commit d28e4dff085c5a87025c9a0a85fb798bd8e9ca17 upstream.
As it turns out, my earlier patch in commit 86d46fdaa12a (block:
ataflop: fix breakage introduced at blk-mq refactoring) was
incomplete. This patch fixes any remaining issues found during
more testing and code review.
Requests exceeding 4 k are handled in 4k segments but
__blk_mq_end_request() is never called on these (still
sectors outstanding on the request). With redo_fd_request()
removed, there is no provision to kick off processing of the
next segment, causing requests exceeding 4k to hang. (By
setting /sys/block/fd0/queue/max_sectors_k <= 4 as workaround,
this behaviour can be avoided).
Instead of reintroducing redo_fd_request(), requeue the remainder
of the request by calling blk_mq_requeue_request() on incomplete
requests (i.e. when blk_update_request() still returns true), and
rely on the block layer to queue the residual as new request.
Both error handling and formatting needs to release the
ST-DMA lock, so call finish_fdc() on these (this was previously
handled by redo_fd_request()). finish_fdc() may be called
legitimately without the ST-DMA lock held - make sure we only
release the lock if we actually held it. In a similar way,
early exit due to errors in ataflop_queue_rq() must release
the lock.
After minor errors, fd_error sets up to recalibrate the drive
but never re-runs the current operation (another task handled by
redo_fd_request() before). Call do_fd_action() to get the next
steps (seek, retry read/write) underway.
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Fixes: 6ec3938cff95f (ataflop: convert to blk-mq)
CC: linux-block@vger.kernel.org
Link: https://lore.kernel.org/r/20211024002013.9332-1-schmitzmic@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[MSch: v5.10 backport merge conflict fix]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 86d46fdaa12ae5befc16b8d73fc85a3ca0399ea6 ]
Refactoring of the Atari floppy driver when converting to blk-mq
has broken the state machine in not-so-subtle ways:
finish_fdc() must be called when operations on the floppy device
have completed. This is crucial in order to relase the ST-DMA
lock, which protects against concurrent access to the ST-DMA
controller by other drivers (some DMA related, most just related
to device register access - broken beyond compare, I know).
When rewriting the driver's old do_request() function, the fact
that finish_fdc() was called only when all queued requests had
completed appears to have been overlooked. Instead, the new
request function calls finish_fdc() immediately after the last
request has been queued. finish_fdc() executes a dummy seek after
most requests, and this overwrites the state machine's interrupt
hander that was set up to wait for completion of the read/write
request just prior. To make matters worse, finish_fdc() is called
before device interrupts are re-enabled, making certain that the
read/write interupt is missed.
Shifting the finish_fdc() call into the read/write request
completion handler ensures the driver waits for the request to
actually complete. With a queue depth of 2, we won't see long
request sequences, so calling finish_fdc() unconditionally just
adds a little overhead for the dummy seeks, and keeps the code
simple.
While we're at it, kill ataflop_commit_rqs() which does nothing
but run finish_fdc() unconditionally, again likely wiping out an
in-flight request.
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Fixes: 6ec3938cff95 ("ataflop: convert to blk-mq")
CC: linux-block@vger.kernel.org
CC: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Link: https://lore.kernel.org/r/20211019061321.26425-1-schmitzmic@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
