+ bcache-remove-unnecessary-select-min_heap.patch added to mm-hotfixes-unstable branch

+ bcache-remove-unnecessary-select-min_heap.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: bcache: remove unnecessary select MIN_HEAP
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     bcache-remove-unnecessary-select-min_heap.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/bcache-remove-unnecessary-select-min_heap.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Kuan-Wei Chiu <visitorckw@gmail.com>
Subject: bcache: remove unnecessary select MIN_HEAP
Date: Sun, 15 Jun 2025 04:23:53 +0800

After reverting the transition to the generic min heap library, bcache no
longer depends on MIN_HEAP.  The select entry can be removed to reduce
code size and shrink the kernel's attack surface.

This change effectively reverts the bcache-related part of commit
92a8b224b833 ("lib/min_heap: introduce non-inline versions of min heap API
functions").

This is part of a series of changes to address a performance regression
caused by the use of the generic min_heap implementation.

As reported by Robert, bcache now suffers from latency spikes, with P100
(max) latency increasing from 600 ms to 2.4 seconds every 5 minutes. 
These regressions degrade bcache's effectiveness as a low-latency cache
layer and lead to frequent timeouts and application stalls in production
environments.

Link: https://lore.kernel.org/lkml/CAJhEC05+0S69z+3+FB2Cd0hD+pCRyWTKLEOsc8BOmH73p1m+KQ@mail.gmail.com
Link: https://lkml.kernel.org/r/20250614202353.1632957-4-visitorckw@gmail.com
Fixes: 866898efbb25 ("bcache: remove heap-related macros and switch to generic min_heap")
Fixes: 92a8b224b833 ("lib/min_heap: introduce non-inline versions of min heap API functions")
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Reported-by: Robert Pang <robertpang@google.com>
Closes: https://lore.kernel.org/linux-bcache/CAJhEC06F_AtrPgw2-7CvCqZgeStgCtitbD-ryuPpXQA-JG5XXw@mail.gmail.com
Acked-by: Coly Li <colyli@kernel.org>
Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/md/bcache/Kconfig |    1 -
 1 file changed, 1 deletion(-)

--- a/drivers/md/bcache/Kconfig~bcache-remove-unnecessary-select-min_heap
+++ a/drivers/md/bcache/Kconfig
@@ -5,7 +5,6 @@ config BCACHE
 	select BLOCK_HOLDER_DEPRECATED if SYSFS
 	select CRC64
 	select CLOSURES
-	select MIN_HEAP
 	help
 	Allows a block device to be used as cache for other devices; uses
 	a btree for indexing and the layout is optimized for SSDs.
_

Patches currently in -mm which might be from visitorckw@gmail.com are

revert-bcache-update-min_heap_callbacks-to-use-default-builtin-swap.patch
revert-bcache-remove-heap-related-macros-and-switch-to-generic-min_heap.patch
bcache-remove-unnecessary-select-min_heap.patch
lib-math-gcd-use-static-key-to-select-implementation-at-runtime.patch
riscv-optimize-gcd-code-size-when-config_riscv_isa_zbb-is-disabled.patch
riscv-optimize-gcd-performance-on-risc-v-without-zbb-extension.patch