btrfs: reduce the number of arguments to btrfs_run_delalloc_range

Instead of a separate page_started argument that tells the callers that
btrfs_run_delalloc_range already started writeback by itself, overload
the return value with a positive 1 in additio to 0 and a negative error
code to indicate that is has already started writeback, and remove the
nr_written argument as that caller can calculate it directly based on
the range, and in fact already does so for the case where writeback
wasn't started yet.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/btrfs_inode.h

@@ -498,8 +498,7 @@ int btrfs_prealloc_file_range_trans(struct inode *inode,
 				    u64 start, u64 num_bytes, u64 min_size,
 				    loff_t actual_len, u64 *alloc_hint);
 int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page,
-			     u64 start, u64 end, int *page_started,
+			     u64 start, u64 end, struct writeback_control *wbc);
-			     unsigned long *nr_written, struct writeback_control *wbc);
 int btrfs_writepage_cow_fixup(struct page *page);
 int btrfs_encoded_io_compression_from_extent(struct btrfs_fs_info *fs_info,
 					     int compress_type);

fs/btrfs/extent_io.c

@@ -1190,10 +1190,7 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
 	u64 delalloc_start = page_start;
 	u64 delalloc_end = page_end;
 	u64 delalloc_to_write = 0;
-	/* How many pages are started by btrfs_run_delalloc_range() */
+	int ret = 0;
-	unsigned long nr_written = 0;
-	int ret;
-	int page_started = 0;
 
 	while (delalloc_start < page_end) {
 		delalloc_end = page_end;
@@ -1202,9 +1199,10 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
 			delalloc_start = delalloc_end + 1;
 			continue;
 		}
+
 		ret = btrfs_run_delalloc_range(inode, page, delalloc_start,
-				delalloc_end, &page_started, &nr_written, wbc);
+					       delalloc_end, wbc);
-		if (ret)
+		if (ret < 0)
 			return ret;
 
 		delalloc_start = delalloc_end + 1;
@@ -1216,6 +1214,16 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
 	 */
 	delalloc_to_write +=
 		DIV_ROUND_UP(delalloc_end + 1 - page_start, PAGE_SIZE);
+
+	/*
+	 * If btrfs_run_dealloc_range() already started I/O and unlocked
+	 * the pages, we just need to account for them here.
+	 */
+	if (ret == 1) {
+		wbc->nr_to_write -= delalloc_to_write;
+		return 1;
+	}
+
 	if (wbc->nr_to_write < delalloc_to_write) {
 		int thresh = 8192;
 
@@ -1225,16 +1233,6 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,
 					 thresh);
 	}
 
-	/* Did btrfs_run_dealloc_range() already unlock and start the IO? */
-	if (page_started) {
-		/*
-		 * We've unlocked the page, so we can't update the mapping's
-		 * writeback index, just update nr_to_write.
-		 */
-		wbc->nr_to_write -= nr_written;
-		return 1;
-	}
-
 	return 0;
 }
 

fs/btrfs/inode.c

@@ -127,8 +127,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback);
 
 static noinline int cow_file_range(struct btrfs_inode *inode,
 				   struct page *locked_page,
-				   u64 start, u64 end, int *page_started,
+				   u64 start, u64 end, u64 *done_offset,
-				   unsigned long *nr_written, u64 *done_offset,
 				   bool keep_locked, bool no_inline);
 static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start,
 				       u64 len, u64 orig_start, u64 block_start,
@@ -1130,8 +1129,6 @@ static void submit_uncompressed_range(struct btrfs_inode *inode,
 {
 	u64 start = async_extent->start;
 	u64 end = async_extent->start + async_extent->ram_size - 1;
-	unsigned long nr_written = 0;
-	int page_started = 0;
 	int ret;
 	struct writeback_control wbc = {
 		.sync_mode		= WB_SYNC_ALL,
@@ -1147,10 +1144,9 @@ static void submit_uncompressed_range(struct btrfs_inode *inode,
 	 * Also we call cow_file_range() with @unlock_page == 0, so that we
 	 * can directly submit them without interruption.
 	 */
-	ret = cow_file_range(inode, locked_page, start, end, &page_started,
+	ret = cow_file_range(inode, locked_page, start, end, NULL, true, false);
-			     &nr_written, NULL, true, false);
 	/* Inline extent inserted, page gets unlocked and everything is done */
-	if (page_started)
+	if (ret == 1)
 		return;
 
