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definitions=2023-09-07_02,2023-09-05_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 phishscore=0 bulkscore=0 suspectscore=0 mlxlogscore=999 malwarescore=0 adultscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2308100000 definitions=main-2309070086 X-Proofpoint-GUID: px4Jb-u_Pu63CueFhsmetRB0M_8gFcXM X-Proofpoint-ORIG-GUID: px4Jb-u_Pu63CueFhsmetRB0M_8gFcXM Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/6/23 18:29, Waiman Long wrote: > On 9/6/23 02:58, Kamalesh Babulal wrote: >> On 9/6/23 06:27, Luiz Capitulino wrote: >> [...] >>> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c >>> index 1fb7f562289d..2b7d74304606 100644 >>> --- a/kernel/cgroup/cgroup.c >>> +++ b/kernel/cgroup/cgroup.c >>> @@ -207,6 +207,8 @@ static u16 have_exit_callback __read_mostly; >>>   static u16 have_release_callback __read_mostly; >>>   static u16 have_canfork_callback __read_mostly; >>>   +static bool have_favordynmods __ro_after_init = IS_ENABLED(CONFIG_CGROUP_FAVOR_DYNMODS); >>> + >>>   /* cgroup namespace for init task */ >>>   struct cgroup_namespace init_cgroup_ns = { >>>       .ns.count    = REFCOUNT_INIT(2), >>> @@ -2243,9 +2245,9 @@ static int cgroup_init_fs_context(struct fs_context *fc) >>>       fc->user_ns = get_user_ns(ctx->ns->user_ns); >>>       fc->global = true; >>>   -#ifdef CONFIG_CGROUP_FAVOR_DYNMODS >>> -    ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS; >>> -#endif >>> +    if (have_favordynmods) >>> +        ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS; >>> + >>>       return 0; >>>   } >>>   @@ -6764,6 +6766,12 @@ static int __init enable_cgroup_debug(char *str) >>>   } >>>   __setup("cgroup_debug", enable_cgroup_debug); >>>   +static int __init cgroup_favordynmods_setup(char *str) >>> +{ >>> +    return (kstrtobool(str, &have_favordynmods) == 0); >>> +} >>> +__setup("cgroup_favordynmods=", cgroup_favordynmods_setup); >>> + >>>   /** >>>    * css_tryget_online_from_dir - get corresponding css from a cgroup dentry >>>    * @dentry: directory dentry of interest >> Consider a case where the kernel is compiled with >> CONFIG_CGROUP_FAVOR_DYNMODS=n and kernel command line is passed with >> cgroup_favordynmods=true, this would set the have_favordynmods to true. >> In cgroup_favordynmods_setup(), should it return 0 with a pr_warn(), >> when CONFIG_CGROUP_FAVOR_DYNMODS=n in the above case, or is this >> expected behavior? > > According to the documentation of __setup: > > /* >  * NOTE: __setup functions return values: >  * @fn returns 1 (or non-zero) if the option argument is "handled" >  * and returns 0 if the option argument is "not handled". >  */ > > So the return value should tell whether the input parameter is a recognizable true or false value, not whether it is true or false. kstrtobool returns 0 if it is a recognizable T/F value or -EINVAL otherwise. So the check is correct. I did double check that before I ack'ed the patch. > Apologies for not being clear in the previous email. It was in two parts, where the first one was more of a question, where if a kernel is compiled with CONFIG_CGROUP_FAVOR_DYNMODS config option disabled and the user attempts to pass cgroup_favordynmods=true in the kernel command line. In this scenario, the have_favordynmods is set to true regardless of the CONFIG_CGROUP_FAVOR_DYNMODS config option being enabled/disabled in the kernel. This allows the user to set CGRP_ROOT_FAVOR_DYNMODS flag without enabling the CONFIG_CGROUP_FAVOR_DYNMODS kernel config. Shouldn't the cgroup_favordynmods kernel parameter be valid only when the kernel is compiled with CONFIG_CGROUP_FAVOR_DYNMODS=y and allows the user to only disable it in the kernel command line instead of allowing them to set/unset have_favordynmods when CONFIG_CGROUP_FAVOR_DYNMODS is disabled. If the above assumption is right, that's where the second part was of email, where I was suggesting the restriction by using ifdef guards in cgroup_favordynmods_setup(), something like: diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 2b7d74304606..5c7d1a0b1dbe 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6768,7 +6768,11 @@ __setup("cgroup_debug", enable_cgroup_debug); static int __init cgroup_favordynmods_setup(char *str) { +#ifdef CGROUP_FAVOR_DYNMODS return (kstrtobool(str, &have_favordynmods) == 0); +#endif + pr_warn("Favor Dynmods not supported\n"); + return 0; } __setup("cgroup_favordynmods=", cgroup_favordynmods_setup); -- Thanks, Kamalesh