From bc1d69d6151f1911ecb120a8dbd65e47210b7a72 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Thu, 21 Feb 2019 11:49:27 -0500 Subject: ext4: add sysfs attr /sys/fs/ext4//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 Signed-off-by: Theodore Ts'o --- fs/ext4/sysfs.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'fs/ext4') 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, "\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; -- cgit v1.2.3-59-g8ed1b