* Re: [PATCH] mm: Don't bother dropping mmap_sem for zero size readahead
[not found] <20200212101356.30759-1-jack@suse.cz>
@ 2020-07-30 11:34 ` SeongJae Park
2020-08-01 10:39 ` Greg KH
0 siblings, 1 reply; 2+ messages in thread
From: SeongJae Park @ 2020-07-30 11:34 UTC (permalink / raw)
To: gregkh, sashal, stable
Cc: Andrew Morton, linux-mm, Josef Bacik, Robert Stupp, Minchan Kim,
Jan Kara
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
^ permalink raw reply [flat|nested] 2+ messages in thread