On 6/17/24 15:04, Christoph Hellwig wrote:
Move the cache control settings into the queue_limits so that the flags can be set atomically with the device queue frozen. Add new features and flags field for the driver set flags, and internal (usually sysfs-controlled) flags in the block layer. Note that we'll eventually remove enough field from queue_limits to bring it back to the previous size. The disable flag is inverted compared to the previous meaning, which means it now survives a rescan, similar to the max_sectors and max_discard_sectors user limits. The FLUSH and FUA flags are now inherited by blk_stack_limits, which simplified the code in dm a lot, but also causes a slight behavior change in that dm-switch and dm-unstripe now advertise a write cache despite setting num_flush_bios to 0. The I/O path will handle this gracefully, but as far as I can tell the lack of num_flush_bios and thus flush support is a pre-existing data integrity bug in those targets that really needs fixing, after which a non-zero num_flush_bios should be required in dm for targets that map to underlying devices. Signed-off-by: Christoph Hellwig <hch@xxxxxx> Acked-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx> [mmc]
A few nits below. With these fixed, Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
+Implementation details for bio based block drivers +-------------------------------------------------- + +For bio based drivers the REQ_PREFLUSH and REQ_FUA bit are simplify passed on
...bit are simplify... -> ...bits are simply...
+to the driver if the drivers sets the BLK_FEAT_WRITE_CACHE flag and the drivers +needs to handle them.
s/drivers/driver (2 times)
-and the driver must handle write requests that have the REQ_FUA bit set -in prep_fn/request_fn. If the FUA bit is not natively supported the block -layer turns it into an empty REQ_OP_FLUSH request after the actual write. +When the BLK_FEAT_FUA flags is set, the REQ_FUA bit simplify passed on for the
s/bit simplify/bit is simply -- Damien Le Moal Western Digital Research
