[PATCH v5 04/12] btrfs: extent_io: Move the BUG_ON() in flush_write_bio() one level up

[Qu Wenruo <wqu@suse.com>]

We have a BUG_ON() in flush_write_bio() to handle the return value of
submit_one_bio().

Move the BUG_ON() one level up to all its callers.

This patch will introduce temporary variable, @flush_ret to keep code
change minimal in this patch. That variable will be cleaned up when
enhancing the error handling later.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 fs/btrfs/extent_io.c | 55 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 41 insertions(+), 14 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 8a2335713a2d..47a579650a61 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -169,15 +169,28 @@ static int __must_check submit_one_bio(struct bio *bio, int mirror_num,
 	return blk_status_to_errno(ret);
 }
 
-static void flush_write_bio(struct extent_page_data *epd)
+/*
+ * A wrapper for submit_one_bio().
+ *
+ * Return 0 if everything is OK.
+ * Return <0 for error.
+ */
+static int __must_check flush_write_bio(struct extent_page_data *epd)
 {
-	if (epd->bio) {
-		int ret;
+	int ret = 0;
 
+	if (epd->bio) {
 		ret = submit_one_bio(epd->bio, 0, 0);
-		BUG_ON(ret < 0); /* -ENOMEM */
+		/*
+		 * Clean up of epd->bio is handled by its endio function.
+		 * And endio is either triggered by successful bio execution
+		 * or the error handler of submit bio hook.
+		 * So at this point, no matter what happened, we don't need
+		 * to clean up epd->bio.
+		 */
 		epd->bio = NULL;
 	}
+	return ret;
 }
 
 int __init extent_io_init(void)
@@ -3510,7 +3523,8 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 
 	if (!btrfs_try_tree_write_lock(eb)) {
 		flush = 1;
-		flush_write_bio(epd);
+		ret = flush_write_bio(epd);
+		BUG_ON(ret < 0);
 		btrfs_tree_lock(eb);
 	}
 
@@ -3519,7 +3533,8 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 		if (!epd->sync_io)
 			return 0;
 		if (!flush) {
-			flush_write_bio(epd);
+			ret = flush_write_bio(epd);
+			BUG_ON(ret < 0);
 			flush = 1;
 		}
 		while (1) {
@@ -3560,7 +3575,8 @@ lock_extent_buffer_for_io(struct extent_buffer *eb,
 
 		if (!trylock_page(p)) {
 			if (!flush) {
-				flush_write_bio(epd);
+				ret = flush_write_bio(epd);
+				BUG_ON(ret < 0);
 				flush = 1;
 			}
 			lock_page(p);
@@ -3751,6 +3767,7 @@ int btree_write_cache_pages(struct address_space *mapping,
 		.sync_io = wbc->sync_mode == WB_SYNC_ALL,
 	};
 	int ret = 0;
+	int flush_ret;
 	int done = 0;
 	int nr_to_write_done = 0;
 	struct pagevec pvec;
@@ -3850,7 +3867,8 @@ int btree_write_cache_pages(struct address_space *mapping,
 		index = 0;
 		goto retry;
 	}
-	flush_write_bio(&epd);
+	flush_ret = flush_write_bio(&epd);
+	BUG_ON(flush_ret < 0);
 	return ret;
 }
 
@@ -3947,7 +3965,8 @@ static int extent_write_cache_pages(struct address_space *mapping,
 			 * tmpfs file mapping
 			 */
 			if (!trylock_page(page)) {
-				flush_write_bio(epd);
+				ret = flush_write_bio(epd);
+				BUG_ON(ret < 0);
 				lock_page(page);
 			}
 
@@ -3957,8 +3976,10 @@ static int extent_write_cache_pages(struct address_space *mapping,
 			}
 
 			if (wbc->sync_mode != WB_SYNC_NONE) {
-				if (PageWriteback(page))
-					flush_write_bio(epd);
+				if (PageWriteback(page)) {
+					ret = flush_write_bio(epd);
+					BUG_ON(ret < 0);
+				}
 				wait_on_page_writeback(page);
 			}
 
@@ -4019,6 +4040,7 @@ static int extent_write_cache_pages(struct address_space *mapping,
 int extent_write_full_page(struct page *page, struct writeback_control *wbc)
 {
 	int ret;
+	int flush_ret;
 	struct extent_page_data epd = {
 		.bio = NULL,
 		.tree = &BTRFS_I(page->mapping->host)->io_tree,
@@ -4028,7 +4050,8 @@ int extent_write_full_page(struct page *page, struct writeback_control *wbc)
 
 	ret = __extent_writepage(page, wbc, &epd);
 
-	flush_write_bio(&epd);
+	flush_ret = flush_write_bio(&epd);
+	BUG_ON(flush_ret < 0);
 	return ret;
 }
 
@@ -4036,6 +4059,7 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
 			      int mode)
 {
 	int ret = 0;
+	int flush_ret;
 	struct address_space *mapping = inode->i_mapping;
 	struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
 	struct page *page;
@@ -4068,7 +4092,8 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
 		start += PAGE_SIZE;
 	}
 
-	flush_write_bio(&epd);
+	flush_ret = flush_write_bio(&epd);
+	BUG_ON(flush_ret < 0);
 	return ret;
 }
 
@@ -4076,6 +4101,7 @@ int extent_writepages(struct address_space *mapping,
 		      struct writeback_control *wbc)
 {
 	int ret = 0;
+	int flush_ret;
 	struct extent_page_data epd = {
 		.bio = NULL,
 		.tree = &BTRFS_I(mapping->host)->io_tree,
@@ -4084,7 +4110,8 @@ int extent_writepages(struct address_space *mapping,
 	};
 
 	ret = extent_write_cache_pages(mapping, wbc, &epd);
-	flush_write_bio(&epd);
+	flush_ret = flush_write_bio(&epd);
+	BUG_ON(flush_ret < 0);
 	return ret;
 }
 
-- 
2.20.1