Now that the exception store implementations are capable of
caching the exceptions on their own, we need a new function
added to the API to allow us to lookup the exceptions.
Adding 'lookup_exception' to the exception store API.
RFC-by: Jonathan Brassow <jbrassow@xxxxxxxxxx>
Index: linux-2.6/drivers/md/dm-exception-store.h
===================================================================
--- linux-2.6.orig/drivers/md/dm-exception-store.h
+++ linux-2.6/drivers/md/dm-exception-store.h
@@ -58,6 +58,16 @@ struct dm_exception_store_type {
void *callback_context);
/*
+ * Look up an exception. For certain exception stores,
+ * this function /may/ block. The caller must specify whether
+ * they can tolerate this. If the function would block and the
+ * user specified can_block=0, -EWOULDBLK will be returned.
+ */
+ int (*lookup_exception) (struct dm_exception_store *store,
+ struct dm_exception **e,
+ chunk_t old, int can_block);
+
+ /*
* The snapshot is invalid, note this in the metadata.
*/
void (*drop_snapshot) (struct dm_exception_store *store);
Index: linux-2.6/drivers/md/dm-snap-persistent.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap-persistent.c
+++ linux-2.6/drivers/md/dm-snap-persistent.c
@@ -711,6 +711,17 @@ static void persistent_commit_exception(
ps->callback_count = 0;
}
+static int persistent_lookup_exception(struct dm_exception_store *store,
+ struct dm_exception **e,
+ chunk_t old, int can_block)
+{
+ struct pstore *ps = get_info(store);
+
+ *e = dm_lookup_exception(ps->table, old);
+
+ return 0;
+}
+
static void persistent_drop_snapshot(struct dm_exception_store *store)
{
struct pstore *ps = get_info(store);
@@ -803,6 +814,7 @@ static struct dm_exception_store_type _p
.read_metadata = persistent_read_metadata,
.prepare_exception = persistent_prepare_exception,
.commit_exception = persistent_commit_exception,
+ .lookup_exception = persistent_lookup_exception,
.drop_snapshot = persistent_drop_snapshot,
.fraction_full = persistent_fraction_full,
.status = persistent_status,
@@ -817,6 +829,7 @@ static struct dm_exception_store_type _p
.read_metadata = persistent_read_metadata,
.prepare_exception = persistent_prepare_exception,
.commit_exception = persistent_commit_exception,
+ .lookup_exception = persistent_lookup_exception,
.drop_snapshot = persistent_drop_snapshot,
.fraction_full = persistent_fraction_full,
.status = persistent_status,
Index: linux-2.6/drivers/md/dm-snap-transient.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap-transient.c
+++ linux-2.6/drivers/md/dm-snap-transient.c
@@ -94,6 +94,17 @@ static void transient_commit_exception(s
callback(callback_context, 1);
}
+static int transient_lookup_exception(struct dm_exception_store *store,
+ struct dm_exception **e,
+ chunk_t old, int can_block)
+{
+ struct transient_c *tc = store->context;
+
+ *e = dm_lookup_exception(tc->table, old);
+
+ return 0;
+}
+
static void transient_fraction_full(struct dm_exception_store *store,
sector_t *numerator, sector_t *denominator)
{
@@ -165,6 +176,7 @@ static struct dm_exception_store_type _t
.read_metadata = transient_read_metadata,
.prepare_exception = transient_prepare_exception,
.commit_exception = transient_commit_exception,
+ .lookup_exception = transient_lookup_exception,
.fraction_full = transient_fraction_full,
.status = transient_status,
};
@@ -178,6 +190,7 @@ static struct dm_exception_store_type _t
.read_metadata = transient_read_metadata,
.prepare_exception = transient_prepare_exception,
.commit_exception = transient_commit_exception,
+ .lookup_exception = transient_lookup_exception,
.fraction_full = transient_fraction_full,
.status = transient_status,
};
Index: linux-2.6/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -994,7 +994,7 @@ static int snapshot_map(struct dm_target
{
struct dm_exception *e;
struct dm_snapshot *s = ti->private;
- int r = DM_MAPIO_REMAPPED;
+ int rtn, r = DM_MAPIO_REMAPPED;
chunk_t chunk;
struct dm_snap_pending_exception *pe = NULL;
@@ -1015,7 +1015,15 @@ static int snapshot_map(struct dm_target
}
/* If the block is already remapped - use that, else remap it */
- e = dm_lookup_exception(s->complete, chunk);
+ rtn = s->store->type->lookup_exception(s->store, &e, chunk, 0);
+ if (rtn) {
+ /*
+ * Could be -EWOULDBLOCK, but we don't handle that yet
+ * and there are currently no exception store
+ * implementations that would require us to.
+ */
+ BUG();
+ }
if (e) {
remap_exception(s, e, bio, chunk);
goto out_unlock;
@@ -1134,7 +1142,7 @@ static int snapshot_status(struct dm_tar
*---------------------------------------------------------------*/
static int __origin_write(struct list_head *snapshots, struct bio *bio)
{
- int r = DM_MAPIO_REMAPPED, first = 0;
+ int rtn, r = DM_MAPIO_REMAPPED, first = 0;
struct dm_snapshot *snap;
struct dm_exception *e;
struct dm_snap_pending_exception *pe, *next_pe, *primary_pe = NULL;
@@ -1168,7 +1176,16 @@ static int __origin_write(struct list_he
* ref_count is initialised to 1 so pending_complete()
* won't destroy the primary_pe while we're inside this loop.
*/
- e = dm_lookup_exception(snap->complete, chunk);
+ rtn = snap->store->type->lookup_exception(snap->store, &e,
+ chunk, 0);
+ if (rtn) {
+ /*
+ * Could be -EWOULDBLOCK, but we don't handle that yet
+ * and there are currently no exception store
+ * implementations that would require us to.
+ */
+ BUG();
+ }
if (e)
goto next_snapshot;
--
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