On Mon, 22 Apr 2013 11:57:52 +0400, Dmitry Monakhov <dmonak...@openvz.org>
wrote:
Non-text part: multipart/mixed
>
Seriously. Am I an only one who use blktrace?
Jens can you please take it?
> Hi,
> Let someone please finally take care of this patch.
> Originally it was submitted here https://lkml.org/lkml/2010/2/28/103
> This patch fix very annoying issue. I've got OK from Jens and Tom
> Zanussi but no one accept it. MAINTAINERS file has no info about relayfs.
> So I've added to CC all people which may be interested in that.
>
> From 1c0d96aece60a8a81c3f0cf1f681a5ff4333a2ff Mon Sep 17 00:00:00 2001
> From: Dmitry Monakhov <dmonak...@openvz.org>
> Date: Mon, 22 Apr 2013 11:41:41 +0400
> Subject: [PATCH] relay: move remove_buf_file inside relay_close_buf
>
> Currently remove_buf_file callback is called from from kobject
> release method. This result in follow issue:
> # blktrace -d /dev/sda1 -d /dev/sda -o test
>
> blktrace_setup()
> dir = create_dir()
> rchan = relay_open(dir,...)
> ->create_buf_file_callback
> buf_file = debugfs_create_file(dir, )
>
> Userspace will open buf_file.
> Later we make a decision to stop tracing
> blktrace_down()
> relay_close(rhcan) /* just decrement kobj reference */
> /* since it is not zero then callback not called */
> debugfs_remove(dir) /* FAIL due to non empty dir */
>
> Later user space will close the file and file will be deleted,
> but directory still exist.
> user_space_close()
> ->file_release
> ->release_buf_file_callback
> ->debugfs_remove(buf_file
> ## TESTCASE:
> # blktrace -d /dev/sda1 -d /dev/sda -o test
> # After that blktrace infrastructure will remain broken in
> # an unusable state so: blktrace -d /dev/sda1 will not work.
>
> In fact this is general issue, blktrace is just one of examples.
> We can not reliably remove parent dir until all users close the
> buf_file.
>
> Solution: We don't have to wait that long. File should be deleted inside
> relay_close_buf().
>
> Signed-off-by: Dmitry Monakhov <dmonak...@openvz.org>
> Acked-by : Jens Axboe <ax...@kernel.dk>
>
> ---
> kernel/relay.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/relay.c b/kernel/relay.c
> index 01ab081..a0d2000 100644
> --- a/kernel/relay.c
> +++ b/kernel/relay.c
> @@ -234,7 +234,6 @@ static void relay_destroy_buf(struct rchan_buf *buf)
> static void relay_remove_buf(struct kref *kref)
> {
> struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
> - buf->chan->cb->remove_buf_file(buf->dentry);
> relay_destroy_buf(buf);
> }
>
> @@ -484,6 +483,7 @@ static void relay_close_buf(struct rchan_buf *buf)
> {
> buf->finalized = 1;
> del_timer_sync(&buf->timer);
> + buf->chan->cb->remove_buf_file(buf->dentry);
> kref_put(&buf->kref, relay_remove_buf);
> }
>
> --
> 1.7.1
>
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