bcache: Rework allocator reserves

We need a reserve for allocating buckets for new btree nodes - and now that
we've got multiple btrees, it really needs to be per btree.

This reworks the reserves so we've got separate freelists for each reserve
instead of watermarks, which seems to make things a bit cleaner, and it adds
some code so that btree_split() can make sure the reserve is available before it
starts.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

1 files changed, 7 insertions, 9 deletions

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 9d062bc5626..94d346e2ea1 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -383,12 +383,12 @@ struct cached_dev {
 	unsigned		writeback_rate_p_term_inverse;
 };
 
-enum alloc_watermarks {
-	WATERMARK_PRIO,
-	WATERMARK_METADATA,
-	WATERMARK_MOVINGGC,
-	WATERMARK_NONE,
-	WATERMARK_MAX
+enum alloc_reserve {
+	RESERVE_BTREE,
+	RESERVE_PRIO,
+	RESERVE_MOVINGGC,
+	RESERVE_NONE,
+	RESERVE_NR,
 };
 
 struct cache {
@@ -400,8 +400,6 @@ struct cache {
 	struct kobject		kobj;
 	struct block_device	*bdev;
 
-	unsigned		watermark[WATERMARK_MAX];
-
 	struct task_struct	*alloc_thread;
 
 	struct closure		prio;
@@ -430,7 +428,7 @@ struct cache {
 	 * because all the data they contained was overwritten), so we only
 	 * need to discard them before they can be moved to the free list.
 	 */
-	DECLARE_FIFO(long, free);
+	DECLARE_FIFO(long, free)[RESERVE_NR];
 	DECLARE_FIFO(long, free_inc);
 	DECLARE_FIFO(long, unused);