[PATCH 5/6] btrfs: move locking and write pointer checking into write_one_eb

[Christoph Hellwig <hch@lst.de>]

Currently only submit_eb_page contains handling for checking against the
write pointer on zoned devices.  This is ok as there is no support for
block size < PAGE_SIZE with zoned devices at the moment, but prevents
us from easily adding new callers of write_one_eb without breaking zoned
device support.

Move the call tolock_extent_buffer_for_io as well as the write pointer
checking and related code into write_one_eb.  To be able to do this,
write_one_eb now needs to set the eb_context pointer if the caller
passed in a non-NULL argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/extent_io.c | 69 +++++++++++++++++++++-----------------------
 1 file changed, 33 insertions(+), 36 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1205b3a3147e7d..c291fc728db047 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1759,12 +1759,39 @@ static void prepare_eb_write(struct extent_buffer *eb)
 	}
 }
 
-static noinline_for_stack void write_one_eb(struct extent_buffer *eb,
-					    struct writeback_control *wbc)
+static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
+					   struct writeback_control *wbc,
+					   struct extent_buffer **eb_context)
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
+	struct btrfs_block_group *zoned_bg = NULL;
 	struct btrfs_bio *bbio;
 
+	if (!btrfs_check_meta_write_pointer(eb->fs_info, eb, &zoned_bg)) {
+		/*
+		 * If for_sync, this hole will be filled with
+		 * trasnsaction commit.
+		 */
+		if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync)
+			return -EAGAIN;
+		return 0;
+	}
+
+	if (eb_context)
+		*eb_context = eb;
+
+	if (!lock_extent_buffer_for_io(eb, wbc)) {
+		btrfs_revert_meta_write_pointer(zoned_bg, eb);
+		return 0;
+	}
+
+	/*
+	 * A non-NULL zoned_bg implies zoned mode and that we are writing the
+	 * last possible block in the zone.
+	 */
+	if (zoned_bg)
+		btrfs_schedule_zone_finish_bg(zoned_bg, eb);
+
 	prepare_eb_write(eb);
 
 	bbio = btrfs_bio_alloc(INLINE_EXTENT_BUFFER_PAGES,
@@ -1801,6 +1828,7 @@ static noinline_for_stack void write_one_eb(struct extent_buffer *eb,
 		}
 	}
 	btrfs_submit_bio(bbio, 0);
+	return 1;
 }
 
 /*
@@ -1868,11 +1896,8 @@ static int submit_eb_subpage(struct page *page, struct writeback_control *wbc)
 		 */
 		if (!eb)
 			continue;
-
-		if (lock_extent_buffer_for_io(eb, wbc)) {
-			write_one_eb(eb, wbc);
+		if (write_one_eb(eb, wbc, NULL) > 0)
 			submitted++;
-		}
 		free_extent_buffer(eb);
 	}
 	return submitted;
@@ -1902,7 +1927,6 @@ static int submit_eb_page(struct page *page, struct writeback_control *wbc,
 			  struct extent_buffer **eb_context)
 {
 	struct address_space *mapping = page->mapping;
-	struct btrfs_block_group *cache = NULL;
 	struct extent_buffer *eb;
 	int ret;
 
@@ -1937,36 +1961,9 @@ static int submit_eb_page(struct page *page, struct writeback_control *wbc,
 	spin_unlock(&mapping->private_lock);
 	if (!ret)
 		return 0;
-
-	if (!btrfs_check_meta_write_pointer(eb->fs_info, eb, &cache)) {
-		/*
-		 * If for_sync, this hole will be filled with
-		 * trasnsaction commit.
-		 */
-		if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync)
-			ret = -EAGAIN;
-		else
-			ret = 0;
-		free_extent_buffer(eb);
-		return ret;
-	}
-
-	*eb_context = eb;
-
-	if (!lock_extent_buffer_for_io(eb, wbc)) {
-		btrfs_revert_meta_write_pointer(cache, eb);
-		free_extent_buffer(eb);
-		return 0;
-	}
-	if (cache) {
-		/*
-		 * Implies write in zoned mode. Mark the last eb in a block group.
-		 */
-		btrfs_schedule_zone_finish_bg(cache, eb);
-	}
-	write_one_eb(eb, wbc);
+	ret = write_one_eb(eb, wbc, eb_context);
 	free_extent_buffer(eb);
-	return 1;
+	return ret;
 }
 
 int btree_write_cache_pages(struct address_space *mapping,
-- 
2.39.2