target/iblock: Use backend REQ_FLUSH hint for WriteCacheEnabled status
This patch allows IBLOCK to check block hints in request_queue->flush_flags
when reporting current backend device WriteCacheEnabled status to a remote
SCSI initiator port.
This is done via a se_subsystem_api->get_write_cache() call instead of a
backend se_device creation time flag, as we expect REQ_FLUSH bits to possibly
change from an underlying blk_queue_flush() by the SCSI disk driver, or
internal raw struct block_device driver usage.
Also go ahead and update iblock_execute_rw() bio I/O path code to use
REQ_FLUSH + REQ_FUA hints when determining WRITE_FUA usage, and make SPC
emulation code use a spc_check_dev_wce() helper to handle both types of
cases for virtual backend subsystem drivers.
(asias: Drop unnecessary comparsion operators)
Reported-by: majianpeng <majianpeng@gmail.com>
Cc: majianpeng <majianpeng@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index f2aa754..d10cbed 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -772,6 +772,12 @@
pr_err("emulate_write_cache not supported for pSCSI\n");
return -EINVAL;
}
+ if (dev->transport->get_write_cache) {
+ pr_warn("emulate_write_cache cannot be changed when underlying"
+ " HW reports WriteCacheEnabled, ignoring request\n");
+ return 0;
+ }
+
dev->dev_attrib.emulate_write_cache = flag;
pr_debug("dev[%p]: SE Device WRITE_CACHE_EMULATION flag: %d\n",
dev, dev->dev_attrib.emulate_write_cache);