From: Matthew Wilcox <willy@infradead.org>
To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-xfs@vger.kernel.org
Subject: Re: Splitting a THP beyond EOF
Date: Tue, 20 Oct 2020 15:26:53 +0100 [thread overview]
Message-ID: <20201020142653.GB20115@casper.infradead.org> (raw)
In-Reply-To: <20201020014357.GW20115@casper.infradead.org>
On Tue, Oct 20, 2020 at 02:43:57AM +0100, Matthew Wilcox wrote:
> I think the easiest way to fix this is to decline to allocate readahead
> pages beyond EOF. That is, if we have a file which is, say, 61 pages
> long, read the last 5 pages into an order-2 THP and an order-0 THP
> instead of allocating an order-3 THP and zeroing the last three pages.
Oh yeah, really easy.
+++ b/mm/readahead.c
@@ -481,6 +481,11 @@ void page_cache_ra_order(struct readahead_control *ractl,
if (order == 1)
order = 0;
}
+ /* Don't allocate pages past EOF */
+ while (index + (1UL << order) - 1 > limit) {
+ if (--order == 1)
+ order = 0;
+ }
err = ra_alloc_page(ractl, index, mark, order, gfp);
if (err)
break;
I've added that to an earlier patch and I've pushed out commit
cd3fa4bc6516 as the head of
http://git.infradead.org/users/willy/pagecache.git/shortlog
next prev parent reply other threads:[~2020-10-20 14:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 1:43 Splitting a THP beyond EOF Matthew Wilcox
2020-10-20 4:59 ` Dave Chinner
2020-10-20 11:21 ` Matthew Wilcox
2020-10-20 21:16 ` Dave Chinner
2020-10-20 22:53 ` Matthew Wilcox
2020-10-21 22:14 ` Dave Chinner
2020-10-21 23:04 ` Matthew Wilcox
2020-10-27 5:31 ` Dave Chinner
2020-10-27 12:14 ` Matthew Wilcox
2020-10-20 14:26 ` Matthew Wilcox [this message]
2020-10-20 14:32 ` Chris Mason
2020-10-21 0:23 ` Matthew Wilcox
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