Re: [PATCH RFC 01/16] block: Add atomic write operations to request_queue limits

On 09/05/2023 01:19, Mike Snitzer wrote:

On Wed, May 3, 2023 at 2:40 PM John Garry [off-list ref] wrote:

quoted

From: Himanshu Madhani <redacted>

Add the following limits:
- atomic_write_boundary
- atomic_write_max_bytes
- atomic_write_unit_max
- atomic_write_unit_min

Signed-off-by: Himanshu Madhani <redacted>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
  Documentation/ABI/stable/sysfs-block | 42 +++++++++++++++++++++
  block/blk-settings.c                 | 56 ++++++++++++++++++++++++++++
  block/blk-sysfs.c                    | 33 ++++++++++++++++
  include/linux/blkdev.h               | 23 ++++++++++++
  4 files changed, 154 insertions(+)

...

quoted

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 896b4654ab00..e21731715a12 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c

@@ -59,6 +59,9 @@ void blk_set_default_limits(struct queue_limits *lim)
         lim->zoned = BLK_ZONED_NONE;
         lim->zone_write_granularity = 0;
         lim->dma_alignment = 511;
+       lim->atomic_write_unit_min = lim->atomic_write_unit_max = 1;
+       lim->atomic_write_max_bytes = 512;
+       lim->atomic_write_boundary = 0;
  }

Not seeing required changes to blk_set_stacking_limits() nor blk_stack_limits().

Sorry to remind you of DM and MD limits stacking requirements. ;)

Hi Mike,

Sorry for the slow response.

The idea is that initially we would not be adding stacked device 
support, so we can leave atomic defaults as min unit we always consider 
atomic, i.e. logical block size/fixed 512B sector size.

Thanks,
John