Re: [RFC PATCH] ext4: auto batched discard support at kernel thread

Kyungmin Park
2011-12-05T10:12:04Z

On 12/5/11, Lukas Czerner <lczerner@redhat.com> wrote:
> On Fri, 2 Dec 2011, Kyungmin Park wrote:
>
>> Hi,
>>
>> It's proof of concept to run kernel thread for batched discard.
>>
>> Now it can run fitrim at user level. but it's not clear which deamon run
>> this activity.
>> In case of android platform, the launcher is candidate
>> but user can change the default launcher then it can't use the fitrim any
>> more.
>
> I do not thing this logic belongs to the kernel. You would be perfectly
> fine just with cron lob (or launcher) running fitrim regularly and it is
> so much easier than pushing this functionality to the kernel side. Not
> talking about the fact that cron (and others) gives you *much* more
> flexibility in running fitrim on regular basis and I do not think you
> want to reimplement cron within the kernel.
>
> Also it seems to me that the problem you're trying to solve should be
> rather solved on the Android (launcher) side.
>
> I am against this functionality, sorry.
No problem, It will be support at user space as original design. e.g.,
system settings

Thank you for all comments.

BR,
Kyungmin Park
>
> Thanks!
> -Lukas
>
>>
>> To address this issue. no dependency with platform. run the fitrim at
>> kernel.
>> Basically don't bother the user it runs at 2 clock. Please note that if
>> it's clean state, it doesn't take much time.
>>
>> Please give opinions and comments.
>>
>> Thank you,
>> Kyungmin Park
>> ---
>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index 5b0e26a..2cad9b3 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -942,6 +942,7 @@ struct ext4_inode_info {
>>
>> #define EXT4_MOUNT2_EXPLICIT_DELALLOC 0x00000001 /* User explicitly
>> specified delalloc */
>> +#define EXT4_MOUNT2_AUTO_DISCARD 0x00000002 /* Auto batched discard */
>>
>> #define clear_opt(sb, opt) EXT4_SB(sb)->s_mount_opt &= \
>> ~EXT4_MOUNT_##opt
>> @@ -1249,6 +1250,10 @@ struct ext4_sb_info {
>>
>> /* record the last minlen when FITRIM is called. */
>> atomic_t s_last_trim_minblks;
>> +
>> + /* timer for periodic auto batched discard */
>> + struct timer_list s_auto_discard;
>> + struct task_struct *s_auto_discard_thread;
>> };
>>
>> static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index 3858767..a2e9920 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -818,6 +818,10 @@ static void ext4_put_super(struct super_block *sb)
>> ext4_abort(sb, "Couldn't clean up the journal");
>> }
>>
>> + if (test_opt2(sb, AUTO_DISCARD)) {
>> + kthread_stop(sbi->s_auto_discard_thread);
>> + del_timer(&sbi->s_auto_discard);
>> + }
>> del_timer(&sbi->s_err_report);
>> ext4_release_system_zone(sb);
>> ext4_mb_release(sb);
>> @@ -1144,6 +1148,9 @@ static int ext4_show_options(struct seq_file *seq,
>> struct vfsmount *vfs)
>> if (test_opt(sb, DISCARD) && !(def_mount_opts & EXT4_DEFM_DISCARD))
>> seq_puts(seq, ",discard");
>>
>> + if (test_opt2(sb, AUTO_DISCARD))
>> + seq_puts(seq, ",auto_batched_discard");
>> +
>> if (test_opt(sb, NOLOAD))
>> seq_puts(seq, ",norecovery");
>>
>> @@ -1333,7 +1340,7 @@ enum {
>> Opt_nomblk_io_submit, Opt_block_validity, Opt_noblock_validity,
>> Opt_inode_readahead_blks, Opt_journal_ioprio,
>> Opt_dioread_nolock, Opt_dioread_lock,
>> - Opt_discard, Opt_nodiscard,
>> + Opt_discard, Opt_nodiscard, Opt_auto_discard,
>> Opt_init_inode_table, Opt_noinit_inode_table,
>> };
>>
>> @@ -1407,6 +1414,7 @@ static const match_table_t tokens = {
>> {Opt_dioread_lock, "dioread_lock"},
>> {Opt_discard, "discard"},
>> {Opt_nodiscard, "nodiscard"},
>> + {Opt_auto_discard, "auto_batched_discard"},
>> {Opt_init_inode_table, "init_itable=%u"},
>> {Opt_init_inode_table, "init_itable"},
>> {Opt_noinit_inode_table, "noinit_itable"},
>> @@ -1886,6 +1894,9 @@ set_qf_format:
>> case Opt_nodiscard:
>> clear_opt(sb, DISCARD);
>> break;
>> + case Opt_auto_discard:
>> + set_opt2(sb, AUTO_DISCARD);
>> + break;
