[Qemu-devel] [PATCH 5/8] block: take lock around bdrv_read implementations

[Paolo Bonzini <pbonzini@redhat.com>]

This does the first part of the conversion to coroutines, by
wrapping bdrv_read implementations to take the read side of the
rwlock.

Drivers that implement bdrv_read rather than bdrv_co_readv can
then benefit from asynchronous operation (at least if the underlying
protocol supports it, which is not the case for raw-win32), even
though they still operate with a bounce buffer.

raw-win32 does not need the lock, because it cannot yield.
nbd also doesn't probably, but better be safe.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/cow.c   |   13 ++++++++++++-
 block/nbd.c   |   13 ++++++++++++-
 block/vmdk.c  |   13 ++++++++++++-
 block/vpc.c   |   13 ++++++++++++-
 block/vvfat.c |   13 ++++++++++++-
 5 files changed, 60 insertions(+), 5 deletions(-)

diff --git a/block/cow.c b/block/cow.c
index d27e0aa..9571549 100644
--- a/block/cow.c
+++ b/block/cow.c
@@ -201,6 +201,17 @@ static int cow_read(BlockDriverState *bs, int64_t sector_num,
     return 0;
 }
 
+static coroutine_fn int cow_co_read(BlockDriverState *bs, int64_t sector_num,
+                                    uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVCowState *s = bs->opaque;
+    qemu_co_rwlock_rdlock(&s->lock);
+    ret = cow_read(bs, sector_num, buf, nb_sectors);
+    qemu_co_rwlock_unlock(&s->lock);
+    return ret;
+}
+
 static int cow_write(BlockDriverState *bs, int64_t sector_num,
                      const uint8_t *buf, int nb_sectors)
 {
@@ -308,7 +319,7 @@ static BlockDriver bdrv_cow = {
     .instance_size	= sizeof(BDRVCowState),
     .bdrv_probe		= cow_probe,
     .bdrv_open		= cow_open,
-    .bdrv_read		= cow_read,
+    .bdrv_read		= cow_co_read,
     .bdrv_write		= cow_write,
     .bdrv_close		= cow_close,
     .bdrv_create	= cow_create,
diff --git a/block/nbd.c b/block/nbd.c
index ec8f086..f8fed92 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -240,6 +240,17 @@ static int nbd_write(BlockDriverState *bs, int64_t sector_num,
     return 0;
 }
 
+static coroutine_fn int nbd_co_read(BlockDriverState *bs, int64_t sector_num,
+                                    uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVNBDState *s = bs->opaque;
+    qemu_co_rwlock_rdlock(&s->lock);
+    ret = nbd_read(bs, sector_num, buf, nb_sectors);
+    qemu_co_rwlock_unlock(&s->lock);
+    return ret;
+}
+
 static void nbd_close(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
@@ -260,7 +271,7 @@ static BlockDriver bdrv_nbd = {
     .format_name	= "nbd",
     .instance_size	= sizeof(BDRVNBDState),
     .bdrv_file_open	= nbd_open,
-    .bdrv_read		= nbd_read,
+    .bdrv_read		= nbd_co_read,
     .bdrv_write		= nbd_write,
     .bdrv_close		= nbd_close,
     .bdrv_getlength	= nbd_getlength,
diff --git a/block/vmdk.c b/block/vmdk.c
index 6afd53e..ff78e25 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1022,6 +1022,17 @@ static int vmdk_read(BlockDriverState *bs, int64_t sector_num,
     return 0;
 }
 
+static coroutine_fn int vmdk_co_read(BlockDriverState *bs, int64_t sector_num,
+                                     uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVVmdkState *s = bs->opaque;
+    qemu_co_rwlock_rdlock(&s->lock);
+    ret = vmdk_read(bs, sector_num, buf, nb_sectors);
+    qemu_co_rwlock_unlock(&s->lock);
+    return ret;
+}
+
 static int vmdk_write(BlockDriverState *bs, int64_t sector_num,
                      const uint8_t *buf, int nb_sectors)
 {
@@ -1540,7 +1551,7 @@ static BlockDriver bdrv_vmdk = {
     .instance_size  = sizeof(BDRVVmdkState),
     .bdrv_probe     = vmdk_probe,
     .bdrv_open      = vmdk_open,
-    .bdrv_read      = vmdk_read,
+    .bdrv_read      = vmdk_co_read,
     .bdrv_write     = vmdk_write,
     .bdrv_close     = vmdk_close,
     .bdrv_create    = vmdk_create,
diff --git a/block/vpc.c b/block/vpc.c
index 7220488..e805769 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -409,6 +409,17 @@ static int vpc_read(BlockDriverState *bs, int64_t sector_num,
     return 0;
 }
 
+static coroutine_fn int vpc_co_read(BlockDriverState *bs, int64_t sector_num,
+                                    uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVVPCState *s = bs->opaque;
+    qemu_co_rwlock_rdlock(&s->lock);
+    ret = vpc_read(bs, sector_num, buf, nb_sectors);
+    qemu_co_rwlock_unlock(&s->lock);
+    return ret;
+}
+
 static int vpc_write(BlockDriverState *bs, int64_t sector_num,
     const uint8_t *buf, int nb_sectors)
 {
@@ -649,7 +660,7 @@ static BlockDriver bdrv_vpc = {
     .instance_size  = sizeof(BDRVVPCState),
     .bdrv_probe     = vpc_probe,
     .bdrv_open      = vpc_open,
-    .bdrv_read      = vpc_read,
+    .bdrv_read      = vpc_co_read,
     .bdrv_write     = vpc_write,
     .bdrv_flush     = vpc_flush,
     .bdrv_close     = vpc_close,
diff --git a/block/vvfat.c b/block/vvfat.c
index 08a72ee..f1d94ad 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1279,6 +1279,17 @@ DLOG(fprintf(stderr, "sector %d not allocated\n", (int)sector_num));
     return 0;
 }
 
+static coroutine_fn int vvfat_co_read(BlockDriverState *bs, int64_t sector_num,
+                                      uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVVVFATState *s = bs->opaque;
+    qemu_co_rwlock_rdlock(&s->lock);
+    ret = vvfat_read(bs, sector_num, buf, nb_sectors);
+    qemu_co_rwlock_unlock(&s->lock);
+    return ret;
+}
+
 /* LATER TODO: statify all functions */
 
 /*
@@ -2803,7 +2814,7 @@ static BlockDriver bdrv_vvfat = {
     .format_name	= "vvfat",
     .instance_size	= sizeof(BDRVVVFATState),
     .bdrv_file_open	= vvfat_open,
-    .bdrv_read		= vvfat_read,
+    .bdrv_read		= vvfat_co_read,
     .bdrv_write		= vvfat_write,
     .bdrv_close		= vvfat_close,
     .bdrv_is_allocated	= vvfat_is_allocated,
-- 
1.7.6