On 5/25/21 11:25 PM, Damien Le Moal wrote:
For zoned targets that cannot support zone append operations, implement an emulation using regular write operations. If the original BIO submitted by the user is a zone append operation, change its clone into a regular write operation directed at the target zone write pointer position. To do so, an array of write pointer offsets (write pointer position relative to the start of a zone) is added to struct mapped_device. All operations that modify a sequential zone write pointer (writes, zone reset, zone finish and zone append) are intersepted in __map_bio() and processed using the new functions dm_zone_map_bio(). Detection of the target ability to natively support zone append operations is done from dm_table_set_restrictions() by calling the function dm_set_zones_restrictions(). A target that does not support zone append operation, either by explicitly declaring it using the new struct dm_target field zone_append_not_supported, or because the device table contains a non-zoned device, has its mapped device marked with the new flag DMF_ZONE_APPEND_EMULATED. The helper function dm_emulate_zone_append() is introduced to test a mapped device for this new flag. Atomicity of the zones write pointer tracking and updates is done using a zone write locking mechanism based on a bitmap. This is similar to the block layer method but based on BIOs rather than struct request. A zone write lock is taken in dm_zone_map_bio() for any clone BIO with an operation type that changes the BIO target zone write pointer position. The zone write lock is released if the clone BIO is failed before submission or when dm_zone_endio() is called when the clone BIO completes. The zone write lock bitmap of the mapped device, together with a bitmap indicating zone types (conv_zones_bitmap) and the write pointer offset array (zwp_offset) are allocated and initialized with a full device zone report in dm_set_zones_restrictions() using the function dm_revalidate_zones(). For failed operations that may have modified a zone write pointer, the zone write pointer offset is marked as invalid in dm_zone_endio(). Zones with an invalid write pointer offset are checked and the write pointer updated using an internal report zone operation when the faulty zone is accessed again by the user. All functions added for this emulation have a minimal overhead for zoned targets natively supporting zone append operations. Regular device targets are also not affected. The added code also does not impact builds with CONFIG_BLK_DEV_ZONED disabled by stubbing out all dm zone related functions. Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx> Reviewed-by: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx> --- drivers/md/dm-core.h | 13 + drivers/md/dm-table.c | 19 +- drivers/md/dm-zone.c | 580 ++++++++++++++++++++++++++++++++-- drivers/md/dm.c | 38 ++- drivers/md/dm.h | 16 +- include/linux/device-mapper.h | 6 + 6 files changed, 618 insertions(+), 54 deletions(-)
Reviewed-by: Hannes Reinecke <hare@xxxxxxx> Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@xxxxxxx +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
