From 1ea806165ec5fb8bca5d9990392fdb4f53a97977 Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Mon, 26 Oct 2026 11:26:50 -0400 Subject: [PATCH] fuse: fix link error with CONFIG_FUSE_PASSTHROUGH=n Commit 2f19d54c055d ("fuse: support 64 bit, server allocated backing ID") moved the CONFIG_FUSE_PASSTHROUGH check out of the backing ioctl handlers and into fuse_get_conn_for_passthrough(). The calls from the handlers into backing.c, which is only built with CONFIG_FUSE_PASSTHROUGH, are now only removed if the compiler inlines that helper. It does not have to, and with gcc 11 and CONFIG_CC_OPTIMIZE_FOR_SIZE it doesn't: dev.c:(.text+0x355c): undefined reference to `fuse_backing_open' nios2-linux-ld: dev.c:(.text+0x3594): undefined reference to `fuse_backing_open_64' nios2-linux-ld: dev.c:(.text+0x35d0): undefined reference to `fuse_backing_close' Check CONFIG_FUSE_PASSTHROUGH in each handler again, as fuse_notify_backing_remove() does. The check still comes after the fuse_get_dev() and -ENOTCONN checks, so the errors userspace sees do not change. Fixes: 2f19d54c055d ("fuse: support 64 bit, server allocated backing ID") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202610171310.uqRzJkIx-lkp@intel.com/ Closes: https://lore.kernel.org/oe-kbuild-all/202610260719.sj08mXBr-lkp@intel.com/ Signed-off-by: Sasha Levin Signed-off-by: Linus Torvalds --- fs/fuse/dev.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 1a40b60afb98..3641abb90d6b 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -2334,9 +2334,6 @@ static struct fuse_conn *fuse_get_conn_for_passthrough(struct file *file) if (!smp_load_acquire(&fud->chan->initialized)) return ERR_PTR(-ENOTCONN); - if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) - return ERR_PTR(-EOPNOTSUPP); - return fud->chan->conn; } @@ -2349,6 +2346,9 @@ static long fuse_dev_ioctl_backing_open(struct file *file, if (IS_ERR(fc)) return PTR_ERR(fc); + if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + return -EOPNOTSUPP; + if (copy_from_user(&map, argp, sizeof(map))) return -EFAULT; @@ -2364,6 +2364,9 @@ static long fuse_dev_ioctl_backing_create(struct file *file, if (IS_ERR(fc)) return PTR_ERR(fc); + if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + return -EOPNOTSUPP; + if (copy_from_user(&map, argp, sizeof(map))) return -EFAULT; @@ -2378,6 +2381,9 @@ static long fuse_dev_ioctl_backing_close(struct file *file, __u32 __user *argp) if (IS_ERR(fc)) return PTR_ERR(fc); + if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + return -EOPNOTSUPP; + if (get_user(backing_id, argp)) return -EFAULT;