Linux-EROFS Archive on lore.kernel.org
 help / color / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-xfs <linux-xfs@vger.kernel.org>,
	William Kucharski <william.kucharski@oracle.com>,
	linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
	linux-mm@kvack.org, ocfs2-devel@oss.oracle.com,
	Dave Chinner <dchinner@redhat.com>,
	linux-fsdevel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org,
	linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v11 24/25] fuse: Convert from readpages to readahead
Date: Mon, 20 Apr 2020 13:14:17 +0200
Message-ID: <CAJfpegsZF=TFQ67vABkE5ghiZoTZF+=_u8tM5U_P6jZeAmv23A@mail.gmail.com> (raw)
In-Reply-To: <20200414150233.24495-25-willy@infradead.org>

On Tue, Apr 14, 2020 at 5:08 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>
> Implement the new readahead operation in fuse by using __readahead_batch()
> to fill the array of pages in fuse_args_pages directly.  This lets us
> inline fuse_readpages_fill() into fuse_readahead().
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> Reviewed-by: William Kucharski <william.kucharski@oracle.com>
> ---
>  fs/fuse/file.c | 99 ++++++++++++++------------------------------------
>  1 file changed, 27 insertions(+), 72 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 9d67b830fb7a..db82fb29dd39 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -915,84 +915,39 @@ static void fuse_send_readpages(struct fuse_io_args *ia, struct file *file)
>         fuse_readpages_end(fc, &ap->args, err);
>  }
>
> -struct fuse_fill_data {
> -       struct fuse_io_args *ia;
> -       struct file *file;
> -       struct inode *inode;
> -       unsigned int nr_pages;
> -       unsigned int max_pages;
> -};
> -
> -static int fuse_readpages_fill(void *_data, struct page *page)
> +static void fuse_readahead(struct readahead_control *rac)
>  {
> -       struct fuse_fill_data *data = _data;
> -       struct fuse_io_args *ia = data->ia;
> -       struct fuse_args_pages *ap = &ia->ap;
> -       struct inode *inode = data->inode;
> +       struct inode *inode = rac->mapping->host;
>         struct fuse_conn *fc = get_fuse_conn(inode);
> +       unsigned int i, max_pages, nr_pages = 0;
>
> -       fuse_wait_on_page_writeback(inode, page->index);
> -
> -       if (ap->num_pages &&
> -           (ap->num_pages == fc->max_pages ||
> -            (ap->num_pages + 1) * PAGE_SIZE > fc->max_read ||
> -            ap->pages[ap->num_pages - 1]->index + 1 != page->index)) {
> -               data->max_pages = min_t(unsigned int, data->nr_pages,
> -                                       fc->max_pages);
> -               fuse_send_readpages(ia, data->file);
> -               data->ia = ia = fuse_io_alloc(NULL, data->max_pages);
> -               if (!ia) {
> -                       unlock_page(page);
> -                       return -ENOMEM;
> -               }
> -               ap = &ia->ap;
> -       }
> -
> -       if (WARN_ON(ap->num_pages >= data->max_pages)) {
> -               unlock_page(page);
> -               fuse_io_free(ia);
> -               return -EIO;
> -       }
> -
> -       get_page(page);
> -       ap->pages[ap->num_pages] = page;
> -       ap->descs[ap->num_pages].length = PAGE_SIZE;
> -       ap->num_pages++;
> -       data->nr_pages--;
> -       return 0;
> -}
> -
> -static int fuse_readpages(struct file *file, struct address_space *mapping,
> -                         struct list_head *pages, unsigned nr_pages)
> -{
> -       struct inode *inode = mapping->host;
> -       struct fuse_conn *fc = get_fuse_conn(inode);
> -       struct fuse_fill_data data;
> -       int err;
> -
> -       err = -EIO;
>         if (is_bad_inode(inode))
> -               goto out;
> +               return;
>
> -       data.file = file;
> -       data.inode = inode;
> -       data.nr_pages = nr_pages;
> -       data.max_pages = min_t(unsigned int, nr_pages, fc->max_pages);
> -;
> -       data.ia = fuse_io_alloc(NULL, data.max_pages);
> -       err = -ENOMEM;
> -       if (!data.ia)
> -               goto out;
> +       max_pages = min(fc->max_pages, fc->max_read / PAGE_SIZE);
>
> -       err = read_cache_pages(mapping, pages, fuse_readpages_fill, &data);
> -       if (!err) {
> -               if (data.ia->ap.num_pages)
> -                       fuse_send_readpages(data.ia, file);
> -               else
> -                       fuse_io_free(data.ia);
> +       for (;;) {
> +               struct fuse_io_args *ia;
> +               struct fuse_args_pages *ap;
> +
> +               nr_pages = readahead_count(rac) - nr_pages;

