linux-kernel - Re: [PATCH 3/6] drivers/IB,qib: do not use mmap

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Message-ID: <20190128233140.GA12530@ziepe.ca>
Date:   Mon, 28 Jan 2019 16:31:40 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     akpm@...ux-foundation.org, dledford@...hat.com, jack@...e.de,
        ira.weiny@...el.com, linux-rdma@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        dennis.dalessandro@...el.com, mike.marciniszyn@...el.com,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 3/6] drivers/IB,qib: do not use mmap_sem

On Mon, Jan 21, 2019 at 09:42:17AM -0800, Davidlohr Bueso wrote:
> The driver uses mmap_sem for both pinned_vm accounting and
> get_user_pages(). By using gup_fast() and letting the mm handle
> the lock if needed, we can no longer rely on the semaphore and
> simplify the whole thing as the pinning is decoupled from the lock.
> 
> This also fixes a bug that __qib_get_user_pages was not taking into
> account the current value of pinned_vm.
> 
> Cc: dennis.dalessandro@...el.com
> Cc: mike.marciniszyn@...el.com
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
> ---
>  drivers/infiniband/hw/qib/qib_user_pages.c | 67 ++++++++++--------------------
>  1 file changed, 22 insertions(+), 45 deletions(-)

I need you to respin this patch/series against the latest rdma tree:

git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git

branch for-next

> diff --git a/drivers/infiniband/hw/qib/qib_user_pages.c b/drivers/infiniband/hw/qib/qib_user_pages.c
> -static int __qib_get_user_pages(unsigned long start_page, size_t num_pages,
> -				struct page **p)
> -{
> -	unsigned long lock_limit;
> -	size_t got;
> -	int ret;
> -
> -	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> -
> -	if (num_pages > lock_limit && !capable(CAP_IPC_LOCK)) {
> -		ret = -ENOMEM;
> -		goto bail;
> -	}
> -
> -	for (got = 0; got < num_pages; got += ret) {
> -		ret = get_user_pages(start_page + got * PAGE_SIZE,
> -				     num_pages - got,
> -				     FOLL_WRITE | FOLL_FORCE,
> -				     p + got, NULL);

As this has been rightly changed to get_user_pages_longterm, and I
think the right answer to solve the conflict is to discard some of
this patch?

Since Andrew is OK with this I can move this ahead once this is
resolved, thanks.

Jason