[PATCH 5.10 330/575] block: ataflop: fix breakage introduced at blk-mq refactoring

[PATCH 5.10 330/575] block: ataflop: fix breakage introduced at blk-mq refactoring

[Greg Kroah-Hartman]

From: Michael Schmitz <schmitzmic@gmail.com>

[ 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>
---
 drivers/block/ataflop.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index 3e881fdb06e0a..cd612cd04767a 100644
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -653,9 +653,6 @@ static inline void copy_buffer(void *from, void *to)
 		*p2++ = *p1++;
 }
 
-  
-  
-
 /* General Interrupt Handling */
 
 static void (*FloppyIRQHandler)( int status ) = NULL;
@@ -1225,6 +1222,7 @@ static void fd_rwsec_done1(int status)
 	}
 	else {
 		/* all sectors finished */
+		finish_fdc();
 		fd_end_request_cur(BLK_STS_OK);
 	}
 	return;
@@ -1472,15 +1470,6 @@ static void setup_req_params( int drive )
 			ReqTrack, ReqSector, (unsigned long)ReqData ));
 }
 
-static void ataflop_commit_rqs(struct blk_mq_hw_ctx *hctx)
-{
-	spin_lock_irq(&ataflop_lock);
-	atari_disable_irq(IRQ_MFP_FDC);
-	finish_fdc();
-	atari_enable_irq(IRQ_MFP_FDC);
-	spin_unlock_irq(&ataflop_lock);
-}
-
 static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 				     const struct blk_mq_queue_data *bd)
 {
@@ -1488,6 +1477,8 @@ static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 	int drive = floppy - unit;
 	int type = floppy->type;
 
+	DPRINT(("Queue request: drive %d type %d last %d\n", drive, type, bd->last));
+
 	spin_lock_irq(&ataflop_lock);
 	if (fd_request) {
 		spin_unlock_irq(&ataflop_lock);
@@ -1547,8 +1538,6 @@ static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 	setup_req_params( drive );
 	do_fd_action( drive );
 
-	if (bd->last)
-		finish_fdc();
 	atari_enable_irq( IRQ_MFP_FDC );
 
 out:
@@ -1959,7 +1948,6 @@ static const struct block_device_operations floppy_fops = {
 
 static const struct blk_mq_ops ataflop_mq_ops = {
 	.queue_rq = ataflop_queue_rq,
-	.commit_rqs = ataflop_commit_rqs,
 };
 
 static struct kobject *floppy_find(dev_t dev, int *part, void *data)
-- 
2.33.0

[PATCH 5.10 360/575] block: ataflop: more blk-mq refactoring fixes

[Greg Kroah-Hartman]

From: Michael Schmitz <schmitzmic@gmail.com>

[ Upstream commit d28e4dff085c5a87025c9a0a85fb798bd8e9ca17 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/block/ataflop.c | 45 +++++++++++++++++++++++++++++++++++------
 1 file changed, 39 insertions(+), 6 deletions(-)

diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index 0a86f9d3a3798..94b76c254db9b 100644
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -456,10 +456,20 @@ static DEFINE_TIMER(fd_timer, check_change);
 	
 static void fd_end_request_cur(blk_status_t err)
 {
+	DPRINT(("fd_end_request_cur(), bytes %d of %d\n",
+		blk_rq_cur_bytes(fd_request),
+		blk_rq_bytes(fd_request)));
+
 	if (!blk_update_request(fd_request, err,
 				blk_rq_cur_bytes(fd_request))) {
+		DPRINT(("calling __blk_mq_end_request()\n"));
 		__blk_mq_end_request(fd_request, err);
 		fd_request = NULL;
+	} else {
+		/* requeue rest of request */
+		DPRINT(("calling blk_mq_requeue_request()\n"));
+		blk_mq_requeue_request(fd_request, true);
+		fd_request = NULL;
 	}
 }
 
@@ -697,12 +707,21 @@ static void fd_error( void )
 	if (fd_request->error_count >= MAX_ERRORS) {
 		printk(KERN_ERR "fd%d: too many errors.\n", SelectedDrive );
 		fd_end_request_cur(BLK_STS_IOERR);
+		finish_fdc();
+		return;
 	}
 	else if (fd_request->error_count == RECALIBRATE_ERRORS) {
 		printk(KERN_WARNING "fd%d: recalibrating\n", SelectedDrive );
 		if (SelectedDrive != -1)
 			SUD.track = -1;
 	}
+	/* need to re-run request to recalibrate */
+	atari_disable_irq( IRQ_MFP_FDC );
+
+	setup_req_params( SelectedDrive );
+	do_fd_action( SelectedDrive );
+
+	atari_enable_irq( IRQ_MFP_FDC );
 }
 
