In fuse_get_user_pages(), set *nbytesp to 0 when struct page **pages
allocation fails. This prevents the caller (fuse_direct_io) from making
incorrect assumptions that could lead to NULL pointer dereferences
when processing the request reply.

Previously, *nbytesp was left unmodified on allocation failure, which
could cause issues if the caller assumed pages had been added to
ap->descs[] when they hadn't.

Reported-by: syzbot+87b8e6ed25dbc41759f7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=87b8e6ed25dbc41759f7
Fixes: 3b97c3652d91 ("fuse: convert direct io to use folios")
Signed-off-by: Bernd Schubert <bschubert@ddn.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Tested-by: Dmitry Antipov <dmantipov@yandex.ru>
Tested-by: David Howells <dhowells@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

For the direct io case, the pages from userspace may be part of a huge
folio, even if all folios in the page cache for fuse are small.

Fix the logic for calculating the offset and length of the folio for
the direct io case, which currently incorrectly assumes that all folios
encountered are one page size.

Fixes: 3b97c3652d91 ("fuse: convert direct io to use folios")
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Bernd Schubert <bschubert@ddn.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

All fuse requests use folios instead of pages for transferring data.
Remove pages from the requests and exclusively use folios.

No functional changes.

[SzM: rename back folio_descs -> descs, etc.]

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Convert direct io requests to use folios instead of pages.

No functional changes.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Convert writeback requests to use folios instead of pages.

No functional changes.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Convert non-writeback write requests to use folios instead of pages.

No functional changes.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Convert read requests to use folios instead of pages.

No functional changes.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

In order to make it easier to switch to folios in the fuse_args_pages
update the places where we update the vmstat counters for writeback to
use the folio related helpers.  On the inc side this is easy as we
already have the folio, on the dec side we have to page_folio() the
pages for now.

Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse_writepage_need_send is called by fuse_writepages_fill() which
already has a folio.  Change fuse_writepage_need_send() to take a folio
instead, add a helper to check if the folio range is under writeback and
use this, as well as the appropriate folio helpers in the rest of the
function.  Update fuse_writepage_need_send() to pass in the folio
directly.

Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Now that the buffered write path is using folios, convert
fuse_do_readpage() to take a folio instead of a page, update it to use
the appropriate folio helpers, and update the callers to pass in the
folio directly instead of a page.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>