From: Peter Xu <peterx@redhat.com>
To: David Stevens <stevensd@chromium.org>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Yang Shi <shy828301@gmail.com>,
David Hildenbrand <david@redhat.com>,
Hugh Dickins <hughd@google.com>, Jiaqi Yan <jiaqiyan@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/khugepaged: fix iteration in collapse_file
Date: Wed, 7 Jun 2023 15:13:46 -0400 [thread overview]
Message-ID: <ZIDW6qFAIwrYBOob@x1n> (raw)
In-Reply-To: <20230607053135.2087354-1-stevensd@google.com>
On Wed, Jun 07, 2023 at 02:31:35PM +0900, David Stevens wrote:
> From: David Stevens <stevensd@chromium.org>
>
> Remove an unnecessary call to xas_set(index) when iterating over the
> target range in collapse_file. The extra call to xas_set reset the xas
> cursor to the top of the tree, causing the xas_next call on the next
> iteration to walk the tree to index instead of advancing to index+1.
> This returned the same page again, which would cause collapse_file to
> fail because the page is already locked.
>
> This bug was hidden when CONFIG_DEBUG_VM was set. When that config was
> used, the xas_load in a subsequent VM_BUG_ON assert would walk xas from
> the top of the tree to index, causing the xas_next call on the next loop
> iteration to advance the cursor as expected.
>
> Fixes: a2e17cc2efc7 ("mm/khugepaged: maintain page cache uptodate flag")
> Signed-off-by: David Stevens <stevensd@chromium.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
--
Peter Xu
next prev parent reply other threads:[~2023-06-07 19:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-07 5:31 David Stevens
2023-06-07 19:13 ` Peter Xu [this message]
2023-06-09 20:02 ` Hugh Dickins
2023-06-10 1:45 ` David Stevens
2023-06-11 18:26 ` Hugh Dickins
2023-06-25 19:06 ` [PATCH] mm/khugepaged: fix regression in collapse_file() Hugh Dickins
2023-06-25 19:42 ` Linus Torvalds
2023-06-29 4:31 ` [PATCH hotfix] " Hugh Dickins
2023-06-29 16:42 ` Linus Torvalds
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