Gh0st
/
linux
mirror of https://github.com/torvalds/linux.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

mm/damon/sysfs: set damon_ctx->min_sz_region only for paddr use case 

damon_ctx->addr_unit is respected only for physical address space
monitoring use case.  Meanwhile, damon_ctx->min_sz_region is used by the
core layer for aligning regions, regardless of whether it is set for
physical address space monitoring or virtual address spaces monitoring. 
And it is set as 'DAMON_MIN_REGION / damon_ctx->addr_unit'.  Hence, if
user sets ->addr_unit on virtual address spaces monitoring mode, regions
can be unexpectedly aligned in <PAGE_SIZE granularity.  It shouldn't cause
crash-like issues but make monitoring and DAMOS behavior difficult to
understand.

Fix the unexpected behavior by setting ->min_sz_region only when it is
configured for physical address space monitoring.

The issue was found from a result of Chris' experiments that thankfully
shared with me off-list.

Link: https://lkml.kernel.org/r/20250917160041.53187-1-sj@kernel.org
Fixes: d8f867fa08 ("mm/damon: add damon_ctx->min_sz_region")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: ze zuo <zuoze1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2025-09-17 08:31:54 -07:00 committed by Andrew Morton
parent 7ef5268a90
commit 8d009da32f
1 changed files with 4 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
mm/damon/sysfs.c
View File

@ -1435,7 +1435,10 @@ static int damon_sysfs_apply_inputs(struct damon_ctx *ctx,
if (err)
return err;
ctx->addr_unit = sys_ctx->addr_unit;
ctx->min_sz_region = max(DAMON_MIN_REGION / sys_ctx->addr_unit, 1);
/* addr_unit is respected by only DAMON_OPS_PADDR */
if (sys_ctx->ops_id == DAMON_OPS_PADDR)
ctx->min_sz_region = max(
DAMON_MIN_REGION / sys_ctx->addr_unit, 1);
err = damon_sysfs_set_attrs(ctx, sys_ctx->attrs);
if (err)
return err;