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[PATCH] block/nfs: avoid BDRV_POLL_WHILE() in nfs_co_get_allocated_file_
From: |
Stefan Hajnoczi |
Subject: |
[PATCH] block/nfs: avoid BDRV_POLL_WHILE() in nfs_co_get_allocated_file_size() |
Date: |
Mon, 3 Apr 2023 19:30:33 -0400 |
Commit 82618d7bc341 ("block: Convert bdrv_get_allocated_file_size() to
co_wrapper") made nfs_get_allocated_file_size() a coroutine. The
coroutine still uses BDRV_POLL_WHILE() to wait for the NFS RPC to
complete.
Take it a step further and yield the coroutine until the RPC completes.
This avoids the blocking, nested event loop and unifies
nfs_co_get_allocated_file_size() with the other coroutine functions that
send RPCs:
- Use nfs_co_init_task() to set up a coroutine NFSRPC task.
- Take client->mutex to protect fd handler state since we're in IO_CODE.
- Use nfs_co_generic_cb() instead of a specialized callback function.
- Yield until the task completes.
Getting rid of BDRV_POLL_WHILE() helps with the multi-queue block layer
effort where we don't want to take the AioContext lock.
This commit passes qemu-iotests/check -nfs, except inactivate-failure,
which also fails before this commit.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block/nfs.c | 45 +++++++++++++++++----------------------------
1 file changed, 17 insertions(+), 28 deletions(-)
diff --git a/block/nfs.c b/block/nfs.c
index 351dc6ec8d..71062c9b47 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -248,14 +248,18 @@ nfs_co_generic_cb(int ret, struct nfs_context *nfs, void
*data,
{
NFSRPC *task = private_data;
task->ret = ret;
- assert(!task->st);
if (task->ret > 0 && task->iov) {
+ assert(!task->st);
if (task->ret <= task->iov->size) {
qemu_iovec_from_buf(task->iov, 0, data, task->ret);
} else {
task->ret = -EIO;
}
}
+ if (task->ret == 0 && task->st) {
+ assert(!task->iov);
+ memcpy(task->st, data, sizeof(struct stat));
+ }
if (task->ret < 0) {
error_report("NFS Error: %s", nfs_get_error(nfs));
}
@@ -713,29 +717,10 @@ static int nfs_has_zero_init(BlockDriverState *bs)
}
#if !defined(_WIN32)
-/* Called (via nfs_service) with QemuMutex held. */
-static void
-nfs_get_allocated_file_size_cb(int ret, struct nfs_context *nfs, void *data,
- void *private_data)
-{
- NFSRPC *task = private_data;
- task->ret = ret;
- if (task->ret == 0) {
- memcpy(task->st, data, sizeof(struct stat));
- }
- if (task->ret < 0) {
- error_report("NFS Error: %s", nfs_get_error(nfs));
- }
-
- /* Set task->complete before reading bs->wakeup. */
- qatomic_mb_set(&task->complete, 1);
- bdrv_wakeup(task->bs);
-}
-
static int64_t coroutine_fn nfs_co_get_allocated_file_size(BlockDriverState
*bs)
{
NFSClient *client = bs->opaque;
- NFSRPC task = {0};
+ NFSRPC task;
struct stat st;
if (bdrv_is_read_only(bs) &&
@@ -743,15 +728,19 @@ static int64_t coroutine_fn
nfs_co_get_allocated_file_size(BlockDriverState *bs)
return client->st_blocks * 512;
}
- task.bs = bs;
+ nfs_co_init_task(bs, &task);
task.st = &st;
- if (nfs_fstat_async(client->context, client->fh,
nfs_get_allocated_file_size_cb,
- &task) != 0) {
- return -ENOMEM;
- }
+ WITH_QEMU_LOCK_GUARD(&client->mutex) {
+ if (nfs_fstat_async(client->context, client->fh, nfs_co_generic_cb,
+ &task) != 0) {
+ return -ENOMEM;
+ }
- nfs_set_events(client);
- BDRV_POLL_WHILE(bs, !task.complete);
+ nfs_set_events(client);
+ }
+ while (!task.complete) {
+ qemu_coroutine_yield();
+ }
return (task.ret < 0 ? task.ret : st.st_blocks * 512);
}
--
2.39.2
- [PATCH] block/nfs: avoid BDRV_POLL_WHILE() in nfs_co_get_allocated_file_size(),
Stefan Hajnoczi <=