Re: [RFC v4+ hot_track 12/19] vfs: add one ioctl interface

On Mon, Oct 29, 2012 at 12:30:54PM +0800, zwu.kernel@gmail.com wrote:

+static int ioctl_heat_info(struct file *file, void __user *argp)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	struct hot_heat_info *heat_info;
+	struct hot_inode_item *he;
+	int ret = 0;
+
+	heat_info = kmalloc(sizeof(struct hot_heat_info),
+				GFP_KERNEL | GFP_NOFS);

heat_info is small enough to fit onto the stack, so you can avoid the
kmalloc, I don't think there are deep callstacks to be expected.
Nevertheless, if you want to use kmalloc here, then please check the
return value and use GFP_KERNEL.

+
+	if (copy_from_user((void *) heat_info,
+			argp,
+			sizeof(struct hot_heat_info)) != 0) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	he = hot_inode_item_find(inode->i_sb->s_hot_root, inode->i_ino);
+	if (!he) {
+		/* we don't have any info on this file yet */
+		ret = -ENODATA;
+		goto err;
+	}
+
+	spin_lock(&he->hot_inode.lock);
+	heat_info->avg_delta_reads =
+		(__u64) he->hot_inode.hot_freq_data.avg_delta_reads;
+	heat_info->avg_delta_writes =
+		(__u64) he->hot_inode.hot_freq_data.avg_delta_writes;
+	heat_info->last_read_time =
+	(__u64) timespec_to_ns(&he->hot_inode.hot_freq_data.last_read_time);
+	heat_info->last_write_time =
+	(__u64) timespec_to_ns(&he->hot_inode.hot_freq_data.last_write_time);
+	heat_info->num_reads =
+		(__u32) he->hot_inode.hot_freq_data.nr_reads;
+	heat_info->num_writes =
+		(__u32) he->hot_inode.hot_freq_data.nr_writes;
+
+	if (heat_info->live > 0) {
+		/*
+		 * got a request for live temperature,
+		 * call hot_hash_calc_temperature to recalculate
+		 */
+		heat_info->temp =
+		inode->i_sb->s_hot_root->hot_func_type->ops.hot_temp_calc_fn(
+					&he->hot_inode.hot_freq_data);
+	} else {
+		/* not live temperature, get it from the hashlist */
+		heat_info->temp = he->hot_inode.hot_freq_data.last_temp;
+	}
+	spin_unlock(&he->hot_inode.lock);
+
+	hot_inode_item_put(he);
+
+	if (copy_to_user(argp, (void *) heat_info,
+			sizeof(struct hot_heat_info))) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+err:
+	kfree(heat_info);
+	return ret;
+}

david