libglusterfs: Implement API that provides page-aligned iobufs

        Backport of: http://review.gluster.org/14672

One of the consumers of a page aligned buffer would be posix's
readv fop on O_DIRECT fds. Today the way it works is by getting
a page-aligned buffer through calloc, pread()ing into this buffer
and then copying its contents into a newly created iobuf's ptr.
This results in an extra memcpy() which can be avoided if we could
implement an api that would return an iobuf whose ptr is
page-aligned. That way the iobuf->ptr can be directly passed to
sys_pread() as a parameter by posix translator.

Change-Id: Ie44c300dc773fef8e1669d609987d47dbd340ac2
BUG: 1351024
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/14826
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Zhou Zhengping <johnzzpcrystal@gmail.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>

1 files changed, 11 insertions, 32 deletions

diff --git a/xlators/storage/posix/src/posix.c b/xlators/storage/posix/src/posix.c
index 7290905807b..836e90614f1 100644
--- a/xlators/storage/posix/src/posix.c
+++ b/xlators/storage/posix/src/posix.c
@@ -2985,8 +2985,6 @@ posix_readv (call_frame_t *frame, xlator_t *this,
         int32_t                op_ret     = -1;
         int32_t                op_errno   = 0;
         int                    _fd        = -1;
-        char                 *buf         = NULL;
-        char                 *alloc_buf   = NULL;
         struct posix_private * priv       = NULL;
         struct iobuf         * iobuf      = NULL;
         struct iobref        * iobref     = NULL;
@@ -3018,42 +3016,24 @@ posix_readv (call_frame_t *frame, xlator_t *this,
                 goto out;
         }
 
-        iobuf = iobuf_get2 (this->ctx->iobuf_pool, size);
+        iobuf = iobuf_get_page_aligned (this->ctx->iobuf_pool, size,
+                                        ALIGN_SIZE);
         if (!iobuf) {
                 op_errno = ENOMEM;
                 goto out;
         }
 
         _fd = pfd->fd;
-        if (pfd->flags & O_DIRECT) {
-                alloc_buf = _page_aligned_alloc (size, &buf);
-                if (!alloc_buf) {
-                        op_ret = -1;
-                        op_errno = errno;
-                        goto out;
-                }
 
-                op_ret = pread (_fd, buf, size, offset);
-                if (op_ret == -1) {
-                        op_errno = errno;
-                        gf_msg (this->name, GF_LOG_ERROR, errno,
-                                P_MSG_READ_FAILED, "read failed on gfid=%s, "
-                                "fd=%p, offset=%"PRIu64" size=%"GF_PRI_SIZET", "
-                                "buf=%p", uuid_utoa (fd->inode->gfid), fd,
-                                offset, size, buf);
-                        goto out;
-                }
-                memcpy(iobuf->ptr, buf, size);
-        } else {
-                op_ret = pread (_fd, iobuf->ptr, size, offset);
-                if (op_ret == -1) {
-                        op_errno = errno;
-                        gf_msg (this->name, GF_LOG_ERROR, errno, P_MSG_READ_FAILED,
-                                "read failed on gfid=%s, fd=%p, offset=%"PRIu64" "
-                                "size=%"GF_PRI_SIZET"", uuid_utoa (fd->inode->gfid), fd,
-                                offset, size);
-                        goto out;
-                }
+        op_ret = pread (_fd, iobuf->ptr, size, offset);
+        if (op_ret == -1) {
+                op_errno = errno;
+                gf_msg (this->name, GF_LOG_ERROR, errno,
+                        P_MSG_READ_FAILED, "read failed on gfid=%s, "
+                        "fd=%p, offset=%"PRIu64" size=%"GF_PRI_SIZET", "
+                        "buf=%p", uuid_utoa (fd->inode->gfid), fd,
+                        offset, size, iobuf->ptr);
+                goto out;
         }
 
         LOCK (&priv->lock);
@@ -3096,7 +3076,6 @@ out:
                 iobref_unref (iobref);
         if (iobuf)
                 iobuf_unref (iobuf);
-        GF_FREE (alloc_buf);
 
         return 0;
 }