On 11/18/19 10:24 AM, Masayoshi Mizuma wrote: > From: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> > > exit_aio() is sometimes stuck in wait_for_completion() after aio is issued > with direct IO and the task receives a signal. > > That is because kioctx in mm->ioctx_table is in use by aio_kiocb. > aio_kiocb->ki_refcnt is 1 at that time. That means iocb_put() isn't > called correctly. > > fuse_get_req() returns as -EINTR when it's blocked and receives a signal. > fuse_direct_IO() deals with the -EINTER as -EIOCBQUEUED and returns as > -EIOCBQUEUED even though the aio isn't queued. > As the result, aio_rw_done() doesn't handle the error, so iocb_put() isn't > called via aio_complete_rw(), which is the callback. > > The flow is something like as: > > io_submit > aio_get_req > refcount_set(&req->ki_refcnt, 2) > __io_submit_one > aio_read > ... > fuse_direct_IO # return as -EIOCBQUEUED > __fuse_direct_read > ... > fuse_get_req # return as -EINTR > aio_rw_done > # Nothing to do because ret is -EIOCBQUEUED... > iocb_put > refcount_dec_and_test(&iocb->ki_refcnt) # 2->1 > > Return as the error code of fuse_direct_io() or __fuse_direct_read() in > fuse_direct_IO() so that aio_rw_done() can handle the error and call > iocb_put(). > > This issue is trucked as a virtio-fs issue: > https://gitlab.com/virtio-fs/qemu/issues/14 > I didn't reproduce this issue on kernel v5.4-rc7, but did on 5.4-rc8. And verified this patch fixed the case in issue 14 on v5.4-rc8 and virtiofsd (virtio-fs-dev 5f068fa9). Tested-by: Cao jin <caoj.fnst@xxxxxxxxxxxxxx> -- Sincerely, Cao jin
