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author | Michael Schmitz <schmitzmic@gmail.com> | 2021-10-19 09:13:21 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-11-18 21:16:34 +0300 |
commit | 456b47cacdc72d31e32b3e7aa5e5f24a611608e5 (patch) | |
tree | 0394a239f1d8a9d196c57766e38607bb3604b478 /block | |
parent | 4eac23d60cbc105b5991e4341d09d165c21145f8 (diff) | |
download | linux-456b47cacdc72d31e32b3e7aa5e5f24a611608e5.tar.xz |
block: ataflop: fix breakage introduced at blk-mq refactoring
[ 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>
Diffstat (limited to 'block')
0 files changed, 0 insertions, 0 deletions