dm bio prison: pass cell memory in
Change the dm_bio_prison interface so that instead of allocating memory
internally, dm_bio_detain is supplied with a pre-allocated cell each
time it is called.
This enables a subsequent patch to move the allocation of the struct
dm_bio_prison_cell outside the thin target's mapping function so it can
no longer block there.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-bio-prison.h b/drivers/md/dm-bio-prison.h
index 53d1a7a..11af2182 100644
--- a/drivers/md/dm-bio-prison.h
+++ b/drivers/md/dm-bio-prison.h
@@ -35,17 +35,36 @@
void dm_bio_prison_destroy(struct dm_bio_prison *prison);
/*
- * This may block if a new cell needs allocating. You must ensure that
- * cells will be unlocked even if the calling thread is blocked.
+ * These two functions just wrap a mempool. This is a transitory step:
+ * Eventually all bio prison clients should manage their own cell memory.
+ *
+ * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
+ * in interrupt context or passed GFP_NOWAIT.
+ */
+struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
+ gfp_t gfp);
+void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
+ struct dm_bio_prison_cell *cell);
+
+/*
+ * An atomic op that combines retrieving a cell, and adding a bio to it.
*
* Returns 1 if the cell was already held, 0 if @inmate is the new holder.
*/
-int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
- struct bio *inmate, struct dm_bio_prison_cell **ref);
+int dm_bio_detain(struct dm_bio_prison *prison,
+ struct dm_cell_key *key,
+ struct bio *inmate,
+ struct dm_bio_prison_cell *cell_prealloc,
+ struct dm_bio_prison_cell **cell_result);
-void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios);
-void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates);
-void dm_cell_error(struct dm_bio_prison_cell *cell);
+void dm_cell_release(struct dm_bio_prison *prison,
+ struct dm_bio_prison_cell *cell,
+ struct bio_list *bios);
+void dm_cell_release_no_holder(struct dm_bio_prison *prison,
+ struct dm_bio_prison_cell *cell,
+ struct bio_list *inmates);
+void dm_cell_error(struct dm_bio_prison *prison,
+ struct dm_bio_prison_cell *cell);
/*----------------------------------------------------------------*/