 
@@ -729,8 +748,10 @@ static int do_format(int drive, int type, struct atari_format_descr *desc)
 	if (type) {
 		type--;
 		if (type >= NUM_DISK_MINORS ||
-		    minor2disktype[type].drive_types > DriveType)
+		    minor2disktype[type].drive_types > DriveType) {
+			finish_fdc();
 			return -EINVAL;
+		}
 	}
 
 	q = unit[drive].disk[type]->queue;
@@ -748,6 +769,7 @@ static int do_format(int drive, int type, struct atari_format_descr *desc)
 	}
 
 	if (!UDT || desc->track >= UDT->blocks/UDT->spt/2 || desc->head >= 2) {
+		finish_fdc();
 		ret = -EINVAL;
 		goto out;
 	}
@@ -788,6 +810,7 @@ static int do_format(int drive, int type, struct atari_format_descr *desc)
 
 	wait_for_completion(&format_wait);
 
+	finish_fdc();
 	ret = FormatError ? -EIO : 0;
 out:
 	blk_mq_unquiesce_queue(q);
@@ -822,6 +845,7 @@ static void do_fd_action( int drive )
 		    else {
 			/* all sectors finished */
 			fd_end_request_cur(BLK_STS_OK);
+			finish_fdc();
 			return;
 		    }
 		}
@@ -1225,8 +1249,8 @@ static void fd_rwsec_done1(int status)
 	}
 	else {
 		/* all sectors finished */
-		finish_fdc();
 		fd_end_request_cur(BLK_STS_OK);
+		finish_fdc();
 	}
 	return;
   
@@ -1348,7 +1372,7 @@ static void fd_times_out(struct timer_list *unused)
 
 static void finish_fdc( void )
 {
-	if (!NeedSeek) {
+	if (!NeedSeek || !stdma_is_locked_by(floppy_irq)) {
 		finish_fdc_done( 0 );
 	}
 	else {
@@ -1383,7 +1407,8 @@ static void finish_fdc_done( int dummy )
 	start_motor_off_timer();
 
 	local_irq_save(flags);
-	stdma_release();
+	if (stdma_is_locked_by(floppy_irq))
+		stdma_release();
 	local_irq_restore(flags);
 
 	DPRINT(("finish_fdc() finished\n"));
@@ -1480,7 +1505,9 @@ static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 	int drive = floppy - unit;
 	int type = floppy->type;
 
-	DPRINT(("Queue request: drive %d type %d last %d\n", drive, type, bd->last));
+	DPRINT(("Queue request: drive %d type %d sectors %d of %d last %d\n",
+		drive, type, blk_rq_cur_sectors(bd->rq),
+		blk_rq_sectors(bd->rq), bd->last));
 
 	spin_lock_irq(&ataflop_lock);
 	if (fd_request) {
@@ -1502,6 +1529,7 @@ static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 		/* drive not connected */
 		printk(KERN_ERR "Unknown Device: fd%d\n", drive );
 		fd_end_request_cur(BLK_STS_IOERR);
+		stdma_release();
 		goto out;
 	}
 		
@@ -1518,11 +1546,13 @@ static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
 		if (--type >= NUM_DISK_MINORS) {
 			printk(KERN_WARNING "fd%d: invalid disk format", drive );
 			fd_end_request_cur(BLK_STS_IOERR);
+			stdma_release();
 			goto out;
 		}
 		if (minor2disktype[type].drive_types > DriveType)  {
 			printk(KERN_WARNING "fd%d: unsupported disk format", drive );
 			fd_end_request_cur(BLK_STS_IOERR);
+			stdma_release();
 			goto out;
 		}
 		type = minor2disktype[type].index;
@@ -1623,6 +1653,7 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode,
 		/* what if type > 0 here? Overwrite specified entry ? */
 		if (type) {
 		        /* refuse to re-set a predefined type for now */
+			finish_fdc();
 			return -EINVAL;
 		}
 
@@ -1690,8 +1721,10 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode,
 
 		/* sanity check */
 		if (setprm.track != dtp->blocks/dtp->spt/2 ||
-		    setprm.head != 2)
+		    setprm.head != 2) {
+			finish_fdc();
 			return -EINVAL;
+		}
 
 		UDT = dtp;
 		set_capacity(disk, UDT->blocks);
-- 
2.33.0