Re: [PATCH 10/26] dm: Use the block layer zone append emulation

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On 2/2/24 15:30, Damien Le Moal wrote:
For targets requiring zone append operation emulation with regular
writes (e.g. dm-crypt), we can use the block layer emulation provided by
zone write plugging. Remove DM implemented zone append emulation and
enable the block layer one.

This is done by setting the max_zone_append_sectors limit of the
mapped device queue to 0 for mapped devices that have a target table
that cannot support native zone append operations. These includes
mixed zoned and non-zoned targets, or targets that explicitly requested
emulation of zone append (e.g. dm-crypt). For these mapped devices, the
new field emulate_zone_append is set to true. dm_split_and_process_bio()
is modified to call blk_zone_write_plug_bio() for such device to let the
block layer transform zone append operations into regular writes. This
is done after ensuring that the submitted BIO is split if it straddles
zone boundaries.

dm_revalidate_zones() is also modified to use the block layer provided
function blk_revalidate_disk_zones() so that all zone resources needed
for zone append emulation are allocated and initialized by the block
layer without DM core needing to do anything. Since the device table is
not yet live when dm_revalidate_zones() is executed, enabling the use of
blk_revalidate_disk_zones() requires adding a pointer to the device
table in struct mapped_device. This avoids errors in
dm_blk_report_zones() trying to get the table with dm_get_live_table().
The mapped device table pointer is set to the table passed as argument
to dm_revalidate_zones() before calling blk_revalidate_disk_zones() and
reset to NULL after this function returns to restore the live table
handling for user call of report zones.

All the code related to zone append emulation is removed from
dm-zone.c. This leads to simplifications of the functions __map_bio()
and dm_zone_endio(). This later function now only needs to deal with
completions of real zone append operations for targets that support it.

Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
  drivers/md/dm-core.h |  11 +-
  drivers/md/dm-zone.c | 470 ++++---------------------------------------
  drivers/md/dm.c      |  44 ++--
  drivers/md/dm.h      |   7 -
  4 files changed, 68 insertions(+), 464 deletions(-)

Reviewed-by: Hannes Reinecke <hare@xxxxxxx>


Dr. Hannes Reinecke                Kernel Storage Architect
hare@xxxxxxx                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Ivo Totev, Andrew McDonald,
Werner Knoblich

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