mm/damon/sysfs-schemes: let damon_sysfs_scheme_set_filters() be used for different...

Patch series "mm/damon: add sysfs dirs for managing DAMOS filters based on
handling layers".

DAMOS filters are categorized into two groups based on their handling
layers, namely core and operations layers.  The categorization affects
when each filter is evaluated.  Core layer handled filters are evaluated
first.  The order meant nothing before, but introduction of allow filters
changed that.

DAMOS sysfs interface provides single directory for filters, namely
'filters'.  Users can install any filters in any order there.  DAMON will
internally categorize those into core and operations layer handled ones,
and apply the evaluation order rule.  The ordering rule is clearly
documented.  But the interface could still confuse users since it is
allowed to install filters on the directory in mixed ways.

Add two sysfs directories for managing filters by handling layers, namely
'core_filters' and 'ops_filters' for filters that handled by core and
operations layer, respectively.  Those are avoided to be used for
installing filters that not handled by the assumed layers.

For backward compatibility, keep 'filters' directory with its curernt
behavior.  Filters installed in the directory will be added to DAMON after
those of 'core_filters' and 'ops_filters' directories, with the automatic
categorizations.  Also recommend users to use the new directories while
noticing 'filters' directory could be deprecated in future on the usage
documents.

Note that new directories provide all features that were provided with
'filters', but just in a more clear way.  Deprecating 'filters' in future
will hence not make an irreversal feature loss.

This patch (of 8):

damon_sysfs_scheme_set_filters() is using a hard-coded directory name,
"filters".  Refactor for general named directories of same files
hierarchy, to use from upcoming changes for adding sibling directories
having files same to those of "filters", and named as "core_filters" and
"ops_filters".

[arnd@arndb.deL avoid Wformat-security warning]
Link: https://lkml.kernel.org/r/20250310135142.4176976-1-arnd@kernel.org
Link: https://lkml.kernel.org/r/20250305222733.59089-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20250305222733.59089-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 66a1c46cee847eebea70e82581bce51cbaa9cf16..d769b24f90a4008241c69ad44534d69b2ad43900 100644 (file)
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1604,7 +1604,9 @@ static int damon_sysfs_scheme_set_watermarks(struct damon_sysfs_scheme *scheme)
        return err;
 }
 
-static int damon_sysfs_scheme_set_filters(struct damon_sysfs_scheme *scheme)
+static int damon_sysfs_scheme_set_filters(struct damon_sysfs_scheme *scheme,
+               const char *name,
+               struct damon_sysfs_scheme_filters **filters_ptr)
 {
        struct damon_sysfs_scheme_filters *filters =
                damon_sysfs_scheme_filters_alloc();
@@ -1614,11 +1616,11 @@ static int damon_sysfs_scheme_set_filters(struct damon_sysfs_scheme *scheme)
                return -ENOMEM;
        err = kobject_init_and_add(&filters->kobj,
                        &damon_sysfs_scheme_filters_ktype, &scheme->kobj,
-                       "filters");
+                       "%s", name);
        if (err)
                kobject_put(&filters->kobj);
        else
-               scheme->filters = filters;
+               *filters_ptr = filters;
        return err;
 }
 
@@ -1670,7 +1672,8 @@ static int damon_sysfs_scheme_add_dirs(struct damon_sysfs_scheme *scheme)
        err = damon_sysfs_scheme_set_watermarks(scheme);
        if (err)
                goto put_quotas_access_pattern_out;
-       err = damon_sysfs_scheme_set_filters(scheme);
+       err = damon_sysfs_scheme_set_filters(scheme, "filters",
+                       &scheme->filters);
        if (err)
                goto put_watermarks_quotas_access_pattern_out;
        err = damon_sysfs_scheme_set_stats(scheme);