On 07/03/2019 04:16 AM, Roman Bolshakov wrote:
WRITE SAME corrupts data on the block device behind iblock if the command is emulated. The emulation code issues (M - 1) * N times more bios than requested, where M is the number of 512 blocks per real block size and N is the NUMBER OF LOGICAL BLOCKS specified in WRITE SAME command. So, for a device with 4k blocks, 7 * N more LBAs gets written after the requested range.
The issue happens because the number of 512 byte sectors to be written is decreased one by one while the real bios are typically from 1 to 8 512 byte sectors per bio.
Fixes: c66ac9db8d4a ("[SCSI] target: Add LIO target core v4.0.0-rc6") Cc: stable@vger.kernel.org Signed-off-by: Roman Bolshakov r.bolshakov@yadro.com Reviewed-by: Bart Van Assche bvanassche@acm.org
drivers/target/target_core_iblock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c index f4a075303e9a..6949ea8bc387 100644 --- a/drivers/target/target_core_iblock.c +++ b/drivers/target/target_core_iblock.c @@ -502,7 +502,7 @@ iblock_execute_write_same(struct se_cmd *cmd) /* Always in 512 byte units for Linux/Block */ block_lba += sg->length >> SECTOR_SHIFT;
sectors -= 1;
sectors -= sg->length >> SECTOR_SHIFT;iblock_submit_bios(&list);
Roman,
The patch looks ok to me. Just one question. How did you hit this?
Did you by any chance export this disk to a ESX initiator and was it doing WRITE SAME to zero out data. But, did the device being used by iblock not support the zero out command (was /sys/block/XYZ/queue/write_zeroes_max_bytes == 0)?
Or, did you just send a WRITE SAME command manually using some tools like sg utils and it had a non zero'd buffer to write out?
Or, was it some other use case?