@@ -1655,7 +1655,7 @@ static inline struct timespec64 inode_set_mtime(struct inode *inode,
static inline time64_t inode_get_ctime_sec(const struct inode *inode)
{
- return inode->i_ctime_sec;
+ return READ_ONCE(inode->i_ctime_sec);
}
static inline long inode_get_ctime_nsec(const struct inode *inode)
@@ -1674,8 +1674,8 @@ static inline struct timespec64 inode_get_ctime(const struct inode *inode)
static inline struct timespec64 inode_set_ctime_to_ts(struct inode *inode,
struct timespec64 ts)
{
- inode->i_ctime_sec = ts.tv_sec;
- inode->i_ctime_nsec = ts.tv_nsec;
+ WRITE_ONCE(inode->i_ctime_sec, ts.tv_sec);
+ WRITE_ONCE(inode->i_ctime_nsec, ts.tv_nsec);
return ts;
}
V2: Thanks for Honza's reply and suggestions. READ_ONCE should indeed be added to the reading position. I added READ_ONCE to `inode_get_ctime_sec()`. The new patch is as follows. ----------------------------------------------------------------- V1: A data race may occur when the function `inode_set_ctime_to_ts()` and the function `inode_get_ctime_sec()` are executed concurrently. When two threads call `aio_read` and `aio_write` respectively, they will be distributed to the read and write functions of the corresponding file system respectively. Taking the btrfs file system as an example, the `btrfs_file_read_iter` and `btrfs_file_write_iter` functions are finally called. These two functions created a data race when they finally called `inode_get_ctime_sec()` and `inode_set_ctime_to_ns()`. The specific call stack that appears during testing is as follows: ``` ============DATA_RACE============ btrfs_delayed_update_inode+0x1f61/0x7ce0 [btrfs] btrfs_update_inode+0x45e/0xbb0 [btrfs] btrfs_dirty_inode+0x2b8/0x530 [btrfs] btrfs_update_time+0x1ad/0x230 [btrfs] touch_atime+0x211/0x440 filemap_read+0x90f/0xa20 btrfs_file_read_iter+0xeb/0x580 [btrfs] aio_read+0x275/0x3a0 io_submit_one+0xd22/0x1ce0 __se_sys_io_submit+0xb3/0x250 do_syscall_64+0xc1/0x190 entry_SYSCALL_64_after_hwframe+0x77/0x7f ============OTHER_INFO============ btrfs_write_check+0xa15/0x1390 [btrfs] btrfs_buffered_write+0x52f/0x29d0 [btrfs] btrfs_do_write_iter+0x53d/0x1590 [btrfs] btrfs_file_write_iter+0x41/0x60 [btrfs] aio_write+0x41e/0x5f0 io_submit_one+0xd42/0x1ce0 __se_sys_io_submit+0xb3/0x250 do_syscall_64+0xc1/0x190 entry_SYSCALL_64_after_hwframe+0x77/0x7f ``` The call chain after traceability is as follows: ``` Thread1: btrfs_delayed_update_inode() -> fill_stack_inode_item() -> inode_get_ctime_sec() Thread2: btrfs_write_check() -> update_time_for_write() -> inode_set_ctime_to_ts() ``` To address this issue, it is recommended to add WRITE_ONCE when writing the `inode->i_ctime_sec` variable. -------------------------------------------------------------- Signed-off-by: Hao-ran Zheng <zhenghaoran@buaa.edu.cn> --- include/linux/fs.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)