[PATCH v4 20/68] btrfs: extent_io: sink less common parameters for __set_extent_bit()

[Qu Wenruo <wqu@suse.com>]

For __set_extent_bit(), those parameter are less common for most
callers:
- exclusive_bits
- failed_start
  Paired together for EXTENT_LOCKED usage.

- extent_changeset
  For qgroup usage.

As a common design principle, less common parameters should have their
default values and only callers really need them will set the parameters
to non-default values.

Sink those parameters into a new structure, extent_io_extra_options.
So most callers won't bother those less used parameters, and make later
expansion easier.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent-io-tree.h | 22 ++++++++++++++
 fs/btrfs/extent_io.c      | 61 ++++++++++++++++++++++++---------------
 2 files changed, 59 insertions(+), 24 deletions(-)

diff --git a/fs/btrfs/extent-io-tree.h b/fs/btrfs/extent-io-tree.h
index 3aaf83376797..dfbb65ac9c8c 100644
--- a/fs/btrfs/extent-io-tree.h
+++ b/fs/btrfs/extent-io-tree.h
@@ -82,6 +82,28 @@ struct extent_state {
 #endif
 };
 
+/*
+ * Extra options for extent io tree operations.
+ *
+ * All of these options are initialized to 0/false/NULL by default,
+ * and most callers should utilize the wrappers other than the extra options.
+ */
+struct extent_io_extra_options {
+	/*
+	 * For __set_extent_bit(), to return -EEXIST when hit an extent with
+	 * @excl_bits set, and update @excl_failed_start.
+	 * Utizlied by EXTENT_LOCKED wrappers.
+	 */
+	u32 excl_bits;
+	u64 excl_failed_start;
+
+	/*
+	 * For __set/__clear_extent_bit() to record how many bytes is modified.
+	 * For qgroup related functions.
+	 */
+	struct extent_changeset *changeset;
+};
+
 int __init extent_state_cache_init(void);
 void __cold extent_state_cache_exit(void);
 
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 4ac315d8753f..5f899b27962b 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -29,6 +29,7 @@ static struct kmem_cache *extent_state_cache;
 static struct kmem_cache *extent_buffer_cache;
 static struct bio_set btrfs_bioset;
 
+static struct extent_io_extra_options default_opts = { 0 };
 static inline bool extent_state_in_tree(const struct extent_state *state)
 {
 	return !RB_EMPTY_NODE(&state->rb_node);
@@ -952,10 +953,10 @@ static void cache_state(struct extent_state *state,
 }
 
 /*
- * set some bits on a range in the tree.  This may require allocations or
+ * Set some bits on a range in the tree.  This may require allocations or
  * sleeping, so the gfp mask is used to indicate what is allowed.
  *
- * If any of the exclusive bits are set, this will fail with -EEXIST if some
+ * If *any* of the exclusive bits are set, this will fail with -EEXIST if some
  * part of the range already has the desired bits set.  The start of the
  * existing range is returned in failed_start in this case.
  *
@@ -964,26 +965,30 @@ static void cache_state(struct extent_state *state,
 
 static int __must_check
 __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
-		 unsigned bits, unsigned exclusive_bits,
-		 u64 *failed_start, struct extent_state **cached_state,
-		 gfp_t mask, struct extent_changeset *changeset)
+		 unsigned bits, struct extent_state **cached_state,
+		 gfp_t mask, struct extent_io_extra_options *extra_opts)
 {
 	struct extent_state *state;
 	struct extent_state *prealloc = NULL;
 	struct rb_node *node;
 	struct rb_node **p;
 	struct rb_node *parent;
+	struct extent_changeset *changeset;
 	int err = 0;
+	u32 exclusive_bits;
+	u64 *failed_start;
 	u64 last_start;
 	u64 last_end;
 
 	btrfs_debug_check_extent_io_range(tree, start, end);
 	trace_btrfs_set_extent_bit(tree, start, end - start + 1, bits);
 
-	if (exclusive_bits)
-		ASSERT(failed_start);
-	else
-		ASSERT(!failed_start);
+	if (!extra_opts)
+		extra_opts = &default_opts;
+	exclusive_bits = extra_opts->excl_bits;
+	failed_start = &extra_opts->excl_failed_start;
+	changeset = extra_opts->changeset;
+
 again:
 	if (!prealloc && gfpflags_allow_blocking(mask)) {
 		/*
@@ -1187,7 +1192,7 @@ int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		   unsigned bits, struct extent_state **cached_state,
 		   gfp_t mask)
 {
-	return __set_extent_bit(tree, start, end, bits, 0, NULL, cached_state,
+	return __set_extent_bit(tree, start, end, bits, cached_state,
 			        mask, NULL);
 }
 
@@ -1414,6 +1419,10 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 int set_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 			   unsigned bits, struct extent_changeset *changeset)
 {
+	struct extent_io_extra_options extra_opts = {
+		.changeset = changeset,
+	};
+
 	/*
 	 * We don't support EXTENT_LOCKED yet, as current changeset will
 	 * record any bits changed, so for EXTENT_LOCKED case, it will
@@ -1422,15 +1431,14 @@ int set_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 	 */
 	BUG_ON(bits & EXTENT_LOCKED);
 
-	return __set_extent_bit(tree, start, end, bits, 0, NULL, NULL, GFP_NOFS,
-				changeset);
+	return __set_extent_bit(tree, start, end, bits, NULL, GFP_NOFS,
+				&extra_opts);
 }
 
 int set_extent_bits_nowait(struct extent_io_tree *tree, u64 start, u64 end,
 			   unsigned bits)
 {
-	return __set_extent_bit(tree, start, end, bits, 0, NULL, NULL,
-				GFP_NOWAIT, NULL);
+	return __set_extent_bit(tree, start, end, bits, NULL, GFP_NOWAIT, NULL);
 }
 
 int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
@@ -1461,16 +1469,18 @@ int clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		     struct extent_state **cached_state)
 {
+	struct extent_io_extra_options extra_opts = {
+		.excl_bits = EXTENT_LOCKED,
+	};
 	int err;
-	u64 failed_start;
 
 	while (1) {
 		err = __set_extent_bit(tree, start, end, EXTENT_LOCKED,
-				       EXTENT_LOCKED, &failed_start,
-				       cached_state, GFP_NOFS, NULL);
+				       cached_state, GFP_NOFS, &extra_opts);
 		if (err == -EEXIST) {
-			wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED);
-			start = failed_start;
+			wait_extent_bit(tree, extra_opts.excl_failed_start, end,
+					EXTENT_LOCKED);
+			start = extra_opts.excl_failed_start;
 		} else
 			break;
 		WARN_ON(start > end);
@@ -1480,14 +1490,17 @@ int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 
 int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end)
 {
+	struct extent_io_extra_options extra_opts = {
+		.excl_bits = EXTENT_LOCKED,
+	};
 	int err;
-	u64 failed_start;
 
-	err = __set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
-			       &failed_start, NULL, GFP_NOFS, NULL);
+	err = __set_extent_bit(tree, start, end, EXTENT_LOCKED,
+			       NULL, GFP_NOFS, &extra_opts);
 	if (err == -EEXIST) {
-		if (failed_start > start)
-			clear_extent_bit(tree, start, failed_start - 1,
+		if (extra_opts.excl_failed_start > start)
+			clear_extent_bit(tree, start,
+					 extra_opts.excl_failed_start - 1,
 					 EXTENT_LOCKED, 1, 0, NULL);
 		return 0;
 	}
-- 
2.28.0