linux-kernel - Re: [PATCH v3] mm/debug: __dump

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Date:   Tue, 12 Nov 2019 14:55:47 -0500
From:   Jerome Glisse <jglisse@...hat.com>
To:     Ralph Campbell <rcampbell@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm/debug: __dump_page() prints an extra line

On Mon, Nov 11, 2019 at 05:26:08PM -0800, Ralph Campbell wrote:
> When dumping struct page information, __dump_page() prints the page type
> with a trailing blank followed by the page flags on a separate line:
> 
> anon
> flags: 0x100000000090034(uptodate|lru|active|head|swapbacked)
> 
> It looks like the intent was to use pr_cont() for printing "flags:"
> but pr_cont() usage is discouraged so fix this by extending the format
> to include the flags into a single line:
> 
> anon flags: 0x100000000090034(uptodate|lru|active|head|swapbacked)
> 
> If the page is file backed, the name might be long so use two lines:
> 
> shmem_aops name:"dev/zero"
> flags: 0x10000000008000c(uptodate|dirty|swapbacked)
> 
> Eliminate pr_conf() usage as well for appending compound_mapcount.
> 
> Signed-off-by: Ralph Campbell <rcampbell@...dia.com>

Would be nice to have a changed since v1 v2 ... i was reading my
inbox in order and i saw Andrew reply after seeing the v2 ... so
where we at here ?

> ---
>  mm/debug.c | 27 +++++++++++++++------------
>  1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/mm/debug.c b/mm/debug.c
> index 8345bb6e4769..772d4cf0691f 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -67,28 +67,31 @@ void __dump_page(struct page *page, const char *reason)
>  	 */
>  	mapcount = PageSlab(page) ? 0 : page_mapcount(page);
>  
> -	pr_warn("page:%px refcount:%d mapcount:%d mapping:%px index:%#lx",
> -		  page, page_ref_count(page), mapcount,
> -		  page->mapping, page_to_pgoff(page));
>  	if (PageCompound(page))
> -		pr_cont(" compound_mapcount: %d", compound_mapcount(page));
> -	pr_cont("\n");
> +		pr_warn("page:%px refcount:%d mapcount:%d mapping:%px "
> +			"index:%#lx compound_mapcount: %d\n",
> +			page, page_ref_count(page), mapcount,
> +			page->mapping, page_to_pgoff(page),
> +			compound_mapcount(page));
> +	else
> +		pr_warn("page:%px refcount:%d mapcount:%d mapping:%px index:%#lx\n",
> +			page, page_ref_count(page), mapcount,
> +			page->mapping, page_to_pgoff(page));
>  	if (PageAnon(page))
> -		pr_warn("anon ");
> +		pr_warn("anon flags: %#lx(%pGp)\n", page->flags, &page->flags);
>  	else if (PageKsm(page))
> -		pr_warn("ksm ");
> +		pr_warn("ksm flags: %#lx(%pGp)\n", page->flags, &page->flags);
>  	else if (mapping) {
> -		pr_warn("%ps ", mapping->a_ops);
>  		if (mapping->host && mapping->host->i_dentry.first) {
>  			struct dentry *dentry;
>  			dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias);
> -			pr_warn("name:\"%pd\" ", dentry);
> -		}
> +			pr_warn("%ps name:\"%pd\"\n", mapping->a_ops, dentry);
> +		} else
> +			pr_warn("%ps\n", mapping->a_ops);
> +		pr_warn("flags: %#lx(%pGp)\n", page->flags, &page->flags);
>  	}
>  	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
>  
> -	pr_warn("flags: %#lx(%pGp)\n", page->flags, &page->flags);
> -
>  hex_only:
>  	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
>  			sizeof(unsigned long), page,
> -- 
> 2.20.1
> 
>