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authorStefan Hajnoczi <stefanha@linux.vnet.ibm.com>2012-01-18 14:40:42 +0000
committerKevin Wolf <kwolf@redhat.com>2012-01-26 11:45:26 +0100
commit470c05047a09cda3de16bb3f98a130d9537357a4 (patch)
treec101557e6ff36ca1fe1465884062433358f85714 /block.c
parent2d3735d3bf61d5c8e154a197a11535cc65044334 (diff)
block: make copy-on-read a per-request flag
Previously copy-on-read could only be enabled for all requests to a block device. This means requests coming from the guest as well as QEMU's internal requests would perform copy-on-read when enabled. For image streaming we want to support finer-grained behavior than just populating the image file from its backing image. Image streaming supports partial streaming where a common backing image is preserved. In this case guest requests should not perform copy-on-read because they would indiscriminately copy data which should be left in a backing image from the backing chain. Introduce a per-request flag for copy-on-read so that a block device can process both regular and copy-on-read requests. Overlapping reads and writes still need to be serialized for correctness when copy-on-read is happening, so add an in-flight reference count to track this. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c49
1 files changed, 38 insertions, 11 deletions
diff --git a/block.c b/block.c
index 43f648437d..edfab49e32 100644
--- a/block.c
+++ b/block.c
@@ -48,6 +48,10 @@
#define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
+typedef enum {
+ BDRV_REQ_COPY_ON_READ = 0x1,
+} BdrvRequestFlags;
+
static void bdrv_dev_change_media_cb(BlockDriverState *bs, bool load);
static BlockDriverAIOCB *bdrv_aio_readv_em(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
@@ -62,7 +66,8 @@ static int coroutine_fn bdrv_co_writev_em(BlockDriverState *bs,
int64_t sector_num, int nb_sectors,
QEMUIOVector *iov);
static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
- int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
+ int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
+ BdrvRequestFlags flags);
static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
@@ -1292,7 +1297,7 @@ static void coroutine_fn bdrv_rw_co_entry(void *opaque)
if (!rwco->is_write) {
rwco->ret = bdrv_co_do_readv(rwco->bs, rwco->sector_num,
- rwco->nb_sectors, rwco->qiov);
+ rwco->nb_sectors, rwco->qiov, 0);
} else {
rwco->ret = bdrv_co_do_writev(rwco->bs, rwco->sector_num,
rwco->nb_sectors, rwco->qiov);
@@ -1500,7 +1505,7 @@ int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset,
return 0;
}
-static int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
+static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
{
/* Perform I/O through a temporary buffer so that users who scribble over
@@ -1523,8 +1528,8 @@ static int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
round_to_clusters(bs, sector_num, nb_sectors,
&cluster_sector_num, &cluster_nb_sectors);
- trace_bdrv_co_copy_on_readv(bs, sector_num, nb_sectors,
- cluster_sector_num, cluster_nb_sectors);
+ trace_bdrv_co_do_copy_on_readv(bs, sector_num, nb_sectors,
+ cluster_sector_num, cluster_nb_sectors);
iov.iov_len = cluster_nb_sectors * BDRV_SECTOR_SIZE;
iov.iov_base = bounce_buffer = qemu_blockalign(bs, iov.iov_len);
@@ -1559,7 +1564,8 @@ err:
* Handle a read request in coroutine context
*/
static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
- int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
+ int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
+ BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
BdrvTrackedRequest req;
@@ -1578,12 +1584,19 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
}
if (bs->copy_on_read) {
+ flags |= BDRV_REQ_COPY_ON_READ;
+ }
+ if (flags & BDRV_REQ_COPY_ON_READ) {
+ bs->copy_on_read_in_flight++;
+ }
+
+ if (bs->copy_on_read_in_flight) {
wait_for_overlapping_requests(bs, sector_num, nb_sectors);
}
tracked_request_begin(&req, bs, sector_num, nb_sectors, false);
- if (bs->copy_on_read) {
+ if (flags & BDRV_REQ_COPY_ON_READ) {
int pnum;
ret = bdrv_co_is_allocated(bs, sector_num, nb_sectors, &pnum);
@@ -1592,7 +1605,7 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
}
if (!ret || pnum != nb_sectors) {
- ret = bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, qiov);
+ ret = bdrv_co_do_copy_on_readv(bs, sector_num, nb_sectors, qiov);
goto out;
}
}
@@ -1601,6 +1614,11 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
out:
tracked_request_end(&req);
+
+ if (flags & BDRV_REQ_COPY_ON_READ) {
+ bs->copy_on_read_in_flight--;
+ }
+
return ret;
}
@@ -1609,7 +1627,16 @@ int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
{
trace_bdrv_co_readv(bs, sector_num, nb_sectors);
- return bdrv_co_do_readv(bs, sector_num, nb_sectors, qiov);
+ return bdrv_co_do_readv(bs, sector_num, nb_sectors, qiov, 0);
+}
+
+int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
+{
+ trace_bdrv_co_copy_on_readv(bs, sector_num, nb_sectors);
+
+ return bdrv_co_do_readv(bs, sector_num, nb_sectors, qiov,
+ BDRV_REQ_COPY_ON_READ);
}
/*
@@ -1637,7 +1664,7 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
bdrv_io_limits_intercept(bs, true, nb_sectors);
}
- if (bs->copy_on_read) {
+ if (bs->copy_on_read_in_flight) {
wait_for_overlapping_requests(bs, sector_num, nb_sectors);
}
@@ -3144,7 +3171,7 @@ static void coroutine_fn bdrv_co_do_rw(void *opaque)
if (!acb->is_write) {
acb->req.error = bdrv_co_do_readv(bs, acb->req.sector,
- acb->req.nb_sectors, acb->req.qiov);
+ acb->req.nb_sectors, acb->req.qiov, 0);
} else {
acb->req.error = bdrv_co_do_writev(bs, acb->req.sector,
acb->req.nb_sectors, acb->req.qiov);