On Fri, Jul 25, 2025 at 04:57:10PM +0530, Hardeep Sharma wrote:

Buffer bouncing is needed only when memory exists above the lowmem region, i.e., when max_low_pfn < max_pfn. The previous check (max_low_pfn >= max_pfn) was inverted and prevented bouncing when it could actually be required.

Note that bouncing depends on CONFIG_HIGHMEM, which is typically enabled on 32-bit ARM where not all memory is permanently mapped into the kernel’s lowmem region.

Fixes: 9bb33f24abbd0 ("block: refactor the bounce buffering code") Cc: stable@vger.kernel.org Signed-off-by: Hardeep Sharma quic_hardshar@quicinc.com

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Changelog v1..v2:

• Updated subject line

block/blk.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk.h b/block/blk.h index 67915b04b3c1..f8a1d64be5a2 100644 --- a/block/blk.h +++ b/block/blk.h @@ -383,7 +383,7 @@ static inline bool blk_queue_may_bounce(struct request_queue *q) { return IS_ENABLED(CONFIG_BOUNCE) && q->limits.bounce == BLK_BOUNCE_HIGH &&

• max_low_pfn >= max_pfn;
  

• max_low_pfn < max_pfn;
  

} static inline struct bio *blk_queue_bounce(struct bio *bio, -- 2.25.1

<formletter>

This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.

</formletter>