From: Jason Xing <kernelxing@xxxxxxxxxxx> KCSAN reported a data-race issue due to two different cpus accessing this member. BUG: KCSAN: data-race in ext4_free_inodes_count / ext4_free_inodes_set write to 0xffff888104a9e00e of 2 bytes by task 4435 on cpu 0: ext4_free_inodes_set+0x1f/0x80 fs/ext4/super.c:397 __ext4_new_inode+0x15c8/0x2290 fs/ext4/ialloc.c:1216 ext4_symlink+0x242/0x580 fs/ext4/namei.c:3393 vfs_symlink+0xc2/0x1a0 fs/namei.c:4475 do_symlinkat+0xe3/0x320 fs/namei.c:4501 __do_sys_symlinkat fs/namei.c:4517 [inline] __se_sys_symlinkat fs/namei.c:4514 [inline] __x64_sys_symlinkat+0x62/0x70 fs/namei.c:4514 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd read to 0xffff888104a9e00e of 2 bytes by task 4440 on cpu 1: ext4_free_inodes_count+0x1c/0x80 fs/ext4/super.c:341 __ext4_new_inode+0xb71/0x2290 fs/ext4/ialloc.c:1040 ext4_symlink+0x242/0x580 fs/ext4/namei.c:3393 vfs_symlink+0xc2/0x1a0 fs/namei.c:4475 do_symlinkat+0xe3/0x320 fs/namei.c:4501 __do_sys_symlinkat fs/namei.c:4517 [inline] __se_sys_symlinkat fs/namei.c:4514 [inline] __x64_sys_symlinkat+0x62/0x70 fs/namei.c:4514 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd value changed: 0x185c -> 0x185b Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx> --- fs/ext4/super.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index cf817a6a6e27..6db71cc1e5cd 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -338,7 +338,7 @@ ext4_fsblk_t ext4_inode_table(struct super_block *sb, __u32 ext4_free_group_clusters(struct super_block *sb, struct ext4_group_desc *bg) { - return le16_to_cpu(bg->bg_free_blocks_count_lo) | + return le16_to_cpu(READ_ONCE(bg->bg_free_blocks_count_lo)) | (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ? (__u32)le16_to_cpu(bg->bg_free_blocks_count_hi) << 16 : 0); } @@ -394,7 +394,7 @@ void ext4_inode_table_set(struct super_block *sb, void ext4_free_group_clusters_set(struct super_block *sb, struct ext4_group_desc *bg, __u32 count) { - bg->bg_free_blocks_count_lo = cpu_to_le16((__u16)count); + WRITE_ONCE(bg->bg_free_blocks_count_lo, cpu_to_le16((__u16)count)); if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT) bg->bg_free_blocks_count_hi = cpu_to_le16(count >> 16); } -- 2.37.3