From: Pankaj Raghav <p.raghav@samsung.com>
To: <dsterba@suse.cz>
Cc: <axboe@kernel.dk>, <damien.lemoal@opensource.wdc.com>,
<pankydev8@gmail.com>, <dsterba@suse.com>, <hch@lst.de>,
<linux-nvme@lists.infradead.org>, <linux-fsdevel@vger.kernel.org>,
<linux-btrfs@vger.kernel.org>, <jiangbo.365@bytedance.com>,
<linux-block@vger.kernel.org>, <gost.dev@samsung.com>,
<linux-kernel@vger.kernel.org>, <dm-devel@redhat.com>
Subject: Re: [PATCH v4 08/13] btrfs:zoned: make sb for npo2 zone devices align with sb log offsets
Date: Wed, 18 May 2022 11:15:52 +0200 [thread overview]
Message-ID: <717a2c83-0678-9310-4c75-9ad5da0472f6@samsung.com> (raw)
In-Reply-To: <20220517124257.GD18596@twin.jikos.cz>
On 2022-05-17 14:42, David Sterba wrote:
> On Mon, May 16, 2022 at 06:54:11PM +0200, Pankaj Raghav wrote:
>> Superblocks for zoned devices are fixed as 2 zones at 0, 512GB and 4TB.
>> These are fixed at these locations so that recovery tools can reliably
>> retrieve the superblocks even if one of the mirror gets corrupted.
>>
>> power of 2 zone sizes align at these offsets irrespective of their
>> value but non power of 2 zone sizes will not align.
>>
>> To make sure the first zone at mirror 1 and mirror 2 align, write zero
>> operation is performed to move the write pointer of the first zone to
>> the expected offset. This operation is performed only after a zone reset
>> of the first zone, i.e., when the second zone that contains the sb is FULL.
>
> Is it a good idea to do the "write zeros", instead of a plain "set write
> pointer"? I assume setting write pointer is instant, while writing
> potentially hundreds of megabytes may take significiant time. As the
> functions may be called from random contexts, the increased time may
> become a problem.
>
Unfortunately it is not possible to just move the WP in zoned devices.
The only alternative that I could use is to do write zeroes which are
natively supported by some devices such as ZNS. It would be nice to know
if someone had a better solution to this instead of doing write zeroes
in zoned devices.
>> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
>> ---
>> fs/btrfs/zoned.c | 68 ++++++++++++++++++++++++++++++++++++++++++++----
>> 1 file changed, 63 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
>> index 3023c871e..805aeaa76 100644
>> --- a/fs/btrfs/zoned.c
>> +++ b/fs/btrfs/zoned.c
>> @@ -760,11 +760,44 @@ int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
>> return 0;
>> }
>>
>> +static int fill_sb_wp_offset(struct block_device *bdev, struct blk_zone *zone,
>> + int mirror, u64 *wp_ret)
>> +{
>> + u64 offset = 0;
>> + int ret = 0;
>> +
>> + ASSERT(!is_power_of_two_u64(zone->len));
>> + ASSERT(zone->wp == zone->start);
>> + ASSERT(mirror != 0);
>
> This could simply accept 0 as the mirror offset too, the calculation is
> trivial.
>
Ok. I will fix it up!
>> +
>> + switch (mirror) {
>> + case 1:
>> + div64_u64_rem(BTRFS_SB_LOG_FIRST_OFFSET >> SECTOR_SHIFT,
>> + zone->len, &offset);
>> + break;
>> + case 2:
>> + div64_u64_rem(BTRFS_SB_LOG_SECOND_OFFSET >> SECTOR_SHIFT,
>> + zone->len, &offset);
>> + break;
>> + }
>> +
>> + ret = blkdev_issue_zeroout(bdev, zone->start, offset, GFP_NOFS, 0);
>> + if (ret)
>> + return ret;
>> +
>> + /*
>> + * Non po2 zone sizes will not align naturally at
>> + * mirror 1 (512GB) and mirror 2 (4TB). The wp of the
>> + * 1st zone in those superblock mirrors need to be
>> + * moved to align at those offsets.
