libglusterfs: cleanup iovec functions

This patch cleans some iovec code and creates two additional helper
functions to simplify management of iovec structures.

  iov_range_copy(struct iovec *dst, uint32_t dst_count, uint32_t dst_offset,
                 struct iovec *src, uint32_t src_count, uint32_t src_offset,
                 uint32_t size);

    This function copies up to 'size' bytes from 'src' at offset
    'src_offset' to 'dst' at 'dst_offset'. It returns the number of
    bytes copied.

  iov_skip(struct iovec *iovec, uint32_t count, uint32_t size);

    This function removes the initial 'size' bytes from 'iovec' and
    returns the updated number of iovec vectors remaining.

The signature of iov_subset() has also been modified to make it safer
and easier to use. The new signature is:

  iov_subset(struct iovec *src, int src_count, uint32_t start, uint32_t size,
             struct iovec **dst, int32_t dst_count);

    This function creates a new iovec array containing the subset of the
    'src' vector starting at 'start' with size 'size'. The resulting
    array is allocated if '*dst' is NULL, or copied to '*dst' if it fits
    (based on 'dst_count'). It returns the number of iovec vectors used.

A new set of functions to iterate through an iovec array have been
created. They can be used to simplify the implementation of other
iovec-based helper functions.

Change-Id: Ia5fe57e388e23392a8d6cdab17670e337cadd587
Updates: bz#1193929
Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/xlators/performance/write-behind/src/write-behind.c b/xlators/performance/write-behind/src/write-behind.c
index 70e281a3c79..aade1c9c563 100644
--- a/xlators/performance/write-behind/src/write-behind.c
+++ b/xlators/performance/write-behind/src/write-behind.c
@@ -971,8 +971,7 @@ __wb_modify_write_request(wb_request_t *req, int synced_size)
     vector = req->stub->args.vector;
     count = req->stub->args.count;
 
-    req->stub->args.count = iov_subset(vector, count, synced_size,
-                                       iov_length(vector, count), vector);
+    req->stub->args.count = iov_skip(vector, count, synced_size);
 
 out:
     return;