fs/buffer.c: add device information for error output in __find_get_block_slow()

On the ext4 mailing list[1], we got some report about errors in
__find_get_block_slow(), but the information is very limited.

If the device information is given, we can know the name of the sick
volume.  Futhermore, we can get the corresponding status of that
block(group, inode block etc) by analyzing the disk layout.

[1] http://marc.info/?l=linux-ext4&m=131379831421147&w=2

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 936d6035f6e2..70a19745cb61 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -213,13 +213,16 @@ __find_get_block_slow(struct block_device *bdev, sector_t block)
          * elsewhere, don't buffer_error if we had some unmapped buffers
          */
         if (all_mapped) {
+                char b[BDEVNAME_SIZE];
+
                 printk("__find_get_block_slow() failed. "
                         "block=%llu, b_blocknr=%llu\n",
                         (unsigned long long)block,
                         (unsigned long long)bh->b_blocknr);
                 printk("b_state=0x%08lx, b_size=%zu\n",
                         bh->b_state, bh->b_size);
-                printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
+                printk("device %s blocksize: %d\n", bdevname(bdev, b),
+                        1 << bd_inode->i_blkbits);
         }
 out_unlock:
         spin_unlock(&bd_mapping->private_lock);