On Tue, May 10, 2022 at 12:22:42PM +0000, cgel.zte@xxxxxxxxx wrote:
> +++ b/Documentation/admin-guide/mm/ksm.rst
> @@ -32,7 +32,7 @@ are swapped back in: ksmd must rediscover their identity and merge again).
> Controlling KSM with madvise
> ============================
>
> -KSM only operates on those areas of address space which an application
> +KSM can operates on those areas of address space which an application
"can operate on"
> +static ssize_t ksm_force_write(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct task_struct *task;
> + struct mm_struct *mm;
> + char buffer[PROC_NUMBUF];
> + int force;
> + int err = 0;
> +
> + memset(buffer, 0, sizeof(buffer));
> + if (count > sizeof(buffer) - 1)
> + count = sizeof(buffer) - 1;
> + if (copy_from_user(buffer, buf, count))
> + return -EFAULT;
> +
> + err = kstrtoint(strstrip(buffer), 0, &force);
> + if (err)
> + return err;
> +
> + if (force != 0 && force != 1)
> + return -EINVAL;
> +
> + task = get_proc_task(file_inode(file));
> + if (!task)
> + return -ESRCH;
> +
> + mm = get_task_mm(task);
> + if (!mm)
> + goto out_put_task;
> +
> + if (mm->ksm_force != force) {
> + if (mmap_write_lock_killable(mm)) {
> + err = -EINTR;
> + goto out_mmput;
> + }
> +
> + if (force == 0)
> + mm->ksm_force = force;
> + else {
> + /*
> + * Force anonymous pages of this mm to be involved in KSM merging
> + * without explicitly calling madvise.
> + */
> + if (!test_bit(MMF_VM_MERGEABLE, &mm->flags))
> + err = __ksm_enter(mm);
> + if (!err)
> + mm->ksm_force = force;
> + }
> +
> + mmap_write_unlock(mm);
> + }
There's a much simpler patch hiding inside this complicated one.
if (force) {
set_bit(MMF_VM_MERGEABLE, &mm->flags));
for each VMA
set VM_MERGEABLE;
err = __ksm_enter(mm);
} else {
clear_bit(MMF_VM_MERGEABLE, &mm->flags));
for each VMA
clear VM_MERGEABLE;
}
... and all the extra complications you added go away.
