block: fix sg SG_DXFER_TO_FROM_DEV regression (ecb554a8) · Commits · 戴 / test

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 <sxzzsf@gmail.com> Tested-by:

zhou sf <sxzzsf@gmail.com> Cc: stable@kernel.org Signed-off-by:

FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Signed-off-by:

Jens Axboe <jens.axboe@oracle.com>

drivers/scsi/sg.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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) {

fs/bio.c

+12 −10

Original line number	Diff line number	Diff line
		@@ -705,14 +705,13 @@ static struct bio_map_data *bio_alloc_map_data(int nr_segs, int iov_count,
		}

		static int __bio_copy_iov(struct bio bio, struct bio_vec iovecs,
		struct sg_iovec *iov, int iov_count, int uncopy,
		int do_free_page)
		struct sg_iovec *iov, int iov_count,
		int to_user, int from_user, int do_free_page)
		{
		int ret = 0, i;
		struct bio_vec *bvec;
		int iov_idx = 0;
		unsigned int iov_off = 0;
		int read = bio_data_dir(bio) == READ;

		__bio_for_each_segment(bvec, bio, i, 0) {
		char *bv_addr = page_address(bvec->bv_page);
		@@ -727,13 +726,14 @@ static int __bio_copy_iov(struct bio bio, struct bio_vec iovecs,
		iov_addr = iov[iov_idx].iov_base + iov_off;

		if (!ret) {
		if (!read && !uncopy)
		ret = copy_from_user(bv_addr, iov_addr,
		bytes);
		if (read && uncopy)
		if (to_user)
		ret = copy_to_user(iov_addr, bv_addr,
		bytes);

		if (from_user)
		ret = copy_from_user(bv_addr, iov_addr,
		bytes);

		if (ret)
		ret = -EFAULT;
		}
		@@ -770,7 +770,8 @@ int bio_uncopy_user(struct bio *bio)

		if (!bio_flagged(bio, BIO_NULL_MAPPED))
		ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs,
		bmd->nr_sgvecs, 1, bmd->is_our_pages);
		bmd->nr_sgvecs, bio_data_dir(bio) == READ,
		0, bmd->is_our_pages);
		bio_free_map_data(bmd);
		bio_put(bio);
		return ret;
		@@ -875,8 +876,9 @@ struct bio bio_copy_user_iov(struct request_queue q,
		/*
		* success
		*/
		if (!write_to_vm && (!map_data \|\| !map_data->null_mapped)) {
		ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 0);
		if ((!write_to_vm && (!map_data \|\| !map_data->null_mapped)) \|\|
		(map_data && map_data->from_user)) {
		ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 1, 0);
		if (ret)
		goto cleanup;
		}

include/linux/blkdev.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -723,6 +723,7 @@ struct rq_map_data {
		int nr_entries;
		unsigned long offset;
		int null_mapped;
		int from_user;
		};

		struct req_iterator {

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