On 2019/3/8 6:44, Damien Le Moal wrote:
> On 2019/03/07 10:19, Chao Yu wrote:
>> On 2019/3/7 2:15, Damien Le Moal wrote:
>>> On 2019/03/06 23:32, Chao Yu wrote:
>>>> On 2019-3-6 14:27, Damien Le Moal wrote:
>>>>> For zoned block devices, an array of zone types for each device is
>>>>> allocated and initialized in order to determine if a section is stored
>>>>> on a sequential zone (zone reset needed) or a conventional zone (no
>>>>> zone reset needed and regular discard applies). Considering this usage,
>>>>> the zone types stored in memory can be replaced with a bitmap to
>>>>> indicate an equivalent information, that is, if a zone is sequential or
>>>>> not. This reduces the memory usage for each zoned device by roughly 8:
>>>>> on a 14TB disk with zones of 256 MB, the zone type array consumes
>>>>> 13x4KB pages while the bitmap uses only 2x4KB pages.
>>>>>
>>>>> This patch changes the f2fs_dev_info structure blkz_type field to the
>>>>> bitmap blkz_seq. Access to this bitmap is done using the helper
>>>>> function f2fs_blkz_is_seq(), which is a rewrite of the function
>>>>> get_blkz_type().
>>>>>
>>>>> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
>>>>> ---
>>>>> Changes from v1:
>>>>> * Use kvfree() instead of kfree() to free the zone bitmap
>>>>>
>>>>> fs/f2fs/f2fs.h | 13 +++++++------
>>>>> fs/f2fs/segment.c | 23 +++++++----------------
>>>>> fs/f2fs/super.c | 13 ++++++++-----
>>>>> 3 files changed, 22 insertions(+), 27 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index 12fabd6735dd..d7b2de930352 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -1067,8 +1067,8 @@ struct f2fs_dev_info {
>>>>> block_t start_blk;
>>>>> block_t end_blk;
>>>>> #ifdef CONFIG_BLK_DEV_ZONED
>>>>> - unsigned int nr_blkz; /* Total number of zones */
>>>>> - u8 *blkz_type; /* Array of zones type */
>>>>> + unsigned int nr_blkz; /* Total number of zones */
>>>>> + unsigned long *blkz_seq; /* Bitmap indicating sequential zones */
>>>>> #endif
>>>>> };
>>>>>
>>>>> @@ -3508,16 +3508,17 @@ F2FS_FEATURE_FUNCS(lost_found, LOST_FOUND);
>>>>> F2FS_FEATURE_FUNCS(sb_chksum, SB_CHKSUM);
>>>>>
>>>>> #ifdef CONFIG_BLK_DEV_ZONED
>>>>> -static inline int get_blkz_type(struct f2fs_sb_info *sbi,
>>>>> - struct block_device *bdev, block_t blkaddr)
>>>>> +static inline bool f2fs_blkz_is_seq(struct f2fs_sb_info *sbi,
>>>>> + struct block_device *bdev, block_t blkaddr)
>>>>> {
>>>>> unsigned int zno = blkaddr >> sbi->log_blocks_per_blkz;
>>>>> int i;
>>>>>
>>>>> for (i = 0; i < sbi->s_ndevs; i++)
>>>>> if (FDEV(i).bdev == bdev)
>>>>> - return FDEV(i).blkz_type[zno];
>>>>> - return -EINVAL;
>>>>> + return test_bit(zno, FDEV(i).blkz_seq);
>>>>> + WARN_ON_ONCE(1);
>>>>> + return false;
>>>>
>>>> How about just handling this case as previous instead of treating device as
>>>> conventional zone?
>>>
>>> Before this patch, if the device is not found, an error was returned, which was
>>> propagated up by __f2fs_issue_discard_zone() as an -EIO. Do you mean to do the
>>> same here too ?
>>
>> Yes.
>
> Regarding this, I noticed that non of the callers of f2fs_target_device_index()
> actually check if the correct device was found, that is, if the block number is
> correct. I am suspecting that block number checks are already done by the time
Usually, f2fs_target_device_index()'s caller should handle the error that
we didn't found correct device index, but actually, I checked its callers,
it would be hard to handle such error, since some paths should guarantee
success at that point.
I suspect we will fail to find device index in f2fs_target_device_index()
only when encountering bit-flip or memory overflow? that would be very
rare, so I prefer to add a f2fs_bug_on in f2fs_target_device_index() to
detect any further bug, how do you think?
> f2fs_target_device_index() is called, which would mean that the correct device
> can always be found and so no special checks are required for f2fs_blkz_is_seq()
> or __f2fs_issue_discard_zone(). Can you confirm this ?
Yes, I'm okay with it.
>
>>> Now that I look at this again, another possible change that I think actually may
>>> make more sense is to pass the devi (device index) variable set by
>>> __f2fs_issue_discard_zone() to this function. No need for the device search loop
>>> doing so and invalid block numbers leading to invalid device indexes can/should
>>> be handled in __f2fs_issue_discard_zone().
>>>
>>> What do you think ?
