[Qemu-block] [PATCH 2/2] block/block-backend.c: remove blk_pread_unthrottled()

[Manos Pitsidianakis]

blk_pread_unthrottled was used to bypass I/O throttling on the BlockBackend in
the case of async I/O. This is not needed anymore and we can just call
blk_pread() directly.

Signed-off-by: Manos Pitsidianakis 
---
 include/sysemu/block-backend.h |  2 --
 block/block-backend.c  | 16 
 hw/block/hd-geometry.c |  7 +--
 3 files changed, 1 insertion(+), 24 deletions(-)

diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index c4e52a5fa3..c881bfdfe4 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -117,8 +117,6 @@ char *blk_get_attached_dev_id(BlockBackend *blk);
 BlockBackend *blk_by_dev(void *dev);
 BlockBackend *blk_by_qdev_id(const char *id, Error **errp);
 void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops, void *opaque);
-int blk_pread_unthrottled(BlockBackend *blk, int64_t offset, uint8_t *buf,
-  int bytes);
 int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
unsigned int bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags);
diff --git a/block/block-backend.c b/block/block-backend.c
index 110a52d5b1..83329fce15 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1145,22 +1145,6 @@ static int blk_prw(BlockBackend *blk, int64_t offset, 
uint8_t *buf,
 return rwco.ret;
 }
 
-int blk_pread_unthrottled(BlockBackend *blk, int64_t offset, uint8_t *buf,
-  int count)
-{
-int ret;
-
-ret = blk_check_byte_request(blk, offset, count);
-if (ret < 0) {
-return ret;
-}
-
-blk_root_drained_begin(blk->root);
-ret = blk_pread(blk, offset, buf, count);
-blk_root_drained_end(blk->root);
-return ret;
-}
-
 int blk_pwrite_zeroes(BlockBackend *blk, int64_t offset,
   int bytes, BdrvRequestFlags flags)
 {
diff --git a/hw/block/hd-geometry.c b/hw/block/hd-geometry.c
index 57ad5012a7..211307f73f 100644
--- a/hw/block/hd-geometry.c
+++ b/hw/block/hd-geometry.c
@@ -62,12 +62,7 @@ static int guess_disk_lchs(BlockBackend *blk,
 
 blk_get_geometry(blk, _sectors);
 
-/**
- * The function will be invoked during startup not only in sync I/O mode,
- * but also in async I/O mode. So the I/O throttling function has to
- * be disabled temporarily here, not permanently.
- */
-if (blk_pread_unthrottled(blk, 0, buf, BDRV_SECTOR_SIZE) < 0) {
+if (blk_pread(blk, 0, buf, BDRV_SECTOR_SIZE) < 0) {
 return -1;
 }
 /* test msdos magic */
-- 
2.11.0

Re: [Qemu-block] [PATCH 2/2] block/block-backend.c: remove blk_pread_unthrottled()

[Kevin Wolf]

Am 20.09.2017 um 13:43 hat Manos Pitsidianakis geschrieben:
> blk_pread_unthrottled was used to bypass I/O throttling on the BlockBackend in
> the case of async I/O. This is not needed anymore and we can just call
> blk_pread() directly.
> 
> Signed-off-by: Manos Pitsidianakis 

We already did a related commit to the same effect in block/io.c:

commit 90c78624f157ba41c3761c1a54864de03a7ec350
Author: Kevin Wolf 
Date:   Thu Apr 7 18:33:29 2016 +0200

block: Don't disable I/O throttling on sync requests

We had to disable I/O throttling with synchronous requests 
because we
didn't use to run timers in nested event loops when the code was
introduced. This isn't true any more, and throttling works just 
fine
even when using the synchronous API.

The removed code is in fact dead code since commit a8823a3b 
('block: Use
blk_co_pwritev() for blk_write()') because I/O throttling can 
only be
set on the top layer, but BlockBackend always uses the coroutine
interface now instead of using the sync API emulation in 
block.c.

Signed-off-by: Kevin Wolf 
Message-Id: <1458660792-3035-2-git-send-email-kw...@redhat.com>
Signed-off-by: Paolo Bonzini 
Acked-by: Stefan Hajnoczi 
Signed-off-by: Kevin Wolf 

The same reasoning (at least the first part) applies to this patch.

Reviewed-by: Kevin Wolf