On Wed, May 17 2017 at 9:55P -0400,
Damien Le Moal <Damien.LeMoal@xxxxxxx> wrote:
> Mike,
>
> (resending using outlook as I am still having troubles reaching
> @redhat.com email domain with any other email client. My apologies
> if multiple copies of this email show up)
>
> On 5/18/17 03:54, Mike Snitzer wrote:
> > On Tue, May 16 2017 at 4:03pm -0400,
> > Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
> >
> >> I see quite a few issues with this patchset (only gotten through patches
> >> 1 - 6). I'll work through it in more detail and share my
> >> feedback/revisions tomorrow. Mostly just cleanups, renames, etc. But
> >> "the fun" is obviously once I get to the last patch.
> >
> > FYI, couldn't get to this like I planned. And I'm taking some time off,
> > won't get back to this until next Tuesday (5/23). To be clear, the
> > things I noticed in the preliminary patches were very benign, but do
> > need cleaning up.
>
> Thank you for the review. Let me know the changes you would like to see
> and I will send an updated series.
>
> > I have every intention of getting this reviewed and staged for 4.13.
>
> That's great. Thanks.
>
> > But would be useful to understand:
> > 1) who will be regression testing this target once it is merged?
>
> Myself, Bart, and all other members of my team will be involved in
> maintaining and testing this. It is critical for us as an SMR disk
> vendor that those disks are supported correctly in Linux. So we will
> maintain and regression test all aspects of the zoned block device
> support constantly.
>
> > 2) what is needed to test it? (I assume SMR drives?)
>
> Yes, SMR drives, but not necessarily physical ones. We are working on
> adding ZBC support to the SCSI target (that is missing). With that, we
> are planning to create a tcm (or tcmu) driver to emulate a host-aware or
> host-managed disk for testing, with a regular disk or file as back-end
> storage. This was also requested by file system maintainers (BtrFS) to
> allow testing of zoned block device support even without physical SMR
> disks available.
>
> Since zoned block device support spans the entire block I/O stack (from
> block layer API down to LLD, with device mapper and SCSI/libata in the
> middle) we are also starting to design new test cases for the newly
> released blktests infrastructure. This will allow automated testing,
> including device mapper targets that supports zoned block devices.
>
> Ideally, we will try to release everything for inclusion in 4.13,
> together with the device mapper support. But all the test parts may get
> spread over one or two release cycles. But again, the goal is to have a
> comprehensive automated test suite for zoned block device, similar to
> what is available for regular block devices.
Thanks for all that context, much appreciated.
I'd like to get your thoughts on replacing the first 3 patches with
something like the following patch (_not_ compile tested).
Basically I'm not interested in training DM for hypothetical zoned block
device configurations. I only want the bare minimum that is needed to
support the dm-zoned target at this point. The fact that dm-zoned is
"drive managed" makes for a much more narrow validation (AFAICT anyway).
I dropped the zone_sectors validation -- we can backfill it if you feel
it important but I wanted to float this simplified patch as is:
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 5f5eae4..0e4407e 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -340,6 +340,30 @@ static int device_area_is_invalid(struct dm_target *ti, struct dm_dev *dev,
return 1;
}
+ /*
+ * If the target is mapped to zoned block device(s), check
+ * that the zones are not partially mapped.
+ */
+ if (bdev_zoned_model(bdev) != BLK_ZONED_NONE) {
+ unsigned int zone_sectors = bdev_zone_sectors(bdev);
+
+ if (start & (zone_sectors - 1)) {
+ DMWARN("%s: start=%llu not aligned to h/w zone size %u of %s",
+ dm_device_name(ti->table->md),
+ (unsigned long long)start,
+ zone_sectors, bdevname(bdev, b));
+ return 1;
+ }
+
+ if (len & (zone_sectors - 1)) {
+ DMWARN("%s: len=%llu not aligned to h/w zone size %u of %s",
+ dm_device_name(ti->table->md),
+ (unsigned long long)len,
+ zone_sectors, bdevname(bdev, b));
+ return 1;
+ }
+ }
+
return 0;
}
@@ -456,6 +480,8 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
q->limits.alignment_offset,
(unsigned long long) start << SECTOR_SHIFT);
+ limits->zoned = blk_queue_zoned_model(q);
+
return 0;
}
@@ -1346,6 +1372,36 @@ bool dm_table_has_no_data_devices(struct dm_table *table)
return true;
}
+static int device_is_zoned_model(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
+{
+ struct request_queue *q = bdev_get_queue(dev->bdev);
+ enum blk_zoned_model zoned_model = *data;
+
+ return q && blk_queue_zoned_model(q) == zoned_model;
+}
+
+static bool dm_table_supports_zoned_model(struct dm_table *t,
+ enum blk_zoned_model zoned_model)
+{
+ struct dm_target *ti;
+ unsigned i;
+
+ for (i = 0; i < dm_table_get_num_targets(t); i++) {
+ ti = dm_table_get_target(t, i);
+
+ if (zoned_model == BLK_ZONED_HM &&
+ !dm_target_supports_zoned_hm(ti->type))
+ return false;
+
+ if (!ti->type->iterate_devices ||
+ !ti->type->iterate_devices(ti, device_is_zoned_model, &zoned_model))
+ return false;
+ }
+
+ return true;
+}
+
/*
* Establish the new table's queue_limits and validate them.
*/
@@ -1355,6 +1411,7 @@ int dm_calculate_queue_limits(struct dm_table *table,
struct dm_target *ti;
struct queue_limits ti_limits;
unsigned i;
+ enum blk_zoned_model zoned_model = BLK_ZONED_NONE;
blk_set_stacking_limits(limits);
@@ -1372,6 +1429,14 @@ int dm_calculate_queue_limits(struct dm_table *table,
ti->type->iterate_devices(ti, dm_set_device_limits,
&ti_limits);
+ if (zoned_model == BLK_ZONED_NONE && ti_limits.zoned != BLK_ZONED_NONE) {
+ /*
+ * After stacking all limits, validate all devices
+ * in table support this zoned model.
+ */
+ zoned_model = ti_limits.zoned;
+ }
+
/* Set I/O hints portion of queue limits */
if (ti->type->io_hints)
ti->type->io_hints(ti, &ti_limits);
@@ -1398,6 +1463,19 @@ int dm_calculate_queue_limits(struct dm_table *table,
(unsigned long long) ti->len);
}
+ /*
+ * Verify that the zoned model, as determined before any .io_hints
+ * override, is the same across all devices in the table.
+ * - but if limits->zoned is not BLK_ZONED_NONE validate match for it
+ */
+ if (limits->zoned != BLK_ZONED_NONE)
+ zoned_model = limits->zoned;
+ if (!dm_table_supports_zoned_model(table, zoned_model)) {
+ DMERR("%s: zoned model is inconsistent across all devices"
+ dm_device_name(table->md));
+ return -EINVAL;
+ }
+
return validate_hardware_logical_block_alignment(table, limits);
}
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index f4c639c..d13fcd2 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -237,6 +237,12 @@ typedef unsigned (*dm_num_write_bios_fn) (struct dm_target *ti, struct bio *bio)
#define DM_TARGET_PASSES_INTEGRITY 0x00000020
#define dm_target_passes_integrity(type) ((type)->features & DM_TARGET_PASSES_INTEGRITY)
+/*
+ * Indicates that a target supports host-managed zoned block devices.
+ */
+#define DM_TARGET_ZONED_HM 0x00000040
+#define dm_target_supports_zoned_hm(type) ((type)->features & DM_TARGET_ZONED_HM)
+
struct dm_target {
struct dm_table *table;
struct target_type *type;
--
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