From: "Kuehling, Felix" <Felix.Kuehling@amd.com>
To: "Christoph Hellwig" <hch@lst.de>,
"Dan Williams" <dan.j.williams@intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Ben Skeggs" <bskeggs@redhat.com>,
"Yang, Philip" <Philip.Yang@amd.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"nouveau@lists.freedesktop.org" <nouveau@lists.freedesktop.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 19/22] mm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot}
Date: Tue, 2 Jul 2019 21:43:58 +0000 [thread overview]
Message-ID: <fedf75d4-4ce2-e0cc-3c77-73ba31bed653@amd.com> (raw)
In-Reply-To: <20190701062020.19239-20-hch@lst.de>
On 2019-07-01 2:20 a.m., Christoph Hellwig wrote:
> We should not have two different error codes for the same condition. In
> addition this really complicates the code due to the special handling of
> EAGAIN that drops the mmap_sem due to the FAULT_FLAG_ALLOW_RETRY logic
> in the core vm.
I think the comment above hmm_range_snapshot needs an update. Also
Documentation/vm/hmm.rst shows some example code using
hmm_range_snapshot that retries on -EAGAIN. That would need to be
updated to use -EBUSY or remove the retry logic altogether.
Other than that, this patch is Reviewed-by: Felix Kuehling
<Felix.Kuehling@amd.com>
Philip, this means we should remove our retry logic again in
amdgpu_ttm_tt_get_user_pages. According to the comment above
hmm_range_fault, it can only return -EAGAIN if the block parameter is
false. I think this statement is now actually true. We set block=true,
so we can't get -EAGAIN. On -EBUSY we can let
amdgpu_amdkfd_restore_userptr_worker schedule the retry (which it does
already anyway).
Regards,
Felix
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> mm/hmm.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index c85ed7d4e2ce..d125df698e2b 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -974,7 +974,7 @@ long hmm_range_snapshot(struct hmm_range *range)
> do {
> /* If range is no longer valid force retry. */
> if (!range->valid)
> - return -EAGAIN;
> + return -EBUSY;
>
> vma = find_vma(hmm->mm, start);
> if (vma == NULL || (vma->vm_flags & device_vma))
> @@ -1069,10 +1069,8 @@ long hmm_range_fault(struct hmm_range *range, bool block)
>
> do {
> /* If range is no longer valid force retry. */
> - if (!range->valid) {
> - up_read(&hmm->mm->mmap_sem);
> - return -EAGAIN;
> - }
> + if (!range->valid)
> + return -EBUSY;
>
> vma = find_vma(hmm->mm, start);
> if (vma == NULL || (vma->vm_flags & device_vma))
next prev parent reply other threads:[~2019-07-02 21:44 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 6:19 dev_pagemap related cleanups v4 Christoph Hellwig
2019-07-01 6:19 ` [PATCH 01/22] mm/hmm.c: suppress compilation warnings when CONFIG_HUGETLB_PAGE is not set Christoph Hellwig
2019-07-01 6:20 ` [PATCH 02/22] mm/hmm: update HMM documentation Christoph Hellwig
2019-07-01 6:20 ` [PATCH 03/22] mm/hmm: clean up some coding style and comments Christoph Hellwig
2019-07-01 6:20 ` [PATCH 04/22] mm/hmm: support automatic NUMA balancing Christoph Hellwig
2019-07-01 6:20 ` [PATCH 05/22] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for non-blocking Christoph Hellwig
2019-07-01 6:20 ` [PATCH 06/22] mm/hmm: fix use after free with struct hmm in the mmu notifiers Christoph Hellwig
2019-07-01 6:20 ` [PATCH 07/22] mm/hmm: Use hmm_mirror not mm as an argument for hmm_range_register Christoph Hellwig
2019-07-01 6:20 ` [PATCH 08/22] mm/hmm: Hold a mmgrab from hmm to mm Christoph Hellwig
2019-07-01 6:20 ` [PATCH 09/22] mm/hmm: Simplify hmm_get_or_create and make it reliable Christoph Hellwig
2019-07-01 6:20 ` [PATCH 10/22] mm/hmm: Remove duplicate condition test before wait_event_timeout Christoph Hellwig
2019-07-01 6:20 ` [PATCH 11/22] mm/hmm: Do not use list*_rcu() for hmm->ranges Christoph Hellwig
2019-07-01 6:20 ` [PATCH 12/22] mm/hmm: Hold on to the mmget for the lifetime of the range Christoph Hellwig
2019-07-01 6:20 ` [PATCH 13/22] mm/hmm: Use lockdep instead of comments Christoph Hellwig
2019-07-01 6:20 ` [PATCH 14/22] mm/hmm: Remove racy protection against double-unregistration Christoph Hellwig
2019-07-01 6:20 ` [PATCH 15/22] mm/hmm: Poison hmm_range during unregister Christoph Hellwig
2019-07-01 6:20 ` [PATCH 16/22] mm/hmm: Remove confusing comment and logic from hmm_release Christoph Hellwig
2019-07-01 6:20 ` [PATCH 17/22] mm/hmm: Fix error flows in hmm_invalidate_range_start Christoph Hellwig
2019-07-01 6:20 ` [PATCH 18/22] mm: return valid info from hmm_range_unregister Christoph Hellwig
2019-07-03 17:22 ` Ralph Campbell
2019-07-01 6:20 ` [PATCH 19/22] mm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot} Christoph Hellwig
2019-07-02 21:43 ` Kuehling, Felix [this message]
2019-07-03 17:32 ` Ralph Campbell
2019-07-01 6:20 ` [PATCH 20/22] mm: move hmm_vma_fault to nouveau Christoph Hellwig
2019-07-03 17:48 ` Ralph Campbell
2019-07-03 17:50 ` [Nouveau] " Ilia Mirkin
2019-07-03 18:03 ` Jason Gunthorpe
2019-07-03 18:05 ` Christoph Hellwig
2019-07-03 18:13 ` Jason Gunthorpe
2019-07-01 6:20 ` [PATCH 21/22] nouveau: unlock mmap_sem on all errors from nouveau_range_fault Christoph Hellwig
2019-07-01 6:20 ` [PATCH 22/22] mm: remove the legacy hmm_pfn_* APIs Christoph Hellwig
2019-07-03 18:01 ` Jason Gunthorpe
2019-07-03 18:03 ` Christoph Hellwig
2019-07-03 18:15 ` Jason Gunthorpe
2019-07-01 8:25 ` dev_pagemap related cleanups v4 Christoph Hellwig
2019-07-02 18:42 ` Jason Gunthorpe
2019-07-02 22:45 ` Weiny, Ira
2019-07-02 22:47 ` Christoph Hellwig
2019-07-02 23:17 ` Dan Williams
2019-07-03 1:08 ` Jason Gunthorpe
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