dm bio prison v2: new interface for the bio prison

The deferred set is gone and all methods have _v2 appended to the end of
their names to allow for continued use of the original bio prison in DM
thin-provisioning.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 152 insertions, 0 deletions

diff --git a/drivers/md/dm-bio-prison-v2.h b/drivers/md/dm-bio-prison-v2.h
new file mode 100644
index 000000000000..6e04234268db
--- /dev/null
+++ b/drivers/md/dm-bio-prison-v2.h
@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2011-2017 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BIO_PRISON_V2_H
+#define DM_BIO_PRISON_V2_H
+
+#include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
+#include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
+
+#include <linux/bio.h>
+#include <linux/rbtree.h>
+#include <linux/workqueue.h>
+
+/*----------------------------------------------------------------*/
+
+int dm_bio_prison_init_v2(void);
+void dm_bio_prison_exit_v2(void);
+
+/*
+ * Sometimes we can't deal with a bio straight away.  We put them in prison
+ * where they can't cause any mischief.  Bios are put in a cell identified
+ * by a key, multiple bios can be in the same cell.  When the cell is
+ * subsequently unlocked the bios become available.
+ */
+struct dm_bio_prison_v2;
+
+/*
+ * Keys define a range of blocks within either a virtual or physical
+ * device.
+ */
+struct dm_cell_key_v2 {
+	int virtual;
+	dm_thin_id dev;
+	dm_block_t block_begin, block_end;
+};
+
+/*
+ * Treat this as opaque, only in header so callers can manage allocation
+ * themselves.
+ */
+struct dm_bio_prison_cell_v2 {
+	// FIXME: pack these
+	bool exclusive_lock;
+	unsigned exclusive_level;
+	unsigned shared_count;
+	struct work_struct *quiesce_continuation;
+
+	struct rb_node node;
+	struct dm_cell_key_v2 key;
+	struct bio_list bios;
+};
+
+struct dm_bio_prison_v2 *dm_bio_prison_create_v2(struct workqueue_struct *wq);
+void dm_bio_prison_destroy_v2(struct dm_bio_prison_v2 *prison);
+
+/*
+ * 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_v2() can only fail if called
+ * in interrupt context or passed GFP_NOWAIT.
+ */
+struct dm_bio_prison_cell_v2 *dm_bio_prison_alloc_cell_v2(struct dm_bio_prison_v2 *prison,
+						    gfp_t gfp);
+void dm_bio_prison_free_cell_v2(struct dm_bio_prison_v2 *prison,
+				struct dm_bio_prison_cell_v2 *cell);
+
+/*
+ * Shared locks have a bio associated with them.
+ *
+ * If the lock is granted the caller can continue to use the bio, and must
+ * call dm_cell_put_v2() to drop the reference count when finished using it.
+ *
+ * If the lock cannot be granted then the bio will be tracked within the
+ * cell, and later given to the holder of the exclusive lock.
+ *
+ * See dm_cell_lock_v2() for discussion of the lock_level parameter.
+ *
+ * Compare *cell_result with cell_prealloc to see if the prealloc was used.
+ * If cell_prealloc was used then inmate wasn't added to it.
+ *
+ * Returns true if the lock is granted.
+ */
+bool dm_cell_get_v2(struct dm_bio_prison_v2 *prison,
+		    struct dm_cell_key_v2 *key,
+		    unsigned lock_level,
+		    struct bio *inmate,
+		    struct dm_bio_prison_cell_v2 *cell_prealloc,
+		    struct dm_bio_prison_cell_v2 **cell_result);
+
+/*
+ * Decrement the shared reference count for the lock.  Returns true if
+ * returning ownership of the cell (ie. you should free it).
+ */
+bool dm_cell_put_v2(struct dm_bio_prison_v2 *prison,
+		    struct dm_bio_prison_cell_v2 *cell);
+
+/*
+ * Locks a cell.  No associated bio.  Exclusive locks get priority.  These
+ * locks constrain whether the io locks are granted according to level.
+ *
+ * Shared locks will still be granted if the lock_level is > (not = to) the
+ * exclusive lock level.
+ *
+ * If an _exclusive_ lock is already held then -EBUSY is returned.
+ *
+ * Return values:
+ *  < 0 - error
+ *  0   - locked; no quiescing needed
+ *  1   - locked; quiescing needed
+ */
+int dm_cell_lock_v2(struct dm_bio_prison_v2 *prison,
+		    struct dm_cell_key_v2 *key,
+		    unsigned lock_level,
+		    struct dm_bio_prison_cell_v2 *cell_prealloc,
+		    struct dm_bio_prison_cell_v2 **cell_result);
+
+void dm_cell_quiesce_v2(struct dm_bio_prison_v2 *prison,
+			struct dm_bio_prison_cell_v2 *cell,
+			struct work_struct *continuation);
+
+/*
+ * Promotes an _exclusive_ lock to a higher lock level.
+ *
+ * Return values:
+ *  < 0 - error
+ *  0   - promoted; no quiescing needed
+ *  1   - promoted; quiescing needed
+ */
+int dm_cell_lock_promote_v2(struct dm_bio_prison_v2 *prison,
+			    struct dm_bio_prison_cell_v2 *cell,
+			    unsigned new_lock_level);
+
+/*
+ * Adds any held bios to the bio list.
+ *
+ * There may be shared locks still held at this point even if you quiesced
+ * (ie. different lock levels).
+ *
+ * Returns true if returning ownership of the cell (ie. you should free
+ * it).
+ */
+bool dm_cell_unlock_v2(struct dm_bio_prison_v2 *prison,
+		       struct dm_bio_prison_cell_v2 *cell,
+		       struct bio_list *bios);
+
+/*----------------------------------------------------------------*/
+
+#endif