From 470c05047a09cda3de16bb3f98a130d9537357a4 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 18 Jan 2012 14:40:42 +0000 Subject: [PATCH] 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 Signed-off-by: Kevin Wolf --- block.c | 49 ++++++++++++++++++++++++++++++++++++++----------- block.h | 2 ++ block_int.h | 3 +++ trace-events | 3 ++- 4 files changed, 45 insertions(+), 12 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); diff --git a/block.h b/block.h index 3bd4398609..a3b0b80859 100644 --- a/block.h +++ b/block.h @@ -142,6 +142,8 @@ int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset, const void *buf, int count); int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov); +int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs, + int64_t sector_num, int nb_sectors, QEMUIOVector *qiov); int coroutine_fn bdrv_co_writev(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov); int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t sector_num, diff --git a/block_int.h b/block_int.h index 311bd2a6fa..07d67ed282 100644 --- a/block_int.h +++ b/block_int.h @@ -218,6 +218,9 @@ struct BlockDriverState { BlockDriverState *backing_hd; BlockDriverState *file; + /* number of in-flight copy-on-read requests */ + unsigned int copy_on_read_in_flight; + /* async read/write emulation */ void *sync_aiocb; diff --git a/trace-events b/trace-events index d2b0c6181d..035d08fe7c 100644 --- a/trace-events +++ b/trace-events @@ -65,9 +65,10 @@ bdrv_aio_readv(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs % bdrv_aio_writev(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs %p sector_num %"PRId64" nb_sectors %d opaque %p" bdrv_lock_medium(void *bs, bool locked) "bs %p locked %d" bdrv_co_readv(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d" +bdrv_co_copy_on_readv(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d" bdrv_co_writev(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d" bdrv_co_io_em(void *bs, int64_t sector_num, int nb_sectors, int is_write, void *acb) "bs %p sector_num %"PRId64" nb_sectors %d is_write %d acb %p" -bdrv_co_copy_on_readv(void *bs, int64_t sector_num, int nb_sectors, int64_t cluster_sector_num, int cluster_nb_sectors) "bs %p sector_num %"PRId64" nb_sectors %d cluster_sector_num %"PRId64" cluster_nb_sectors %d" +bdrv_co_do_copy_on_readv(void *bs, int64_t sector_num, int nb_sectors, int64_t cluster_sector_num, int cluster_nb_sectors) "bs %p sector_num %"PRId64" nb_sectors %d cluster_sector_num %"PRId64" cluster_nb_sectors %d" # hw/virtio-blk.c virtio_blk_req_complete(void *req, int status) "req %p status %d"