 	if (ret < 0) {
@@ -1360,8 +1356,8 @@ static u64 get_extent_allocation_hint(struct btrfs_inode *inode, u64 start,
  *
  * When this function fails, it unlocks all pages except @locked_page.
  *
- * When this function successfully creates an inline extent, it sets page_started
+ * When this function successfully creates an inline extent, it returns 1 and
- * to 1 and unlocks all pages including locked_page and starts I/O on them.
+ * unlocks all pages including locked_page and starts I/O on them.
  * (In reality inline extents are limited to a single page, so locked_page is
  * the only page handled anyway).
  *
@@ -1378,9 +1374,8 @@ static u64 get_extent_allocation_hint(struct btrfs_inode *inode, u64 start,
  * example.
  */
 static noinline int cow_file_range(struct btrfs_inode *inode,
-				   struct page *locked_page,
+				   struct page *locked_page, u64 start, u64 end,
-				   u64 start, u64 end, int *page_started,
+				   u64 *done_offset,
-				   unsigned long *nr_written, u64 *done_offset,
 				   bool keep_locked, bool no_inline)
 {
 	struct btrfs_root *root = inode->root;
@@ -1440,9 +1435,6 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 				     EXTENT_DELALLOC_NEW | EXTENT_DEFRAG |
 				     EXTENT_DO_ACCOUNTING, PAGE_UNLOCK |
 				     PAGE_START_WRITEBACK | PAGE_END_WRITEBACK);
-			*nr_written = *nr_written +
-			     (end - start + PAGE_SIZE) / PAGE_SIZE;
-			*page_started = 1;
 			/*
 			 * locked_page is locked by the caller of
 			 * writepage_delalloc(), not locked by
@@ -1452,11 +1444,11 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 			 * as it doesn't have any subpage::writers recorded.
 			 *
 			 * Here we manually unlock the page, since the caller
-			 * can't use page_started to determine if it's an
+			 * can't determine if it's an inline extent or a
-			 * inline extent or a compressed extent.
+			 * compressed extent.
 			 */
 			unlock_page(locked_page);
-			goto out;
+			return 1;
 		} else if (ret < 0) {
 			goto out_unlock;
 		}
@@ -1570,7 +1562,6 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 		if (ret)
 			goto out_unlock;
 	}
-out:
 	return ret;
 
 out_drop_extent_cache:
@@ -1721,10 +1712,8 @@ static noinline void async_cow_free(struct btrfs_work *work)
 }
 
 static bool run_delalloc_compressed(struct btrfs_inode *inode,
-				    struct writeback_control *wbc,
+				    struct page *locked_page, u64 start,
-				    struct page *locked_page,
+				    u64 end, struct writeback_control *wbc)
-				    u64 start, u64 end, int *page_started,
-				    unsigned long *nr_written)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct cgroup_subsys_state *blkcg_css = wbc_blkcg_css(wbc);
@@ -1806,34 +1795,25 @@ static bool run_delalloc_compressed(struct btrfs_inode *inode,
 
 		btrfs_queue_work(fs_info->delalloc_workers, &async_chunk[i].work);
 
