linux-kernel - [PATCH] btrfs: avoid link error with CONFIG_NO_AUTO

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Message-Id: <20181103153941.1881966-1-arnd@arndb.de>
Date:   Sat,  3 Nov 2018 16:39:28 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Changbin Du <changbin.du@...il.com>,
        Anand Jain <anand.jain@...cle.com>,
        Nikolay Borisov <nborisov@...e.com>,
        Misono Tomohiro <misono.tomohiro@...fujitsu.com>,
        Qu Wenruo <wqu@...e.com>, Gu Jinxiang <gujx@...fujitsu.com>,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] btrfs: avoid link error with CONFIG_NO_AUTO_INLINE

On 32-bit ARM with gcc-8, I see a link error with the addition of the
CONFIG_NO_AUTO_INLINE option:

fs/btrfs/super.o: In function `btrfs_statfs':
super.c:(.text+0x67b8): undefined reference to `__aeabi_uldivmod'
super.c:(.text+0x67fc): undefined reference to `__aeabi_uldivmod'
super.c:(.text+0x6858): undefined reference to `__aeabi_uldivmod'
super.c:(.text+0x6920): undefined reference to `__aeabi_uldivmod'
super.c:(.text+0x693c): undefined reference to `__aeabi_uldivmod'
fs/btrfs/super.o:super.c:(.text+0x6958): more undefined references to `__aeabi_uldivmod' follow

So far this is the only file that shows the behavior, so I'd propose
to just work around it by marking the functions as 'static inline'
that normally get inlined here.

The reference to __aeabi_uldivmod comes from a div_u64() which has an
optimization for a constant division that uses a straight '/' operator
when the result should be known to the compiler. My interpretation is
that as we turn off inlining, gcc still expects the result to be constant
but fails to use that constant value.

Cc: Changbin Du <changbin.du@...il.com>
Fixes: 943b8435c3bd ("kernel hacking: add a config option to disable compiler auto-inlining")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/btrfs/super.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index c3c1e7bee49d..b7af0b8936ad 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1922,7 +1922,7 @@ static int btrfs_remount(struct super_block *sb, int *flags,
 }
 
 /* Used to sort the devices by max_avail(descending sort) */
-static int btrfs_cmp_device_free_bytes(const void *dev_info1,
+static inline int btrfs_cmp_device_free_bytes(const void *dev_info1,
 				       const void *dev_info2)
 {
 	if (((struct btrfs_device_info *)dev_info1)->max_avail >
@@ -1951,8 +1951,8 @@ static inline void btrfs_descending_sort_devices(
  * The helper to calc the free space on the devices that can be used to store
  * file data.
  */
-static int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
-				       u64 *free_bytes)
+static inline int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
+					      u64 *free_bytes)
 {
 	struct btrfs_device_info *devices_info;
 	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-- 
2.18.0