linux-kernel - Re: [PATCH v2 22/29] maple_tree: Use maple copy node for mas_wr

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Message-ID: <ce123a4f-c35b-465e-bef1-30a86274316c@sirena.org.uk>
Date: Wed, 28 Jan 2026 10:53:11 +0000
From: Mark Brown <broonie@...nel.org>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	maple-tree@...ts.infradead.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Suren Baghdasaryan <surenb@...gle.com>,
	Matthew Wilcox <willy@...radead.org>,
	Sidhartha Kumar <sidhartha.kumar@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Alice Ryhl <aliceryhl@...gle.com>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Arnd Bergmann <arnd@...db.de>,
	Christian Kujau <lists@...dbynature.de>, Aishwarya.TCV@....com
Subject: Re: [PATCH v2 22/29] maple_tree: Use maple copy node for
 mas_wr_rebalance() operation

On Tue, Jan 27, 2026 at 11:05:54PM +0000, Mark Brown wrote:
> On Wed, Jan 21, 2026 at 11:45:19AM -0500, Liam R. Howlett wrote:

> > Stop using the maple big node for rebalance operations by changing to
> > more align with spanning store.  The rebalance operation needs its own
> > data calculation in rebalance_data().

> > In the event of too much data, the rebalance tries to push the data
> > using push_data_sib().  If there is insufficient data, the rebalance
> > operation will rebalance against a sibling (found with rebalance_sib()).

> These appear to bisect to this commit, there were some issues with the
> setup of the bisect which fortunately don't seem to have confused things
> and some timeouts stopped the last couple of jobs completing but we've
> got adjacent commits showing passes and fails and of the two candidates
> the other is a refactoring that doesn't look at all plausible.  I'm
> rerunning a clean bisect but expect it to confirm this result.

Confirmed:

git bisect start
# status: waiting for both good and bad commits
# bad: [615aad0f61e0c7a898184a394dc895c610100d4f] Add linux-next specific files for 20260126
git bisect bad 615aad0f61e0c7a898184a394dc895c610100d4f
# status: waiting for good commit(s), bad commit known
# good: [50814c5ce8d8f6751fd49c818abeb8853f8be2df] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
git bisect good 50814c5ce8d8f6751fd49c818abeb8853f8be2df
# bad: [b047f48069330e050431e9ad762bd838af43337f] Merge branch 'mtd/next' of https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git
git bisect bad b047f48069330e050431e9ad762bd838af43337f
# bad: [75fe66db9e85a2fd9743f7598a2aaea9eb5fbfd7] Merge branch 'xtensa-for-next' of https://github.com/jcmvbkbc/linux-xtensa.git
git bisect bad 75fe66db9e85a2fd9743f7598a2aaea9eb5fbfd7
# bad: [0578997f52fb9a1b9adfc5fe5a95ceab4bb331d2] Merge branch 'soc_fsl' of https://git.kernel.org/pub/scm/linux/kernel/git/chleroy/linux.git
git bisect bad 0578997f52fb9a1b9adfc5fe5a95ceab4bb331d2
# bad: [a85886367078a64dcffefe0ccd9054f6237b791a] Merge branch 'mm-unstable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect bad a85886367078a64dcffefe0ccd9054f6237b791a
# good: [3b545d6116fcf6d257bf2d50e7607351fdc81b76] mm/memory: add tree limit to free_pgtables()
git bisect good 3b545d6116fcf6d257bf2d50e7607351fdc81b76
# good: [8d2b3ef6f7d7b0a531c4c733224583af946a424b] maple_tree: inline mas_wr_spanning_rebalance()
git bisect good 8d2b3ef6f7d7b0a531c4c733224583af946a424b
# good: [b75bed193d677f6ae26df8851f4d5546fb7d3599] tsacct: skip all kernel threads
git bisect good b75bed193d677f6ae26df8851f4d5546fb7d3599
# good: [4aededd81f86a8090ea8c294071425aa12116ef8] Merge branch 'pin-init-next' of https://github.com/Rust-for-Linux/linux.git
git bisect good 4aededd81f86a8090ea8c294071425aa12116ef8
# good: [201b27d852d1aecf3abce28721c6004ec2690b8d] Merge branch 'mm-nonmm-stable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect good 201b27d852d1aecf3abce28721c6004ec2690b8d
# bad: [7bc25a7aa0443b3beb3610e505d3147eece02766] maple_tree: add cp_converged() helper
git bisect bad 7bc25a7aa0443b3beb3610e505d3147eece02766
# good: [a2c17a4f4db66772701547fc30f66d1df2fceafb] maple_tree: add cp_is_new_root() helper
git bisect good a2c17a4f4db66772701547fc30f66d1df2fceafb
# bad: [525e5511c009c0d6725e534134ec31eeba148da0] maple_tree: add copy_tree_location() helper
git bisect bad 525e5511c009c0d6725e534134ec31eeba148da0
# bad: [6ad069085c621d39fad4d1835af7e563975dcf7e] maple_tree: use maple copy node for mas_wr_rebalance() operation
git bisect bad 6ad069085c621d39fad4d1835af7e563975dcf7e
# first bad commit: [6ad069085c621d39fad4d1835af7e563975dcf7e] maple_tree: use maple copy node for mas_wr_rebalance() operation

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