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Subject[PATCH 1/8] mm/damon/dbgfs: add mappings between 'schemes' file's action inputs and 'damos_action' values
Date
DAMON debugfs interface assumes users will write 'damos_action' value
directly to the 'schemes' file. This makes adding new 'damos_action' in
the middle of its definition breaks the backward compatibility of DAMON
debugfs interface, as values of some 'damos_action' could be changed.
To support backward compatibility in the cases, this commit adds
mappings between the user inputs and 'damos_action' value and makes
DAMON debugfs code uses those.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
mm/damon/dbgfs.c | 64 +++++++++++++++++++++++++++++++++++++-----------
1 file changed, 50 insertions(+), 14 deletions(-)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 5ae810927309..cb8a7e9926a4 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -97,6 +97,31 @@ static ssize_t dbgfs_attrs_write(struct file *file,
return ret;
}

+/*
+ * Return corresponding dbgfs' scheme action value (int) for the given
+ * damos_action if the given damos_action value is valid and supported by
+ * dbgfs, negative error code otherwise.
+ */
+static int damos_action_to_dbgfs_scheme_action(enum damos_action action)
+{
+ switch (action) {
+ case DAMOS_WILLNEED:
+ return 0;
+ case DAMOS_COLD:
+ return 1;
+ case DAMOS_PAGEOUT:
+ return 2;
+ case DAMOS_HUGEPAGE:
+ return 3;
+ case DAMOS_NOHUGEPAGE:
+ return 4;
+ case DAMOS_STAT:
+ return 5;
+ default:
+ return -EINVAL;
+ }
+}
+
static ssize_t sprint_schemes(struct damon_ctx *c, char *buf, ssize_t len)
{
struct damos *s;
@@ -109,7 +134,7 @@ static ssize_t sprint_schemes(struct damon_ctx *c, char *buf, ssize_t len)
s->min_sz_region, s->max_sz_region,
s->min_nr_accesses, s->max_nr_accesses,
s->min_age_region, s->max_age_region,
- s->action,
+ damos_action_to_dbgfs_scheme_action(s->action),
s->quota.ms, s->quota.sz,
s->quota.reset_interval,
s->quota.weight_sz,
@@ -160,18 +185,27 @@ static void free_schemes_arr(struct damos **schemes, ssize_t nr_schemes)
kfree(schemes);
}

-static bool damos_action_valid(int action)
+/*
+ * Return corresponding damos_action for the given dbgfs input for a scheme
+ * action if the input is valid, negative error code otherwise.
+ */
+static enum damos_action dbgfs_scheme_action_to_damos_action(int dbgfs_action)
{
- switch (action) {
- case DAMOS_WILLNEED:
- case DAMOS_COLD:
- case DAMOS_PAGEOUT:
- case DAMOS_HUGEPAGE:
- case DAMOS_NOHUGEPAGE:
- case DAMOS_STAT:
- return true;
+ switch (dbgfs_action) {
+ case 0:
+ return DAMOS_WILLNEED;
+ case 1:
+ return DAMOS_COLD;
+ case 2:
+ return DAMOS_PAGEOUT;
+ case 3:
+ return DAMOS_HUGEPAGE;
+ case 4:
+ return DAMOS_NOHUGEPAGE;
+ case 5:
+ return DAMOS_STAT;
default:
- return false;
+ return -EINVAL;
}
}

@@ -189,7 +223,8 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
int pos = 0, parsed, ret;
unsigned long min_sz, max_sz;
unsigned int min_nr_a, max_nr_a, min_age, max_age;
- unsigned int action;
+ unsigned int action_input;
+ enum damos_action action;

schemes = kmalloc_array(max_nr_schemes, sizeof(scheme),
GFP_KERNEL);
@@ -204,7 +239,7 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
ret = sscanf(&str[pos],
"%lu %lu %u %u %u %u %u %lu %lu %lu %u %u %u %u %lu %lu %lu %lu%n",
&min_sz, &max_sz, &min_nr_a, &max_nr_a,
- &min_age, &max_age, &action, &quota.ms,
+ &min_age, &max_age, &action_input, &quota.ms,
&quota.sz, &quota.reset_interval,
&quota.weight_sz, &quota.weight_nr_accesses,
&quota.weight_age, &wmarks.metric,
@@ -212,7 +247,8 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
&wmarks.low, &parsed);
if (ret != 18)
break;
- if (!damos_action_valid(action))
+ action = dbgfs_scheme_action_to_damos_action(action_input);
+ if ((int)action < 0)
goto fail;

if (min_sz > max_sz || min_nr_a > max_nr_a || min_age > max_age)
--
2.25.1
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