From: SeongJae Park <sjpark@amazon.com>
To: <gregkh@linuxfoundation.org>, <sashal@kernel.org>,
<stable@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
"Josef Bacik" <josef@toxicpanda.com>, Robert Stupp <snazy@gmx.de>,
Minchan Kim <minchan@kernel.org>, Jan Kara <jack@suse.cz>
Subject: Re: [PATCH] mm: Don't bother dropping mmap_sem for zero size readahead
Date: Thu, 30 Jul 2020 13:34:35 +0200 [thread overview]
Message-ID: <20200730113435.2280-1-sjpark@amazon.com> (raw)
In-Reply-To: <20200212101356.30759-1-jack@suse.cz>
Hello,
The commit fixed by this patch[1] was merged in v5.1 and this patch was merged
in the mainline in v5.7 (5c72feee3e45b40a3c96c7145ec422899d0e8964). Thus, the
issue affects [v5.1, v5.6]. I was also able to reproduce the issue and confirm
the fix works on v5.4 based kernels.
However, I couldn't find this fix in neither latest stable/linux-5.4.y, nor
stable-queue/master. Could you please put this patch in the queue?
[1] https://lore.kernel.org/linux-mm/20200212101356.30759-1-jack@suse.cz/
Thanks,
SeongJae Park
On Wed, 12 Feb 2020 11:13:56 +0100 Jan Kara <jack@suse.cz> wrote:
> When handling a page fault, we drop mmap_sem to start async readahead so
> that we don't block on IO submission with mmap_sem held. However
> there's no point to drop mmap_sem in case readahead is disabled. Handle
> that case to avoid pointless dropping of mmap_sem and retrying the
> fault. This was actually reported to block mlockall(MCL_CURRENT)
> indefinitely.
>
> Fixes: 6b4c9f446981 ("filemap: drop the mmap_sem for all blocking operations")
> Reported-by: Minchan Kim <minchan@kernel.org>
> Reported-by: Robert Stupp <snazy@gmx.de>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> mm/filemap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Andrew, could you please pick up this patch? Minchan also tripped over this
> bug...
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 1146fcfa3215..3d39c437b07e 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2458,7 +2458,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
> pgoff_t offset = vmf->pgoff;
>
> /* If we don't want any read-ahead, don't bother */
> - if (vmf->vma->vm_flags & VM_RAND_READ)
> + if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
> return fpin;
> if (ra->mmap_miss > 0)
> ra->mmap_miss--;
> --
> 2.16.4
next parent reply other threads:[~2020-07-30 11:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200212101356.30759-1-jack@suse.cz>
2020-07-30 11:34 ` SeongJae Park [this message]
2020-08-01 10:39 ` [PATCH] mm: Don't bother dropping mmap_sem for zero size readahead Greg KH
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