From: Hugh Dickins <hughd@google.com>
To: Yang Shi <shy828301@gmail.com>
Cc: Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@kernel.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
David Hildenbrand <david@redhat.com>,
Suren Baghdasaryan <surenb@google.com>,
Qi Zheng <zhengqi.arch@bytedance.com>,
Mel Gorman <mgorman@techsingularity.net>,
Peter Xu <peterx@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
Alistair Popple <apopple@nvidia.com>,
Ralph Campbell <rcampbell@nvidia.com>,
Ira Weiny <ira.weiny@intel.com>,
Steven Price <steven.price@arm.com>,
SeongJae Park <sj@kernel.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Zack Rusin <zackr@vmware.com>, Jason Gunthorpe <jgg@ziepe.ca>,
Axel Rasmussen <axelrasmussen@google.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Minchan Kim <minchan@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
Song Liu <song@kernel.org>,
Thomas Hellstrom <thomas.hellstrom@linux.intel.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 25/31] mm/gup: remove FOLL_SPLIT_PMD use of pmd_trans_unstable()
Date: Thu, 25 May 2023 14:16:34 -0700 (PDT) [thread overview]
Message-ID: <7538c751-9bee-75f9-50a5-1bc12f919e8e@google.com> (raw)
In-Reply-To: <CAHbLzkrkGx-+OVLexWAx0THeOsD1C1DHt2VjgnkYJe-MqeW3Zw@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1130 bytes --]
On Wed, 24 May 2023, Yang Shi wrote:
> On Tue, May 23, 2023 at 9:26 PM Hugh Dickins <hughd@google.com> wrote:
> > On Mon, 22 May 2023, Yang Shi wrote:
> >
> > > For other unstable cases, it will return -ENOMEM instead of -EBUSY.
> >
> > I don't think so: the possibly-failing __pte_alloc() only gets called
> > in the pmd_none() case.
>
> I mean what if pmd is not none for huge zero page. If it is not
> pmd_none pte_alloc() just returns 0,
Yes, I agree with you on that.
> then returns -ENOMEM instead of -EBUSY.
But disagree with you on that.
return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) :
follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
Doesn't that say that if pte_alloc() returns 0, then follow_page_mask()
will call follow_page_pte() and return whatever that returns?
> Or it is impossible that pmd end up being pmd_huge_trans or
> !pmd_present? It should be very unlikely, for example, migration does
> skip huge zero page, but I'm not sure whether there is any corner case
> that I missed.
I'm assuming both are possible there (but not asserting that they are).
Hugh
next prev parent reply other threads:[~2023-05-25 21:16 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-22 4:46 [PATCH 00/31] mm: allow pte_offset_map[_lock]() to fail Hugh Dickins
2023-05-22 4:49 ` [PATCH 01/31] mm: use pmdp_get_lockless() without surplus barrier() Hugh Dickins
2023-05-24 22:29 ` Peter Xu
2023-05-25 22:35 ` Hugh Dickins
2023-05-26 16:48 ` Peter Xu
2023-05-24 22:54 ` Yu Zhao
2023-05-22 4:51 ` [PATCH 02/31] mm/migrate: remove cruft from migration_entry_wait()s Hugh Dickins
2023-05-23 1:45 ` Alistair Popple
2023-05-24 1:57 ` Hugh Dickins
2023-05-22 4:52 ` [PATCH 03/31] mm/pgtable: kmap_local_page() instead of kmap_atomic() Hugh Dickins
2023-05-26 22:22 ` Peter Xu
2023-05-26 22:42 ` Peter Xu
2023-05-22 4:53 ` [PATCH 04/31] mm/pgtable: allow pte_offset_map[_lock]() to fail Hugh Dickins
2023-05-22 11:17 ` Qi Zheng
2023-05-24 2:22 ` Hugh Dickins
2023-05-24 3:11 ` Qi Zheng
2023-07-05 14:48 ` Aneesh Kumar K.V
2023-07-05 22:26 ` Hugh Dickins
2023-05-22 4:54 ` [PATCH 05/31] mm/filemap: allow pte_offset_map_lock() " Hugh Dickins
2023-05-22 11:23 ` Qi Zheng
2023-05-24 2:35 ` Hugh Dickins
