* [to-be-updated] percpu-do-not-trust-hint-starts-when-they-are-not-set.patch removed from -mm tree
@ 2026-05-18 17:54 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2026-05-18 17:54 UTC (permalink / raw)
To: mm-commits, joonwonkang, akpm
The quilt patch titled
Subject: percpu: do not trust hint starts when they are not set
has been removed from the -mm tree. Its filename was
percpu-do-not-trust-hint-starts-when-they-are-not-set.patch
This patch was dropped because an updated version will be issued
------------------------------------------------------
From: Joonwon Kang <joonwonkang@google.com>
Subject: percpu: do not trust hint starts when they are not set
Date: Sun, 10 May 2026 07:21:47 +0000
contig_hint_start can be trusted outside the hint update function since it
will be updated everytime contig_hint is broken. On the other hand,
scan_hint_start might still be invalid anywhere in the code due to the
broken scan_hint not being updated promptly. If those starts are trusted
when they are not set, it could lead to false invalidation or update of
the hints.
Link: https://lore.kernel.org/20260510072149.1279887-2-joonwonkang@google.com
Signed-off-by: Joonwon Kang <joonwonkang@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: <dodam@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/percpu.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
--- a/mm/percpu.c~percpu-do-not-trust-hint-starts-when-they-are-not-set
+++ a/mm/percpu.c
@@ -640,12 +640,13 @@ static void pcpu_block_update(struct pcp
if (contig > block->contig_hint) {
/* promote the old contig_hint to be the new scan_hint */
- if (start > block->contig_hint_start) {
+ if (block->contig_hint && start > block->contig_hint_start) {
if (block->contig_hint > block->scan_hint) {
block->scan_hint_start =
block->contig_hint_start;
block->scan_hint = block->contig_hint;
- } else if (start < block->scan_hint_start) {
+ } else if (block->scan_hint &&
+ start < block->scan_hint_start) {
/*
* The old contig_hint == scan_hint. But, the
* new contig is larger so hold the invariant
@@ -664,10 +665,12 @@ static void pcpu_block_update(struct pcp
__ffs(start) > __ffs(block->contig_hint_start))) {
/* start has a better alignment so use it */
block->contig_hint_start = start;
- if (start < block->scan_hint_start &&
+ if (block->scan_hint &&
+ start < block->scan_hint_start &&
block->contig_hint > block->scan_hint)
block->scan_hint = 0;
- } else if (start > block->scan_hint_start ||
+ } else if ((block->scan_hint &&
+ start > block->scan_hint_start) ||
block->contig_hint > block->scan_hint) {
/*
* Knowing contig == contig_hint, update the scan_hint
@@ -845,7 +848,8 @@ static void pcpu_block_update_hint_alloc
PCPU_BITMAP_BLOCK_BITS,
s_off + bits);
- if (pcpu_region_overlap(s_block->scan_hint_start,
+ if (s_block->scan_hint &&
+ pcpu_region_overlap(s_block->scan_hint_start,
s_block->scan_hint_start + s_block->scan_hint,
s_off,
s_off + bits))
@@ -889,7 +893,8 @@ static void pcpu_block_update_hint_alloc
/* reset the block */
e_block++;
} else {
- if (e_off > e_block->scan_hint_start)
+ if (e_block->scan_hint &&
+ e_off > e_block->scan_hint_start)
e_block->scan_hint = 0;
e_block->left_free = 0;
@@ -922,7 +927,8 @@ static void pcpu_block_update_hint_alloc
if (nr_empty_pages)
pcpu_update_empty_pages(chunk, -nr_empty_pages);
- if (pcpu_region_overlap(chunk_md->scan_hint_start,
+ if (chunk_md->scan_hint &&
+ pcpu_region_overlap(chunk_md->scan_hint_start,
chunk_md->scan_hint_start +
chunk_md->scan_hint,
bit_off,
_
Patches currently in -mm which might be from joonwonkang@google.com are
a.patch
percpu-introduce-struct-pcpu_region.patch
percpu-fix-hint-invariant-breakage.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
* [to-be-updated] percpu-do-not-trust-hint-starts-when-they-are-not-set.patch removed from -mm tree
@ 2026-05-29 4:51 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2026-05-29 4:51 UTC (permalink / raw)
To: mm-commits, tj, dennis, joonwonkang, akpm
The quilt patch titled
Subject: percpu: do not trust hint starts when they are not set
has been removed from the -mm tree. Its filename was
percpu-do-not-trust-hint-starts-when-they-are-not-set.patch
This patch was dropped because an updated version will be issued
------------------------------------------------------
From: Joonwon Kang <joonwonkang@google.com>
Subject: percpu: do not trust hint starts when they are not set
Date: Wed, 13 May 2026 08:51:14 +0000
contig_hint_start can be trusted outside the hint update function since it
will be updated everytime contig_hint is broken. On the other hand,
scan_hint_start might still be invalid anywhere in the code due to the
broken scan_hint not being updated promptly. If those starts are trusted
when they are not set, it could lead to false invalidation or update of
the hints.
