From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 13/25] fs: Add zero_user_large
Date: Tue, 18 Feb 2020 17:16:34 +0300 [thread overview]
Message-ID: <20200218141634.zhhjgtv44ux23l3l@box> (raw)
In-Reply-To: <20200214160342.GA7778@bombadil.infradead.org>
On Fri, Feb 14, 2020 at 08:03:42AM -0800, Matthew Wilcox wrote:
> On Fri, Feb 14, 2020 at 04:52:48PM +0300, Kirill A. Shutemov wrote:
> > On Tue, Feb 11, 2020 at 08:18:33PM -0800, Matthew Wilcox wrote:
> > > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> > >
> > > We can't kmap() a THP, so add a wrapper around zero_user() for large
> > > pages.
> >
> > I would rather address it closer to the root: make zero_user_segments()
> > handle compound pages.
>
> Hah. I ended up doing that, but hadn't sent it out. I don't like
> how ugly it is:
>
> @@ -219,18 +219,57 @@ static inline void zero_user_segments(struct page *page,
> unsigned start1, unsigned end1,
> unsigned start2, unsigned end2)
> {
> - void *kaddr = kmap_atomic(page);
> -
> - BUG_ON(end1 > PAGE_SIZE || end2 > PAGE_SIZE);
> -
> - if (end1 > start1)
> - memset(kaddr + start1, 0, end1 - start1);
> -
> - if (end2 > start2)
> - memset(kaddr + start2, 0, end2 - start2);
> -
> - kunmap_atomic(kaddr);
> - flush_dcache_page(page);
> + unsigned int i;
> +
> + BUG_ON(end1 > thp_size(page) || end2 > thp_size(page));
> +
> + for (i = 0; i < hpage_nr_pages(page); i++) {
> + void *kaddr;
> + unsigned this_end;
> +
> + if (end1 == 0 && start2 >= PAGE_SIZE) {
> + start2 -= PAGE_SIZE;
> + end2 -= PAGE_SIZE;
> + continue;
> + }
> +
> + if (start1 >= PAGE_SIZE) {
> + start1 -= PAGE_SIZE;
> + end1 -= PAGE_SIZE;
> + if (start2) {
> + start2 -= PAGE_SIZE;
> + end2 -= PAGE_SIZE;
> + }
You assume start2/end2 is always after start1/end1 in the page.
Is it always true? If so, I would add BUG_ON() for it.
Otherwise, looks good.
> + continue;
> + }
> +
> + kaddr = kmap_atomic(page + i);
> +
> + this_end = min_t(unsigned, end1, PAGE_SIZE);
> + if (end1 > start1)
> + memset(kaddr + start1, 0, this_end - start1);
> + end1 -= this_end;
> + start1 = 0;
> +
> + if (start2 >= PAGE_SIZE) {
> + start2 -= PAGE_SIZE;
> + end2 -= PAGE_SIZE;
> + } else {
> + this_end = min_t(unsigned, end2, PAGE_SIZE);
> + if (end2 > start2)
> + memset(kaddr + start2, 0, this_end - start2);
> + end2 -= this_end;
> + start2 = 0;
> + }
> +
> + kunmap_atomic(kaddr);
> + flush_dcache_page(page + i);
> +
> + if (!end1 && !end2)
> + break;
> + }
> +
> + BUG_ON((start1 | start2 | end1 | end2) != 0);
> }
>
> I think at this point it has to move out-of-line too.
>
> > > +static inline void zero_user_large(struct page *page,
> > > + unsigned start, unsigned size)
> > > +{
> > > + unsigned int i;
> > > +
> > > + for (i = 0; i < thp_order(page); i++) {
> > > + if (start > PAGE_SIZE) {
> >
> > Off-by-one? >= ?
>
> Good catch; I'd also noticed that when I came to redo the zero_user_segments().
