When nilfs returned -EIO as an error code, it's not always clear if it
came from the underlying block device or not.  This will mend the issue
by having low level I/O routines of nilfs output an error message when
they detected an I/O error.
Link: http://lkml.kernel.org/r/1464875891-5443-7-git-send-email-konishi.ryusuke@lab.ntt.co.jp
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 
  out_no_wait:
        if (!buffer_uptodate(bh)) {
+               nilfs_msg(btree->b_inode->i_sb, KERN_ERR,
+                         "I/O error reading b-tree node block (ino=%lu, blocknr=%llu)",
+                         btree->b_inode->i_ino, (unsigned long long)ptr);
                brelse(bh);
                return -EIO;
        }
 
 int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *bh)
 {
        wait_on_buffer(bh);
-       if (!buffer_uptodate(bh))
+       if (!buffer_uptodate(bh)) {
+               struct inode *inode = bh->b_page->mapping->host;
+
+               nilfs_msg(inode->i_sb, KERN_ERR,
+                         "I/O error reading %s block for GC (ino=%lu, vblocknr=%llu)",
+                         buffer_nilfs_node(bh) ? "node" : "data",
+                         inode->i_ino, (unsigned long long)bh->b_blocknr);
                return -EIO;
+       }
        if (buffer_dirty(bh))
                return -EEXIST;
 
 
 
  out_no_wait:
        err = -EIO;
-       if (!buffer_uptodate(first_bh))
+       if (!buffer_uptodate(first_bh)) {
+               nilfs_msg(inode->i_sb, KERN_ERR,
+                         "I/O error reading meta-data file (ino=%lu, block-offset=%lu)",
+                         inode->i_ino, block);
                goto failed_bh;
+       }
  out:
        *out_bh = first_bh;
        return 0;