On Thu, Mar 13, 2014 at 05:39:42PM -0400, Naoya Horiguchi wrote:
> Unifying error reporting between memory error and normal IO errors is ideal
> in a long run, but at first let's solve it separately. I hope that some code
> in this patch will be helpful when thinking of the unification.
The mechanisms should be very similar, right?
It may be better to do both at the same time.
> index 60829565e552..1e8966919044 100644
> --- v3.14-rc6.orig/include/linux/fs.h
> +++ v3.14-rc6/include/linux/fs.h
> @@ -475,6 +475,9 @@ struct block_device {
> #define PAGECACHE_TAG_DIRTY 0
> #define PAGECACHE_TAG_WRITEBACK 1
> #define PAGECACHE_TAG_TOWRITE 2
> +#ifdef CONFIG_MEMORY_FAILURE
> +#define PAGECACHE_TAG_HWPOISON 3
> +#endif
No need to ifdef defines
> @@ -1133,6 +1139,10 @@ static void do_generic_file_read(struct file *filp, loff_t *ppos,
> if (unlikely(page == NULL))
> goto no_cached_page;
> }
> + if (unlikely(PageHWPoison(page))) {
> + error = -EHWPOISON;
> + goto readpage_error;
> + }
Didn't we need this check before independent of the rest of the patch?
> if (PageReadahead(page)) {
> page_cache_async_readahead(mapping,
> ra, filp, page,
> @@ -2100,6 +2110,10 @@ inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, i
> if (unlikely(*pos < 0))
> return -EINVAL;
>
> + if (unlikely(mapping_hwpoisoned_range(file->f_mapping, *pos,
> + *pos + *count)))
> + return -EHWPOISON;
How expensive is that check? This will happen on every write.
Can it be somehow combined with the normal page cache lookup?
> * Dirty pagecache page
> + *
> + * Memory error reporting (important especially on dirty pagecache error
> + * because dirty data is lost) with AS_EIO flag has some problems:
It doesn't make sense to have changelogs in comments. That is what
git is for. At some point noone will care about the previous code.
> + * To solve these, we handle dirty pagecache errors by replacing the error
This part of the comment is good.
> + pgoff_t index;
> + struct inode *inode = NULL;
> + struct page *new;
>
> SetPageError(p);
> - /* TBD: print more information about the file. */
> if (mapping) {
> + index = page_index(p);
> + /*
> + * we take inode refcount to keep it's pagecache or mapping
> + * on the memory until the error is resolved.
How does that work? Who "resolves" the error?
> + */
> + inode = igrab(mapping->host);
> + pr_info("MCE %#lx: memory error on dirty pagecache (page offset:%lu, inode:%lu, dev:%s)\n",
Add the word file somewhere, you need to explain this in terms normal
sysadmins and not only kernel hackers can understand.
-Andi
--
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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