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[Qemu-devel] [PULL 09/41] block: honour BlockLimits in bdrv_co_do_write_
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 09/41] block: honour BlockLimits in bdrv_co_do_write_zeroes |
Date: |
Fri, 29 Nov 2013 17:45:24 +0100 |
From: Peter Lieven <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Peter Lieven <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 49 insertions(+), 16 deletions(-)
diff --git a/block.c b/block.c
index 3759582..b4194da 100644
--- a/block.c
+++ b/block.c
@@ -2711,32 +2711,65 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState
*bs,
BDRV_REQ_COPY_ON_READ);
}
+/* if no limit is specified in the BlockLimits use a default
+ * of 32768 512-byte sectors (16 MiB) per request.
+ */
+#define MAX_WRITE_ZEROES_DEFAULT 32768
+
static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
QEMUIOVector qiov;
- struct iovec iov;
- int ret;
+ struct iovec iov = {0};
+ int ret = 0;
- /* TODO Emulate only part of misaligned requests instead of letting block
- * drivers return -ENOTSUP and emulate everything */
+ int max_write_zeroes = bs->bl.max_write_zeroes ?
+ bs->bl.max_write_zeroes : MAX_WRITE_ZEROES_DEFAULT;
- /* First try the efficient write zeroes operation */
- if (drv->bdrv_co_write_zeroes) {
- ret = drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors, flags);
- if (ret != -ENOTSUP) {
- return ret;
+ while (nb_sectors > 0 && !ret) {
+ int num = nb_sectors;
+
+ /* align request */
+ if (bs->bl.write_zeroes_alignment &&
+ num >= bs->bl.write_zeroes_alignment &&
+ sector_num % bs->bl.write_zeroes_alignment) {
+ if (num > bs->bl.write_zeroes_alignment) {
+ num = bs->bl.write_zeroes_alignment;
+ }
+ num -= sector_num % bs->bl.write_zeroes_alignment;
}
- }
- /* Fall back to bounce buffer if write zeroes is unsupported */
- iov.iov_len = nb_sectors * BDRV_SECTOR_SIZE;
- iov.iov_base = qemu_blockalign(bs, iov.iov_len);
- memset(iov.iov_base, 0, iov.iov_len);
- qemu_iovec_init_external(&qiov, &iov, 1);
+ /* limit request size */
+ if (num > max_write_zeroes) {
+ num = max_write_zeroes;
+ }
+
+ ret = -ENOTSUP;
+ /* First try the efficient write zeroes operation */
+ if (drv->bdrv_co_write_zeroes) {
+ ret = drv->bdrv_co_write_zeroes(bs, sector_num, num, flags);
+ }
+
+ if (ret == -ENOTSUP) {
+ /* Fall back to bounce buffer if write zeroes is unsupported */
+ iov.iov_len = num * BDRV_SECTOR_SIZE;
+ if (iov.iov_base == NULL) {
+ /* allocate bounce buffer only once and ensure that it
+ * is big enough for this and all future requests.
+ */
+ size_t bufsize = num <= nb_sectors ? num : max_write_zeroes;
+ iov.iov_base = qemu_blockalign(bs, bufsize * BDRV_SECTOR_SIZE);
+ memset(iov.iov_base, 0, bufsize * BDRV_SECTOR_SIZE);
+ }
+ qemu_iovec_init_external(&qiov, &iov, 1);
- ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, &qiov);
+ ret = drv->bdrv_co_writev(bs, sector_num, num, &qiov);
+ }
+
+ sector_num += num;
+ nb_sectors -= num;
+ }
qemu_vfree(iov.iov_base);
return ret;
--
1.8.1.4
- [Qemu-devel] [PULL 00/41] Block patches for 2.0 (flushing block-next), Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 04/41] block: add logical block provisioning info to BlockDriverInfo, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 02/41] block: add flags to bdrv_*_write_zeroes, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 01/41] block: make BdrvRequestFlags public, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 03/41] block: introduce BDRV_REQ_MAY_UNMAP request flag, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 07/41] block: add BlockLimits structure to BlockDriverState, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 06/41] block/iscsi: add .bdrv_get_info, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 05/41] block: add wrappers for logical block provisioning information, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 08/41] block/raw: copy BlockLimits on raw_open, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 09/41] block: honour BlockLimits in bdrv_co_do_write_zeroes,
Kevin Wolf <=
- [Qemu-devel] [PULL 10/41] block: honour BlockLimits in bdrv_co_discard, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 11/41] iscsi: set limits in BlockDriverState, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 12/41] iscsi: simplify iscsi_co_discard, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 13/41] iscsi: add bdrv_co_write_zeroes, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 14/41] block: introduce bdrv_make_zero, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 15/41] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 16/41] qemu-img: add support for fully allocated images, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 17/41] qemu-img: conditionally zero out target on convert, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 18/41] util/error: Save errno from clobbering, Kevin Wolf, 2013/11/29
- [Qemu-devel] [PULL 19/41] Test coroutine execution order, Kevin Wolf, 2013/11/29