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authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2019-02-21 11:49:27 -0500
committerTheodore Ts'o <tytso@mit.edu>2019-02-21 11:49:27 -0500
commitbc1d69d6151f1911ecb120a8dbd65e47210b7a72 (patch)
tree894a447e6f9669653f4668ab3f791534d6b5f460 /fs
parent231fe82b5609c5d679f81073739c6132aaf166ea (diff)
ext4: add sysfs attr /sys/fs/ext4/<disk>/journal_task
This is useful for moving journal thread into cgroup or for tracing it with ftrace/perf/blktrace. For now the only way is `pgrep jbd2/$DISK` but this is not reliable: name may be longer than "comm" limit and any task could mock it. Attribute shows pid in current pid-namespace or 0 if task is unreachable. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext4/sysfs.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index 9212a026a1f1..1748e6362d97 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -30,6 +30,7 @@ typedef enum {
attr_feature,
attr_pointer_ui,
attr_pointer_atomic,
+ attr_journal_task,
} attr_id_t;
typedef enum {
@@ -125,6 +126,14 @@ static ssize_t trigger_test_error(struct ext4_sb_info *sbi,
return count;
}
+static ssize_t journal_task_show(struct ext4_sb_info *sbi, char *buf)
+{
+ if (!sbi->s_journal)
+ return snprintf(buf, PAGE_SIZE, "<none>\n");
+ return snprintf(buf, PAGE_SIZE, "%d\n",
+ task_pid_vnr(sbi->s_journal->j_task));
+}
+
#define EXT4_ATTR(_name,_mode,_id) \
static struct ext4_attr ext4_attr_##_name = { \
.attr = {.name = __stringify(_name), .mode = _mode }, \
@@ -188,6 +197,7 @@ EXT4_RW_ATTR_SBI_UI(msg_ratelimit_burst, s_msg_ratelimit_state.burst);
EXT4_RO_ATTR_ES_UI(errors_count, s_error_count);
EXT4_ATTR(first_error_time, 0444, first_error_time);
EXT4_ATTR(last_error_time, 0444, last_error_time);
+EXT4_ATTR(journal_task, 0444, journal_task);
static unsigned int old_bump_val = 128;
EXT4_ATTR_PTR(max_writeback_mb_bump, 0444, pointer_ui, &old_bump_val);
@@ -217,6 +227,7 @@ static struct attribute *ext4_attrs[] = {
ATTR_LIST(errors_count),
ATTR_LIST(first_error_time),
ATTR_LIST(last_error_time),
+ ATTR_LIST(journal_task),
NULL,
};
@@ -304,6 +315,8 @@ static ssize_t ext4_attr_show(struct kobject *kobj,
return print_tstamp(buf, sbi->s_es, s_first_error_time);
case attr_last_error_time:
return print_tstamp(buf, sbi->s_es, s_last_error_time);
+ case attr_journal_task:
+ return journal_task_show(sbi, buf);
}
return 0;