When setting a channel attached tape online under Linux 2.6.31, the
"vol_id" process from udev hangs in sync_page():
2 sync_page+144 [0x1dfaac]
3 __wait_on_bit_lock+194 [0x58c23e]
4 __lock_page+116 [0x1df9dc]
5 truncate_inode_pages_range+728 [0x1ed7cc]
6 __blkdev_put+244 [0x25f738]
7 __fput+300 [0x229c4c]
8 filp_close+122 [0x225a3a]
The reason for that is an error in the request queue handling. It can
happen that we fetch a request, but do not process it further because
the number of queued requests exceeds TAPEBLOCK_MIN_REQUEUE.
To fix this, we should call blk_peek_request() instead of
blk_fetch_request() in the while condition and fetch the request in
the loop body afterwards.
This bug was introduced with the patch "block: implement and enforce
request peek/start/fetch" (9934c8c045)
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
03cadd36d5