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    SubjectRe: [f2fs-dev] [PATCH 2/2] f2fs: tune discard speed with storage usage rate
    On 08/15, Ju Hyung Park wrote:
    > btrfs also distinguishes high/low end SSDs with mount option "ssd" and
    > "ssd_spread".
    > I believe there is no implementation inside btrfs to do it automatically.
    >
    > Providing users an option with a well made documentation is acceptable imo.

    Yeah, I was thinking about this as well. How about adding "-o disk=%s" where
    %s can be ufs/emmc/ssd/low_ssd/nvme/...?
    And, we also can decide the device type automatically w/ kmsg by default.

    >
    > And I personally think, if the default goes to a dynamically deciding
    > method, it should tell it to kmsg.
    >
    > Thanks,
    >
    > On Wed, Aug 15, 2018, 12:31 PM Chao Yu <yuchao0@huawei.com> wrote:
    >
    > > On 2018/8/15 11:20, Jaegeuk Kim wrote:
    > > > On 08/15, Chao Yu wrote:
    > > >> On 2018/8/15 10:56, Jaegeuk Kim wrote:
    > > >>> On 08/15, Chao Yu wrote:
    > > >>>> On 2018/8/15 10:33, Jaegeuk Kim wrote:
    > > >>>>> On 08/15, Chao Yu wrote:
    > > >>>>>> On 2018/8/15 1:23, Jaegeuk Kim wrote:
    > > >>>>>>> On 08/14, Chao Yu wrote:
    > > >>>>>>>> On 2018/8/14 12:19, Jaegeuk Kim wrote:
    > > >>>>>>>>> On 08/10, Chao Yu wrote:
    > > >>>>>>>>>> Previously, discard speed was fixed mostly, and in high usage
    > > rate
    > > >>>>>>>>>> device, we will speed up issuing discard, but it doesn't make
    > > sense
    > > >>>>>>>>>> that in a non-full filesystem, we still issue discard with slow
    > > speed.
    > > >>>>>>>>>
    > > >>>>>>>>> Could you please elaborate the problem in more detail? The speed
    > > depends
    > > >>>>>>>>> on how many candidates?
    > > >>>>>>>>
    > > >>>>>>>> undiscard blocks are all 4k granularity.
    > > >>>>>>>> a) utility: filesystem: 20% + undiscard blocks: 20% = flash
    > > storage: 40%
    > > >>>>>>>> b) utility: filesystem: 40% + undiscard blocks: 25% = flash
    > > storage: 65%
    > > >>>>>>>> c) utility: filesystem: 60% + undiscard blocks: 30% = flash
    > > storage: 100%
    > > >>>>>>>>
    > > >>>>>>>>
    > > >>>>>>>> 1. for case c), we need to speed up issuing discard based on
    > > utilization of
    > > >>>>>>>> "filesystem + undiscard" instead of just utilization of
    > > filesystem.
    > > >>>>>>>>
    > > >>>>>>>> - if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) {
    > > >>>>>>>> - dpolicy->granularity = 1;
    > > >>>>>>>> - dpolicy->max_interval =
    > > DEF_MIN_DISCARD_ISSUE_TIME;
    > > >>>>>>>> - }
    > > >>>>>>>>
    > > >>>>>>>> 2. If free space in storage touches therein threshold,
    > > performance will be very
    > > >>>>>>>> sensitive. In low-end storage, with high usage in space, even
    > > free space is
    > > >>>>>>>> reduced by 1%, performance will decrease a lot.
    > > >>>>>>>
    > > >>>>>>> So, we may need to distinguish low-end vs. high-end storage. In
    > > high-end case,
    > > >>>>>>> it'd be better to avoid IO contention, while low-end device wants
    > > to get more
    > > >>>>>>> discard commands as much as possible. So, how about adding an
    > > option for this
    > > >>>>>>> as a tunable point?
    > > >>>>>>
    > > >>>>>> Agreed, how about adding a sysfs entry discard_tunning:
    > > >>>>>> 1: enabled, use 4k granularity, self-adapted speed based on real
    > > device free space.