Hmm.  I see what's going on here, but it's confusing.   Why is
__readahead_batch() decrementing the readahead count at the start,
rather than at the end?

At the very least it needs a comment about why nr_pages is calculated this way.

> +               if (nr_pages > max_pages)
> +                       nr_pages = max_pages;
> +               if (nr_pages == 0)
> +                       break;
> +               ia = fuse_io_alloc(NULL, nr_pages);
> +               if (!ia)
> +                       return;
> +               ap = &ia->ap;
> +               nr_pages = __readahead_batch(rac, ap->pages, nr_pages);
> +               for (i = 0; i < nr_pages; i++) {
> +                       fuse_wait_on_page_writeback(inode,
> +                                                   readahead_index(rac) + i);

What's wrong with ap->pages[i]->index?  Are we trying to wean off using ->index?

Thanks,
Miklos

  reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-14 15:02 [PATCH v11 00/25] Change readahead API Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox
2020-04-15  9:10   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 02/25] mm: Return void from various readahead functions Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 03/25] mm: Ignore return value of ->readpages Matthew Wilcox
2020-04-15  9:17   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox
2020-04-15  9:19   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 05/25] mm: Add new readahead_control API Matthew Wilcox
2020-04-15  1:17   ` Andrew Morton
2020-04-15  2:18     ` Matthew Wilcox
2020-04-15  4:56       ` Andrew Morton
2020-04-15 11:22         ` Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox
2020-04-15  9:30   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox
2020-04-15  9:31   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 11/25] mm: Add readahead address space operation Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 18/25] erofs: Convert uncompressed files " Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 19/25] erofs: Convert compressed " Matthew Wilcox
2020-04-21  5:42   ` Andrew Morton
2020-04-21  7:28     ` Gao Xiang via Linux-erofs
2020-04-14 15:02 ` [PATCH v11 20/25] ext4: Convert " Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 24/25] fuse: Convert from readpages to readahead Matthew Wilcox
2020-04-20 11:14   ` Miklos Szeredi [this message]
2020-04-20 11:43     ` Matthew Wilcox
2020-04-20 11:54       ` Miklos Szeredi
2020-04-14 15:02 ` [PATCH v11 25/25] iomap: " Matthew Wilcox

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAJfpegsZF=TFQ67vABkE5ghiZoTZF+=_u8tM5U_P6jZeAmv23A@mail.gmail.com' \
    --to=miklos@szeredi.hu \
    --cc=akpm@linux-foundation.org \
    --cc=cluster-devel@redhat.com \
    --cc=dchinner@redhat.com \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=linux-erofs@lists.ozlabs.org \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-f2fs-devel@lists.sourceforge.net \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-xfs@vger.kernel.org \
    --cc=ocfs2-devel@oss.oracle.com \
    --cc=william.kucharski@oracle.com \
    --cc=willy@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-EROFS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-erofs/0 linux-erofs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-erofs linux-erofs/ https://lore.kernel.org/linux-erofs \
		linux-erofs@lists.ozlabs.org linux-erofs@ozlabs.org
	public-inbox-index linux-erofs

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.ozlabs.lists.linux-erofs


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git