2023-05-24 3:14 ` Qi Zheng
2023-05-22 4:55 ` [PATCH 06/31] mm/page_vma_mapped: delete bogosity in page_vma_mapped_walk() Hugh Dickins
2023-05-22 4:57 ` [PATCH 07/31] mm/page_vma_mapped: reformat map_pte() with less indentation Hugh Dickins
2023-05-22 4:58 ` [PATCH 08/31] mm/page_vma_mapped: pte_offset_map_nolock() not pte_lockptr() Hugh Dickins
2023-05-22 11:41 ` Qi Zheng
2023-05-24 2:44 ` Hugh Dickins
2023-05-22 5:00 ` [PATCH 09/31] mm/pagewalkers: ACTION_AGAIN if pte_offset_map_lock() fails Hugh Dickins
2023-05-23 18:07 ` SeongJae Park
2023-05-22 5:01 ` [PATCH 10/31] mm/pagewalk: walk_pte_range() allow for pte_offset_map() Hugh Dickins
2023-05-22 5:03 ` [PATCH 11/31] mm/vmwgfx: simplify pmd & pud mapping dirty helpers Hugh Dickins
2023-05-22 5:04 ` [PATCH 12/31] mm/vmalloc: vmalloc_to_page() use pte_offset_kernel() Hugh Dickins
2023-05-22 7:27 ` Lorenzo Stoakes
2023-05-22 5:05 ` [PATCH 13/31] mm/hmm: retry if pte_offset_map() fails Hugh Dickins
2023-05-22 12:11 ` Qi Zheng
2023-05-23 2:39 ` Alistair Popple
2023-05-23 6:06 ` Qi Zheng
2023-05-24 2:50 ` Hugh Dickins
2023-05-24 5:16 ` Alistair Popple
2023-05-22 5:06 ` [PATCH 14/31] fs/userfaultfd: " Hugh Dickins
2023-05-24 22:31 ` Peter Xu
2023-05-22 5:07 ` [PATCH 15/31] mm/userfaultfd: allow pte_offset_map_lock() to fail Hugh Dickins
2023-05-24 22:44 ` Peter Xu
2023-05-25 22:06 ` Hugh Dickins
2023-05-26 16:25 ` Peter Xu
2023-05-22 5:08 ` [PATCH 16/31] mm/debug_vm_pgtable,page_table_check: warn pte map fails Hugh Dickins
2023-05-22 5:10 ` [PATCH 17/31] mm/various: give up if pte_offset_map[_lock]() fails Hugh Dickins
2023-05-22 12:24 ` Qi Zheng
2023-05-22 12:37 ` Qi Zheng
2023-05-24 3:20 ` Hugh Dickins
2023-05-22 5:12 ` [PATCH 18/31] mm/mprotect: delete pmd_none_or_clear_bad_unless_trans_huge() Hugh Dickins
2023-05-22 5:13 ` [PATCH 19/31] mm/mremap: retry if either pte_offset_map_*lock() fails Hugh Dickins
2023-05-22 5:15 ` [PATCH 20/31] mm/madvise: clean up pte_offset_map_lock() scans Hugh Dickins
2023-05-22 5:17 ` [PATCH 21/31] mm/madvise: clean up force_shm_swapin_readahead() Hugh Dickins
2023-05-22 5:18 ` [PATCH 22/31] mm/swapoff: allow pte_offset_map[_lock]() to fail Hugh Dickins
2023-05-22 5:19 ` [PATCH 23/31] mm/mglru: allow pte_offset_map_nolock() " Hugh Dickins
2023-05-22 5:26 ` Yu Zhao
2023-05-22 5:20 ` [PATCH 24/31] mm/migrate_device: allow pte_offset_map_lock() " Hugh Dickins
2023-05-23 2:23 ` Alistair Popple
2023-05-24 3:45 ` Hugh Dickins
2023-05-24 5:11 ` Alistair Popple
2023-05-22 5:22 ` [PATCH 25/31] mm/gup: remove FOLL_SPLIT_PMD use of pmd_trans_unstable() Hugh Dickins
2023-05-23 2:26 ` Yang Shi
2023-05-23 2:44 ` Yang Shi
2023-05-24 4:26 ` Hugh Dickins
2023-05-24 22:45 ` Yang Shi
2023-05-25 21:16 ` Hugh Dickins [this message]
2023-05-25 22:33 ` Yang Shi
2023-05-22 5:23 ` [PATCH 26/31] mm/huge_memory: split huge pmd under one pte_offset_map() Hugh Dickins
2023-05-22 23:35 ` Yang Shi
2023-05-22 5:24 ` [PATCH 27/31] mm/khugepaged: allow pte_offset_map[_lock]() to fail Hugh Dickins
2023-05-22 23:54 ` Yang Shi
2023-05-24 4:44 ` Hugh Dickins
2023-05-24 21:59 ` Yang Shi
2023-05-22 5:25 ` [PATCH 28/31] mm/memory: " Hugh Dickins
2023-05-22 5:26 ` [PATCH 29/31] mm/memory: handle_pte_fault() use pte_offset_map_nolock() Hugh Dickins
2023-05-22 12:52 ` Qi Zheng
2023-05-24 4:54 ` Hugh Dickins
2023-05-22 5:27 ` [PATCH 30/31] mm/pgtable: delete pmd_trans_unstable() and friends Hugh Dickins
2023-05-22 5:29 ` [PATCH 31/31] perf/core: Allow pte_offset_map() to fail Hugh Dickins
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