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

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

diff --git a/samples/damon/prcl.c b/samples/damon/prcl.c index 056b1b21a0fe..5597e6a08ab2 100644 --- a/samples/damon/prcl.c +++ b/samples/damon/prcl.c @@ -122,8 +122,12 @@ static int damon_sample_prcl_enable_store( 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; }