The patch titled Subject: samples/damon: fix damon sample prcl for start failure has been added to the -mm mm-hotfixes-unstable branch. Its filename is samples-damon-fix-damon-sample-prcl-for-start-failure.patch

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

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: Honggyu Kim honggyu.kim@sk.com Subject: samples/damon: fix damon sample prcl for start failure Date: Wed, 2 Jul 2025 09:02:01 +0900

Patch series "mm/damon: fix divide by zero and its samples", v3.

This series includes fixes against damon and its samples to make it safer when damon sample starting fails.

It includes the following changes. - fix unexpected divide by zero crash for zero size regions - fix bugs for damon samples in case of start failures

This patch (of 4):

The damon_sample_prcl_start() can fail so we must reset the "enable" parameter to "false" again for proper rollback.

In such cases, setting Y to "enable" then N triggers the following crash because damon sample start failed but the "enable" stays as Y.

[ 2441.419649] damon_sample_prcl: start [ 2454.146817] damon_sample_prcl: stop [ 2454.146862] ------------[ cut here ]------------ [ 2454.146865] kernel BUG at mm/slub.c:546! [ 2454.148183] Oops: invalid opcode: 0000 [#1] SMP NOPTI ... [ 2454.167555] Call Trace: [ 2454.167822] <TASK> [ 2454.168061] damon_destroy_ctx+0x78/0x140 [ 2454.168454] damon_sample_prcl_enable_store+0x8d/0xd0 [ 2454.168932] param_attr_store+0xa1/0x120 [ 2454.169315] module_attr_store+0x20/0x50 [ 2454.169695] sysfs_kf_write+0x72/0x90 [ 2454.170065] kernfs_fop_write_iter+0x150/0x1e0 [ 2454.170491] vfs_write+0x315/0x440 [ 2454.170833] ksys_write+0x69/0xf0 [ 2454.171162] __x64_sys_write+0x19/0x30 [ 2454.171525] x64_sys_call+0x18b2/0x2700 [ 2454.171900] do_syscall_64+0x7f/0x680 [ 2454.172258] ? exit_to_user_mode_loop+0xf6/0x180 [ 2454.172694] ? clear_bhb_loop+0x30/0x80 [ 2454.173067] ? clear_bhb_loop+0x30/0x80 [ 2454.173439] entry_SYSCALL_64_after_hwframe+0x76/0x7e

Link: https://lkml.kernel.org/r/20250702000205.1921-1-honggyu.kim@sk.com Link: https://lkml.kernel.org/r/20250702000205.1921-2-honggyu.kim@sk.com Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: Honggyu Kim honggyu.kim@sk.com Reviewed-by: SeongJae Park sj@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

samples/damon/prcl.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/samples/damon/prcl.c~samples-damon-fix-damon-sample-prcl-for-start-failure +++ a/samples/damon/prcl.c @@ -122,8 +122,12 @@ static int damon_sample_prcl_enable_stor if (enable == enabled) return 0;

- if (enable) - return damon_sample_prcl_start(); + if (enable) { + err = damon_sample_prcl_start(); + if (err) + enable = false; + return err; + } damon_sample_prcl_stop(); return 0; } _

Patches currently in -mm which might be from honggyu.kim@sk.com are

samples-damon-fix-damon-sample-prcl-for-start-failure.patch samples-damon-fix-damon-sample-wsse-for-start-failure.patch samples-damon-fix-damon-sample-mtier-for-start-failure.patch mm-damon-fix-divide-by-zero-in-damon_get_intervals_score.patch