linux-kernel - Re: [PATCH v4 07/13] btrfs: zoned: use generic btrfs zone helpers to support npo2 zoned devices

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Date:   Wed, 18 May 2022 11:40:22 +0200
From:   Pankaj Raghav <p.raghav@...sung.com>
To:     <dsterba@...e.cz>
CC:     <axboe@...nel.dk>, <damien.lemoal@...nsource.wdc.com>,
        <pankydev8@...il.com>, <dsterba@...e.com>, <hch@....de>,
        <linux-nvme@...ts.infradead.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-btrfs@...r.kernel.org>, <jiangbo.365@...edance.com>,
        <linux-block@...r.kernel.org>, <gost.dev@...sung.com>,
        <linux-kernel@...r.kernel.org>, <dm-devel@...hat.com>,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: Re: [PATCH v4 07/13] btrfs: zoned: use generic btrfs zone helpers
 to support npo2 zoned devices

On 2022-05-17 14:30, David Sterba wrote:
> On Mon, May 16, 2022 at 06:54:10PM +0200, Pankaj Raghav wrote:
>> Add helpers to calculate alignment, round up and round down
>> for zoned devices. These helpers encapsulates the necessary handling for
>> power_of_2 and non-power_of_2 zone sizes. Optimized calculations are
>> performed for zone sizes that are power_of_2 with log and shifts.
>>
>> btrfs_zoned_is_aligned() is added instead of reusing bdev_zone_aligned()
>> helper due to some use cases in btrfs where zone alignment is checked
>> before having access to the underlying block device such as in this
>> function: btrfs_load_block_group_zone_info().
>>
>> Use the generic btrfs zone helpers to calculate zone index, check zone
>> alignment, round up and round down operations.
>>
>> The zone_size_shift field is not needed anymore as generic helpers are
>> used for calculation.
> 
> Overall this looks reasonable to me.
> 
>> Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
>> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
>> ---
>>  fs/btrfs/volumes.c | 24 +++++++++-------
>>  fs/btrfs/zoned.c   | 72 ++++++++++++++++++++++------------------------
>>  fs/btrfs/zoned.h   | 43 +++++++++++++++++++++++----
>>  3 files changed, 85 insertions(+), 54 deletions(-)
>>
>> --- a/fs/btrfs/zoned.c
>> +++ b/fs/btrfs/zoned.c
>> @@ -1108,14 +1101,14 @@ int btrfs_reset_device_zone(struct btrfs_device *device, u64 physical,
>>  int btrfs_ensure_empty_zones(struct btrfs_device *device, u64 start, u64 size)
>>  {
>>  	struct btrfs_zoned_device_info *zinfo = device->zone_info;
>> -	const u8 shift = zinfo->zone_size_shift;
>> -	unsigned long begin = start >> shift;
>> -	unsigned long end = (start + size) >> shift;
>> +	unsigned long begin = bdev_zone_no(device->bdev, start >> SECTOR_SHIFT);
>> +	unsigned long end =
>> +		bdev_zone_no(device->bdev, (start + size) >> SECTOR_SHIFT);
> 
> There are unsinged long types here though I'd rather see u64, better for
> a separate patch. Fixed width types are cleaner here and in the zoned
> code as there's always some conversion to/from sectors.
> 
Ok. I will probably send a separate patch to convert them to fix width
types. Is it ok if I do it as a separate patch instead of including it
in this series?
>>  	u64 pos;
>>  	int ret;
>>  
>> -	ASSERT(IS_ALIGNED(start, zinfo->zone_size));
>> -	ASSERT(IS_ALIGNED(size, zinfo->zone_size));
>> +	ASSERT(btrfs_zoned_is_aligned(start, zinfo->zone_size));
>> +	ASSERT(btrfs_zoned_is_aligned(size, zinfo->zone_size));
>>  
>>  	if (end > zinfo->nr_zones)
>>  		return -ERANGE;
>> --- a/fs/btrfs/zoned.h
>> +++ b/fs/btrfs/zoned.h
>> @@ -30,6 +30,36 @@ struct btrfs_zoned_device_info {
>>  	u32 sb_zone_location[BTRFS_SUPER_MIRROR_MAX];
>>  };
>>  
>> +static inline bool btrfs_zoned_is_aligned(u64 pos, u64 zone_size)
>> +{
>> +	u64 remainder = 0;
>> +
>> +	if (is_power_of_two_u64(zone_size))
>> +		return IS_ALIGNED(pos, zone_size);
>> +
>> +	div64_u64_rem(pos, zone_size, &remainder);
>> +	return remainder == 0;
>> +}
>> +
>> +static inline u64 btrfs_zoned_roundup(u64 pos, u64 zone_size)
>> +{
>> +	if (is_power_of_two_u64(zone_size))
>> +		return ALIGN(pos, zone_size);
> 
> Please use round_up as the rounddown helper uses round_down
> 
Ah, good catch. I will use it instead. Thanks.
>> +
>> +	return div64_u64(pos + zone_size - 1, zone_size) * zone_size;
>> +}
>> +
>> +static inline u64 btrfs_zoned_rounddown(u64 pos, u64 zone_size)
>> +{
>> +	u64 remainder = 0;
>> +	if (is_power_of_two_u64(zone_size))
>> +		return round_down(pos, zone_size);
>> +
>> +	div64_u64_rem(pos, zone_size, &remainder);
>> +	pos -= remainder;
>> +	return pos;
>> +}
>> +
>>  #ifdef CONFIG_BLK_DEV_ZONED
>>  int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>>  		       struct blk_zone *zone);