[PATCH 4.19 098/168] scsi: mesh: Fix panic after host or bus reset

Greg Kroah-Hartman
2020-08-17T17:39:51Z

From: Finn Thain <fthain@telegraphics.com.au>

[ Upstream commit edd7dd2292ab9c3628b65c4d04514c3068ad54f6 ]

Booting Linux with a Conner CP3200 drive attached to the MESH SCSI bus
results in EH measures and a panic:

[ 25.499838] mesh: configured for synchronous 5 MB/s
[ 25.787154] mesh: performing initial bus reset...
[ 29.867115] scsi host0: MESH
[ 29.929527] mesh: target 0 synchronous at 3.6 MB/s
[ 29.998763] scsi 0:0:0:0: Direct-Access CONNER CP3200-200mb-3.5 4040 PQ: 0 ANSI: 1 CCS
[ 31.989975] sd 0:0:0:0: [sda] 415872 512-byte logical blocks: (213 MB/203 MiB)
[ 32.070975] sd 0:0:0:0: [sda] Write Protect is off
[ 32.137197] sd 0:0:0:0: [sda] Mode Sense: 5b 00 00 08
[ 32.209661] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 32.332708] sda: [mac] sda1 sda2 sda3
[ 32.417733] sd 0:0:0:0: [sda] Attached SCSI disk
... snip ...
[ 76.687067] mesh_abort((ptrval))
[ 76.743606] mesh: state at (ptrval), regs at (ptrval), dma at (ptrval)
[ 76.810798] ct=6000 seq=86 bs=4017 fc= 0 exc= 0 err= 0 im= 7 int= 0 sp=85
[ 76.880720] dma stat=84e0 cmdptr=1f73d000
[ 76.941387] phase=4 msgphase=0 conn_tgt=0 data_ptr=24576
[ 77.005567] dma_st=1 dma_ct=0 n_msgout=0
[ 77.065456] target 0: req=(ptrval) goes_out=0 saved_ptr=0
[ 77.130512] mesh_abort((ptrval))
[ 77.187670] mesh: state at (ptrval), regs at (ptrval), dma at (ptrval)
[ 77.255594] ct=6000 seq=86 bs=4017 fc= 0 exc= 0 err= 0 im= 7 int= 0 sp=85
[ 77.325778] dma stat=84e0 cmdptr=1f73d000
[ 77.387239] phase=4 msgphase=0 conn_tgt=0 data_ptr=24576
[ 77.453665] dma_st=1 dma_ct=0 n_msgout=0
[ 77.515900] target 0: req=(ptrval) goes_out=0 saved_ptr=0
[ 77.582902] mesh_host_reset
[ 88.187083] Kernel panic - not syncing: mesh: double DMA start !
[ 88.254510] CPU: 0 PID: 358 Comm: scsi_eh_0 Not tainted 5.6.13-pmac #1
[ 88.323302] Call Trace:
[ 88.378854] [e16ddc58] [c0027080] panic+0x13c/0x308 (unreliable)
[ 88.446221] [e16ddcb8] [c02b2478] mesh_start.part.12+0x130/0x414
[ 88.513298] [e16ddcf8] [c02b2fc8] mesh_queue+0x54/0x70
[ 88.577097] [e16ddd18] [c02a1848] scsi_send_eh_cmnd+0x374/0x384
[ 88.643476] [e16dddc8] [c02a1938] scsi_eh_tur+0x5c/0xb8
[ 88.707878] [e16dddf8] [c02a1ab8] scsi_eh_test_devices+0x124/0x178
[ 88.775663] [e16dde28] [c02a2094] scsi_eh_ready_devs+0x588/0x8a8
[ 88.843124] [e16dde98] [c02a31d8] scsi_error_handler+0x344/0x520
[ 88.910697] [e16ddf08] [c00409c8] kthread+0xe4/0xe8
[ 88.975166] [e16ddf38] [c000f234] ret_from_kernel_thread+0x14/0x1c
[ 89.044112] Rebooting in 180 seconds..

In theory, a panic can happen after a bus or host reset with dma_started
flag set. Fix this by halting the DMA before reinitializing the host.
Don't assume that ms->current_req is set when halt_dma() is invoked as it
may not hold for bus or host reset.

BTW, this particular Conner drive can be made to work by inhibiting
disconnect/reselect with 'mesh.resel_targets=0'.

Link: https://lore.kernel.org/r/3952bc691e150a7128b29120999b6092071b039a.1595460351.git.fthain@telegraphics.com.au
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: Paul Mackerras <paulus@ozlabs.org>
Reported-and-tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/mesh.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/mesh.c b/drivers/scsi/mesh.c
index 82e01dbe90af4..7c0eaa9ea1edf 100644
--- a/drivers/scsi/mesh.c
+++ b/drivers/scsi/mesh.c
@@ -1044,6 +1044,8 @@ static void handle_error(struct mesh_state *ms)
while ((in_8(&mr->bus_status1) & BS1_RST) != 0)
udelay(1);
printk("done\n");
+ if (ms->dma_started)
+ halt_dma(ms);
handle_reset(ms);
/* request_q is empty, no point in mesh_start() */
return;
@@ -1356,7 +1358,8 @@ static void halt_dma(struct mesh_state *ms)
ms->conn_tgt, ms->data_ptr, scsi_bufflen(cmd),
ms->tgts[ms->conn_tgt].data_goes_out);
}
- scsi_dma_unmap(cmd);
+ if (cmd)
+ scsi_dma_unmap(cmd);
ms->dma_started = 0;
}

@@ -1711,6 +1714,9 @@ static int mesh_host_reset(struct scsi_cmnd *cmd)

spin_lock_irqsave(ms->host->host_lock, flags);

+ if (ms->dma_started)
+ halt_dma(ms);
+
/* Reset the controller & dbdma channel */
out_le32(&md->control, (RUN|PAUSE|FLUSH|WAKE) << 16); /* stop dma */
out_8(&mr->exception, 0xff); /* clear all exception bits */
--
2.25.1