linux-kernel - Re: [PATCH RESEND v3 01/10] mm/vma: rename VMA_LOCK_OFFSET to VM_REFCNT_EXCLUDE_READERS

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Message-ID: <6c8b63cc-d357-4e70-89d4-07afd004bc83@suse.cz>
Date: Thu, 22 Jan 2026 17:26:13 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...nel.org>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>, Mike Rapoport
 <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Shakeel Butt <shakeel.butt@...ux.dev>,
 Jann Horn <jannh@...gle.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Will Deacon <will@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
 Waiman Long <longman@...hat.com>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Clark Williams <clrkwllms@...nel.org>, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH RESEND v3 01/10] mm/vma: rename VMA_LOCK_OFFSET to
 VM_REFCNT_EXCLUDE_READERS_FLAG

On 1/22/26 14:01, Lorenzo Stoakes wrote:
> The VMA_LOCK_OFFSET value encodes a flag which vma->vm_refcnt is set to in
> order to indicate that a VMA is in the process of having VMA read-locks
> excluded in __vma_enter_locked() (that is, first checking if there are any
> VMA read locks held, and if there are, waiting on them to be released).
> 
> This happens when a VMA write lock is being established, or a VMA is being
> marked detached and discovers that the VMA reference count is elevated due
> to read-locks temporarily elevating the reference count only to discover a
> VMA write lock is in place.
> 
> The naming does not convey any of this, so rename VMA_LOCK_OFFSET to
> VM_REFCNT_EXCLUDE_READERS_FLAG (with a sensible new prefix to differentiate
> from the newly introduced VMA_*_BIT flags).
> 
> Also rename VMA_REF_LIMIT to VM_REFCNT_LIMIT to make this consistent also.
> 
> Update comments to reflect this.
> 
> No functional change intended.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

git grep tells me VMA_LOCK_OFFSET is still used in
tools/testing/vma/vma_internal.h but I guess it doesn't break the tests?