    > > >>>>>> 0: disabled, use dcc->discard_granularity, fixed speed.
    > > >>>>>>
    > > >>>>>> By default: enabled
    > > >>>>>>
    > > >>>>>> How do you think?
    > > >>>>>
    > > >>>>> I don't think this is proper with a sysfs entry, since we already
    > > know the
    > > >>>>
    > > >>>> You mean by storage capacity? <= 32GB means low-end?
    > > >>>
    > > >>> Yes, that's current condition to judge it. If there is any other
    > > method, it'd be
    > > >>
    > > >> That would be hard code...
    > > >>
    > > >> Still I have not got any other method to do the judgment except
    > > capacity.
    > > >
    > > > Maybe ufs or emmc?
    > >
    > > Yeah, that's may be a good way.
    > >
    > > I remember very initial version UFS has very poor discard performance, for
    > > that
    > > kind of storage, it will be not accurate?
    > >
    > > Let me check whether there is a flag to distinguish ufs/emmc.
    > >
    > > Thanks,
    > >
    > > >
    > > >>
    > > >> Thanks,
    > > >>
    > > >>> better to change it.
    > > >>>
    > > >>>>
    > > >>>> Thanks,
    > > >>>>
    > > >>>>> device type when mounting the partition. We won't require to change
    > > the policy
    > > >>>>> on the fly. And, I still don't get to change the default.
    > > >>>>>
    > > >>>>>>
    > > >>>>>> Thanks,
    > > >>>>>>
    > > >>>>>>>
    > > >>>>>>>>
    > > >>>>>>>> IMO, in above cases, we'd better to issue discard with high speed
    > > for c), middle
    > > >>>>>>>> speed for b), and low speed for a).
    > > >>>>>>>>
    > > >>>>>>>> How do you think?
    > > >>>>>>>>
    > > >>>>>>>> Thanks,
    > > >>>>>>>>
    > > >>>>>>>>>
    > > >>>>>>>>> Thanks,
    > > >>>>>>>>>
    > > >>>>>>>>>>
    > > >>>>>>>>>> Anyway, it comes out undiscarded block makes FTL GC be lower
    > > efficient
    > > >>>>>>>>>> and causing high lifetime overhead.
    > > >>>>>>>>>>
    > > >>>>>>>>>> Let's tune discard speed as below:
    > > >>>>>>>>>>
    > > >>>>>>>>>> a. adjust default issue interval:
    > > >>>>>>>>>> original after
    > > >>>>>>>>>> min_interval: 50ms 100ms
    > > >>>>>>>>>> mid_interval: 500ms 1000ms
    > > >>>>>>>>>> max_interval: 60000ms 10000ms
    > > >>>>>>>>>>
    > > >>>>>>>>>> b. if last time we stop issuing discard due to IO interruption
    > > of user,
    > > >>>>>>>>>> let's reset all {min,mid,max}_interval to default one.
    > > >>>>>>>>>>
    > > >>>>>>>>>> c. tune {min,mid,max}_interval with below calculation method:
    > > >>>>>>>>>>
    > > >>>>>>>>>> base_interval = default_interval / 10;
    > > >>>>>>>>>> total_interval = default_interval - base_interval;
    > > >>>>>>>>>> interval = base_interval + total_interval * (100 - dev_util) /
    > > 100;
    > > >>>>>>>>>>
    > > >>>>>>>>>> For example:
    > > >>>>>>>>>> min_interval (:100ms)
    > > >>>>>>>>>> dev_util (%) interval (ms)
    > > >>>>>>>>>> 0 100
    > > >>>>>>>>>> 10 91
    > > >>>>>>>>>> 20 82
    > > >>>>>>>>>> 30 73
    > > >>>>>>>>>> ...
