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[Qemu-devel] [PULL 2/9] block: implement BDRV_REQ_PREFETCH
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PULL 2/9] block: implement BDRV_REQ_PREFETCH |
Date: |
Thu, 15 Aug 2019 13:30:32 -0500 |
From: Vladimir Sementsov-Ogievskiy <address@hidden>
Do effective copy-on-read request when we don't need data actually. It
will be used for block-stream and NBD_CMD_CACHE.
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
[eblake: comment grammar fix]
Signed-off-by: Eric Blake <address@hidden>
---
include/block/block.h | 8 +++++++-
block/io.c | 18 ++++++++++++------
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index 50a07c1c3385..a9df34ff94b6 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -88,8 +88,14 @@ typedef enum {
* fallback. */
BDRV_REQ_NO_FALLBACK = 0x100,
+ /*
+ * BDRV_REQ_PREFETCH may be used only together with BDRV_REQ_COPY_ON_READ
+ * on read request and means that caller doesn't really need data to be
+ * written to qiov parameter which may be NULL.
+ */
+ BDRV_REQ_PREFETCH = 0x200,
/* Mask of valid flags */
- BDRV_REQ_MASK = 0x1ff,
+ BDRV_REQ_MASK = 0x3ff,
} BdrvRequestFlags;
typedef struct BlockSizes {
diff --git a/block/io.c b/block/io.c
index 06305c6ea62e..9d99858b554b 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1167,7 +1167,8 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs,
uint64_t offset,
}
static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
- int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
+ int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
+ int flags)
{
BlockDriverState *bs = child->bs;
@@ -1278,9 +1279,11 @@ static int coroutine_fn
bdrv_co_do_copy_on_readv(BdrvChild *child,
goto err;
}
- qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
- pnum - skip_bytes);
- } else {
+ if (!(flags & BDRV_REQ_PREFETCH)) {
+ qemu_iovec_from_buf(qiov, progress, bounce_buffer + skip_bytes,
+ pnum - skip_bytes);
+ }
+ } else if (!(flags & BDRV_REQ_PREFETCH)) {
/* Read directly into the destination */
qemu_iovec_init(&local_qiov, qiov->niov);
qemu_iovec_concat(&local_qiov, qiov, progress, pnum - skip_bytes);
@@ -1331,7 +1334,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild
*child,
* potential fallback support, if we ever implement any read flags
* to pass through to drivers. For now, there aren't any
* passthrough flags. */
- assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ)));
+ assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ |
+ BDRV_REQ_PREFETCH)));
/* Handle Copy on Read and associated serialisation */
if (flags & BDRV_REQ_COPY_ON_READ) {
@@ -1359,7 +1363,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild
*child,
}
if (!ret || pnum != bytes) {
- ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov);
+ ret = bdrv_co_do_copy_on_readv(child, offset, bytes, qiov, flags);
+ goto out;
+ } else if (flags & BDRV_REQ_PREFETCH) {
goto out;
}
}
--
2.20.1
- [Qemu-devel] [PULL 0/9] First batch of 4.2 NBD patches, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 1/9] qapi: Add InetSocketAddress member keep-alive, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 7/9] block/nbd: move from quit to state, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 8/9] block/nbd: add cmdline and qapi parameter reconnect-delay, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 6/9] block/nbd: use non-blocking io channel for nbd negotiation, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 2/9] block: implement BDRV_REQ_PREFETCH,
Eric Blake <=
- [Qemu-devel] [PULL 3/9] block/stream: use BDRV_REQ_PREFETCH, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 4/9] nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 5/9] block/nbd: split connection_co start out of nbd_client_connect, Eric Blake, 2019/08/15
- [Qemu-devel] [PULL 9/9] block/nbd: refactor nbd connection parameters, Eric Blake, 2019/08/15
- Re: [Qemu-devel] [PULL 0/9] First batch of 4.2 NBD patches, Peter Maydell, 2019/08/16