| Message ID | 20190513063754.1520-3-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [01/10] block: don't decrement nr_phys_segments for physically contigous segments | expand |
On Mon, May 13, 2019 at 08:37:46AM +0200, Christoph Hellwig wrote: > We currently fail to update the front/back segment size in the bio when > deciding to allow an otherwise gappy segement to a device with a > virt boundary. The reason why this did not cause problems is that > devices with a virt boundary fundamentally don't use segments as we > know it and thus don't care. Make that assumption formal by forcing > an unlimited segement size in this case. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > block/blk-settings.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/block/blk-settings.c b/block/blk-settings.c > index 3facc41476be..2ae348c101a0 100644 > --- a/block/blk-settings.c > +++ b/block/blk-settings.c > @@ -310,6 +310,9 @@ void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) > __func__, max_size); > } > > + /* see blk_queue_virt_boundary() for the explanation */ > + WARN_ON_ONCE(q->limits.virt_boundary_mask); > + > q->limits.max_segment_size = max_size; > } > EXPORT_SYMBOL(blk_queue_max_segment_size); > @@ -742,6 +745,14 @@ EXPORT_SYMBOL(blk_queue_segment_boundary); > void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask) > { > q->limits.virt_boundary_mask = mask; > + > + /* > + * Devices that require a virtual boundary do not support scatter/gather > + * I/O natively, but instead require a descriptor list entry for each > + * page (which might not be idential to the Linux PAGE_SIZE). Because > + * of that they are not limited by our notion of "segment size". > + */ > + q->limits.max_segment_size = UINT_MAX; > } > EXPORT_SYMBOL(blk_queue_virt_boundary); All drivers which set virt boundary do not set max segment size, and guess the DMA controller may partition data in unit of (virt_boundary + 1), so in theory this patch is correct. Reviewed-by: Ming Lei <ming.lei@redhat.com> Thanks, Ming
diff --git a/block/blk-settings.c b/block/blk-settings.c index 3facc41476be..2ae348c101a0 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -310,6 +310,9 @@ void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) __func__, max_size); } + /* see blk_queue_virt_boundary() for the explanation */ + WARN_ON_ONCE(q->limits.virt_boundary_mask); + q->limits.max_segment_size = max_size; } EXPORT_SYMBOL(blk_queue_max_segment_size); @@ -742,6 +745,14 @@ EXPORT_SYMBOL(blk_queue_segment_boundary); void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask) { q->limits.virt_boundary_mask = mask; + + /* + * Devices that require a virtual boundary do not support scatter/gather + * I/O natively, but instead require a descriptor list entry for each + * page (which might not be idential to the Linux PAGE_SIZE). Because + * of that they are not limited by our notion of "segment size". + */ + q->limits.max_segment_size = UINT_MAX; } EXPORT_SYMBOL(blk_queue_virt_boundary);
We currently fail to update the front/back segment size in the bio when deciding to allow an otherwise gappy segement to a device with a virt boundary. The reason why this did not cause problems is that devices with a virt boundary fundamentally don't use segments as we know it and thus don't care. Make that assumption formal by forcing an unlimited segement size in this case. Signed-off-by: Christoph Hellwig <hch@lst.de> --- block/blk-settings.c | 11 +++++++++++ 1 file changed, 11 insertions(+)