linux-kernel - [RFT 04/15] kfifo: remove support for physically non-contiguous memory

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Message-ID: <20240319095315.27624-6-jirislaby@kernel.org>
Date: Tue, 19 Mar 2024 10:53:04 +0100
From: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To: linux-serial@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	"Jiri Slaby (SUSE)" <jirislaby@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stefani Seibold <stefani@...bold.net>
Subject: [RFT 04/15] kfifo: remove support for physically non-contiguous memory

First, there is no such user. The only user of this interface is
caam_rng_fill_async() and that uses kfifo_alloc() -> kmalloc().

Second, the implementation does not allow anything else than direct
mapping and kmalloc() (due to virt_to_phys()), anyway.

Therefore, there is no point in having this dead (and complex) code in
the kernel.

Note the setup_sgl_buf() function now boils down to simple sg_set_buf().
That is called twice from setup_sgl() to take care of kfifo buffer
wrap-around.

setup_sgl_buf() will be extended shortly, so keeping it in place.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Stefani Seibold <stefani@...bold.net>
---
 lib/kfifo.c | 38 +++++---------------------------------
 1 file changed, 5 insertions(+), 33 deletions(-)

diff --git a/lib/kfifo.c b/lib/kfifo.c
index a36bfdbdb17d..d5830960ab87 100644
--- a/lib/kfifo.c
+++ b/lib/kfifo.c
@@ -305,43 +305,15 @@ int __kfifo_to_user(struct __kfifo *fifo, void __user *to,
 }
 EXPORT_SYMBOL(__kfifo_to_user);
 
-static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
-		int nents, unsigned int len)
+static unsigned int setup_sgl_buf(struct scatterlist *sgl, void *buf,
+				  int nents, unsigned int len)
 {
-	int n;
-	unsigned int l;
-	unsigned int off;
-	struct page *page;
-
-	if (!nents)
+	if (!nents || !len)
 		return 0;
 
-	if (!len)
-		return 0;
+	sg_set_buf(sgl, buf, len);
 
-	n = 0;
-	page = virt_to_page(buf);
-	off = offset_in_page(buf);
-	l = 0;
-
-	while (len >= l + PAGE_SIZE - off) {
-		struct page *npage;
-
-		l += PAGE_SIZE;
-		buf += PAGE_SIZE;
-		npage = virt_to_page(buf);
-		if (page_to_phys(page) != page_to_phys(npage) - l) {
-			sg_set_page(sgl, page, l - off, off);
-			sgl = sg_next(sgl);
-			if (++n == nents || sgl == NULL)
-				return n;
-			page = npage;
-			len -= l - off;
-			l = off = 0;
-		}
-	}
-	sg_set_page(sgl, page, len, off);
-	return n + 1;
+	return 1;
 }
 
 static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,
-- 
2.44.0