>
--
Kirill A. Shutemov
next prev parent reply other threads:[~2020-02-18 14:16 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-12 4:18 [PATCH v2 00/25] Large pages in the page cache Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 01/25] mm: Use vm_fault error code directly Matthew Wilcox
2020-02-12 7:34 ` Christoph Hellwig
2020-02-12 4:18 ` [PATCH v2 02/25] mm: Optimise find_subpage for !THP Matthew Wilcox
2020-02-12 7:41 ` Christoph Hellwig
2020-02-12 13:02 ` Matthew Wilcox
2020-02-12 17:52 ` Christoph Hellwig
2020-02-13 13:50 ` Kirill A. Shutemov
2020-02-12 4:18 ` [PATCH v2 03/25] mm: Use VM_BUG_ON_PAGE in clear_page_dirty_for_io Matthew Wilcox
2020-02-12 7:38 ` Christoph Hellwig
2020-02-13 13:50 ` Kirill A. Shutemov
2020-02-12 4:18 ` [PATCH v2 04/25] mm: Unexport find_get_entry Matthew Wilcox
2020-02-12 7:37 ` Christoph Hellwig
2020-02-13 13:51 ` Kirill A. Shutemov
2020-02-12 4:18 ` [PATCH v2 05/25] mm: Fix documentation of FGP flags Matthew Wilcox
2020-02-12 7:42 ` Christoph Hellwig
2020-02-12 19:11 ` Matthew Wilcox
2020-02-13 14:00 ` Kirill A. Shutemov
2020-02-13 13:59 ` Kirill A. Shutemov
2020-02-13 14:34 ` Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 06/25] mm: Allow hpages to be arbitrary order Matthew Wilcox
2020-02-13 14:11 ` Kirill A. Shutemov
2020-02-13 14:30 ` Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 07/25] mm: Introduce thp_size Matthew Wilcox
2020-02-13 14:19 ` Kirill A. Shutemov
2020-02-12 4:18 ` [PATCH v2 08/25] mm: Introduce thp_order Matthew Wilcox
2020-02-13 14:20 ` Kirill A. Shutemov
2020-02-12 4:18 ` [PATCH v2 09/25] fs: Add a filesystem flag for large pages Matthew Wilcox
2020-02-12 7:43 ` Christoph Hellwig
2020-02-12 14:59 ` Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 10/25] fs: Introduce i_blocks_per_page Matthew Wilcox
2020-02-12 7:44 ` Christoph Hellwig
2020-02-12 15:05 ` Matthew Wilcox
2020-02-12 17:54 ` Christoph Hellwig
2020-02-13 15:40 ` Kirill A. Shutemov
2020-02-13 16:07 ` Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 11/25] fs: Make page_mkwrite_check_truncate thp-aware Matthew Wilcox
2020-02-13 15:44 ` Kirill A. Shutemov
2020-02-13 16:26 ` Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 12/25] mm: Add file_offset_of_ helpers Matthew Wilcox
2020-02-12 7:46 ` Christoph Hellwig
2020-02-12 4:18 ` [PATCH v2 13/25] fs: Add zero_user_large Matthew Wilcox
2020-02-14 13:52 ` Kirill A. Shutemov
2020-02-14 16:03 ` Matthew Wilcox
2020-02-18 14:16 ` Kirill A. Shutemov [this message]
2020-02-18 16:13 ` Matthew Wilcox
2020-02-18 17:10 ` Kirill A. Shutemov
2020-02-18 18:07 ` Matthew Wilcox
2020-02-21 12:42 ` Kirill A. Shutemov
2020-02-12 4:18 ` [PATCH v2 14/25] iomap: Support arbitrarily many blocks per page Matthew Wilcox
2020-02-12 8:05 ` Christoph Hellwig
2020-02-12 4:18 ` [PATCH v2 15/25] iomap: Support large pages in iomap_adjust_read_range Matthew Wilcox
2020-02-12 8:11 ` Christoph Hellwig
2020-02-12 4:18 ` [PATCH v2 16/25] iomap: Support large pages in read paths Matthew Wilcox
2020-02-12 8:13 ` Christoph Hellwig
2020-02-12 17:45 ` Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 17/25] iomap: Support large pages in write paths Matthew Wilcox
2020-02-12 8:17 ` Christoph Hellwig
2020-02-12 4:18 ` [PATCH v2 18/25] iomap: Inline data shouldn't see large pages Matthew Wilcox
2020-02-12 8:05 ` Christoph Hellwig
2020-02-12 4:18 ` [PATCH v2 19/25] xfs: Support " Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 20/25] mm: Make prep_transhuge_page return its argument Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 21/25] mm: Add __page_cache_alloc_order Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 22/25] mm: Allow large pages to be added to the page cache Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 23/25] mm: Allow large pages to be removed from " Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 24/25] mm: Add large page readahead Matthew Wilcox
2020-02-12 4:18 ` [PATCH v2 25/25] mm: Align THP mappings for non-DAX Matthew Wilcox
2020-02-12 7:50 ` Christoph Hellwig
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