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-rw-r--r--drivers/md/dm-bio-prison-v1.h138
1 files changed, 138 insertions, 0 deletions
diff --git a/drivers/md/dm-bio-prison-v1.h b/drivers/md/dm-bio-prison-v1.h
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+++ b/drivers/md/dm-bio-prison-v1.h
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+/*
+ * Copyright (C) 2011-2017 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BIO_PRISON_H
+#define DM_BIO_PRISON_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>
+
+/*----------------------------------------------------------------*/
+
+/*
+ * 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;
+
+/*
+ * Keys define a range of blocks within either a virtual or physical
+ * device.
+ */
+struct dm_cell_key {
+ 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 {
+ struct list_head user_list; /* for client use */
+ struct rb_node node;
+
+ struct dm_cell_key key;
+ struct bio *holder;
+ struct bio_list bios;
+};
+
+struct dm_bio_prison *dm_bio_prison_create(void);
+void dm_bio_prison_destroy(struct dm_bio_prison *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() 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);
+
+/*
+ * Creates, or retrieves a cell that overlaps the given key.
+ *
+ * Returns 1 if pre-existing cell returned, zero if new cell created using
+ * @cell_prealloc.
+ */
+int dm_get_cell(struct dm_bio_prison *prison,
+ struct dm_cell_key *key,
+ struct dm_bio_prison_cell *cell_prealloc,
+ struct dm_bio_prison_cell **cell_result);
+
+/*
+ * An atomic op that combines retrieving or creating 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 *cell_prealloc,
+ struct dm_bio_prison_cell **cell_result);
+
+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, int error);
+
+/*
+ * Visits the cell and then releases. Guarantees no new inmates are
+ * inserted between the visit and release.
+ */
+void dm_cell_visit_release(struct dm_bio_prison *prison,
+ void (*visit_fn)(void *, struct dm_bio_prison_cell *),
+ void *context, struct dm_bio_prison_cell *cell);
+
+/*
+ * Rather than always releasing the prisoners in a cell, the client may
+ * want to promote one of them to be the new holder. There is a race here
+ * though between releasing an empty cell, and other threads adding new
+ * inmates. So this function makes the decision with its lock held.
+ *
+ * This function can have two outcomes:
+ * i) An inmate is promoted to be the holder of the cell (return value of 0).
+ * ii) The cell has no inmate for promotion and is released (return value of 1).
+ */
+int dm_cell_promote_or_release(struct dm_bio_prison *prison,
+ struct dm_bio_prison_cell *cell);
+
+/*----------------------------------------------------------------*/
+
+/*
+ * We use the deferred set to keep track of pending reads to shared blocks.
+ * We do this to ensure the new mapping caused by a write isn't performed
+ * until these prior reads have completed. Otherwise the insertion of the
+ * new mapping could free the old block that the read bios are mapped to.
+ */
+
+struct dm_deferred_set;
+struct dm_deferred_entry;
+
+struct dm_deferred_set *dm_deferred_set_create(void);
+void dm_deferred_set_destroy(struct dm_deferred_set *ds);
+
+struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
+void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
+int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
+
+/*----------------------------------------------------------------*/
+
+#endif