qemu/block/export, branch master

block: remove outdated AioContext locking comments

2023-12-21T21:49:27Z

The AioContext lock no longer exists. There is one noteworthy change: - * More specifically, these functions use BDRV_POLL_WHILE(bs), which - * requires the caller to be either in the main thread and hold - * the BlockdriverState (bs) AioContext lock, or directly in the - * home thread that runs the bs AioContext. Calling them from - * another thread in another AioContext would cause deadlocks. + * More specifically, these functions use BDRV_POLL_WHILE(bs), which requires + * the caller to be either in the main thread or directly in the home thread + * that runs the bs AioContext. Calling them from another thread in another + * AioContext would cause deadlocks. I am not sure whether deadlocks are still possible. Maybe they have just moved to the fine-grained locks that have replaced the AioContext. Since I am not sure if the deadlocks are gone, I have kept the substance unchanged and just removed mention of the AioContext. Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake Message-ID: <20231205182011.1976568-15-stefanha@redhat.com> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf

block: remove AioContext locking

2023-12-21T21:49:27Z

This is the big patch that removes aio_context_acquire()/aio_context_release() from the block layer and affected block layer users. There isn't a clean way to split this patch and the reviewers are likely the same group of people, so I decided to do it in one patch. Signed-off-by: Stefan Hajnoczi Reviewed-by: Eric Blake Reviewed-by: Kevin Wolf Reviewed-by: Paul Durrant Message-ID: <20231205182011.1976568-7-stefanha@redhat.com> Signed-off-by: Kevin Wolf

export/vhost-user-blk: Fix consecutive drains

2023-11-28T13:56:32Z

The vhost-user-blk export implement AioContext switches in its drain implementation. This means that on drain_begin, it detaches the server from its AioContext and on drain_end, attaches it again and schedules the server->co_trip coroutine in the updated AioContext. However, nothing guarantees that server->co_trip is even safe to be scheduled. Not only is it unclear that the coroutine is actually in a state where it can be reentered externally without causing problems, but with two consecutive drains, it is possible that the scheduled coroutine didn't have a chance yet to run and trying to schedule an already scheduled coroutine a second time crashes with an assertion failure. Following the model of NBD, this commit makes the vhost-user-blk export shut down server->co_trip during drain so that resuming the export means creating and scheduling a new coroutine, which is always safe. There is one exception: If the drain call didn't poll (for example, this happens in the context of bdrv_graph_wrlock()), then the coroutine didn't have a chance to shut down. However, in this case the AioContext can't have changed; changing the AioContext always involves a polling drain. So in this case we can simply assert that the AioContext is unchanged and just leave the coroutine running or wake it up if it has yielded to wait for the AioContext to be attached again. Fixes: e1054cd4aad03a493a5d1cded7508f7c348205bf Fixes: https://issues.redhat.com/browse/RHEL-1708 Signed-off-by: Kevin Wolf Message-ID: <20231127115755.22846-1-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf

block: Mark bdrv_first_blk() and bdrv_is_root_node() GRAPH_RDLOCK

2023-10-12T14:31:33Z

This adds GRAPH_RDLOCK annotations to declare that callers of bdrv_first_blk() and bdrv_is_root_node() need to hold a reader lock for the graph. These functions are the only functions in block-backend.c that access the parent list of a node. Signed-off-by: Kevin Wolf Message-ID: <20230929145157.45443-5-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf

block: spelling fixes

2023-09-08T10:08:52Z

Signed-off-by: Michael Tokarev Reviewed-by: Eric Blake

vhost-user: fully use new backend/frontend naming

2023-06-26T13:50:00Z

Slave/master nomenclature was replaced with backend/frontend in commit 1fc19b65279a ("vhost-user: Adopt new backend naming") This patch replaces all remaining uses of master and slave in the codebase. Signed-off-by: Emmanouil Pitsidianakis Message-Id: <20230613080849.2115347-1-manos.pitsidianakis@linaro.org> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Marc-André Lureau

