bcachefs: Allocator refactoring

This uses the kthread_wait_freezable() macro to simplify a lot of the
allocator thread code, along with cleaning up bch2_invalidate_bucket2().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_foreground.c

 // SPDX-License-Identifier: GPL-2.0
 /*
- * Primary bucket allocation code
- *
  * Copyright 2012 Google, Inc.
  *
- * Allocation in bcache is done in terms of buckets:
- *
- * Each bucket has associated an 8 bit gen; this gen corresponds to the gen in
- * btree pointers - they must match for the pointer to be considered valid.
- *
- * Thus (assuming a bucket has no dirty data or metadata in it) we can reuse a
- * bucket simply by incrementing its gen.
- *
- * The gens (along with the priorities; it's really the gens are important but
- * the code is named as if it's the priorities) are written in an arbitrary list
- * of buckets on disk, with a pointer to them in the journal header.
- *
- * When we invalidate a bucket, we have to write its new gen to disk and wait
- * for that write to complete before we use it - otherwise after a crash we
- * could have pointers that appeared to be good but pointed to data that had
- * been overwritten.
- *
- * Since the gens and priorities are all stored contiguously on disk, we can
- * batch this up: We fill up the free_inc list with freshly invalidated buckets,
- * call prio_write(), and when prio_write() finishes we pull buckets off the
- * free_inc list and optionally discard them.
- *
- * free_inc isn't the only freelist - if it was, we'd often have to sleep while
- * priorities and gens were being written before we could allocate. c->free is a
- * smaller freelist, and buckets on that list are always ready to be used.
- *
- * If we've got discards enabled, that happens when a bucket moves from the
- * free_inc list to the free list.
- *
- * It's important to ensure that gens don't wrap around - with respect to
- * either the oldest gen in the btree or the gen on disk. This is quite
- * difficult to do in practice, but we explicitly guard against it anyways - if
- * a bucket is in danger of wrapping around we simply skip invalidating it that
- * time around, and we garbage collect or rewrite the priorities sooner than we
- * would have otherwise.
+ * Foreground allocator code: allocate buckets from freelist, and allocate in
+ * sector granularity from writepoints.
  *
  * bch2_bucket_alloc() allocates a single bucket from a specific device.
  *
  * bch2_bucket_alloc_set() allocates one or more buckets from different devices
  * in a given filesystem.
- *
- * invalidate_buckets() drives all the processes described above. It's called
- * from bch2_bucket_alloc() and a few other places that need to make sure free
- * buckets are ready.
- *
- * invalidate_buckets_(lru|fifo)() find buckets that are available to be
- * invalidated, and then invalidate them and stick them on the free_inc list -
- * in either lru or fifo order.
  */
 
 #include "bcachefs.h"

fs/bcachefs/trace.h

@@ -380,24 +380,27 @@ DEFINE_EVENT(bch_fs, gc_cannot_inc_gens,
 
 /* Allocator */
 
-TRACE_EVENT(alloc_batch,
-	TP_PROTO(struct bch_dev *ca, size_t free, size_t total),
-	TP_ARGS(ca, free, total),
+TRACE_EVENT(alloc_scan,
+	TP_PROTO(struct bch_dev *ca, u64 found, u64 inc_gen, u64 inc_gen_skipped),
+	TP_ARGS(ca, found, inc_gen, inc_gen_skipped),
 
 	TP_STRUCT__entry(
-		__array(char,		uuid,	16	)
-		__field(size_t,		free		)
-		__field(size_t,		total		)
+		__field(dev_t,		dev		)
+		__field(u64,		found		)
+		__field(u64,		inc_gen		)
+		__field(u64,		inc_gen_skipped	)
 	),
 
 	TP_fast_assign(
-		memcpy(__entry->uuid, ca->uuid.b, 16);
-		__entry->free = free;
-		__entry->total = total;
+		__entry->dev		= ca->disk_sb.bdev->bd_dev;
+		__entry->found		= found;
+		__entry->inc_gen	= inc_gen;
+		__entry->inc_gen_skipped = inc_gen_skipped;
 	),
 
-	TP_printk("%pU free %zu total %zu",
-		__entry->uuid, __entry->free, __entry->total)
+	TP_printk("%d,%d found %llu inc_gen %llu inc_gen_skipped %llu",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->found, __entry->inc_gen, __entry->inc_gen_skipped)
 );
 
 TRACE_EVENT(invalidate,
@@ -417,8 +420,10 @@ TRACE_EVENT(invalidate,
 	),
 
 	TP_printk("invalidated %u sectors at %d,%d sector=%llu",
-		  __entry->sectors, MAJOR(__entry->dev),
-		  MINOR(__entry->dev), __entry->offset)
+		  __entry->sectors,
+		  MAJOR(__entry->dev),
+		  MINOR(__entry->dev),
+		  __entry->offset)
 );
 
 DECLARE_EVENT_CLASS(bucket_alloc,
@@ -426,16 +431,18 @@ DECLARE_EVENT_CLASS(bucket_alloc,
 	TP_ARGS(ca, reserve),
 
 	TP_STRUCT__entry(
-		__array(char,			uuid,	16)
-		__field(enum alloc_reserve,	reserve	  )
+		__field(dev_t,			dev	)
+		__field(enum alloc_reserve,	reserve	)
 	),
 
 	TP_fast_assign(
-		memcpy(__entry->uuid, ca->uuid.b, 16);
-		__entry->reserve = reserve;
+		__entry->dev		= ca->disk_sb.bdev->bd_dev;
+		__entry->reserve	= reserve;
 	),
 
-	TP_printk("%pU reserve %d", __entry->uuid, __entry->reserve)
+	TP_printk("%d,%d reserve %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->reserve)
 );
 
 DEFINE_EVENT(bucket_alloc, bucket_alloc,