From: Jason Gunthorpe <jgg@ziepe.ca>
To: Stanislav Kinsburskii <skinsburskii@gmail.com>
Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org,
david@kernel.org, corbet@lwn.net, leon@kernel.org,
ljs@kernel.org, mhocko@suse.com, rppt@kernel.org,
shuah@kernel.org, skhan@linuxfoundation.org, surenb@google.com,
vbabka@kernel.org, kys@microsoft.com, haiyangz@microsoft.com,
wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
linux-hyperv@vger.kernel.org
Subject: Re: [PATCH v6 2/4] mm/hmm: add hmm_range_fault_unlocked() for mmap lock-drop support
Date: Mon, 6 Jul 2026 15:02:08 -0300 [thread overview]
Message-ID: <20260706180208.GB118978@ziepe.ca> (raw)
In-Reply-To: <178336050736.504354.6052508493877924780.stgit@skinsburskii>
On Mon, Jul 06, 2026 at 10:55:07AM -0700, Stanislav Kinsburskii wrote:
> +The caller must not hold ``mmap_read_lock`` before the call.
> +``hmm_range_fault_unlocked()`` takes the mmap read lock internally and allows
> +``handle_mm_fault()`` to drop it during fault handling. If the mmap lock is
> +dropped, the function returns ``-EBUSY``. The caller must then restart the
> +walk from ``range->start`` with a fresh notifier sequence. ``-EINTR`` is
> +returned if a fatal signal is pending during retry handling.
It doesn't make sense to me to expose this to the caller, the caller
isn't holding the lock and there is no reason to redo the mmu_interval
at this point, so why not just loop inside hmm_range_fault_unlocked ?
Jason
next prev parent reply other threads:[~2026-07-06 18:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-06 17:54 [PATCH v6 0/4] mm/hmm: Add mmap lock-drop support for userfaultfd-backed mappings Stanislav Kinsburskii
2026-07-06 17:55 ` [PATCH v6 1/4] mm/hmm: move page fault handling out of walk callbacks Stanislav Kinsburskii
2026-07-06 17:55 ` [PATCH v6 2/4] mm/hmm: add hmm_range_fault_unlocked() for mmap lock-drop support Stanislav Kinsburskii
2026-07-06 18:02 ` Jason Gunthorpe [this message]
2026-07-06 17:55 ` [PATCH v6 3/4] selftests/mm: add userfaultfd test for HMM unlocked path Stanislav Kinsburskii
2026-07-06 17:55 ` [PATCH v6 4/4] mshv: Use hmm_range_fault_unlocked() for region faults Stanislav Kinsburskii
2026-07-06 18:16 ` Jason Gunthorpe
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