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, 3 insertions, 7 deletions

diff --git a/xlators/performance/read-ahead/src/page.c b/xlators/performance/read-ahead/src/page.c
index 344026352f9..8a58ad8bb7a 100644
--- a/xlators/performance/read-ahead/src/page.c
+++ b/xlators/performance/read-ahead/src/page.c
@@ -347,19 +347,15 @@ ra_frame_fill(ra_page_t *page, call_frame_t *frame)
         new->size = copy_size;
         new->iobref = iobref_ref(page->iobref);
         new->count = iov_subset(page->vector, page->count, src_offset,
-                                src_offset + copy_size, NULL);
-        new->vector = GF_CALLOC(new->count, sizeof(struct iovec),
-                                gf_ra_mt_iovec);
-        if (new->vector == NULL) {
+                                copy_size, &new->vector, 0);
+        if (new->count < 0) {
             local->op_ret = -1;
             local->op_errno = ENOMEM;
+            iobref_unref(new->iobref);
             GF_FREE(new);
             goto out;
         }
 
-        new->count = iov_subset(page->vector, page->count, src_offset,
-                                src_offset + copy_size, new->vector);
-
         new->next = fill;
         new->prev = new->next->prev;
         new->next->prev = new;