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SubjectRe: [PATCH 2/8] scsi: take the DMA max mapping size into account
On Tue, Jun 18, 2019 at 4:57 AM Bart Van Assche <bvanassche@acm.org> wrote:
>
> On 6/17/19 5:19 AM, Christoph Hellwig wrote:
> > We need to limit the devices max_sectors to what the DMA mapping
> > implementation can support. If not we risk running out of swiotlb
> > buffers easily.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> > drivers/scsi/scsi_lib.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > index d333bb6b1c59..f233bfd84cd7 100644
> > --- a/drivers/scsi/scsi_lib.c
> > +++ b/drivers/scsi/scsi_lib.c
> > @@ -1768,6 +1768,8 @@ void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
> > blk_queue_max_integrity_segments(q, shost->sg_prot_tablesize);
> > }
> >
> > + shost->max_sectors = min_t(unsigned int, shost->max_sectors,
> > + dma_max_mapping_size(dev) << SECTOR_SHIFT);
> > blk_queue_max_hw_sectors(q, shost->max_sectors);
> > if (shost->unchecked_isa_dma)
> > blk_queue_bounce_limit(q, BLK_BOUNCE_ISA);
>
> Does dma_max_mapping_size() return a value in bytes? Is
> shost->max_sectors a number of sectors? If so, are you sure that "<<
> SECTOR_SHIFT" is the proper conversion? Shouldn't that be ">>
> SECTOR_SHIFT" instead?

Now the patch has been committed, '<< SECTOR_SHIFT' needs to be fixed.

Also the following kernel oops is triggered on qemu, and looks
device->dma_mask is NULL.

[ 5.826483] scsi host0: Virtio SCSI HBA
[ 5.829302] st: Version 20160209, fixed bufsize 32768, s/g segs 256
[ 5.831042] SCSI Media Changer driver v0.25
[ 5.832491] ==================================================================
[ 5.833332] BUG: KASAN: null-ptr-deref in
dma_direct_max_mapping_size+0x30/0x94
[ 5.833332] Read of size 8 at addr 0000000000000000 by task kworker/u17:0/7
[ 5.835506] nvme nvme0: pci function 0000:00:07.0
[ 5.833332]
[ 5.833332] CPU: 2 PID: 7 Comm: kworker/u17:0 Not tainted 5.3.0-rc1 #1328
[ 5.836999] ahci 0000:00:1f.2: version 3.0
[ 5.833332] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS ?-20180724_192412-buildhw-07.phx4
[ 5.833332] Workqueue: events_unbound async_run_entry_fn
[ 5.833332] Call Trace:
[ 5.833332] dump_stack+0x6f/0x9d
[ 5.833332] ? dma_direct_max_mapping_size+0x30/0x94
[ 5.833332] __kasan_report+0x161/0x189
[ 5.833332] ? dma_direct_max_mapping_size+0x30/0x94
[ 5.833332] kasan_report+0xe/0x12
[ 5.833332] dma_direct_max_mapping_size+0x30/0x94
[ 5.833332] __scsi_init_queue+0xd8/0x1f3
[ 5.833332] scsi_mq_alloc_queue+0x62/0x89
[ 5.833332] scsi_alloc_sdev+0x38c/0x479
[ 5.833332] scsi_probe_and_add_lun+0x22d/0x1093
[ 5.833332] ? kobject_set_name_vargs+0xa4/0xb2
[ 5.833332] ? mutex_lock+0x88/0xc4
[ 5.833332] ? scsi_free_host_dev+0x4a/0x4a
[ 5.833332] ? _raw_spin_lock_irqsave+0x8c/0xde
[ 5.833332] ? _raw_write_unlock_irqrestore+0x23/0x23
[ 5.833332] ? ata_tdev_match+0x22/0x45
[ 5.833332] ? attribute_container_add_device+0x160/0x17e
[ 5.833332] ? rpm_resume+0x26a/0x7c0
[ 5.833332] ? kobject_get+0x12/0x43
[ 5.833332] ? rpm_put_suppliers+0x7e/0x7e
[ 5.833332] ? _raw_spin_lock_irqsave+0x8c/0xde
[ 5.833332] ? _raw_write_unlock_irqrestore+0x23/0x23
[ 5.833332] ? scsi_target_destroy+0x135/0x135
[ 5.833332] __scsi_scan_target+0x14b/0x6aa
[ 5.833332] ? pvclock_clocksource_read+0xc0/0x14e
[ 5.833332] ? scsi_add_device+0x20/0x20
[ 5.833332] ? rpm_resume+0x1ae/0x7c0
[ 5.833332] ? rpm_put_suppliers+0x7e/0x7e
[ 5.833332] ? _raw_spin_lock_irqsave+0x8c/0xde
[ 5.833332] ? _raw_write_unlock_irqrestore+0x23/0x23
[ 5.833332] ? pick_next_task_fair+0x976/0xa3d
[ 5.833332] ? mutex_lock+0x88/0xc4
[ 5.833332] scsi_scan_channel+0x76/0x9e
[ 5.833332] scsi_scan_host_selected+0x131/0x176
[ 5.833332] ? scsi_scan_host+0x241/0x241
[ 5.833332] do_scan_async+0x27/0x219
[ 5.833332] ? scsi_scan_host+0x241/0x241
[ 5.833332] async_run_entry_fn+0xdc/0x23d
[ 5.833332] process_one_work+0x327/0x539
[ 5.833332] worker_thread+0x330/0x492
[ 5.833332] ? rescuer_thread+0x41f/0x41f
[ 5.833332] kthread+0x1c6/0x1d5
[ 5.833332] ? kthread_park+0xd3/0xd3
[ 5.833332] ret_from_fork+0x1f/0x30
[ 5.833332] ==================================================================



Thanks,
Ming Lei

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