    > > >>>>>>>>>> 80 28
    > > >>>>>>>>>> 90 19
    > > >>>>>>>>>> 100 10
    > > >>>>>>>>>>
    > > >>>>>>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
    > > >>>>>>>>>> ---
    > > >>>>>>>>>> fs/f2fs/f2fs.h | 11 ++++----
    > > >>>>>>>>>> fs/f2fs/segment.c | 64
    > > +++++++++++++++++++++++++++++++++++++----------
    > > >>>>>>>>>> fs/f2fs/segment.h | 9 +++++++
    > > >>>>>>>>>> fs/f2fs/super.c | 2 +-
    > > >>>>>>>>>> 4 files changed, 67 insertions(+), 19 deletions(-)
    > > >>>>>>>>>>
    > > >>>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
    > > >>>>>>>>>> index 273ffdaf4891..a1dd2e1c3cb9 100644
    > > >>>>>>>>>> --- a/fs/f2fs/f2fs.h
    > > >>>>>>>>>> +++ b/fs/f2fs/f2fs.h
    > > >>>>>>>>>> @@ -185,10 +185,9 @@ enum {
    > > >>>>>>>>>>
    > > >>>>>>>>>> #define MAX_DISCARD_BLOCKS(sbi) BLKS_PER_SEC(sbi)
    > > >>>>>>>>>> #define DEF_MAX_DISCARD_REQUEST 8 /* issue 8
    > > discards per round */
    > > >>>>>>>>>> -#define DEF_MIN_DISCARD_ISSUE_TIME 50 /* 50 ms, if
    > > exists */
    > > >>>>>>>>>> -#define DEF_MID_DISCARD_ISSUE_TIME 500 /* 500 ms, if
    > > device busy */
    > > >>>>>>>>>> -#define DEF_MAX_DISCARD_ISSUE_TIME 60000 /* 60 s, if no
    > > candidates */
    > > >>>>>>>>>> -#define DEF_DISCARD_URGENT_UTIL 80 /* do more
    > > discard over 80% */
    > > >>>>>>>>>> +#define DEF_MIN_DISCARD_ISSUE_TIME 100 /* 100 ms, if
    > > exists */
    > > >>>>>>>>>> +#define DEF_MID_DISCARD_ISSUE_TIME 1000 /* 1000 ms, if
    > > device busy */
    > > >>>>>>>>>> +#define DEF_MAX_DISCARD_ISSUE_TIME 10000 /* 10000 ms, if no
    > > candidates */
    > > >>>>>>>>>> #define DEF_CP_INTERVAL 60 /* 60 secs
    > > */
    > > >>>>>>>>>> #define DEF_IDLE_INTERVAL 5 /* 5 secs */
    > > >>>>>>>>>>
    > > >>>>>>>>>> @@ -248,7 +247,8 @@ struct discard_entry {
    > > >>>>>>>>>> };
    > > >>>>>>>>>>
    > > >>>>>>>>>> /* default discard granularity of inner discard thread, unit:
    > > block count */
    > > >>>>>>>>>> -#define DEFAULT_DISCARD_GRANULARITY 1
    > > >>>>>>>>>> +#define MID_DISCARD_GRANULARITY 16
    > > >>>>>>>>>> +#define MIN_DISCARD_GRANULARITY 1
    > > >>>>>>>>>>
    > > >>>>>>>>>> /* max discard pend list number */
    > > >>>>>>>>>> #define MAX_PLIST_NUM 512
    > > >>>>>>>>>> @@ -330,6 +330,7 @@ struct discard_cmd_control {
    > > >>>>>>>>>> atomic_t discard_cmd_cnt; /* # of cached cmd
    > > count */
    > > >>>>>>>>>> struct rb_root root; /* root of discard
    > > rb-tree */
    > > >>>>>>>>>> bool rbtree_check; /* config for
    > > consistence check */
    > > >>>>>>>>>> + bool io_interrupted; /* last state of
    > > io interrupted */
    > > >>>>>>>>>> };
    > > >>>>>>>>>>
    > > >>>>>>>>>> /* for the list of fsync inodes, used only during recovery */
    > > >>>>>>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
    > > >>>>>>>>>> index 8b52e8dfb12f..9564aaf1f27b 100644
    > > >>>>>>>>>> --- a/fs/f2fs/segment.c
    > > >>>>>>>>>> +++ b/fs/f2fs/segment.c
    > > >>>>>>>>>> @@ -968,6 +968,44 @@ static void __check_sit_bitmap(struct
    > > f2fs_sb_info *sbi,
    > > >>>>>>>>>> #endif
    > > >>>>>>>>>> }
    > > >>>>>>>>>>
    > > >>>>>>>>>> +static void __adjust_discard_speed(unsigned int *interval,
    > > >>>>>>>>>> + unsigned int def_interval, int
    > > dev_util)
    > > >>>>>>>>>> +{
    > > >>>>>>>>>> + unsigned int base_interval, total_interval;
    > > >>>>>>>>>> +
    > > >>>>>>>>>> + base_interval = def_interval / 10;
    > > >>>>>>>>>> + total_interval = def_interval - base_interval;
    > > >>>>>>>>>> +
    > > >>>>>>>>>> + /*
    > > >>>>>>>>>> + * if def_interval = 100, adjusted interval should be in
    > > range of
    > > >>>>>>>>>> + * [10, 100].
