From: Hugh Dickins <hughd@google.com>
To: Suren Baghdasaryan <surenb@google.com>
Cc: akpm@linux-foundation.org, willy@infradead.org,
liam.howlett@oracle.com, lorenzo.stoakes@oracle.com,
mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org,
mjguzik@gmail.com, oliver.sang@intel.com,
mgorman@techsingularity.net, david@redhat.com,
peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net,
paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com,
hdanton@sina.com, hughd@google.com, minchan@google.com,
jannh@google.com, shakeel.butt@linux.dev,
souravpanda@google.com, pasha.tatashin@soleen.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@android.com
Subject: Re: [PATCH v2 4/5] mm: make vma cache SLAB_TYPESAFE_BY_RCU
Date: Tue, 12 Nov 2024 21:08:07 -0800 (PST) [thread overview]
Message-ID: <6d0c5c2d-2963-489a-2376-8edaeb064de3@google.com> (raw)
In-Reply-To: <CAJuCfpFd2_7q6pi1=G9B0VW5ynCWhkkDDA3PU293FPtT_CcBQA@mail.gmail.com>
On Tue, 12 Nov 2024, Suren Baghdasaryan wrote:
>
> Thinking about this some more, I don't think this works. I'm relying
> on vma_start_read() to stabilize the vma, however the lock I'm taking
> is part of the vma which can be reused from under us. So, the lock I'm
> taking might be reinitialized after I take the lock...
> I need to figure out a way to stabilize the vma in some other manner
> before taking this lock.
(I'm not paying attention and following the patches, I just happened
to notice this remark: forgive me if I'm out of context and have
misunderstood, but hope this might help:)
But this is exactly the problem SLAB_TYPESAFE_BY_RCU was invented for.
You just have to be careful that the locks are initialized only when the
slab is first created (allocated from buddy), not reinitialized whenever
a new object is allocated from that slab.
Hugh
next prev parent reply other threads:[~2024-11-13 5:08 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-12 19:46 [PATCH v2 0/5] move per-vma lock into vm_area_struct Suren Baghdasaryan
2024-11-12 19:46 ` [PATCH v2 1/5] mm: introduce vma_start_read_locked{_nested} helpers Suren Baghdasaryan
2024-11-13 14:10 ` Lorenzo Stoakes
2024-11-13 15:30 ` Suren Baghdasaryan
2024-11-12 19:46 ` [PATCH v2 2/5] mm: move per-vma lock into vm_area_struct Suren Baghdasaryan
2024-11-13 14:28 ` Lorenzo Stoakes
2024-11-13 14:45 ` Vlastimil Babka
2024-11-13 14:58 ` Lorenzo Stoakes
2024-11-13 15:09 ` Vlastimil Babka
2024-11-13 14:53 ` Mateusz Guzik
2024-11-13 14:59 ` Lorenzo Stoakes
2024-11-13 15:01 ` Lorenzo Stoakes
2024-11-13 15:45 ` Suren Baghdasaryan
2024-11-13 15:42 ` Suren Baghdasaryan
2024-11-12 19:46 ` [PATCH v2 3/5] mm: mark vma as detached until it's added into vma tree Suren Baghdasaryan
2024-11-13 14:43 ` Lorenzo Stoakes
2024-11-13 15:37 ` Suren Baghdasaryan
2024-11-12 19:46 ` [PATCH v2 4/5] mm: make vma cache SLAB_TYPESAFE_BY_RCU Suren Baghdasaryan
2024-11-13 2:57 ` Suren Baghdasaryan
2024-11-13 5:08 ` Hugh Dickins [this message]
2024-11-13 6:03 ` Suren Baghdasaryan
2024-11-13 6:52 ` Hugh Dickins
2024-11-13 8:19 ` Suren Baghdasaryan
2024-11-13 8:58 ` Vlastimil Babka
2024-11-13 12:38 ` Liam R. Howlett
2024-11-13 13:57 ` Matthew Wilcox
2024-11-13 15:22 ` Liam R. Howlett
2024-11-13 15:25 ` Suren Baghdasaryan
2024-11-13 15:29 ` Liam R. Howlett
2024-11-13 15:47 ` Suren Baghdasaryan
2024-11-13 19:05 ` Suren Baghdasaryan
2024-11-14 16:18 ` Suren Baghdasaryan
2024-11-14 16:21 ` Vlastimil Babka
2024-11-13 16:44 ` Jann Horn
2024-11-13 20:59 ` Matthew Wilcox
2024-11-13 21:23 ` Jann Horn
2024-11-12 19:46 ` [PATCH v2 5/5] docs/mm: document latest changes to vm_lock Suren Baghdasaryan
2024-11-12 19:51 ` Suren Baghdasaryan
2024-11-13 14:46 ` Lorenzo Stoakes
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