aio: remove aio_disable_external() API

2023-05-30T15:37:26Z

All callers now pass is_external=false to aio_set_fd_handler() and aio_set_event_notifier(). The aio_disable_external() API that temporarily disables fd handlers that were registered is_external=true is therefore dead code. Remove aio_disable_external(), aio_enable_external(), and the is_external arguments to aio_set_fd_handler() and aio_set_event_notifier(). The entire test-fdmon-epoll test is removed because its sole purpose was testing aio_disable_external(). Parts of this patch were generated using the following coccinelle (https://coccinelle.lip6.fr/) semantic patch: @@ expression ctx, fd, is_external, io_read, io_write, io_poll, io_poll_ready, opaque; @@ - aio_set_fd_handler(ctx, fd, is_external, io_read, io_write, io_poll, io_poll_ready, opaque) + aio_set_fd_handler(ctx, fd, io_read, io_write, io_poll, io_poll_ready, opaque) @@ expression ctx, notifier, is_external, io_read, io_poll, io_poll_ready; @@ - aio_set_event_notifier(ctx, notifier, is_external, io_read, io_poll, io_poll_ready) + aio_set_event_notifier(ctx, notifier, io_read, io_poll, io_poll_ready) Reviewed-by: Juan Quintela Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Stefan Hajnoczi Message-Id: <20230516190238.8401-21-stefanha@redhat.com> Signed-off-by: Kevin Wolf

block/fuse: do not set is_external=true on FUSE fd

2023-05-30T15:32:02Z

This is part of ongoing work to remove the aio_disable_external() API. Use BlockDevOps .drained_begin/end/poll() instead of aio_set_fd_handler(is_external=true). As a side-effect the FUSE export now follows AioContext changes like the other export types. Signed-off-by: Stefan Hajnoczi Reviewed-by: Kevin Wolf Message-Id: <20230516190238.8401-16-stefanha@redhat.com> Signed-off-by: Kevin Wolf

block/export: don't require AioContext lock around blk_exp_ref/unref()

2023-05-30T15:32:02Z

The FUSE export calls blk_exp_ref/unref() without the AioContext lock. Instead of fixing the FUSE export, adjust blk_exp_ref/unref() so they work without the AioContext lock. This way it's less error-prone. Suggested-by: Paolo Bonzini Signed-off-by: Stefan Hajnoczi Reviewed-by: Kevin Wolf Message-Id: <20230516190238.8401-15-stefanha@redhat.com> Signed-off-by: Kevin Wolf

block/export: rewrite vduse-blk drain code

2023-05-30T15:32:02Z

vduse_blk_detach_ctx() waits for in-flight requests using AIO_WAIT_WHILE(). This is not allowed according to a comment in bdrv_set_aio_context_commit(): /* * Take the old AioContex when detaching it from bs. * At this point, new_context lock is already acquired, and we are now * also taking old_context. This is safe as long as bdrv_detach_aio_context * does not call AIO_POLL_WHILE(). */ Use this opportunity to rewrite the drain code in vduse-blk: - Use the BlockExport refcount so that vduse_blk_exp_delete() is only called when there are no more requests in flight. - Implement .drained_poll() so in-flight request coroutines are stopped by the time .bdrv_detach_aio_context() is called. - Remove AIO_WAIT_WHILE() from vduse_blk_detach_ctx() to solve the .bdrv_detach_aio_context() constraint violation. It's no longer needed due to the previous changes. - Always handle the VDUSE file descriptor, even in drained sections. The VDUSE file descriptor doesn't submit I/O, so it's safe to handle it in drained sections. This ensures that the VDUSE kernel code gets a fast response. - Suspend virtqueue fd handlers in .drained_begin() and resume them in .drained_end(). This eliminates the need for the aio_set_fd_handler(is_external=true) flag, which is being removed from QEMU. This is a long list but splitting it into individual commits would probably lead to git bisect failures - the changes are all related. Signed-off-by: Stefan Hajnoczi Reviewed-by: Kevin Wolf Message-Id: <20230516190238.8401-14-stefanha@redhat.com> Signed-off-by: Kevin Wolf