On Tue, May 25 2010 at 8:49am -0400,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
> On Tue, May 25 2010 at 7:18am -0400,
> Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx> wrote:
>
> > > +/*
> > > + * Fully initialize a request-based queue (->elevator, ->request_fn, etc).
> > > + */
> > > +static int dm_init_request_based_queue(struct mapped_device *md)
> > > +{
> > > + struct request_queue *q = NULL;
> > > +
> > > + /* Avoid re-initializing the queue if already fully initialized */
> > > + if (!md->queue->elevator) {
> > > + /* Fully initialize the queue */
> > > + q = blk_init_allocated_queue(md->queue, dm_request_fn, NULL);
> > > + if (!q)
> > > + return 0;
> >
> > When blk_init_allocated_queue() fails, the block-layer seems not to
> > guarantee that the queue is still available.
>
> Ouch, yes this portion of blk_init_allocated_queue_node() is certainly
> problematic:
>
> if (blk_init_free_list(q)) {
> kmem_cache_free(blk_requestq_cachep, q);
> return NULL;
> }
>
> Cc'ing Jens as I think it would be advantageous for us to push the above
> kmem_cache_free() into the callers where it really makes sense, e.g.:
> blk_init_queue_node().
>
> So on blk_init_allocated_queue_node() failure blk_init_queue_node() will
> take care to cleanup the queue that it assumes it is managing
> completely.
>
> My patch (linux-2.6-block.git's commit: 01effb0) that split out
> blk_init_allocated_queue_node() from blk_init_queue_node() opened up
> this issue. I'm fairly confident we'll get it fixed by the time 2.6.35
> ships.
Jens,
How about something like the following?
block: avoid unconditionally freeing previously allocated request_queue
On blk_init_allocated_queue_node failure, only free request_queue if
it is wasn't previously allocated outside the block layer
(e.g. blk_init_queue_node was blk_init_allocated_queue_node caller).
This addresses a regression introduced by the following commit:
01effb0 block: allow initialization of previously allocated request_queue
Otherwise the request_queue may be free'd out from underneath a caller
that is managing the request_queue directly (e.g. caller uses
blk_alloc_queue + blk_init_allocated_queue_node).
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
block/blk-core.c | 31 ++++++++++++++++++++++++++-----
1 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 3bc5579..c0179b7 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -528,6 +528,24 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
}
EXPORT_SYMBOL(blk_alloc_queue_node);
+static void blk_free_partial_queue(struct request_queue *q)
+{
+ /* Free q if blk_init_queue failed early enough. */
+ int free_request_queue = 0;
+ struct request_list *rl;
+
+ if (!q)
+ return;
+
+ /* Was blk_init_free_list the cause for failure? */
+ rl = &q->rq;
+ if (!rl->rq_pool)
+ free_request_queue = 1;
+
+ if (free_request_queue)
+ kmem_cache_free(blk_requestq_cachep, q);
+}
+
/**
* blk_init_queue - prepare a request queue for use with a block device
* @rfn: The function to be called to process requests that have been
@@ -570,9 +588,14 @@ EXPORT_SYMBOL(blk_init_queue);
struct request_queue *
blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
{
- struct request_queue *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
+ struct request_queue *uninit_q, *q;
+
+ uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
+ q = blk_init_allocated_queue_node(uninit_q, rfn, lock, node_id);
+ if (!q)
+ blk_free_partial_queue(uninit_q);
- return blk_init_allocated_queue_node(q, rfn, lock, node_id);
+ return q;
}
EXPORT_SYMBOL(blk_init_queue_node);
@@ -592,10 +615,8 @@ blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn,
return NULL;
q->node = node_id;
- if (blk_init_free_list(q)) {
- kmem_cache_free(blk_requestq_cachep, q);
+ if (blk_init_free_list(q))
return NULL;
- }
q->request_fn = rfn;
q->prep_rq_fn = NULL;
--
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