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Biederman" , "Guilherme G . Piccoli" Subject: Re: [RFC v2 2/2] kernel/sysctl: support handling command line aliases Message-ID: <20200329150022.GA823603@rani.riverdale.lan> References: <20200325120345.12946-1-vbabka@suse.cz> <20200325120345.12946-2-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200325120345.12946-2-vbabka@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed, Mar 25, 2020 at 01:03:45PM +0100, Vlastimil Babka wrote: > We can now handle sysctl parameters on kernel command line, but historically > some parameters introduced their own command line equivalent, which we don't > want to remove for compatibility reasons. We can however convert them to the > generic infrastructure with a table translating the legacy command line > parameters to their sysctl names, and removing the one-off param handlers. > > This patch adds the support and makes the first conversion to demonstrate it, > on the (deprecated) numa_zonelist_order parameter. > > Signed-off-by: Vlastimil Babka > --- > kernel/sysctl.c | 39 +++++++++++++++++++++++++++++++++++---- > mm/page_alloc.c | 9 --------- > 2 files changed, 35 insertions(+), 13 deletions(-) > > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 18c7f5606d55..fd72853396f9 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1971,6 +1971,22 @@ static struct ctl_table dev_table[] = { > { } > }; > > +struct sysctl_alias { > + char *kernel_param; > + char *sysctl_param; > +}; > + > +/* > + * Historically some settings had both sysctl and a command line parameter. > + * With the generic sysctl. parameter support, we can handle them at a single > + * place and only keep the historical name for compatibility. This is not meant > + * to add brand new aliases. > + */ > +static struct sysctl_alias sysctl_aliases[] = { > + {"numa_zonelist_order", "vm.numa_zonelist_order" }, > + { } > +}; > + > int __init sysctl_init(void) > { > struct ctl_table_header *hdr; > @@ -1980,6 +1996,18 @@ int __init sysctl_init(void) > return 0; > } > > +char *sysctl_find_alias(char *param) This function should probably be declared static? > +{ > + struct sysctl_alias *alias; > + > + for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) { > + if (strcmp(alias->kernel_param, param) == 0) > + return alias->sysctl_param; > + } > + > + return NULL; > +} > + > /* Set sysctl value passed on kernel command line. */ > int process_sysctl_arg(char *param, char *val, > const char *unused, void *arg) > @@ -1990,10 +2018,13 @@ int process_sysctl_arg(char *param, char *val, > loff_t ppos = 0; > struct ctl_table *ctl, *found = NULL; > > - if (strncmp(param, "sysctl.", sizeof("sysctl.") - 1)) > - return 0; > - > - param += sizeof("sysctl.") - 1; > + if (strncmp(param, "sysctl.", sizeof("sysctl.") - 1) == 0) { > + param += sizeof("sysctl.") - 1; > + } else { > + param = sysctl_find_alias(param); > + if (!param) > + return 0; > + } > > remaining = param; > ctl = &sysctl_base_table[0]; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3c4eb750a199..de7a134b1b8a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5460,15 +5460,6 @@ static int __parse_numa_zonelist_order(char *s) > return 0; > } > > -static __init int setup_numa_zonelist_order(char *s) > -{ > - if (!s) > - return 0; > - > - return __parse_numa_zonelist_order(s); > -} > -early_param("numa_zonelist_order", setup_numa_zonelist_order); > - > char numa_zonelist_order[] = "Node"; > > /* > -- > 2.25.1 >