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Message-ID: <CAOzc2px2POjBU-6X=YB+rd-87vhDx0cUu0m8EFWA=Q_Peu1gUg@mail.gmail.com>
Date: Thu, 10 Nov 2022 10:36:43 -0800
From: Vishal Moola <vishal.moola@...il.com>
To: miklos@...redi.hu
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH 2/5] fuse: Convert fuse_try_move_page() to use folios
On Tue, Nov 1, 2022 at 11:24 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Tue, Nov 01, 2022 at 10:53:23AM -0700, Vishal Moola (Oracle) wrote:
> > Converts the function to try to move folios instead of pages. Also
> > converts fuse_check_page() to fuse_get_folio() since this is its only
> > caller. This change removes 15 calls to compound_head().
>
> This all looks good. I wonder if we should't add an assertion that the
> page we're trying to steal is !large? It seems to me that there are
> assumptions in this part of fuse that it's only dealing with order-0
> pages, and if someone gives it a page that's part of a large folio,
> it's going to be messy. Miklos, any thoughts?
Miklos, could you please look over this patch?
> > Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
> > ---
> > fs/fuse/dev.c | 55 ++++++++++++++++++++++++++-------------------------
> > 1 file changed, 28 insertions(+), 27 deletions(-)
> >
> > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > index 26817a2db463..204c332cd343 100644
> > --- a/fs/fuse/dev.c
> > +++ b/fs/fuse/dev.c
> > @@ -764,11 +764,11 @@ static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size)
> > return ncpy;
> > }
> >
> > -static int fuse_check_page(struct page *page)
> > +static int fuse_check_folio(struct folio *folio)
> > {
> > - if (page_mapcount(page) ||
> > - page->mapping != NULL ||
> > - (page->flags & PAGE_FLAGS_CHECK_AT_PREP &
> > + if (folio_mapped(folio) ||
> > + folio->mapping != NULL ||
> > + (folio->flags & PAGE_FLAGS_CHECK_AT_PREP &
> > ~(1 << PG_locked |
> > 1 << PG_referenced |
> > 1 << PG_uptodate |
> > @@ -778,7 +778,7 @@ static int fuse_check_page(struct page *page)
> > 1 << PG_reclaim |
> > 1 << PG_waiters |
> > LRU_GEN_MASK | LRU_REFS_MASK))) {
> > - dump_page(page, "fuse: trying to steal weird page");
> > + dump_page(&folio->page, "fuse: trying to steal weird page");
> > return 1;
> > }
> > return 0;
> > @@ -787,11 +787,11 @@ static int fuse_check_page(struct page *page)
> > static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
> > {
> > int err;
> > - struct page *oldpage = *pagep;
> > - struct page *newpage;
> > + struct folio *oldfolio = page_folio(*pagep);
> > + struct folio *newfolio;
> > struct pipe_buffer *buf = cs->pipebufs;
> >
> > - get_page(oldpage);
> > + folio_get(oldfolio);
> > err = unlock_request(cs->req);
> > if (err)
> > goto out_put_old;
> > @@ -814,35 +814,36 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
> > if (!pipe_buf_try_steal(cs->pipe, buf))
> > goto out_fallback;
> >
> > - newpage = buf->page;
> > + newfolio = page_folio(buf->page);
> >
> > - if (!PageUptodate(newpage))
> > - SetPageUptodate(newpage);
> > + if (!folio_test_uptodate(newfolio))
> > + folio_mark_uptodate(newfolio);
> >
> > - ClearPageMappedToDisk(newpage);
> > + folio_clear_mappedtodisk(newfolio);
> >
> > - if (fuse_check_page(newpage) != 0)
> > + if (fuse_check_folio(newfolio) != 0)
> > goto out_fallback_unlock;
> >
> > /*
> > * This is a new and locked page, it shouldn't be mapped or
> > * have any special flags on it
> > */
> > - if (WARN_ON(page_mapped(oldpage)))
> > + if (WARN_ON(folio_mapped(oldfolio)))
> > goto out_fallback_unlock;
> > - if (WARN_ON(page_has_private(oldpage)))
> > + if (WARN_ON(folio_has_private(oldfolio)))
> > goto out_fallback_unlock;
> > - if (WARN_ON(PageDirty(oldpage) || PageWriteback(oldpage)))
> > + if (WARN_ON(folio_test_dirty(oldfolio) ||
> > + folio_test_writeback(oldfolio)))
> > goto out_fallback_unlock;
> > - if (WARN_ON(PageMlocked(oldpage)))
> > + if (WARN_ON(folio_test_mlocked(oldfolio)))
> > goto out_fallback_unlock;
> >
> > - replace_page_cache_folio(page_folio(oldpage), page_folio(newpage));
> > + replace_page_cache_folio(oldfolio, newfolio);
> >
> > - get_page(newpage);
> > + folio_get(newfolio);
> >
> > if (!(buf->flags & PIPE_BUF_FLAG_LRU))
> > - lru_cache_add(newpage);
> > + folio_add_lru(newfolio);
> >
> > /*
> > * Release while we have extra ref on stolen page. Otherwise
> > @@ -855,28 +856,28 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
> > if (test_bit(FR_ABORTED, &cs->req->flags))
> > err = -ENOENT;
> > else
> > - *pagep = newpage;
> > + *pagep = &newfolio->page;
> > spin_unlock(&cs->req->waitq.lock);
> >
> > if (err) {
> > - unlock_page(newpage);
> > - put_page(newpage);
> > + folio_unlock(newfolio);
> > + folio_put(newfolio);
> > goto out_put_old;
> > }
> >
> > - unlock_page(oldpage);
> > + folio_unlock(oldfolio);
> > /* Drop ref for ap->pages[] array */
> > - put_page(oldpage);
> > + folio_put(oldfolio);
> > cs->len = 0;
> >
> > err = 0;
> > out_put_old:
> > /* Drop ref obtained in this function */
> > - put_page(oldpage);
> > + folio_put(oldfolio);
> > return err;
> >
> > out_fallback_unlock:
> > - unlock_page(newpage);
> > + folio_unlock(newfolio);
> > out_fallback:
> > cs->pg = buf->page;
> > cs->offset = buf->offset;
> > --
> > 2.38.1
> >
> >
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