btrfs-progs: Show detail error message when write sb failed in write_dev_supers()

fsck-tests.sh failed and show following message in my node:
  # ./fsck-tests.sh
     [TEST]   001-bad-file-extent-bytenr
  disk-io.c:1444: write_dev_supers: Assertion `ret != BTRFS_SUPER_INFO_SIZE` failed.
  /root/btrfsprogs/btrfs-image(write_all_supers+0x2d2)[0x41031c]
  /root/btrfsprogs/btrfs-image(write_ctree_super+0xc5)[0x41042e]
  /root/btrfsprogs/btrfs-image(btrfs_commit_transaction+0x208)[0x410976]
  /root/btrfsprogs/btrfs-image[0x438780]
  /root/btrfsprogs/btrfs-image(main+0x3d5)[0x438c5c]
  /lib64/libc.so.6(__libc_start_main+0xfd)[0x335e01ecdd]
  /root/btrfsprogs/btrfs-image[0x4074e9]
  failed to restore image /root/btrfsprogs/tests/fsck-tests/001-bad-file-extent-bytenr/default_case.img
  #

  # cat fsck-tests-results.txt
  === Entering /root/btrfsprogs/tests/fsck-tests/001-bad-file-extent-bytenr
  restoring image default_case.img
  failed to restore image /root/btrfsprogs/tests/fsck-tests/001-bad-file-extent-bytenr/default_case.img
  #

Reason:
  I run above test in a NFS mountpoint, it don't have enouth space to write
  all superblock to image file, and don't support sparse file.
  So write_dev_supers() failed in writing sb and output above message.

It takes me quite of time to know what happened, we can save these time
by output exact information in write-sb-fail case.

After patch:
  # ./fsck-tests.sh
    [TEST]   001-bad-file-extent-bytenr
  WARNING: Write sb failed: File too large
  disk-io.c:1492: write_all_supers: Assertion `ret` failed.
  ...
  #

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/disk-io.c b/disk-io.c
index 8496ade..c3da18c 100644 (file)
--- a/disk-io.c
+++ b/disk-io.c
@@ -1412,7 +1412,8 @@ static int write_dev_supers(struct btrfs_root *root,
                ret = pwrite64(device->fd, root->fs_info->super_copy,
                                BTRFS_SUPER_INFO_SIZE,
                                root->fs_info->super_bytenr);
-               BUG_ON(ret != BTRFS_SUPER_INFO_SIZE);
+               if (ret != BTRFS_SUPER_INFO_SIZE)
+                       goto write_err;
                return 0;
        }
 
@@ -1434,10 +1435,19 @@ static int write_dev_supers(struct btrfs_root *root,
                 */
                ret = pwrite64(device->fd, root->fs_info->super_copy,
                                BTRFS_SUPER_INFO_SIZE, bytenr);
-               BUG_ON(ret != BTRFS_SUPER_INFO_SIZE);
+               if (ret != BTRFS_SUPER_INFO_SIZE)
+                       goto write_err;
        }
 
        return 0;
+
+write_err:
+       if (ret > 0)
+               fprintf(stderr, "WARNING: failed to write all sb data\n");
+       else
+               fprintf(stderr, "WARNING: failed to write sb: %s\n",
+                       strerror(errno));
+       return ret;
 }
 
 int write_all_supers(struct btrfs_root *root)