From 3e60913579b2fefa74eeb3269426e864f4afa7e7 Mon Sep 17 00:00:00 2001 From: Xiubo Li Date: Tue, 28 Nov 2017 12:40:36 -0600 Subject: 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 Signed-off-by: Mike Christie Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_user.c | 30 +++++++++++++++++++++++++----- 1 file changed, 25 insertions(+), 5 deletions(-) (limited to 'drivers/target') diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c index 5d1daea51079..8d0dc471fce8 100644 --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -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); } -- cgit v1.2.3