linux-kernel - [PATCH] fs: fuse: fix max() of incompatible types

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Message-Id: <20251223215442.720828-1-arnd@kernel.org>
Date: Tue, 23 Dec 2025 22:54:03 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Miklos Szeredi <miklos@...redi.hu>,
	Christian Brauner <brauner@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Joanne Koong <joannelkoong@...il.com>,
	"Darrick J. Wong" <djwong@...nel.org>,
	Jeff Layton <jlayton@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] fs: fuse: fix max() of incompatible types

From: Arnd Bergmann <arnd@...db.de>

The 'max()' value of a 'long long' and an 'unsigned int' is problematic
if the former is negative:

In function 'fuse_wr_pages',
    inlined from 'fuse_perform_write' at fs/fuse/file.c:1347:27:
include/linux/compiler_types.h:652:45: error: call to '__compiletime_assert_390' declared with attribute error: min(((pos + len - 1) >> 12) - (pos >> 12) + 1, max_pages) signedness error
  652 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
      |                                             ^

Use a temporary variable to make it clearer what is going on here.

Fixes: 0f5bb0cfb0b4 ("fs: use min() or umin() instead of min_t()")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/fuse/file.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 4f71eb5a9bac..d3dec67d73fc 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1323,8 +1323,10 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 static inline unsigned int fuse_wr_pages(loff_t pos, size_t len,
 				     unsigned int max_pages)
 {
-	return min(((pos + len - 1) >> PAGE_SHIFT) - (pos >> PAGE_SHIFT) + 1,
-		   max_pages);
+	unsigned int pages = ((pos + len - 1) >> PAGE_SHIFT) -
+			     (pos >> PAGE_SHIFT) + 1;
+
+	return min(pages, max_pages);
 }
 
 static ssize_t fuse_perform_write(struct kiocb *iocb, struct iov_iter *ii)
-- 
2.39.5