>> case Opt_dioread_nolock:
>> set_opt(sb, DIOREAD_NOLOCK);
>> break;
>> @@ -2763,6 +2774,71 @@ static void print_daily_error_info(unsigned long
>> arg)
>> mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ); /* Once a day */
>> }
>>
>> +/*
>> + * This function is called once a day to make a trim the device
>> + */
>> +static int ext4_auto_batched_discard_thread(void *data)
>> +{
>> + struct super_block *sb = data;
>> + struct ext4_sb_info *sbi = EXT4_SB(sb);
>> + struct fstrim_range range;
>> + struct timeval now;
>> + struct tm tm;
>> + long next;
>> + int ret;
>> +
>> + set_freezable();
>> +
>> + for (;;) {
>> + if (kthread_should_stop())
>> + break;
>> +
>> + if (try_to_freeze())
>> + continue;
>> +
>> + range.start = 0;
>> + range.len = ~(__u64)0;
>> + range.minlen = SZ_1M;
>> +
>> + ret = ext4_trim_fs(sb, &range);
>> + if (ret < 0)
>> + ext4_msg(sb, KERN_NOTICE, "error count: %u", ret);
>> + else
>> + ext4_msg(sb, KERN_NOTICE, "trimmed size %llu",
>> + range.len);
>> +
>> + do_gettimeofday(&now);
>> + time_to_tm((time_t) now.tv_sec, 0, &tm);
>> +
>> + /* Run the every day at 2 clock */
>> + /* XXX need to consider the timezone? */
>> + next = 2 - tm.tm_hour;
>> + if (next <= 0)
>> + next += 24;
>> + next *= 60*60*HZ;
>> +
>> + /* Re-arm the timer for next trim */
>> + mod_timer(&sbi->s_auto_discard, jiffies + next);
>> +
>> + set_current_state(TASK_INTERRUPTIBLE);
>> + schedule();
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void ext4_auto_batched_discard(unsigned long arg)
>> +{
>> + struct super_block *sb = (struct super_block *) arg;
>> + struct ext4_sb_info *sbi = EXT4_SB(sb);
>> +
>> + /*
>> + * The ext4_trim_fs can't run at timer context
>> + * So use the created kthread.
>> + */
>> + wake_up_process(sbi->s_auto_discard_thread);
>> +}
>> +
>> /* Find next suitable group and run ext4_init_inode_table */
>> static int ext4_run_li_request(struct ext4_li_request *elr)
>> {
>> @@ -3576,6 +3652,21 @@ static int ext4_fill_super(struct super_block *sb,
>> void *data, int silent)
>> sbi->s_err_report.function = print_daily_error_info;
>> sbi->s_err_report.data = (unsigned long) sb;
>>
>> + if (test_opt2(sb, AUTO_DISCARD)) {
>> + init_timer(&sbi->s_auto_discard);
>> + sbi->s_auto_discard.function = ext4_auto_batched_discard;
>> + sbi->s_auto_discard.data = (unsigned long) sb;
>> + sbi->s_auto_discard_thread =
>> + kthread_create(ext4_auto_batched_discard_thread, sb,
>> + "ext4-batched-discard");
>> + if (IS_ERR(sbi->s_auto_discard_thread)) {
>> + err = PTR_ERR(sbi->s_auto_discard_thread);
>> + goto failed_mount2;
>> + }
>> + /* One hour is enough to know the time */
>> + mod_timer(&sbi->s_auto_discard, jiffies + 1*60*60*HZ);
>> + }
>> +
>> err = percpu_counter_init(&sbi->s_freeclusters_counter,
>> ext4_count_free_clusters(sb));
>> if (!err) {
>> @@ -3848,6 +3939,10 @@ failed_mount_wq:
>> sbi->s_journal = NULL;
>> }
>> failed_mount3:
>> + if (test_opt2(sb, AUTO_DISCARD)) {
>> + kthread_stop(sbi->s_auto_discard_thread);
>> + del_timer(&sbi->s_auto_discard);
>> + }
>> del_timer(&sbi->s_err_report);
>> if (sbi->s_flex_groups)
>> ext4_kvfree(sbi->s_flex_groups);
>> @@ -4546,6 +4641,22 @@ static int ext4_remount(struct super_block *sb, int
>> *flags, char *data)
>> if (sbi->s_journal == NULL)
>> ext4_commit_super(sb, 1);
>>
>> + if (test_opt2(sb, AUTO_DISCARD) && !sbi->s_auto_discard_thread) {
>> + init_timer(&sbi->s_auto_discard);
>> + sbi->s_auto_discard.function = ext4_auto_batched_discard;
>> + sbi->s_auto_discard.data = (unsigned long) sb;
>> + sbi->s_auto_discard_thread =
>> + kthread_create(ext4_auto_batched_discard_thread, sb,
>> + "ext4-batched-discard");
>> + if (IS_ERR(sbi->s_auto_discard_thread)) {
>> + err = PTR_ERR(sbi->s_auto_discard_thread);
>> + goto restore_opts;
>> + }
>> +
>> + /* One hour is enough to know the time */
>> + mod_timer(&sbi->s_auto_discard, jiffies + 1*60*60*HZ);
>> + }
>> +
>> #ifdef CONFIG_QUOTA
>> /* Release old quota file names */
>> for (i = 0; i < MAXQUOTAS; i++)
>>
>
> --
>