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gluster: Do not move coroutine into BDS context

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The request coroutine may not run in the BDS AioContext.  We should wake
it in its own context, not move it.

With that, we can remove GlusterAIOCB.aio_context.

Also add a comment why aio_co_schedule() is safe to use in this way.

**Note:** Due to a lack of a gluster set-up, I have not tested this
commit.  It seemed safe enough to send anyway, just maybe not to
qemu-stable.  To be clear, I don’t know of any user-visible bugs that
would arise from the state without this patch; the request coroutine is
moved into the main BDS AioContext, so guest device completion code will
run in a different context than where the request started, which can’t
be good, but I haven’t actually confirmed any bugs (due to not being
able to test it).

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20251110154854.151484-7-hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Hanna Czenczek
2025-11-10 16:48:41 +01:00
committed by Kevin Wolf
parent 53d5c7ffac
commit 7214ad20da
1 changed files with 11 additions and 6 deletions
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17
block/gluster.c
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@@ -56,7 +56,6 @@ typedef struct GlusterAIOCB {
int64_t size;
int ret;
Coroutine *coroutine;
AioContext *aio_context;
} GlusterAIOCB;
typedef struct BDRVGlusterState {
@@ -743,7 +742,17 @@ static void gluster_finish_aiocb(struct glfs_fd *fd, ssize_t ret,
acb->ret = -EIO; /* Partial read/write - fail it */
}
aio_co_schedule(acb->aio_context, acb->coroutine);
/*
* Safe to call: The coroutine will yield exactly once awaiting this
* scheduling, and the context is its own context, so it will be scheduled
* once it does yield.
*
* (aio_co_wake() would call qemu_get_current_aio_context() to check whether
* we are in the same context, but we are not in a qemu thread, so we cannot
* do that. Use aio_co_schedule() directly.)
*/
aio_co_schedule(qemu_coroutine_get_aio_context(acb->coroutine),
acb->coroutine);
}
static void qemu_gluster_parse_flags(int bdrv_flags, int *open_flags)
@@ -1006,7 +1015,6 @@ static coroutine_fn int qemu_gluster_co_pwrite_zeroes(BlockDriverState *bs,
acb.size = bytes;
acb.ret = 0;
acb.coroutine = qemu_coroutine_self();
acb.aio_context = bdrv_get_aio_context(bs);
ret = glfs_zerofill_async(s->fd, offset, bytes, gluster_finish_aiocb, &acb);
if (ret < 0) {
@@ -1184,7 +1192,6 @@ static coroutine_fn int qemu_gluster_co_rw(BlockDriverState *bs,
acb.size = size;
acb.ret = 0;
acb.coroutine = qemu_coroutine_self();
acb.aio_context = bdrv_get_aio_context(bs);
if (write) {
ret = glfs_pwritev_async(s->fd, qiov->iov, qiov->niov, offset, 0,
@@ -1251,7 +1258,6 @@ static coroutine_fn int qemu_gluster_co_flush_to_disk(BlockDriverState *bs)
acb.size = 0;
acb.ret = 0;
acb.coroutine = qemu_coroutine_self();
acb.aio_context = bdrv_get_aio_context(bs);
ret = glfs_fsync_async(s->fd, gluster_finish_aiocb, &acb);
if (ret < 0) {
@@ -1299,7 +1305,6 @@ static coroutine_fn int qemu_gluster_co_pdiscard(BlockDriverState *bs,
acb.size = 0;
acb.ret = 0;
acb.coroutine = qemu_coroutine_self();
acb.aio_context = bdrv_get_aio_context(bs);
ret = glfs_discard_async(s->fd, offset, bytes, gluster_finish_aiocb, &acb);
if (ret < 0) {