Link: https://lore.kernel.org/20260513085117.1024175-2-joonwonkang@google.com
Signed-off-by: Joonwon Kang <joonwonkang@google.com>
Reviewed-by: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/percpu.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
--- a/mm/percpu.c~percpu-do-not-trust-hint-starts-when-they-are-not-set
+++ a/mm/percpu.c
@@ -640,12 +640,13 @@ static void pcpu_block_update(struct pcp
if (contig > block->contig_hint) {
/* promote the old contig_hint to be the new scan_hint */
- if (start > block->contig_hint_start) {
+ if (block->contig_hint && start > block->contig_hint_start) {
if (block->contig_hint > block->scan_hint) {
block->scan_hint_start =
block->contig_hint_start;
block->scan_hint = block->contig_hint;
- } else if (start < block->scan_hint_start) {
+ } else if (block->scan_hint &&
+ start < block->scan_hint_start) {
/*
* The old contig_hint == scan_hint. But, the
* new contig is larger so hold the invariant
@@ -664,10 +665,12 @@ static void pcpu_block_update(struct pcp
__ffs(start) > __ffs(block->contig_hint_start))) {
/* start has a better alignment so use it */
block->contig_hint_start = start;
- if (start < block->scan_hint_start &&
+ if (block->scan_hint &&
+ start < block->scan_hint_start &&
block->contig_hint > block->scan_hint)
block->scan_hint = 0;
- } else if (start > block->scan_hint_start ||
+ } else if ((block->scan_hint &&
+ start > block->scan_hint_start) ||
block->contig_hint > block->scan_hint) {
/*
* Knowing contig == contig_hint, update the scan_hint
@@ -845,7 +848,8 @@ static void pcpu_block_update_hint_alloc
PCPU_BITMAP_BLOCK_BITS,
s_off + bits);
- if (pcpu_region_overlap(s_block->scan_hint_start,
+ if (s_block->scan_hint &&
+ pcpu_region_overlap(s_block->scan_hint_start,
s_block->scan_hint_start + s_block->scan_hint,
s_off,
s_off + bits))
@@ -889,7 +893,8 @@ static void pcpu_block_update_hint_alloc
/* reset the block */
e_block++;
} else {
- if (e_off > e_block->scan_hint_start)
+ if (e_block->scan_hint &&
+ e_off > e_block->scan_hint_start)
e_block->scan_hint = 0;
e_block->left_free = 0;
@@ -922,7 +927,8 @@ static void pcpu_block_update_hint_alloc
if (nr_empty_pages)
pcpu_update_empty_pages(chunk, -nr_empty_pages);
- if (pcpu_region_overlap(chunk_md->scan_hint_start,
+ if (chunk_md->scan_hint &&
+ pcpu_region_overlap(chunk_md->scan_hint_start,
chunk_md->scan_hint_start +
chunk_md->scan_hint,
bit_off,
_
Patches currently in -mm which might be from joonwonkang@google.com are
percpu-introduce-struct-pcpu_region.patch
percpu-fix-hint-invariant-breakage.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
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