>> + */
>
> Please move this comment to the helper fill_sb_wp_offset itself, there
> it's more discoverable.
>
Ok.
>> + is_sb_offset_write_req =
>> + (zones_empty || (reset_zone_nr == 0)) && mirror &&
>> + !is_power_of_2(zones[0].len);
>
> Accepting 0 as the mirror number would also get rid of this wild
> expression substituting and 'if'.
>
>>
>> if (reset && reset->cond != BLK_ZONE_COND_EMPTY) {
>> ASSERT(sb_zone_is_full(reset));
>> @@ -795,6 +846,13 @@ static int sb_log_location(struct block_device *bdev, struct blk_zone *zones,
>> reset->cond = BLK_ZONE_COND_EMPTY;
>> reset->wp = reset->start;
>> }
>> +
>> + if (is_sb_offset_write_req) {
>
> And get rid of the conditional. The point of supporting both po2 and
> nonpo2 is to hide any implementation details to wrappers as much as
> possible.
>
Alright. I will move the logic to the wrapper instead of having the
conditional in this function.
>> + ret = fill_sb_wp_offset(bdev, &zones[0], mirror, &wp);
>> + if (ret)
>> + return ret;
>> + }
>> +
>> } else if (ret != -ENOENT) {
>> /*
>> * For READ, we want the previous one. Move write pointer to
Thanks for your comments.
next prev parent reply other threads:[~2022-05-18 9:16 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20220516165418eucas1p2be592d9cd4b35f6b71d39ccbe87f3fef@eucas1p2.samsung.com>
2022-05-16 16:54 ` [PATCH v4 00/13] support non power of 2 zoned devices Pankaj Raghav
[not found] ` <CGME20220516165419eucas1p104aadda60df323e6154bfc3b92103b7b@eucas1p1.samsung.com>
2022-05-16 16:54 ` [PATCH v4 01/13] block: make blkdev_nr_zones and blk_queue_zone_no generic for npo2 zsze Pankaj Raghav
[not found] ` <CGME20220516165421eucas1p2515446ac290987bdb9af24ffb835b287@eucas1p2.samsung.com>
2022-05-16 16:54 ` [PATCH v4 02/13] block: allow blk-zoned devices to have non-power-of-2 zone size Pankaj Raghav
2022-05-16 19:05 ` Pankaj Raghav
[not found] ` <CGME20220516165422eucas1p174acec28848a9c2178376f092af3fa1c@eucas1p1.samsung.com>
2022-05-16 16:54 ` [PATCH v4 03/13] nvme: zns: Allow ZNS drives that have non-power_of_2 " Pankaj Raghav
[not found] ` <CGME20220516165424eucas1p2ee38cd64260539e5cac8d1fa4d0cba38@eucas1p2.samsung.com>
2022-05-16 16:54 ` [PATCH v4 04/13] nvmet: Allow ZNS target to support non-power_of_2 zone sizes Pankaj Raghav
2022-05-17 14:19 ` Johannes Thumshirn
[not found] ` <CGME20220516165425eucas1p29fcd11d7051d9d3a9a9efc17cd3b6999@eucas1p2.samsung.com>
2022-05-16 16:54 ` [PATCH v4 05/13] btrfs: zoned: Cache superblock location in btrfs_zoned_device_info Pankaj Raghav
2022-05-16 21:58 ` David Sterba
2022-05-17 7:55 ` Pankaj Raghav
[not found] ` <CGME20220516165427eucas1p1cfd87ca44ec314ea1d2ddc8ece7259f9@eucas1p1.samsung.com>
2022-05-16 16:54 ` [PATCH v4 06/13] btrfs: zoned: Make sb_zone_number function non power of 2 compatible Pankaj Raghav
2022-05-17 6:53 ` Johannes Thumshirn
2022-05-17 11:51 ` David Sterba