    > > >>>>>>>>>> + */
    > > >>>>>>>>>> + *interval = base_interval + total_interval * (100 -
    > > dev_util) / 100;
    > > >>>>>>>>>> +}
    > > >>>>>>>>>> +
    > > >>>>>>>>>> +static void __tune_discard_policy(struct f2fs_sb_info *sbi,
    > > >>>>>>>>>> + struct discard_policy
    > > *dpolicy)
    > > >>>>>>>>>> +{
    > > >>>>>>>>>> + struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
    > > >>>>>>>>>> + int dev_util;
    > > >>>>>>>>>> +
    > > >>>>>>>>>> + if (dcc->io_interrupted) {
    > > >>>>>>>>>> + dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> + dpolicy->mid_interval = DEF_MID_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> + dpolicy->max_interval = DEF_MAX_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> + return;
    > > >>>>>>>>>> + }
    > > >>>>>>>>>> +
    > > >>>>>>>>>> + dev_util = dev_utilization(sbi);
    > > >>>>>>>>>> +
    > > >>>>>>>>>> + __adjust_discard_speed(&dpolicy->min_interval,
    > > >>>>>>>>>> + DEF_MIN_DISCARD_ISSUE_TIME,
    > > dev_util);
    > > >>>>>>>>>> + __adjust_discard_speed(&dpolicy->mid_interval,
    > > >>>>>>>>>> + DEF_MID_DISCARD_ISSUE_TIME,
    > > dev_util);
    > > >>>>>>>>>> + __adjust_discard_speed(&dpolicy->max_interval,
    > > >>>>>>>>>> + DEF_MAX_DISCARD_ISSUE_TIME,
    > > dev_util);
    > > >>>>>>>>>> +}
    > > >>>>>>>>>> +
    > > >>>>>>>>>> static void __init_discard_policy(struct f2fs_sb_info *sbi,
    > > >>>>>>>>>> struct discard_policy *dpolicy,
    > > >>>>>>>>>> int discard_type, unsigned int
    > > granularity)
    > > >>>>>>>>>> @@ -982,20 +1020,11 @@ static void __init_discard_policy(struct
    > > f2fs_sb_info *sbi,
    > > >>>>>>>>>> dpolicy->io_aware_gran = MAX_PLIST_NUM;
    > > >>>>>>>>>>
    > > >>>>>>>>>> if (discard_type == DPOLICY_BG) {
    > > >>>>>>>>>> - dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> - dpolicy->mid_interval = DEF_MID_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> - dpolicy->max_interval = DEF_MAX_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> dpolicy->io_aware = true;
    > > >>>>>>>>>> dpolicy->sync = false;
    > > >>>>>>>>>> dpolicy->ordered = true;
    > > >>>>>>>>>> - if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) {
    > > >>>>>>>>>> - dpolicy->granularity = 1;
    > > >>>>>>>>>> - dpolicy->max_interval =
    > > DEF_MIN_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> - }
    > > >>>>>>>>>> + __tune_discard_policy(sbi, dpolicy);
    > > >>>>>>>>>> } else if (discard_type == DPOLICY_FORCE) {
    > > >>>>>>>>>> - dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> - dpolicy->mid_interval = DEF_MID_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> - dpolicy->max_interval = DEF_MAX_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> dpolicy->io_aware = false;
