From: Marc Dionne <marc.dionne@auristor.com>
To: David Howells <dhowells@redhat.com>
Cc: linux-afs@lists.infradead.org,
Markus Suvanto <markus.suvanto@gmail.com>,
linux-fsdevel@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/6] afs: Fix page leak
Date: Wed, 8 Sep 2021 17:37:02 -0300 [thread overview]
Message-ID: <CAB9dFdtNJBYp-e5TeTUQW5vuHGp6x+j_KPwxnkTuxvdJ-SY3pw@mail.gmail.com> (raw)
In-Reply-To: <163111666635.283156.177701903478910460.stgit@warthog.procyon.org.uk>
On Wed, Sep 8, 2021 at 12:58 PM David Howells <dhowells@redhat.com> wrote:
>
> There's a loop in afs_extend_writeback() that adds extra pages to a write
> we want to make to improve the efficiency of the writeback by making it
> larger. This loop stops, however, if we hit a page we can't write back
> from immediately, but it doesn't get rid of the page ref we speculatively
> acquired.
>
> This was caused by the removal of the cleanup loop when the code switched
> from using find_get_pages_contig() to xarray scanning as the latter only
> gets a single page at a time, not a batch.
>
> Fix this by putting the page on a ref on an early break from the loop.
> Unfortunately, we can't just add that page to the pagevec we're employing
> as we'll go through that and add those pages to the RPC call.
>
> This was found by the generic/074 test. It leaks ~4GiB of RAM each time it
> is run - which can be observed with "top".
>
> Fixes: e87b03f5830e ("afs: Prepare for use of THPs")
> Reported-by: Marc Dionne <marc.dionne@auristor.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: linux-afs@lists.infradead.org
> ---
>
> fs/afs/write.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/fs/afs/write.c b/fs/afs/write.c
> index c0534697268e..66b235266893 100644
> --- a/fs/afs/write.c
> +++ b/fs/afs/write.c
> @@ -471,13 +471,18 @@ static void afs_extend_writeback(struct address_space *mapping,
> }
>
> /* Has the page moved or been split? */
> - if (unlikely(page != xas_reload(&xas)))
> + if (unlikely(page != xas_reload(&xas))) {
> + put_page(page);
> break;
> + }
>
> - if (!trylock_page(page))
> + if (!trylock_page(page)) {
> + put_page(page);
> break;
> + }
> if (!PageDirty(page) || PageWriteback(page)) {
> unlock_page(page);
> + put_page(page);
> break;
> }
>
> @@ -487,6 +492,7 @@ static void afs_extend_writeback(struct address_space *mapping,
> t = afs_page_dirty_to(page, priv);
> if (f != 0 && !new_content) {
> unlock_page(page);
> + put_page(page);
> break;
> }
>
>
>
>
Reviewed-By: Marc Dionne <marc.dionne@auristor.com>
Tested-By: Marc Dionne <marc.dionne@auristor.com>
Marc
next prev parent reply other threads:[~2021-09-08 20:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-08 15:57 [PATCH 0/6] afs: Fixes for 3rd party-induced data corruption David Howells
2021-09-08 15:57 ` [PATCH 1/6] afs: Fix missing put on afs_read objects and missing get on the key therein David Howells
2021-09-10 21:10 ` Marc Dionne
2021-09-08 15:57 ` [PATCH 2/6] afs: Fix page leak David Howells
2021-09-08 20:37 ` Marc Dionne [this message]
2021-09-08 15:57 ` [PATCH 3/6] afs: Add missing vnode validation checks David Howells
2021-09-08 15:58 ` [PATCH 4/6] afs: Fix incorrect triggering of sillyrename on 3rd-party invalidation David Howells
2021-09-08 15:58 ` [PATCH 5/6] afs: Fix mmap coherency vs 3rd-party changes David Howells
2021-09-08 15:58 ` [PATCH 6/6] afs: Try to avoid taking RCU read lock when checking vnode validity David Howells
2021-09-09 7:40 ` [PATCH 0/6] afs: Fixes for 3rd party-induced data corruption markus.suvanto
2021-09-10 21:19 ` [PATCH 7/6] afs: Fix corruption in reads at fpos 2G-4G from an OpenAFS server David Howells
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