>>
>> That will be better, please go ahead. :)
>
> I made the change but while testing I got fsync() failures due to write commands
> being issued to full sequential zones. The test case is the following simple script:
>
> #!/bin/bash
>
> for (( i = 1; i <= 2000; ++i )); do
> dd if=/dev/zero of=/mnt/foo.$i bs=65536 count=1600 conv=fsync
> done
>
> that I run on top of a dm-linear device aggregating 10 conventional zones + 256
> sequential zones of a real SMR disk.
>
> The problem systematically happens by rerunning the above script which causes
> the files to be overwritten. The problem also happens when the disk space used
> reaches 75% or above.
>
> The problem is probably not related to this patch, but I need to further
> investigate. So putting this patch on hold for now.
Oh, that is strange, maybe we can add some tracepoints (e.g. fsync,
writepages, writepage...) to find clue of such failure.
Thanks,
>
>>
>> Thanks,
>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>> }
>>>>> #endif
>>>>>
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 9b79056d705d..65941070776c 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -1703,19 +1703,8 @@ static int __f2fs_issue_discard_zone(struct f2fs_sb_info *sbi,
>>>>> blkstart -= FDEV(devi).start_blk;
>>>>> }
>>>>>
>>>>> - /*
>>>>> - * We need to know the type of the zone: for conventional zones,
>>>>> - * use regular discard if the drive supports it. For sequential
>>>>> - * zones, reset the zone write pointer.
>>>>> - */
>>>>> - switch (get_blkz_type(sbi, bdev, blkstart)) {
>>>>> -
>>>>> - case BLK_ZONE_TYPE_CONVENTIONAL:
>>>>> - if (!blk_queue_discard(bdev_get_queue(bdev)))
>>>>> - return 0;
>>>>> - return __queue_discard_cmd(sbi, bdev, lblkstart, blklen);
>>>>> - case BLK_ZONE_TYPE_SEQWRITE_REQ:
>>>>> - case BLK_ZONE_TYPE_SEQWRITE_PREF:
>>>>> + /* For sequential zones, reset the zone write pointer */
>>>>> + if (f2fs_blkz_is_seq(sbi, bdev, blkstart)) {
>>>>> sector = SECTOR_FROM_BLOCK(blkstart);
>>>>> nr_sects = SECTOR_FROM_BLOCK(blklen);
>>>>>
>>>>> @@ -1730,10 +1719,12 @@ static int __f2fs_issue_discard_zone(struct f2fs_sb_info *sbi,
>>>>> trace_f2fs_issue_reset_zone(bdev, blkstart);
>>>>> return blkdev_reset_zones(bdev, sector,
>>>>> nr_sects, GFP_NOFS);
>>>>> - default:
>>>>> - /* Unknown zone type: broken device ? */
>>>>> - return -EIO;
>>>>> }
>>>>> +
>>>>> + /* For conventional zones, use regular discard if supported */
>>>>> + if (!blk_queue_discard(bdev_get_queue(bdev)))
>>>>> + return 0;
>>>>> + return __queue_discard_cmd(sbi, bdev, lblkstart, blklen);
>>>>> }
>>>>> #endif
>>>>>
>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>> index c46a1d4318d4..91d7429be554 100644
>>>>> --- a/fs/f2fs/super.c
>>>>> +++ b/fs/f2fs/super.c
>>>>> @@ -1017,7 +1017,7 @@ static void destroy_device_list(struct f2fs_sb_info *sbi)
>>>>> for (i = 0; i < sbi->s_ndevs; i++) {
>>>>> blkdev_put(FDEV(i).bdev, FMODE_EXCL);
>>>>> #ifdef CONFIG_BLK_DEV_ZONED
>>>>> - kvfree(FDEV(i).blkz_type);
>>>>> + kvfree(FDEV(i).blkz_seq);
>>>>> #endif
>>>>> }
>>>>> kvfree(sbi->devs);
>>>>> @@ -2765,9 +2765,11 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
>>>>> if (nr_sectors & (bdev_zone_sectors(bdev) - 1))
>>>>> FDEV(devi).nr_blkz++;
>>>>>
>>>>> - FDEV(devi).blkz_type = f2fs_kmalloc(sbi, FDEV(devi).nr_blkz,
>>>>> - GFP_KERNEL);
>>>>> - if (!FDEV(devi).blkz_type)
>>>>> + FDEV(devi).blkz_seq = f2fs_kzalloc(sbi,
>>>>> + BITS_TO_LONGS(FDEV(devi).nr_blkz)
>>>>> + * sizeof(unsigned long),
>>>>> + GFP_KERNEL);
>>>>> + if (!FDEV(devi).blkz_seq)
>>>>> return -ENOMEM;
>>>>>
>>>>> #define F2FS_REPORT_NR_ZONES 4096
>>>>> @@ -2794,7 +2796,8 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
>>>>> }
>>>>>
>>>>> for (i = 0; i < nr_zones; i++) {
>>>>> - FDEV(devi).blkz_type[n] = zones[i].type;
>>>>> + if (zones[i].type != BLK_ZONE_TYPE_CONVENTIONAL)
>>>>> + set_bit(n, FDEV(devi).blkz_seq);
>>>>> sector += zones[i].len;
>>>>> n++;
>>>>> }
>>>>>
>>>>
>>>
>>>
>>
>>
>
>