    > > >>>>>>>>>> } else if (discard_type == DPOLICY_FSTRIM) {
    > > >>>>>>>>>> dpolicy->io_aware = false;
    > > >>>>>>>>>> @@ -1353,6 +1382,8 @@ static unsigned int
    > > __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi,
    > > >>>>>>>>>> if (!issued && io_interrupted)
    > > >>>>>>>>>> issued = -1;
    > > >>>>>>>>>>
    > > >>>>>>>>>> + dcc->io_interrupted = io_interrupted;
    > > >>>>>>>>>> +
    > > >>>>>>>>>> return issued;
    > > >>>>>>>>>> }
    > > >>>>>>>>>>
    > > >>>>>>>>>> @@ -1370,7 +1401,7 @@ static int __issue_discard_cmd(struct
    > > f2fs_sb_info *sbi,
    > > >>>>>>>>>> if (i + 1 < dpolicy->granularity)
    > > >>>>>>>>>> break;
    > > >>>>>>>>>>
    > > >>>>>>>>>> - if (i < DEFAULT_DISCARD_GRANULARITY &&
    > > dpolicy->ordered)
    > > >>>>>>>>>> + if (i < MID_DISCARD_GRANULARITY &&
    > > dpolicy->ordered)
    > > >>>>>>>>>> return __issue_discard_cmd_orderly(sbi,
    > > dpolicy);
    > > >>>>>>>>>>
    > > >>>>>>>>>> pend_list = &dcc->pend_list[i];
    > > >>>>>>>>>> @@ -1407,6 +1438,8 @@ static int __issue_discard_cmd(struct
    > > f2fs_sb_info *sbi,
    > > >>>>>>>>>> if (!issued && io_interrupted)
    > > >>>>>>>>>> issued = -1;
    > > >>>>>>>>>>
    > > >>>>>>>>>> + dcc->io_interrupted = io_interrupted;
    > > >>>>>>>>>> +
    > > >>>>>>>>>> return issued;
    > > >>>>>>>>>> }
    > > >>>>>>>>>>
    > > >>>>>>>>>> @@ -1576,7 +1609,11 @@ static int issue_discard_thread(void
    > > *data)
    > > >>>>>>>>>> struct f2fs_sb_info *sbi = data;
    > > >>>>>>>>>> struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
    > > >>>>>>>>>> wait_queue_head_t *q = &dcc->discard_wait_queue;
    > > >>>>>>>>>> - struct discard_policy dpolicy;
    > > >>>>>>>>>> + struct discard_policy dpolicy = {
    > > >>>>>>>>>> + .min_interval = DEF_MIN_DISCARD_ISSUE_TIME,
    > > >>>>>>>>>> + .mid_interval = DEF_MID_DISCARD_ISSUE_TIME,
    > > >>>>>>>>>> + .max_interval = DEF_MAX_DISCARD_ISSUE_TIME,
    > > >>>>>>>>>> + };
    > > >>>>>>>>>> unsigned int wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
    > > >>>>>>>>>> int issued;
    > > >>>>>>>>>>
    > > >>>>>>>>>> @@ -1929,7 +1966,7 @@ static int
    > > create_discard_cmd_control(struct f2fs_sb_info *sbi)
    > > >>>>>>>>>> if (!dcc)
    > > >>>>>>>>>> return -ENOMEM;
    > > >>>>>>>>>>
    > > >>>>>>>>>> - dcc->discard_granularity = DEFAULT_DISCARD_GRANULARITY;
    > > >>>>>>>>>> + dcc->discard_granularity = MIN_DISCARD_GRANULARITY;
    > > >>>>>>>>>> INIT_LIST_HEAD(&dcc->entry_list);
    > > >>>>>>>>>> for (i = 0; i < MAX_PLIST_NUM; i++)
    > > >>>>>>>>>> INIT_LIST_HEAD(&dcc->pend_list[i]);
    > > >>>>>>>>>> @@ -1945,6 +1982,7 @@ static int
    > > create_discard_cmd_control(struct f2fs_sb_info *sbi)
    > > >>>>>>>>>> dcc->next_pos = 0;
    > > >>>>>>>>>> dcc->root = RB_ROOT;
