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, 2 insertions, 18 deletions

diff --git a/xlators/performance/io-cache/src/io-cache.c b/xlators/performance/io-cache/src/io-cache.c
index 95ba2e19b9e..711afdf700d 100644
--- a/xlators/performance/io-cache/src/io-cache.c
+++ b/xlators/performance/io-cache/src/io-cache.c
@@ -87,14 +87,6 @@ ioc_update_pages(call_frame_t *frame, ioc_inode_t *ioc_inode,
           write_offset = 0;
     off_t page_offset = 0, page_end = 0;
     ioc_page_t *trav = NULL;
-    struct iovec pagevector =
-                     {
-                         0,
-                     },
-                 writevector = {
-                     0,
-                 };
-    int pvcount = 0, wvcount;
 
     size = iov_length(vector, count);
     size = min(size, op_ret);
@@ -120,16 +112,8 @@ ioc_update_pages(call_frame_t *frame, ioc_inode_t *ioc_inode,
                     page_end = trav->size;
                 }
 
-                wvcount = iov_subset(vector, count, write_offset,
-                                     write_offset + (page_end - page_offset),
-                                     &writevector);
-                if (wvcount) {
-                    pvcount = iov_subset(trav->vector, trav->count, page_offset,
-                                         page_end, &pagevector);
-                    if (pvcount) {
-                        iov_copy(&pagevector, pvcount, &writevector, wvcount);
-                    }
-                }
+                iov_range_copy(trav->vector, trav->count, page_offset, vector,
+                               count, write_offset, page_end - page_offset);
             } else if (trav) {
                 if (!trav->waitq)
                     ioc_inode->table->cache_used -= __ioc_page_destroy(trav);