On Fri, Jul 01, 2022 at 07:07:45PM +0100, Al Viro wrote:
> On Fri, Jul 01, 2022 at 11:53:44AM -0600, Keith Busch wrote:
> > On Fri, Jul 01, 2022 at 06:40:40PM +0100, Al Viro wrote:
> > > -static void bio_put_pages(struct page **pages, size_t size, size_t off)
> > > -{
> > > - size_t i, nr = DIV_ROUND_UP(size + (off & ~PAGE_MASK), PAGE_SIZE);
> > > -
> > > - for (i = 0; i < nr; i++)
> > > - put_page(pages[i]);
> > > -}
> > > -
> > > static int bio_iov_add_page(struct bio *bio, struct page *page,
> > > unsigned int len, unsigned int offset)
> > > {
> > > @@ -1228,11 +1220,11 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> > > * the iov data will be picked up in the next bio iteration.
> > > */
> > > size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
> > > - if (size > 0)
> > > - size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
> > > if (unlikely(size <= 0))
> > > return size ? size : -EFAULT;
> > > + nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
> > >
> > > + size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
> >
> > This isn't quite right. The result of the ALIGN_DOWN could be 0, so whatever
> > page we got before would be leaked since unused pages are only released on an
> > add_page error. I was about to reply with a patch that fixes this, but here's
> > the one that I'm currently testing:
>
> AFAICS, result is broken; you might end up consuming some data and leaving
> iterator not advanced at all. With no way for the caller to tell which way it
> went.
How about the following?
commit 5e3e9769404de54734c110b2040bdb93593e0f1b
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Fri Jul 1 13:15:36 2022 -0400
__bio_iov_iter_get_pages(): make sure we don't leak page refs on failure
Calculate the number of pages we'd grabbed before trimming size down.
And don't bother with bio_put_pages() - an explicit cleanup loop is
easier to follow...
Fixes: b1a000d3b8ec "block: relax direct io memory alignment"
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
diff --git a/block/bio.c b/block/bio.c
index 933ea3210954..a9fe20cb71fe 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1151,14 +1151,6 @@ void bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter)
bio_set_flag(bio, BIO_CLONED);
}
-static void bio_put_pages(struct page **pages, size_t size, size_t off)
-{
- size_t i, nr = DIV_ROUND_UP(size + (off & ~PAGE_MASK), PAGE_SIZE);
-
- for (i = 0; i < nr; i++)
- put_page(pages[i]);
-}
-
static int bio_iov_add_page(struct bio *bio, struct page *page,
unsigned int len, unsigned int offset)
{
@@ -1211,6 +1203,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
ssize_t size, left;
unsigned len, i;
size_t offset;
+ int ret;
/*
* Move page array up in the allocated memory for the bio vecs as far as
@@ -1228,14 +1221,13 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
* the iov data will be picked up in the next bio iteration.
*/
size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
- if (size > 0)
- size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
if (unlikely(size <= 0))
return size ? size : -EFAULT;
+ nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
+ size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
for (left = size, i = 0; left > 0; left -= len, i++) {
struct page *page = pages[i];
- int ret;
len = min_t(size_t, PAGE_SIZE - offset, left);
if (bio_op(bio) == REQ_OP_ZONE_APPEND)
@@ -1244,15 +1236,15 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
else
ret = bio_iov_add_page(bio, page, len, offset);
- if (ret) {
- bio_put_pages(pages + i, left, offset);
- return ret;
- }
+ if (ret)
+ break;
offset = 0;
}
+ while (i < nr_pages)
+ put_page(pages[i++]);
- iov_iter_advance(iter, size);
- return 0;
+ iov_iter_advance(iter, size - left);
+ return ret;
}
/**