[not found] ` <CGME20220516165428eucas1p1374b5f9592db3ca6a6551aff975537ce@eucas1p1.samsung.com>
2022-05-16 16:54 ` [PATCH v4 07/13] btrfs: zoned: use generic btrfs zone helpers to support npo2 zoned devices Pankaj Raghav
2022-05-17 12:30 ` David Sterba
2022-05-18 9:40 ` Pankaj Raghav
2022-05-18 11:21 ` David Sterba
2022-05-19 4:13 ` Naohiro Aota
[not found] ` <CGME20220516165429eucas1p272c8b4325a488675f08f2d7016aa6230@eucas1p2.samsung.com>
2022-05-16 16:54 ` [PATCH v4 08/13] btrfs:zoned: make sb for npo2 zone devices align with sb log offsets Pankaj Raghav
2022-05-17 6:50 ` Johannes Thumshirn
2022-05-17 8:00 ` Pankaj Raghav
2022-05-17 12:42 ` David Sterba
2022-05-18 9:15 ` Pankaj Raghav [this message]
2022-05-19 7:57 ` Johannes Thumshirn
2022-05-20 9:06 ` Pankaj Raghav
2022-05-20 9:15 ` Johannes Thumshirn
2022-05-19 7:59 ` Naohiro Aota
2022-05-20 9:09 ` Pankaj Raghav
[not found] ` <CGME20220516165430eucas1p214cca8eaba1db2c98d947444cad4f18f@eucas1p2.samsung.com>
2022-05-16 16:54 ` [PATCH v4 09/13] btrfs: zoned: relax the alignment constraint for zoned devices Pankaj Raghav
[not found] ` <CGME20220516165432eucas1p2e1ea74d44738e44745f49e37b6b9e503@eucas1p2.samsung.com>
2022-05-16 16:54 ` [PATCH v4 10/13] zonefs: allow non power of 2 " Pankaj Raghav
[not found] ` <CGME20220516165434eucas1p12b178fb83cc93470933e3d72c40e9004@eucas1p1.samsung.com>
2022-05-16 16:54 ` [PATCH v4 11/13] null_blk: " Pankaj Raghav
2022-05-17 4:12 ` kernel test robot
[not found] ` <CGME20220516165435eucas1p1dff8d9d039a76278ef1c09dba4b4e1fe@eucas1p1.samsung.com>
2022-05-16 16:54 ` [PATCH v4 12/13] null_blk: use zone_size_sects_shift for " Pankaj Raghav
[not found] ` <CGME20220516165436eucas1p178d079302dae3a9fca696b13b0390deb@eucas1p1.samsung.com>
2022-05-16 16:54 ` [PATCH v4 13/13] dm-zoned: ensure only power of 2 zone sizes are allowed Pankaj Raghav
2022-05-17 8:10 ` [PATCH v4 00/13] support non power of 2 zoned devices Christoph Hellwig
2022-05-17 9:18 ` Javier González
2022-05-18 8:00 ` Christoph Hellwig
2022-05-19 15:25 ` Javier González
2022-05-17 15:34 ` [dm-devel] " Theodore Ts'o
2022-05-18 23:06 ` Luis Chamberlain
2022-05-19 3:08 ` Damien Le Moal
2022-05-19 3:12 ` Luis Chamberlain
2022-05-19 3:19 ` Damien Le Moal
2022-05-19 7:34 ` Johannes Thumshirn
2022-05-20 3:47 ` Damien Le Moal
2022-05-20 6:07 ` Hannes Reinecke
2022-05-20 6:27 ` Javier González
2022-05-20 6:41 ` Damien Le Moal
[not found] ` <CGME20220520065941eucas1p105cf273ede995dc4bf92f3245fad09b1@eucas1p1.samsung.com>
2022-05-20 6:59 ` Javier González
2022-05-20 9:30 ` Pankaj Raghav
2022-05-20 17:18 ` David Sterba
2022-05-23 8:25 ` Pankaj Raghav
2022-05-20 9:30 ` Johannes Thumshirn
[not found] ` <CGME20220520101610eucas1p1822ca6014e2a1d55ae74476f83c4de1d@eucas1p1.samsung.com>
2022-05-20 10:16 ` Javier González
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