    > > >>>>>>>>>> dcc->rbtree_check = false;
    > > >>>>>>>>>> + dcc->io_interrupted = false;
    > > >>>>>>>>>>
    > > >>>>>>>>>> init_waitqueue_head(&dcc->discard_wait_queue);
    > > >>>>>>>>>> SM_I(sbi)->dcc_info = dcc;
    > > >>>>>>>>>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
    > > >>>>>>>>>> index 422b0ceb1eaa..63b4da72cd34 100644
    > > >>>>>>>>>> --- a/fs/f2fs/segment.h
    > > >>>>>>>>>> +++ b/fs/f2fs/segment.h
    > > >>>>>>>>>> @@ -616,6 +616,15 @@ static inline int utilization(struct
    > > f2fs_sb_info *sbi)
    > > >>>>>>>>>> sbi->user_block_count);
    > > >>>>>>>>>> }
    > > >>>>>>>>>>
    > > >>>>>>>>>> +static inline int dev_utilization(struct f2fs_sb_info *sbi)
    > > >>>>>>>>>> +{
    > > >>>>>>>>>> + unsigned int dev_blks;
    > > >>>>>>>>>> +
    > > >>>>>>>>>> + dev_blks = valid_user_blocks(sbi) +
    > > SM_I(sbi)->dcc_info->undiscard_blks;
    > > >>>>>>>>>> + return div_u64((u64)dev_blks * 100,
    > > >>>>>>>>>> + MAIN_SEGS(sbi) << sbi->log_blocks_per_seg);
    > > >>>>>>>>>> +}
    > > >>>>>>>>>> +
    > > >>>>>>>>>> /*
    > > >>>>>>>>>> * Sometimes f2fs may be better to drop out-of-place update
    > > policy.
    > > >>>>>>>>>> * And, users can control the policy through sysfs entries.
    > > >>>>>>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
    > > >>>>>>>>>> index b055f2ea77c5..55ed76daad23 100644
    > > >>>>>>>>>> --- a/fs/f2fs/super.c
    > > >>>>>>>>>> +++ b/fs/f2fs/super.c
    > > >>>>>>>>>> @@ -2862,7 +2862,7 @@ static void f2fs_tuning_parameters(struct
    > > f2fs_sb_info *sbi)
    > > >>>>>>>>>> /* adjust parameters according to the volume size */
    > > >>>>>>>>>> if (sm_i->main_segments <= SMALL_VOLUME_SEGMENTS) {
    > > >>>>>>>>>> F2FS_OPTION(sbi).alloc_mode = ALLOC_MODE_REUSE;
    > > >>>>>>>>>> - sm_i->dcc_info->discard_granularity = 1;
    > > >>>>>>>>>> + sm_i->dcc_info->discard_granularity =
    > > MIN_DISCARD_GRANULARITY;
    > > >>>>>>>>>> sm_i->ipu_policy = 1 << F2FS_IPU_FORCE;
    > > >>>>>>>>>> }
    > > >>>>>>>>>>
    > > >>>>>>>>>> --
    > > >>>>>>>>>> 2.18.0.rc1
    > > >>>>>>>>>
    > > >>>>>>>>> .
    > > >>>>>>>>>
    > > >>>>>>>
    > > >>>>>>> .
    > > >>>>>>>
    > > >>>>>
    > > >>>>> .
    > > >>>>>
    > > >>>
    > > >>> .
    > > >>>
    > > >
    > > > .
    > > >
    > >
    > >
    > >
    > > ------------------------------------------------------------------------------
    > > Check out the vibrant tech community on one of the world's most
    > > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
    > > _______________________________________________
    > > Linux-f2fs-devel mailing list
    > > Linux-f2fs-devel@lists.sourceforge.net
    > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
    > >

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