On Wed, Dec 22, 2010 at 04:27:36PM -0800, Andrew Morton wrote:
> On Fri, 10 Dec 2010 15:31:26 +0800
> shaohui.zheng@xxxxxxxxx wrote:
>
> > From: Shaohui Zheng <shaohui.zheng@xxxxxxxxx>
> >
> > Add add_memory interface to support to memory hotplug emulation for each online
> > node under debugfs. The reserved memory can be added into desired node with
> > this interface.
> >
> > The layout on debugfs:
> > mem_hotplug/node0/add_memory
> > mem_hotplug/node1/add_memory
> > mem_hotplug/node2/add_memory
> > ...
> >
> > Add a memory section(128M) to node 3(boots with mem=1024m)
> >
> > echo 0x40000000 > mem_hotplug/node3/add_memory
> >
> >
> > ...
> >
> > +#ifdef CONFIG_ARCH_MEMORY_PROBE
> > +
> > +static ssize_t add_memory_store(struct file *file, const char __user *buf,
> > + size_t count, loff_t *ppos)
> > +{
> > + u64 phys_addr = 0;
>
> Even more unneeded initalisation.
>
> Please check the whole patchset for this. It's bad because it can
> sometimes generate more code and because it can sometimes hide bugs by
> suppressing used-uninitialsied warnings.
>
Yes, It is a my habit to initialize variable when define it. I will check them
one by one.
> > + int nid = file->private_data - NULL;
>
> Well that was sneaky.
>
> It would be more conventional to just use the typecast:
>
> int nid = (long)file->private_data;
>
>
An explicit typecast looks much better.
> > + int ret;
> > +
> > + printk(KERN_INFO "Add a memory section to node: %d.\n", nid);
> > + phys_addr = simple_strtoull(buf, NULL, 0);
>
> checkpatch
>
We ignored the warning for function simple_strtoull in the whole patchset.
We will solve it one by one.
> > + ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT);
> > + if (ret)
> > + count = ret;
> > +
> > + return count;
> > +}
> > +
> > +static int add_memory_open(struct inode *inode, struct file *file)
> > +{
> > + file->private_data = inode->i_private;
>
> Was this usage of i_private and private_data documented in comments
> somewhere?
>
Yes, I added the usage information when create the add_memory entry, it seems
that I should also add comment here.
/* the nid information was represented by the offset of pointer(NULL+nid) */
if (!debugfs_create_file("add_memory", S_IWUSR, node_debug_root,
NULL + nid, &add_memory_file_ops))
> > + return 0;
> > +}
> > +
> > +static const struct file_operations add_memory_file_ops = {
> > + .open = add_memory_open,
> > + .write = add_memory_store,
> > + .llseek = generic_file_llseek,
> > +};
> > +
> > +/*
> > + * Create add_memory debugfs entry under specified node
> > + */
> > +static int debugfs_create_add_memory_entry(int nid)
> > +{
> > + char buf[32];
> > + static struct dentry *node_debug_root;
> > +
> > + snprintf(buf, sizeof(buf), "node%d", nid);
> > + node_debug_root = debugfs_create_dir(buf, memhp_debug_root);
> > + if (!node_debug_root)
> > + return -ENOMEM;
>
> hm, debugfs_create_dir() was poorly designed - it should return an
> ERR_PTR() so callers don't need to assume ENOMEM, which may be incorrect.
>
Totally agree. I see that the simliar call on debugfs_create_dir. For the failure,
most of them assume ENOMEM, some of them assume as EINVAL.
> > + /* the nid information was represented by the offset of pointer(NULL+nid) */
> > + if (!debugfs_create_file("add_memory", S_IWUSR, node_debug_root,
> > + NULL + nid, &add_memory_file_ops))
> > + return -ENOMEM;
> > +
> > + return 0;
> > +}
> > +
> > +static int __init memory_debug_init(void)
> > +{
> > + int nid;
> > +
> > + if (!memhp_debug_root)
> > + memhp_debug_root = debugfs_create_dir("mem_hotplug", NULL);
> > + if (!memhp_debug_root)
> > + return -ENOMEM;
> > +
> > + for_each_online_node(nid)
> > + debugfs_create_add_memory_entry(nid);
> > +
> > + return 0;
> > +}
> > +
> > +module_init(memory_debug_init);
> > +#else
> > +static debugfs_create_add_memory_entry(int nid)
>
> "static int".
>
Good catching.
> > +{
> > + return 0;
> > +}
> > +#endif /* CONFIG_ARCH_MEMORY_PROBE */
> > +
> > static ssize_t add_node_store(struct file *file, const char __user *buf,
> > size_t count, loff_t *ppos)
> > {
> > @@ -963,6 +1038,8 @@
> > return -ENOMEM;
> >
> > ret = add_memory(nid, start, size);
> > +
> > + debugfs_create_add_memory_entry(nid);
> > return ret ? ret : count;
> > }
> >
> >
> > ...
> >
--
Thanks & Regards,
Shaohui
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