Re: [patch] scsi: revert "[SCSI] Get rid of scsi_cmnd->done"



On Wed, 2 Jan 2008, James Bottomley wrote:

To say that another way:

"the code is functionally equivalent, EXCEPT IT ISN'T, and it's
known to be broken".

wouldn't you say my version is more honest and correct?

No. Just because a bug appears when a particular piece of code is in
and disappears when it is reverted doesn't automatically equate to the
code in question being buggy.

But it *DOES* mean that it's not equivalent.

Look at the taxonomy of the bug. This is the form of the error:

buffer I/O error on device sr0, logical block 20304
attempt to access beyond end of device
sr0: rw=0, want=81224, limit=40944

The last limit is the most suggestive, that comes straight from
bdev->bd_inode->i_size>>9 and is supposed to be the size of the block
device in 512 byte blocks. For a 4.7GB DVD, it's a little small.
Nothing in the sr code sets this directly (although it does come from
get_blkdev() for the first opener). pktcdvd does set it, though ... and
probably wrongly if the drive in question isn't UDF formatted.

.. but you're ignoring the fact that if pktcdvd sets it wrong, then it
should be visible with the pre-commit kernel *also*.

In other words, you continue to ignore the fact that BEHAVIOUR CHANGED.

Why?

Linus
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