On Thu, Feb 09, 2017 at 01:55:05PM -0800, Matthew Wilcox wrote: > On Thu, Jan 26, 2017 at 02:57:50PM +0300, Kirill A. Shutemov wrote: > > +++ b/mm/filemap.c > > @@ -1886,6 +1886,7 @@ static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos, > > if (unlikely(page == NULL)) > > goto no_cached_page; > > } > > + page = compound_head(page); > > We got this page from find_get_page(), which gets it from > pagecache_get_page(), which gets it from find_get_entry() ... which > (unless I'm lost in your patch series) returns the head page. So this > line is redundant, right? No. pagecache_get_page() returns subpage. See description of the first patch. > But then down in filemap_fault, we have: > > VM_BUG_ON_PAGE(page->index != offset, page); > > ... again, maybe I'm lost somewhere in your patch series, but I don't see > anywhere you remove that line (or modify it). This should be fine as find_get_page() returns subpage. > So are you not testing > with VM debugging enabled, or are you not doing a test which includes > mapping a file with huge pages, reading from it (to get the page in cache), > then faulting on an address that is not in the first 4kB of that 2MB? > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Kirill A. Shutemov
