Re: [PATCH 2/2 v2] mm: print out information of file affected by memory error

Andrew Morton
2012-11-05T22:01:57Z

On Fri, 2 Nov 2012 12:33:13 -0400
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:

> Printing out the information about which file can be affected by a
> memory error in generic_error_remove_page() is helpful for user to
> estimate the impact of the error.
>
> Changelog v2:
> - dereference mapping->host after if (!mapping) check for robustness
>
> ...
>
> --- v3.7-rc3.orig/mm/truncate.c
> +++ v3.7-rc3/mm/truncate.c
> @@ -151,14 +151,20 @@ int truncate_inode_page(struct address_space *mapping, struct page *page)
> */
> int generic_error_remove_page(struct address_space *mapping, struct page *page)
> {
> + struct inode *inode;
> +
> if (!mapping)
> return -EINVAL;
> + inode = mapping->host;
> /*
> * Only punch for normal data pages for now.
> * Handling other types like directories would need more auditing.
> */
> - if (!S_ISREG(mapping->host->i_mode))
> + if (!S_ISREG(inode->i_mode))
> return -EIO;
> + pr_info("MCE %#lx: file info pgoff:%lu, inode:%lu, dev:%s\n",
> + page_to_pfn(page), page_index(page),
> + inode->i_ino, inode->i_sb->s_id);
> return truncate_inode_page(mapping, page);
> }
> EXPORT_SYMBOL(generic_error_remove_page);

A couple of things.

- I worry that if a hardware error occurs, it might affect a large
amount of memory all at the same time. For example, if a 4G memory
block goes bad, this message will be printed a million times?

- hard-wiring "MCE" in here seems a bit of a layering violation?
What right does the generic, core .error_remove_page() implementation
have to assume that it was called because of an MCE? Many CPU types
don't eveh have such a thing?