-		*nr_written += nr_pages;
 		start = cur_end + 1;
 	}
-	*page_started = 1;
 	return true;
 }
 
 static noinline int run_delalloc_zoned(struct btrfs_inode *inode,
 				       struct page *locked_page, u64 start,
-				       u64 end, int *page_started,
+				       u64 end, struct writeback_control *wbc)
-				       unsigned long *nr_written,
-				       struct writeback_control *wbc)
 {
 	u64 done_offset = end;
 	int ret;
 	bool locked_page_done = false;
 
 	while (start <= end) {
-		ret = cow_file_range(inode, locked_page, start, end, page_started,
+		ret = cow_file_range(inode, locked_page, start, end, &done_offset,
-				     nr_written, &done_offset, true, false);
+				     true, false);
 		if (ret && ret != -EAGAIN)
 			return ret;
 
-		if (*page_started) {
-			ASSERT(ret == 0);
-			return 0;
-		}
-
 		if (ret == 0)
 			done_offset = end;
 
@@ -1854,9 +1834,7 @@ static noinline int run_delalloc_zoned(struct btrfs_inode *inode,
 		start = done_offset + 1;
 	}
 
-	*page_started = 1;
+	return 1;
-
-	return 0;
 }
 
 static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info,
@@ -1889,8 +1867,6 @@ static int fallback_to_cow(struct btrfs_inode *inode, struct page *locked_page,
 	const bool is_reloc_ino = btrfs_is_data_reloc_root(inode->root);
 	const u64 range_bytes = end + 1 - start;
 	struct extent_io_tree *io_tree = &inode->io_tree;
-	int page_started = 0;
-	unsigned long nr_written;
 	u64 range_start = start;
 	u64 count;
 	int ret;
@@ -1951,9 +1927,8 @@ static int fallback_to_cow(struct btrfs_inode *inode, struct page *locked_page,
 	 * is written out and unlocked directly and a normal NOCOW extent
 	 * doesn't work.
 	 */
-	ret = cow_file_range(inode, locked_page, start, end, &page_started,
+	ret = cow_file_range(inode, locked_page, start, end, NULL, false, true);
-			     &nr_written, NULL, false, true);
+	ASSERT(ret != 1);
-	ASSERT(!page_started);
 	return ret;
 }
 
@@ -2389,15 +2364,14 @@ static bool should_nocow(struct btrfs_inode *inode, u64 start, u64 end)
  * being touched for the first time.
  */
 int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page,
-		u64 start, u64 end, int *page_started, unsigned long *nr_written,
+			     u64 start, u64 end, struct writeback_control *wbc)
-		struct writeback_control *wbc)
 {
-	int ret = 0;
 	const bool zoned = btrfs_is_zoned(inode->root->fs_info);
+	int ret;
 
 	/*
-	 * The range must cover part of the @locked_page, or the returned
+	 * The range must cover part of the @locked_page, or a return of 1
-	 * @page_started can confuse the caller.
+	 * can confuse the caller.
 	 */
 	ASSERT(!(end <= page_offset(locked_page) ||
 		 start >= page_offset(locked_page) + PAGE_SIZE));
@@ -2417,20 +2391,17 @@ int btrfs_run_delalloc_range(struct btrfs_inode *inode, struct page *locked_page
 
 	if (btrfs_inode_can_compress(inode) &&
 	    inode_need_compress(inode, start, end) &&
-	    run_delalloc_compressed(inode, wbc, locked_page, start,
+	    run_delalloc_compressed(inode, locked_page, start, end, wbc))
-				    end, page_started, nr_written))
+		return 1;
-		goto out;
 
 	if (zoned)
-		ret = run_delalloc_zoned(inode, locked_page, start, end,
+		ret = run_delalloc_zoned(inode, locked_page, start, end, wbc);
-					 page_started, nr_written, wbc);
 	else
-		ret = cow_file_range(inode, locked_page, start, end,
+		ret = cow_file_range(inode, locked_page, start, end, NULL,
-				     page_started, nr_written, NULL, false, false);
+				     false, false);
 
 out:
-	ASSERT(ret <= 0);
+	if (ret < 0)
-	if (ret)
 		btrfs_cleanup_ordered_extents(inode, locked_page, start,
 					      end - start + 1);
 	return ret;