On Thu, 3 Jul 2025 06:52:44 -0700, Christoph Hellwig wrote:
> On Tue, Jul 01, 2025 at 10:48:47PM +0800, alexjlzheng@xxxxxxxxx wrote:
> > From: Jinliang Zheng <alexjlzheng@xxxxxxxxxxx>
> >
> > In the buffer write path, iomap_set_range_uptodate() is called every
> > time iomap_end_write() is called. But if folio_test_uptodate() holds, we
> > know that all blocks in this folio are already in the uptodate state, so
> > there is no need to go deep into the critical section of state_lock to
> > execute bitmap_set().
> >
> > Although state_lock may not have significant lock contention due to
> > folio lock, this patch at least reduces the number of instructions.
>
> That means the uptodate bitmap is stale in that case. That would
Hi, after days of silence, I re-read this email thread to make sure I
didn't miss something important.
I realized that maybe we are not aligned and I didn't understand your
sentence above. Would you mind explaining your meaning in more detail?
In addition, what I want to say is that once folio_test_uptodate() is
true, all bits in ifs->state are in the uptodate state. So there is no
need to acquire the lock and set it again. This repeated setting happens
in __iomap_write_end().
thanks,
Jinliang Zheng. :)
> only matter if we could clear the folio uptodate bit and still
> expect the page content to survive. Which sounds dubious and I could
> not find anything relevant grepping the tree, but I'm adding the
> linux-mm list just in case.
>
> >
> > Signed-off-by: Jinliang Zheng <alexjlzheng@xxxxxxxxxxx>
> > ---
> > fs/iomap/buffered-io.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > index 3729391a18f3..fb4519158f3a 100644
> > --- a/fs/iomap/buffered-io.c
> > +++ b/fs/iomap/buffered-io.c
> > @@ -71,6 +71,9 @@ static void iomap_set_range_uptodate(struct folio *folio, size_t off,
> > unsigned long flags;
> > bool uptodate = true;
> >
> > + if (folio_test_uptodate(folio))
> > + return;
> > +
> > if (ifs) {
> > spin_lock_irqsave(&ifs->state_lock, flags);
> > uptodate = ifs_set_range_uptodate(folio, ifs, off, len);
> > --
> > 2.49.0
> >
> >
> ---end quoted text---
