From: Cao jin <caoj.fnst@cn.fujitsu.com>
To: Masayoshi Mizuma <msys.mizuma@gmail.com>,
Miklos Szeredi <miklos@szeredi.hu>,
<linux-fsdevel@vger.kernel.org>
Cc: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>,
<linux-kernel@vger.kernel.org>, <virtio-fs@redhat.com>
Subject: Re: [PATCH] fuse: Fix the return code of fuse_direct_IO() to deal with the error for aio
Date: Thu, 21 Nov 2019 13:51:31 +0800 [thread overview]
Message-ID: <c80528c2-31ee-ccfc-127b-66bc7f93b669@cn.fujitsu.com> (raw)
In-Reply-To: <20191118022410.21023-1-msys.mizuma@gmail.com>
On 11/18/19 10:24 AM, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
>
> 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@cn.fujitsu.com>
--
Sincerely,
Cao jin
next prev parent reply other threads:[~2019-11-21 5:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-18 2:24 [PATCH] fuse: Fix the return code of fuse_direct_IO() to deal with the error for aio Masayoshi Mizuma
2019-11-21 5:51 ` Cao jin [this message]
2019-11-25 12:38 ` Miklos Szeredi
2019-11-25 16:58 ` Masayoshi Mizuma
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