On 10/18/2016 12:40 AM, Damien Le Moal wrote:
This series introduces support for zoned block devices. It integrates
earlier submissions by Hannes Reinecke and Shaun Tancheff. Compared to the
previous series version, the code was significantly simplified by limiting
support to zoned devices satisfying the following conditions:
1) All zones of the device are the same size, with the exception of an
   eventual last smaller runt zone.
2) For host-managed disks, reads must be unrestricted (read commands do not
   fail due to zone or write pointer alignement constraints).
Zoned disks that do not satisfy these 2 conditions are ignored.

These 2 conditions allowed dropping the zone information cache implemented
in the previous version. This simplifies the code and also reduces the memory
consumption at run time. Support for zoned devices now only require one bit
per zone (less than 8KB in total). This bit field is used to write-lock
zones and prevent the concurrent execution of multiple write commands in
the same zone. This avoids write ordering problems at dispatch time, for
both the simple queue and scsi-mq settings.

The new operations introduced to suport zone manipulation was reduced to
only the two main ZBC/ZAC defined commands: REPORT ZONES (REQ_OP_ZONE_REPORT)
and RESET WRITE POINTER (REQ_OP_ZONE_RESET). This brings the total number of
operations defined to 8, which fits in the 3 bits (REQ_OP_BITS) reserved for
operation code in bio->bi_opf and req->cmd_flags.

Most of the ZBC specific code is kept out of sd.c and implemented in the
new file sd_zbc.c. Similarly, at the block layer, most of the zoned block
device code is implemented in the new blk-zoned.c.

For host-managed zoned block devices, the sequential write constraint of
write pointer zones is exposed to the user. Users of the disk (applications,
file systems or device mappers) must sequentially write to zones. This means
that for raw block device accesses from applications, buffered writes are
unreliable and direct I/Os must be used (or buffered writes with O_SYNC).

Access to zone manipulation operations is also provided to applications
through a set of new ioctls. This allows applications operating on raw
block devices (e.g. mkfs.xxx) to discover a device zone layout and
manipulate zone state.

This is starting to look mergeable to me. Any objections in getting this
applied for 4.10? Looks like 6/7 should go through the SCSI tree, but I
can queue up the rest.

Jens Axboe

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