Re: [RFC PATCH] mm: trace filemap add and del

Robert Jarzmik
2012-11-21T10:36:21Z

Andrew Morton <akpm@linux-foundation.org> writes:
>> + TP_STRUCT__entry(
>> + __field(struct page *, page)
>> + __field(unsigned long, i_no)
>
> May as well call this i_ino - there's little benefit in using a
> different identifier.
Agreed for patch V2.
>
>> + __field(unsigned long, pageofs)
>
> "index".
Agreed for patch V2.

>
>> + __field(dev_t, s_dev)
>
> Perhaps use super_block.s_id here
If you imply by that that dereferencing page->mapping->host->i_sb and looking
for field s_dev, then I don't agree. Sometimes i_sb is NULL from what I recall,
especially in cases where the read page is from a journaling partition.

So unless I didn't understand you, I'll keep this part as well as the following,
to cover :
- a mapping of an actual file
- a mapping of a partition block

>
>> + ),
>> +
>> + TP_fast_assign(
>> + __entry->page = page;
>> + __entry->i_no = page->mapping->host->i_ino;
>> + __entry->pageofs = page->index;
>> + if (page->mapping->host->i_sb)
>> + __entry->s_dev = page->mapping->host->i_sb->s_dev;
>> + else
>> + __entry->s_dev = page->mapping->host->i_rdev;
>
> and hence avoid all this stuff.
See above.

>
>> + ),
>> +
>> + TP_printk("page=%p pfn=%lu blk=%d:%d inode+ofs=%lu+%lu",
>> + __entry->page,
>> + page_to_pfn(__entry->page),
>> + MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
>> + __entry->i_no,
>> + __entry->pageofs << PAGE_SHIFT)
>> +);
>> +
>> +TRACE_EVENT(mm_filemap_add_to_page_cache,
>
Agreed for patch V2.

Thanks for the review.

--
Robert