[PATCH] btrfs: disk-io: Kill the BUG_ON()s in write_and_map_eb()

[Qu Wenruo <wqu@suse.com>]

All callers of write_and_map_eb(), except btrfs-corrupt-block, have
handled error, but inside write_and_map_eb() itself, the only error handling
is BUG_ON().

This patch will kill all the BUG_ON()s inside write_and_map_eb(), and
enhance the the caller in btrfs-corrupt-block() to handle the error.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 btrfs-corrupt-block.c       |  9 ++++++++-
 cmds/rescue-super-recover.c |  3 ++-
 disk-io.c                   | 26 +++++++++++++++++++++++---
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/btrfs-corrupt-block.c b/btrfs-corrupt-block.c
index 95df871a7822..3c236e146176 100644
--- a/btrfs-corrupt-block.c
+++ b/btrfs-corrupt-block.c
@@ -771,8 +771,15 @@ static int corrupt_metadata_block(struct btrfs_fs_info *fs_info, u64 block,
 		u64 bogus = generate_u64(orig);
 
 		btrfs_set_header_generation(eb, bogus);
-		write_and_map_eb(fs_info, eb);
+		ret = write_and_map_eb(fs_info, eb);
 		free_extent_buffer(eb);
+		if (ret < 0) {
+			errno = -ret;
+			fprintf(stderr,
+				"failed to write extent buffer at %llu: %m",
+				eb->start);
+			return ret;
+		}
 		break;
 		}
 	case BTRFS_METADATA_BLOCK_SHIFT_ITEMS:
diff --git a/cmds/rescue-super-recover.c b/cmds/rescue-super-recover.c
index 5d6bea836c8b..62f4f7754720 100644
--- a/cmds/rescue-super-recover.c
+++ b/cmds/rescue-super-recover.c
@@ -276,7 +276,8 @@ int btrfs_recover_superblocks(const char *dname,
 				  struct super_block_record, list);
 
 	root = open_ctree(record->device_name, record->bytenr,
-			  OPEN_CTREE_RECOVER_SUPER | OPEN_CTREE_WRITES);
+			  OPEN_CTREE_RECOVER_SUPER | OPEN_CTREE_WRITES |
+			  OPEN_CTREE_EXCLUSIVE);
 	if (!root) {
 		ret = 3;
 		goto no_recover;
diff --git a/disk-io.c b/disk-io.c
index e8a2e4afa93a..9ff62fcd54d1 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -487,20 +487,40 @@ int write_and_map_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
 	length = eb->len;
 	ret = btrfs_map_block(fs_info, WRITE, eb->start, &length,
 			      &multi, 0, &raid_map);
+	if (ret < 0) {
+		errno = -ret;
+		error("failed to map bytenr %llu length %u: %m",
+			eb->start, eb->len);
+		goto out;
+	}
 
 	if (raid_map) {
 		ret = write_raid56_with_parity(fs_info, eb, multi,
 					       length, raid_map);
-		BUG_ON(ret);
+		if (ret < 0) {
+			errno = -ret;
+			error(
+		"failed to write raid56 stripe for bytenr %llu length %llu: %m",
+				eb->start, length);
+			goto out;
+		}
 	} else while (dev_nr < multi->num_stripes) {
-		BUG_ON(ret);
 		eb->fd = multi->stripes[dev_nr].dev->fd;
 		eb->dev_bytenr = multi->stripes[dev_nr].physical;
 		multi->stripes[dev_nr].dev->total_ios++;
 		dev_nr++;
 		ret = write_extent_to_disk(eb);
-		BUG_ON(ret);
+		if (ret < 0) {
+			errno = -ret;
+			error(
+"failed to write bytenr %llu length %u devid %llu dev_bytenr %llu: %m",
+				eb->start, eb->len,
+				multi->stripes[dev_nr].dev->devid,
+				eb->dev_bytenr);
+			goto out;
+		}
 	}
+out:
 	kfree(raid_map);
 	kfree(multi);
 	return 0;
-- 
2.25.1