[PATCH] block: Fix page refcounts for unaligned buffers in __bio_release_pages()

[PATCH] block: Fix page refcounts for unaligned buffers in __bio_release_pages()

[Tony Battersby]

commit 38b43539d64b2fa020b3b9a752a986769f87f7a6 upstream.

Fix an incorrect number of pages being released for buffers that do not
start at the beginning of a page.

  [ Tony: backport to v6.1 by replacing bio_release_page() loop with
    folio_put_refs() as commits fd363244e883 and e4cc64657bec are not
    present. ]

Fixes: 1b151e2435fc ("block: Remove special-casing of compound pages")
Cc: stable@vger.kernel.org
Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Tested-by: Greg Edwards <gedwards@ddn.com>
Link: https://lore.kernel.org/r/86e592a9-98d4-4cff-a646-0c0084328356@cybernetics.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

This is the backport for 6.1.

The upstream patch should apply cleanly to 6.6, 6.7, and 6.8.

This patch does not need to be backported to 5.15, 5.10, 5.4, or 4.19,
since the backport of 1b151e2435fc to those kernels did not include
the bug fixed by this patch.

 block/bio.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 74c2818c7ec9..3318e0022fdf 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1112,19 +1112,16 @@ void __bio_release_pages(struct bio *bio, bool mark_dirty)
 	struct folio_iter fi;
 
 	bio_for_each_folio_all(fi, bio) {
-		struct page *page;
-		size_t done = 0;
+		size_t nr_pages;
 
 		if (mark_dirty) {
 			folio_lock(fi.folio);
 			folio_mark_dirty(fi.folio);
 			folio_unlock(fi.folio);
 		}
-		page = folio_page(fi.folio, fi.offset / PAGE_SIZE);
-		do {
-			folio_put(fi.folio);
-			done += PAGE_SIZE;
-		} while (done < fi.length);
+		nr_pages = (fi.offset + fi.length - 1) / PAGE_SIZE -
+			   fi.offset / PAGE_SIZE + 1;
+		folio_put_refs(fi.folio, nr_pages);
 	}
 }
 EXPORT_SYMBOL_GPL(__bio_release_pages);

base-commit: 61adba85cc40287232a539e607164f273260e0fe
-- 
2.25.1

Re: [PATCH] block: Fix page refcounts for unaligned buffers in __bio_release_pages()

[Greg KH]

On Wed, Mar 13, 2024 at 10:02:23AM -0400, Tony Battersby wrote:
> commit 38b43539d64b2fa020b3b9a752a986769f87f7a6 upstream.
> 
> Fix an incorrect number of pages being released for buffers that do not
> start at the beginning of a page.
> 
>   [ Tony: backport to v6.1 by replacing bio_release_page() loop with
>     folio_put_refs() as commits fd363244e883 and e4cc64657bec are not
>     present. ]

Now queued up, thanks.

greg k-h