[Qemu-devel] [PATCH 1/2] glusterfs: fix max_discard

["Denis V. Lunev" <den@openvz.org>]

qemu_gluster_co_discard calculates size to discard as follows
    size_t size = nb_sectors * BDRV_SECTOR_SIZE;
    ret = glfs_discard_async(s->fd, offset, size, &gluster_finish_aiocb, acb);

glfs_discard_async is declared as follows:
  int glfs_discard_async (glfs_fd_t *fd, off_t length, size_t lent,
                          glfs_io_cbk fn, void *data) __THROW
This is problematic on i686 as sizeof(size_t) == 4.

Set bl_max_discard to SIZE_MAX >> BDRV_SECTOR_BITS to avoid overflow
on i386.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Peter Lieven <pl@kamp.de>
---
 block/gluster.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/block/gluster.c b/block/gluster.c
index 1eb3a8c..47bf92d 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -622,6 +622,13 @@ out:
     return ret;
 }
 
+static void qemu_gluster_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+#if SIZE_MAX == UINT_MAX
+    bs->bl.max_discard = SIZE_MAX >> BDRV_SECTOR_BITS;
+#endif
+}
+
 #ifdef CONFIG_GLUSTERFS_DISCARD
 static coroutine_fn int qemu_gluster_co_discard(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors)
@@ -735,6 +742,7 @@ static BlockDriver bdrv_gluster = {
 #ifdef CONFIG_GLUSTERFS_DISCARD
     .bdrv_co_discard              = qemu_gluster_co_discard,
 #endif
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_write_zeroes         = qemu_gluster_co_write_zeroes,
 #endif
@@ -762,6 +770,7 @@ static BlockDriver bdrv_gluster_tcp = {
 #ifdef CONFIG_GLUSTERFS_DISCARD
     .bdrv_co_discard              = qemu_gluster_co_discard,
 #endif
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_write_zeroes         = qemu_gluster_co_write_zeroes,
 #endif
@@ -789,6 +798,7 @@ static BlockDriver bdrv_gluster_unix = {
 #ifdef CONFIG_GLUSTERFS_DISCARD
     .bdrv_co_discard              = qemu_gluster_co_discard,
 #endif
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_write_zeroes         = qemu_gluster_co_write_zeroes,
 #endif
@@ -816,6 +826,7 @@ static BlockDriver bdrv_gluster_rdma = {
 #ifdef CONFIG_GLUSTERFS_DISCARD
     .bdrv_co_discard              = qemu_gluster_co_discard,
 #endif
+    .bdrv_refresh_limits          = qemu_gluster_refresh_limits,
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_write_zeroes         = qemu_gluster_co_write_zeroes,
 #endif
-- 
1.9.1