btrfs: zoned: introduce block group context to btrfs_eb_write_context

For metadata write out on the zoned mode, we call
btrfs_check_meta_write_pointer() to check if an extent buffer to be written
is aligned to the write pointer.

We look up a block group containing the extent buffer for every extent
buffer, which takes unnecessary effort as the writing extent buffers are
mostly contiguous.

Introduce "zoned_bg" to cache the block group working on.  Also, while
at it, rename "cache" to "block_group".

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -1809,7 +1809,6 @@ static int submit_eb_page(struct page *page, struct btrfs_eb_write_context *ctx)
 {
 	struct writeback_control *wbc = ctx->wbc;
 	struct address_space *mapping = page->mapping;
-	struct btrfs_block_group *cache = NULL;
 	struct extent_buffer *eb;
 	int ret;
 
@@ -1847,7 +1846,7 @@ static int submit_eb_page(struct page *page, struct btrfs_eb_write_context *ctx)
 
 	ctx->eb = eb;
 
-	if (!btrfs_check_meta_write_pointer(eb->fs_info, eb, &cache)) {
+	if (!btrfs_check_meta_write_pointer(eb->fs_info, ctx)) {
 		/*
 		 * If for_sync, this hole will be filled with
 		 * trasnsaction commit.
@@ -1861,18 +1860,15 @@ static int submit_eb_page(struct page *page, struct btrfs_eb_write_context *ctx)
 	}
 
 	if (!lock_extent_buffer_for_io(eb, wbc)) {
-		btrfs_revert_meta_write_pointer(cache, eb);
+		btrfs_revert_meta_write_pointer(ctx->zoned_bg, eb);
-		if (cache)
-			btrfs_put_block_group(cache);
 		free_extent_buffer(eb);
 		return 0;
 	}
-	if (cache) {
+	if (ctx->zoned_bg) {
 		/*
 		 * Implies write in zoned mode. Mark the last eb in a block group.
 		 */
-		btrfs_schedule_zone_finish_bg(cache, eb);
+		btrfs_schedule_zone_finish_bg(ctx->zoned_bg, eb);
-		btrfs_put_block_group(cache);
 	}
 	write_one_eb(eb, wbc);
 	free_extent_buffer(eb);
@@ -1985,6 +1981,9 @@ retry:
 		ret = 0;
 	if (!ret && BTRFS_FS_ERROR(fs_info))
 		ret = -EROFS;
+
+	if (ctx.zoned_bg)
+		btrfs_put_block_group(ctx.zoned_bg);
 	btrfs_zoned_meta_io_unlock(fs_info);
 	return ret;
 }

fs/btrfs/extent_io.h

@@ -96,6 +96,8 @@ struct extent_buffer {
 struct btrfs_eb_write_context {
 	struct writeback_control *wbc;
 	struct extent_buffer *eb;
+	/* Block group @eb resides in. Only used for zoned mode. */
+	struct btrfs_block_group *zoned_bg;
 };
 
 /*

fs/btrfs/zoned.c

@@ -1748,30 +1748,35 @@ out:
 }
 
 bool btrfs_check_meta_write_pointer(struct btrfs_fs_info *fs_info,
-				    struct extent_buffer *eb,
+				    struct btrfs_eb_write_context *ctx)
-				    struct btrfs_block_group **cache_ret)
 {
-	struct btrfs_block_group *cache;
+	const struct extent_buffer *eb = ctx->eb;
-	bool ret = true;
+	struct btrfs_block_group *block_group = ctx->zoned_bg;
 
 	if (!btrfs_is_zoned(fs_info))
 		return true;
 
-	cache = btrfs_lookup_block_group(fs_info, eb->start);
+	if (block_group) {
-	if (!cache)
+		if (block_group->start > eb->start ||
-		return true;
+		    block_group->start + block_group->length <= eb->start) {
-
+			btrfs_put_block_group(block_group);
-	if (cache->meta_write_pointer != eb->start) {
+			block_group = NULL;
-		btrfs_put_block_group(cache);
+			ctx->zoned_bg = NULL;
-		cache = NULL;
+		}
-		ret = false;
-	} else {
-		cache->meta_write_pointer = eb->start + eb->len;
 	}
 
-	*cache_ret = cache;
+	if (!block_group) {
+		block_group = btrfs_lookup_block_group(fs_info, eb->start);
+		if (!block_group)
+			return true;
+		ctx->zoned_bg = block_group;
+	}
 
-	return ret;
+	if (block_group->meta_write_pointer != eb->start)
+		return false;
+	block_group->meta_write_pointer = eb->start + eb->len;
+
+	return true;
 }
 
 void btrfs_revert_meta_write_pointer(struct btrfs_block_group *cache,

fs/btrfs/zoned.h

@@ -59,8 +59,7 @@ void btrfs_redirty_list_add(struct btrfs_transaction *trans,
 bool btrfs_use_zone_append(struct btrfs_bio *bbio);
 void btrfs_record_physical_zoned(struct btrfs_bio *bbio);
 bool btrfs_check_meta_write_pointer(struct btrfs_fs_info *fs_info,
-				    struct extent_buffer *eb,
+				    struct btrfs_eb_write_context *ctx);
-				    struct btrfs_block_group **cache_ret);
 void btrfs_revert_meta_write_pointer(struct btrfs_block_group *cache,
 				     struct extent_buffer *eb);
 int btrfs_zoned_issue_zeroout(struct btrfs_device *device, u64 physical, u64 length);
@@ -190,8 +189,7 @@ static inline void btrfs_record_physical_zoned(struct btrfs_bio *bbio)
 }
 
 static inline bool btrfs_check_meta_write_pointer(struct btrfs_fs_info *fs_info,
-			       struct extent_buffer *eb,
+						  struct btrfs_eb_write_context *ctx)
-			       struct btrfs_block_group **cache_ret)
 {
 	return true;
 }