From ecb554a846f8e9d2a58f6d6c118168a63ac065aa Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori Date: Thu, 9 Jul 2009 14:46:53 +0200 Subject: block: fix sg SG_DXFER_TO_FROM_DEV regression I overlooked SG_DXFER_TO_FROM_DEV support when I converted sg to use the block layer mapping API (2.6.28). Douglas Gilbert explained SG_DXFER_TO_FROM_DEV: http://www.spinics.net/lists/linux-scsi/msg37135.html = The semantics of SG_DXFER_TO_FROM_DEV were: - copy user space buffer to kernel (LLD) buffer - do SCSI command which is assumed to be of the DATA_IN (data from device) variety. This would overwrite some or all of the kernel buffer - copy kernel (LLD) buffer back to the user space. The idea was to detect short reads by filling the original user space buffer with some marker bytes ("0xec" it would seem in this report). The "resid" value is a better way of detecting short reads but that was only added this century and requires co-operation from the LLD. = This patch changes the block layer mapping API to support this semantics. This simply adds another field to struct rq_map_data and enables __bio_copy_iov() to copy data from user space even with READ requests. It's better to add the flags field and kills null_mapped and the new from_user fields in struct rq_map_data but that approach makes it difficult to send this patch to stable trees because st and osst drivers use struct rq_map_data (they were converted to use the block layer in 2.6.29 and 2.6.30). Well, I should clean up the block layer mapping API. zhou sf reported this regiression and tested this patch: http://www.spinics.net/lists/linux-scsi/msg37128.html http://www.spinics.net/lists/linux-scsi/msg37168.html Reported-by: zhou sf Tested-by: zhou sf Cc: stable@kernel.org Signed-off-by: FUJITA Tomonori Signed-off-by: Jens Axboe --- drivers/scsi/sg.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/scsi/sg.c') diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 4d6f2fe1cfe..9230402c45a 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1656,6 +1656,10 @@ static int sg_start_req(Sg_request *srp, unsigned char *cmd) md->nr_entries = req_schp->k_use_sg; md->offset = 0; md->null_mapped = hp->dxferp ? 0 : 1; + if (dxfer_dir == SG_DXFER_TO_FROM_DEV) + md->from_user = 1; + else + md->from_user = 0; } if (iov_count) { -- cgit v1.2.3-70-g09d2