
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@xxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
block/blk-ioc.c | 12 ++++++------
block/cfq-iosched.c | 2 +-
include/linux/iocontext.h | 6 +++---
3 files changed, 10 insertions(+), 10 deletions(-)
diff -puN block/blk-ioc.c~block-prevent-possible-io_context-refcount-overflow block/blk-ioc.c
--- a/block/blk-ioc.c~block-prevent-possible-io_context-refcount-overflow
+++ a/block/blk-ioc.c
@@ -35,9 +35,9 @@ int put_io_context(struct io_context *io
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_
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
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 *
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 -puN block/cfq-iosched.c~block-prevent-possible-io_context-refcount-overflow block/cfq-iosched.c
--- a/block/cfq-iosched.c~block-prevent-possible-io_context-refcount-overflow
+++ a/block/cfq-iosched.c
@@ -1282,7 +1282,7 @@ static void cfq_dispatch_request(struct
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;
}
}
diff -puN include/linux/iocontext.h~block-prevent-possible-io_context-refcount-overflow include/linux/iocontext.h
--- a/include/linux/iocontext.h~block-prevent-possible-io_context-refcount-overflow
+++ a/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_tas
* 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;
}
_
Patches currently in -mm which might be from knikanth@xxxxxxxxxx are
block-prevent-possible-io_context-refcount-overflow.patch
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