From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Wolfgang Bumiller <w.bumiller@proxmox.com>
Date: Wed, 30 Nov 2016 10:27:47 +0100
Subject: [PATCH] glusterfs: allow partial reads

This should deal with qemu bug #1644754 until upstream
decides which way to go. The general direction seems to be
away from sector based block APIs and with that in mind, and
when comparing to other network block backends (eg. nfs)
treating partial reads as errors doesn't seem to make much
sense.
---
 block/gluster.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/block/gluster.c b/block/gluster.c
index 8fab26481c..24296a39b3 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -41,6 +41,7 @@ typedef struct GlusterAIOCB {
     int ret;
     Coroutine *coroutine;
     AioContext *aio_context;
+    bool is_write;
 } GlusterAIOCB;
 
 typedef struct BDRVGlusterState {
@@ -709,8 +710,10 @@ static void gluster_finish_aiocb(struct glfs_fd *fd, ssize_t ret, void *arg)
         acb->ret = 0; /* Success */
     } else if (ret < 0) {
         acb->ret = -errno; /* Read/Write failed */
+    } else if (acb->is_write) {
+        acb->ret = -EIO; /* Partial write - fail it */
     } else {
-        acb->ret = -EIO; /* Partial read/write - fail it */
+        acb->ret = 0; /* Success */
     }
 
     aio_co_schedule(acb->aio_context, acb->coroutine);
@@ -958,6 +961,7 @@ static coroutine_fn int qemu_gluster_co_pwrite_zeroes(BlockDriverState *bs,
     acb.ret = 0;
     acb.coroutine = qemu_coroutine_self();
     acb.aio_context = bdrv_get_aio_context(bs);
+    acb.is_write = true;
 
     ret = glfs_zerofill_async(s->fd, offset, size, gluster_finish_aiocb, &acb);
     if (ret < 0) {
@@ -1083,9 +1087,11 @@ static coroutine_fn int qemu_gluster_co_rw(BlockDriverState *bs,
     acb.aio_context = bdrv_get_aio_context(bs);
 
     if (write) {
+        acb.is_write = true;
         ret = glfs_pwritev_async(s->fd, qiov->iov, qiov->niov, offset, 0,
                                  gluster_finish_aiocb, &acb);
     } else {
+        acb.is_write = false;
         ret = glfs_preadv_async(s->fd, qiov->iov, qiov->niov, offset, 0,
                                 gluster_finish_aiocb, &acb);
     }
@@ -1158,6 +1164,7 @@ static coroutine_fn int qemu_gluster_co_flush_to_disk(BlockDriverState *bs)
     acb.ret = 0;
     acb.coroutine = qemu_coroutine_self();
     acb.aio_context = bdrv_get_aio_context(bs);
+    acb.is_write = true;
 
     ret = glfs_fsync_async(s->fd, gluster_finish_aiocb, &acb);
     if (ret < 0) {
@@ -1204,6 +1211,7 @@ static coroutine_fn int qemu_gluster_co_pdiscard(BlockDriverState *bs,
     acb.ret = 0;
     acb.coroutine = qemu_coroutine_self();
     acb.aio_context = bdrv_get_aio_context(bs);
+    acb.is_write = true;
 
     ret = glfs_discard_async(s->fd, offset, size, gluster_finish_aiocb, &acb);
     if (ret < 0) {
-- 
2.11.0