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[Qemu-block] [PULL 28/37] block: add BlockBackend->in_flight counter
From: |
Kevin Wolf |
Subject: |
[Qemu-block] [PULL 28/37] block: add BlockBackend->in_flight counter |
Date: |
Fri, 2 Mar 2018 19:54:39 +0100 |
From: Stefan Hajnoczi <address@hidden>
BlockBackend currently relies on BlockDriverState->in_flight to track
requests for blk_drain(). There is a corner case where
BlockDriverState->in_flight cannot be used though: blk->root can be NULL
when there is no medium. This results in a segfault when the NULL
pointer is dereferenced.
Introduce a BlockBackend->in_flight counter for aio requests so it works
even when blk->root == NULL.
Based on a patch by Kevin Wolf <address@hidden>.
Signed-off-by: Kevin Wolf <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
block.c | 2 +-
block/block-backend.c | 60 +++++++++++++++++++++++++++++++++++++++++++++------
2 files changed, 54 insertions(+), 8 deletions(-)
diff --git a/block.c b/block.c
index 9e4da81213..a83037c2a5 100644
--- a/block.c
+++ b/block.c
@@ -4713,7 +4713,7 @@ out:
AioContext *bdrv_get_aio_context(BlockDriverState *bs)
{
- return bs->aio_context;
+ return bs ? bs->aio_context : qemu_get_aio_context();
}
AioWait *bdrv_get_aio_wait(BlockDriverState *bs)
diff --git a/block/block-backend.c b/block/block-backend.c
index 0266ac990b..a775a3dd2f 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -73,6 +73,14 @@ struct BlockBackend {
int quiesce_counter;
VMChangeStateEntry *vmsh;
bool force_allow_inactivate;
+
+ /* Number of in-flight aio requests. BlockDriverState also counts
+ * in-flight requests but aio requests can exist even when blk->root is
+ * NULL, so we cannot rely on its counter for that case.
+ * Accessed with atomic ops.
+ */
+ unsigned int in_flight;
+ AioWait wait;
};
typedef struct BlockBackendAIOCB {
@@ -1225,11 +1233,22 @@ int blk_make_zero(BlockBackend *blk, BdrvRequestFlags
flags)
return bdrv_make_zero(blk->root, flags);
}
+static void blk_inc_in_flight(BlockBackend *blk)
+{
+ atomic_inc(&blk->in_flight);
+}
+
+static void blk_dec_in_flight(BlockBackend *blk)
+{
+ atomic_dec(&blk->in_flight);
+ aio_wait_kick(&blk->wait);
+}
+
static void error_callback_bh(void *opaque)
{
struct BlockBackendAIOCB *acb = opaque;
- bdrv_dec_in_flight(acb->common.bs);
+ blk_dec_in_flight(acb->blk);
acb->common.cb(acb->common.opaque, acb->ret);
qemu_aio_unref(acb);
}
@@ -1240,7 +1259,7 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
{
struct BlockBackendAIOCB *acb;
- bdrv_inc_in_flight(blk_bs(blk));
+ blk_inc_in_flight(blk);
acb = blk_aio_get(&block_backend_aiocb_info, blk, cb, opaque);
acb->blk = blk;
acb->ret = ret;
@@ -1263,7 +1282,7 @@ static const AIOCBInfo blk_aio_em_aiocb_info = {
static void blk_aio_complete(BlkAioEmAIOCB *acb)
{
if (acb->has_returned) {
- bdrv_dec_in_flight(acb->common.bs);
+ blk_dec_in_flight(acb->rwco.blk);
acb->common.cb(acb->common.opaque, acb->rwco.ret);
qemu_aio_unref(acb);
}
@@ -1284,7 +1303,7 @@ static BlockAIOCB *blk_aio_prwv(BlockBackend *blk,
int64_t offset, int bytes,
BlkAioEmAIOCB *acb;
Coroutine *co;
- bdrv_inc_in_flight(blk_bs(blk));
+ blk_inc_in_flight(blk);
acb = blk_aio_get(&blk_aio_em_aiocb_info, blk, cb, opaque);
acb->rwco = (BlkRwCo) {
.blk = blk,
@@ -1521,14 +1540,41 @@ int blk_flush(BlockBackend *blk)
void blk_drain(BlockBackend *blk)
{
- if (blk_bs(blk)) {
- bdrv_drain(blk_bs(blk));
+ BlockDriverState *bs = blk_bs(blk);
+
+ if (bs) {
+ bdrv_drained_begin(bs);
+ }
+
+ /* We may have -ENOMEDIUM completions in flight */
+ AIO_WAIT_WHILE(&blk->wait,
+ blk_get_aio_context(blk),
+ atomic_mb_read(&blk->in_flight) > 0);
+
+ if (bs) {
+ bdrv_drained_end(bs);
}
}
void blk_drain_all(void)
{
- bdrv_drain_all();
+ BlockBackend *blk = NULL;
+
+ bdrv_drain_all_begin();
+
+ while ((blk = blk_all_next(blk)) != NULL) {
+ AioContext *ctx = blk_get_aio_context(blk);
+
+ aio_context_acquire(ctx);
+
+ /* We may have -ENOMEDIUM completions in flight */
+ AIO_WAIT_WHILE(&blk->wait, ctx,
+ atomic_mb_read(&blk->in_flight) > 0);
+
+ aio_context_release(ctx);
+ }
+
+ bdrv_drain_all_end();
}
void blk_set_on_error(BlockBackend *blk, BlockdevOnError on_read_error,
--
2.13.6
- [Qemu-block] [PULL 19/37] vpc: Switch to .bdrv_co_block_status(), (continued)
- [Qemu-block] [PULL 19/37] vpc: Switch to .bdrv_co_block_status(), Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 20/37] vvfat: Switch to .bdrv_co_block_status(), Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 21/37] block: Drop unused .bdrv_co_get_block_status(), Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 22/37] block: fix write with zero flag set and iovector provided, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 23/37] iotest 033: add misaligned write-zeroes test via truncate, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 26/37] aio: rename aio_context_in_iothread() to in_aio_context_home_thread(), Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 24/37] specs/qcow2: Fix documentation of the compressed cluster descriptor, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 25/37] docs: document how to use the l2-cache-entry-size parameter, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 27/37] block: extract AIO_WAIT_WHILE() from BlockDriverState, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 28/37] block: add BlockBackend->in_flight counter,
Kevin Wolf <=
- [Qemu-block] [PULL 30/37] Revert "IDE: Do not flush empty CDROM drives", Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 29/37] block: test blk_aio_flush() with blk->root == NULL, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 32/37] qcow2: make qcow2_co_create2() a coroutine_fn, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 31/37] block: rename .bdrv_create() to .bdrv_co_create_opts(), Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 33/37] qemu-img: Make resize error message more general, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 34/37] block/ssh: Pull ssh_grow_file() from ssh_create(), Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 35/37] block/ssh: Make ssh_grow_file() blocking, Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 36/37] block/ssh: Add basic .bdrv_truncate(), Kevin Wolf, 2018/03/02
- [Qemu-block] [PULL 37/37] qcow2: Replace align_offset() with ROUND_UP(), Kevin Wolf, 2018/03/02
- Re: [Qemu-block] [Qemu-devel] [PULL 00/37] Block layer patches, Peter Maydell, 2018/03/05