netdev - Re: Kernel oops with 6.14 when enabling TLS

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Message-ID: <Z8dA8l1NR-xmFWyq@casper.infradead.org>
Date: Tue, 4 Mar 2025 18:05:38 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Hannes Reinecke <hare@...e.com>
Cc: Vlastimil Babka <vbabka@...e.cz>, Boris Pismenny <borisp@...dia.com>,
	John Fastabend <john.fastabend@...il.com>,
	Jakub Kicinski <kuba@...nel.org>, Sagi Grimberg <sagi@...mberg.me>,
	"linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
	"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
	linux-mm@...ck.org, Harry Yoo <harry.yoo@...cle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Kernel oops with 6.14 when enabling TLS

On Tue, Mar 04, 2025 at 04:53:09PM +0000, Matthew Wilcox wrote:
> Right, that's what happened in the block layer.  We mark the bio with
> BIO_PAGE_PINNED if the pincount needs to be dropped.  As a transitional
> period, we had BIO_PAGE_REFFED which indicated that the page refcount
> needed to be dropped.  Perhaps there's something similar that network
> could be doing.

Until that time ... how does this look as a quick hack to avoid
reverting the slab change?

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d6fed25243c3..ca08a923ac6d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1520,7 +1520,10 @@ static inline void folio_get(struct folio *folio)
 
 static inline void get_page(struct page *page)
 {
-	folio_get(page_folio(page));
+	struct folio *folio = page_folio(page);
+	if (WARN_ON_ONCE(folio_test_slab(folio)))
+		return;
+	folio_get(folio);
 }
 
 static inline __must_check bool try_get_page(struct page *page)
@@ -1614,6 +1617,8 @@ static inline void put_page(struct page *page)
 {
 	struct folio *folio = page_folio(page);
 
+	if (folio_test_slab(folio))
+		return;
 	folio_put(folio);
 }
 
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 65f550cb5081..8c7fdb7d8c8f 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1190,8 +1190,12 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
 		if (!n)
 			return -ENOMEM;
 		p = *pages;
-		for (int k = 0; k < n; k++)
-			get_page(p[k] = page + k);
+		for (int k = 0; k < n; k++) {
+			struct folio *folio = page_folio(page);
+			p[k] = page + k;
+			if (!folio_test_slab(folio))
+				folio_get(folio);
+		}
 		maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start);
 		i->count -= maxsize;
 		i->iov_offset += maxsize;