[RFC 1/2] block: implement an unprep function corresponding directly to prep

James Bottomley
2010-06-30T17:01:12Z

So this is more directly what I'm thinking. It gives us an exactly
correct place to hang the discard allocation in SCSI. The next patch
shows a potential implementation in sd.

I think it should avoid all the leaks people have been seeing trying to
move the discard allocation/free into scsi. I also think it should
facilitate sending discard through SCSI as a REQ_TYPE_FS.

James

---

diff --git a/block/blk-core.c b/block/blk-core.c
index f84cce4..aab798e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -608,6 +608,7 @@ blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn,

q->request_fn = rfn;
q->prep_rq_fn = NULL;
+ q->unprep_rq_fn = NULL;
q->unplug_fn = generic_unplug_device;
q->queue_flags = QUEUE_FLAG_DEFAULT;
q->queue_lock = lock;
@@ -2119,6 +2120,26 @@ static bool blk_update_bidi_request(struct request *rq, int error,
return false;
}

+/**
+ * blk_unprep_request - unprepare a request
+ * @req: the request
+ *
+ * This function makes a request ready for complete resubmission (or
+ * completion). It happens only after all error handling is complete,
+ * so represents the appropriate moment to deallocate any resources
+ * that were allocated to the request in the prep_rq_fn. The queue
+ * lock is held when calling this.
+ */
+void blk_unprep_request(struct request *req)
+{
+ struct request_queue *q = req->q;
+
+ req->cmd_flags &= ~REQ_DONTPREP;
+ if (q->unprep_rq_fn)
+ q->unprep_rq_fn(q, req);
+}
+EXPORT_SYMBOL_GPL(blk_unprep_request);
+
/*
* queue lock must be held
*/
@@ -2134,6 +2155,10 @@ static void blk_finish_request(struct request *req, int error)

blk_delete_timer(req);

+ if (req->cmd_flags & REQ_DONTPREP)
+ blk_unprep_request(req);
+
+
blk_account_io_done(req);

if (req->end_io)
diff --git a/block/blk-settings.c b/block/blk-settings.c
index f5ed5a1..a234f4b 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -37,6 +37,23 @@ void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
EXPORT_SYMBOL(blk_queue_prep_rq);

/**
+ * blk_queue_unprep_rq - set an unprepare_request function for queue
+ * @q: queue
+ * @ufn: unprepare_request function
+ *
+ * It's possible for a queue to register an unprepare_request callback
+ * which is invoked before the request is finally completed. The goal
+ * of the function is to deallocate any data that was allocated in the
+ * prepare_request callback.
+ *
+ */
+void blk_queue_unprep_rq(struct request_queue *q, unprep_rq_fn *ufn)
+{
+ q->unprep_rq_fn = ufn;
+}
+EXPORT_SYMBOL(blk_queue_unprep_rq);
+
+/**
* blk_queue_merge_bvec - set a merge_bvec function for queue
* @q: queue
* @mbfn: merge_bvec_fn
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 1646fe7..868b2f2 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -85,7 +85,7 @@ static void scsi_unprep_request(struct request *req)
{
struct scsi_cmnd *cmd = req->special;

- req->cmd_flags &= ~REQ_DONTPREP;
+ blk_unprep_request(req);
req->special = NULL;

scsi_put_command(cmd);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 09a8402..16d97ee 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -264,6 +264,7 @@ struct request_pm_state
typedef void (request_fn_proc) (struct request_queue *q);
typedef int (make_request_fn) (struct request_queue *q, struct bio *bio);
typedef int (prep_rq_fn) (struct request_queue *, struct request *);
+typedef void (unprep_rq_fn) (struct request_queue *, struct request *);
typedef void (unplug_fn) (struct request_queue *);

struct bio_vec;
@@ -346,6 +347,7 @@ struct request_queue
request_fn_proc *request_fn;
make_request_fn *make_request_fn;
prep_rq_fn *prep_rq_fn;
+ unprep_rq_fn *unprep_rq_fn;
unplug_fn *unplug_fn;
merge_bvec_fn *merge_bvec_fn;
prepare_flush_fn *prepare_flush_fn;
@@ -915,6 +917,7 @@ extern void blk_complete_request(struct request *);
extern void __blk_complete_request(struct request *);
extern void blk_abort_request(struct request *);
extern void blk_abort_queue(struct request_queue *);
+extern void blk_unprep_request(struct request *);

/*
* Access functions for manipulating queue properties
@@ -959,6 +962,7 @@ extern int blk_queue_dma_drain(struct request_queue *q,
extern void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn);
extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
+extern void blk_queue_unprep_rq(struct request_queue *, unprep_rq_fn *ufn);
extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);
extern void blk_queue_dma_alignment(struct request_queue *, int);
extern void blk_queue_update_dma_alignment(struct request_queue *, int);