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tcmu: clean up the scatter helper 

Add some comments to make the scatter code to be more readable,
and drop unused arg to new_iov.

Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Xiubo Li 2017-11-28 12:40:36 -06:00 committed by Nicholas Bellinger
parent 3c0f26ff9d
commit 3e60913579
1 changed files with 25 additions and 5 deletions
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30
drivers/target/target_core_user.c
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@ -492,8 +492,7 @@ static inline size_t head_to_end(size_t head, size_t size)
return size - head;
}
static inline void new_iov(struct iovec **iov, int *iov_cnt,
struct tcmu_dev *udev)
static inline void new_iov(struct iovec **iov, int *iov_cnt)
{
struct iovec *iovec;
@ -546,19 +545,38 @@ static void scatter_data_area(struct tcmu_dev *udev,
to = kmap_atomic(page);
}
copy_bytes = min_t(size_t, sg_remaining,
block_remaining);
/*
* Covert to virtual offset of the ring data area.
*/
to_offset = get_block_offset_user(udev, dbi,
block_remaining);
/*
* The following code will gather and map the blocks
* to the same iovec when the blocks are all next to
* each other.
*/
copy_bytes = min_t(size_t, sg_remaining,
block_remaining);
if (*iov_cnt != 0 &&
to_offset == iov_tail(*iov)) {
/*
* Will append to the current iovec, because
* the current block page is next to the
* previous one.
*/
(*iov)->iov_len += copy_bytes;
} else {
new_iov(iov, iov_cnt, udev);
/*
* Will allocate a new iovec because we are
* first time here or the current block page
* is not next to the previous one.
*/
new_iov(iov, iov_cnt);
(*iov)->iov_base = (void __user *)to_offset;
(*iov)->iov_len = copy_bytes;
}
if (copy_data) {
offset = DATA_BLOCK_SIZE - block_remaining;
memcpy(to + offset,
@ -566,11 +584,13 @@ static void scatter_data_area(struct tcmu_dev *udev,
copy_bytes);
tcmu_flush_dcache_range(to, copy_bytes);
}
sg_remaining -= copy_bytes;
block_remaining -= copy_bytes;
}
kunmap_atomic(from - sg->offset);
}
if (to)
kunmap_atomic(to);
}