On 12/18, Chao Yu wrote:
> On 2018/12/14 13:01, Jaegeuk Kim wrote:
> > Sometimes, I could observe # of issuing_discard to be 1 which blocks
> > background
> > jobs due to is_idle()=false.
> > The only way to get out of it was to trigger gc_urgent. This patch avoids
> > that
> > by checking any candidates as done in the list.
>
> Well, as below code, once we issued discard commands, we will wait all
> queued discard end their IO, so do you know what flow can cause such
> condition...?
It's very subtle, and I suspect somehow race condition not from here.
>
> issued = __issue_discard_cmd(sbi, &dpolicy);
> if (issued > 0) {
> __wait_all_discard_cmd(sbi, &dpolicy);
>
> Or, I doubt that 'issued' statistical info could be wrong.
No, it simply came back to 0 with this patch. So, something is pending
in the queue even if it is done.
Thanks,
>
> Thanks,
>
> >
> > Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
> > ---
> > fs/f2fs/segment.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 49ea9009ab5a..acbbc924e518 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1651,6 +1651,10 @@ static int issue_discard_thread(void *data)
> > if (dcc->discard_wake)
> > dcc->discard_wake = 0;
> >
> > + /* clean up pending candidates before going to sleep */
> > + if (atomic_read(&dcc->queued_discard))
> > + __wait_all_discard_cmd(sbi, NULL);
> > +
> > if (try_to_freeze())
> > continue;
> > if (f2fs_readonly(sbi->sb))
> >
