btrfs: extent_io: Introduce new function clear_record_extent_bits()

Introduce new function clear_record_extent_bits(), which will clear bits
for given range and record the details about which ranges are cleared
and how many bytes in total it changes.

This provides the basis for later qgroup reserve codes.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/extent_io.c

@@ -141,6 +141,8 @@ static void add_extent_changeset(struct extent_state *state, unsigned bits,
 		return;
 	if (set && (state->state & bits) == bits)
 		return;
+	if (!set && (state->state & bits) == 0)
+		return;
 	changeset->bytes_changed += state->end - state->start + 1;
 	ret = ulist_add(changeset->range_changed, state->start, state->end,
 			GFP_ATOMIC);
@@ -529,7 +531,8 @@ static struct extent_state *next_state(struct extent_state *state)
  */
 static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
 					    struct extent_state *state,
-					    unsigned *bits, int wake)
+					    unsigned *bits, int wake,
+					    struct extent_changeset *changeset)
 {
 	struct extent_state *next;
 	unsigned bits_to_clear = *bits & ~EXTENT_CTLBITS;
@@ -540,6 +543,7 @@ static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
 		tree->dirty_bytes -= range;
 	}
 	clear_state_cb(tree, state, bits);
+	add_extent_changeset(state, bits_to_clear, changeset, 0);
 	state->state &= ~bits_to_clear;
 	if (wake)
 		wake_up(&state->wq);
@@ -587,10 +591,10 @@ static void extent_io_tree_panic(struct extent_io_tree *tree, int err)
  *
  * This takes the tree lock, and returns 0 on success and < 0 on error.
  */
-int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
-		     unsigned bits, int wake, int delete,
-		     struct extent_state **cached_state,
-		     gfp_t mask)
+static int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
+			      unsigned bits, int wake, int delete,
+			      struct extent_state **cached_state,
+			      gfp_t mask, struct extent_changeset *changeset)
 {
 	struct extent_state *state;
 	struct extent_state *cached;
@@ -689,7 +693,8 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		if (err)
 			goto out;
 		if (state->end <= end) {
-			state = clear_state_bit(tree, state, &bits, wake);
+			state = clear_state_bit(tree, state, &bits, wake,
+						changeset);
 			goto next;
 		}
 		goto search_again;
@@ -710,13 +715,13 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		if (wake)
 			wake_up(&state->wq);
 
-		clear_state_bit(tree, prealloc, &bits, wake);
+		clear_state_bit(tree, prealloc, &bits, wake, changeset);
 
 		prealloc = NULL;
 		goto out;
 	}
 
-	state = clear_state_bit(tree, state, &bits, wake);
+	state = clear_state_bit(tree, state, &bits, wake, changeset);
 next:
 	if (last_end == (u64)-1)
 		goto out;
@@ -1151,7 +1156,7 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 	if (state->start == start && state->end <= end) {
 		set_state_bits(tree, state, &bits, NULL);
 		cache_state(state, cached_state);
-		state = clear_state_bit(tree, state, &clear_bits, 0);
+		state = clear_state_bit(tree, state, &clear_bits, 0, NULL);
 		if (last_end == (u64)-1)
 			goto out;
 		start = last_end + 1;
@@ -1192,7 +1197,8 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		if (state->end <= end) {
 			set_state_bits(tree, state, &bits, NULL);
 			cache_state(state, cached_state);
-			state = clear_state_bit(tree, state, &clear_bits, 0);
+			state = clear_state_bit(tree, state, &clear_bits, 0,
+						NULL);
 			if (last_end == (u64)-1)
 				goto out;
 			start = last_end + 1;
@@ -1254,7 +1260,7 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 
 		set_state_bits(tree, prealloc, &bits, NULL);
 		cache_state(prealloc, cached_state);
-		clear_state_bit(tree, prealloc, &clear_bits, 0);
+		clear_state_bit(tree, prealloc, &clear_bits, 0, NULL);
 		prealloc = NULL;
 		goto out;
 	}
@@ -1309,6 +1315,14 @@ int set_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 				changeset);
 }
 
+int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
+		     unsigned bits, int wake, int delete,
+		     struct extent_state **cached, gfp_t mask)
+{
+	return __clear_extent_bit(tree, start, end, bits, wake, delete,
+				  cached, mask, NULL);
+}
+
 int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		      unsigned bits, gfp_t mask)
 {
@@ -1320,6 +1334,20 @@ int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 	return clear_extent_bit(tree, start, end, bits, wake, 0, NULL, mask);
 }
 
+int clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
+			     unsigned bits, gfp_t mask,
+			     struct extent_changeset *changeset)
+{
+	/*
+	 * Don't support EXTENT_LOCKED case, same reason as
+	 * set_record_extent_bits().
+	 */
+	BUG_ON(bits & EXTENT_LOCKED);
+
+	return __clear_extent_bit(tree, start, end, bits, 0, 0, NULL, mask,
+				  changeset);
+}
+
 int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
 			struct extent_state **cached_state, gfp_t mask)
 {

fs/btrfs/extent_io.h

@@ -222,6 +222,9 @@ int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		   struct extent_state *cached_state);
 int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		      unsigned bits, gfp_t mask);
+int clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
+			     unsigned bits, gfp_t mask,
+			     struct extent_changeset *changeset);
 int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 		     unsigned bits, int wake, int delete,
 		     struct extent_state **cached, gfp_t mask);