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authorXiubo Li <lixiubo@cmss.chinamobile.com>2017-11-28 12:40:36 -0600
committerNicholas Bellinger <nab@linux-iscsi.org>2018-01-12 15:07:16 -0800
commit3e60913579b2fefa74eeb3269426e864f4afa7e7 (patch)
tree6b6f6b5ce54e2a90a45d36fd70bc7fc103f869f3 /drivers/target/target_core_user.c
parent3c0f26ff9d040c6193b33689bbc03103854dba4d (diff)
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>
Diffstat (limited to 'drivers/target/target_core_user.c')
-rw-r--r--drivers/target/target_core_user.c30
1 files changed, 25 insertions, 5 deletions
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);
}

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