Re: [PATCH v3 02/27] btrfs: Get zone information of zoned block devices

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2019/08/15 21:47, Anand Jain wrote:
> On 8/8/19 5:30 PM, Naohiro Aota wrote:
>> If a zoned block device is found, get its zone information (number of zones
>> and zone size) using the new helper function btrfs_get_dev_zonetypes().  To
>> avoid costly run-time zone report commands to test the device zones type
>> during block allocation, attach the seq_zones bitmap to the device
>> structure to indicate if a zone is sequential or accept random writes. Also
>> it attaches the empty_zones bitmap to indicate if a zone is empty or not.
>>
>> This patch also introduces the helper function btrfs_dev_is_sequential() to
>> test if the zone storing a block is a sequential write required zone and
>> btrfs_dev_is_empty_zone() to test if the zone is a empty zone.
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
>> ---
>>   fs/btrfs/Makefile  |   2 +-
>>   fs/btrfs/hmzoned.c | 162 +++++++++++++++++++++++++++++++++++++++++++++
>>   fs/btrfs/hmzoned.h |  79 ++++++++++++++++++++++
>>   fs/btrfs/volumes.c |  18 ++++-
>>   fs/btrfs/volumes.h |   4 ++
>>   5 files changed, 262 insertions(+), 3 deletions(-)
>>   create mode 100644 fs/btrfs/hmzoned.c
>>   create mode 100644 fs/btrfs/hmzoned.h
>>
>> diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
>> index 76a843198bcb..8d93abb31074 100644
>> --- a/fs/btrfs/Makefile
>> +++ b/fs/btrfs/Makefile
>> @@ -11,7 +11,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
>>   	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
>>   	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
>>   	   uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o \
>> -	   block-rsv.o delalloc-space.o
>> +	   block-rsv.o delalloc-space.o hmzoned.o
>>   
>>   btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
>>   btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
>> diff --git a/fs/btrfs/hmzoned.c b/fs/btrfs/hmzoned.c
>> new file mode 100644
>> index 000000000000..bfd04792dd62
>> --- /dev/null
>> +++ b/fs/btrfs/hmzoned.c
>> @@ -0,0 +1,162 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
>> + * Authors:
>> + *	Naohiro Aota	<naohiro.aota@wdc.com>
>> + *	Damien Le Moal	<damien.lemoal@wdc.com>
>> + */
>> +
>> +#include <linux/slab.h>
>> +#include <linux/blkdev.h>
>> +#include "ctree.h"
>> +#include "volumes.h"
>> +#include "hmzoned.h"
>> +#include "rcu-string.h"
>> +
>> +/* Maximum number of zones to report per blkdev_report_zones() call */
>> +#define BTRFS_REPORT_NR_ZONES   4096
>> +
>> +static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
>> +			       struct blk_zone **zones_ret,
>> +			       unsigned int *nr_zones, gfp_t gfp_mask)
>> +{
>> +	struct blk_zone *zones = *zones_ret;
>> +	int ret;
>> +
>> +	if (!zones) {
>> +		zones = kcalloc(*nr_zones, sizeof(struct blk_zone), GFP_KERNEL);
>> +		if (!zones)
>> +			return -ENOMEM;
>> +	}
>> +
>> +	ret = blkdev_report_zones(device->bdev, pos >> SECTOR_SHIFT,
>> +				  zones, nr_zones, gfp_mask);
>> +	if (ret != 0) {
>> +		btrfs_err_in_rcu(device->fs_info,
>> +				 "get zone at %llu on %s failed %d", pos,
>> +				 rcu_str_deref(device->name), ret);
>> +		return ret;
>> +	}
>> +	if (!*nr_zones)
>> +		return -EIO;
>> +
>> +	*zones_ret = zones;
>> +
>> +	return 0;
>> +}
>> +
>> +int btrfs_get_dev_zone_info(struct btrfs_device *device)
>> +{
>> +	struct btrfs_zoned_device_info *zone_info = NULL;
>> +	struct block_device *bdev = device->bdev;
>> +	sector_t nr_sectors = bdev->bd_part->nr_sects;
>> +	sector_t sector = 0;
>> +	struct blk_zone *zones = NULL;
>> +	unsigned int i, nreported = 0, nr_zones;
>> +	unsigned int zone_sectors;
>> +	int ret;
>> +
>> +	if (!bdev_is_zoned(bdev))
>> +		return 0;
>> +
>> +	zone_info = kzalloc(sizeof(*zone_info), GFP_KERNEL);
>> +	if (!zone_info)
>> +		return -ENOMEM;
>> +
>> +	zone_sectors = bdev_zone_sectors(bdev);
>> +	ASSERT(is_power_of_2(zone_sectors));
>> +	zone_info->zone_size = (u64)zone_sectors << SECTOR_SHIFT;
>> +	zone_info->zone_size_shift = ilog2(zone_info->zone_size);
>> +	zone_info->nr_zones = nr_sectors >> ilog2(bdev_zone_sectors(bdev));
>> +	if (nr_sectors & (bdev_zone_sectors(bdev) - 1))
>> +		zone_info->nr_zones++;
>> +
>> +	zone_info->seq_zones = kcalloc(BITS_TO_LONGS(zone_info->nr_zones),
>> +				       sizeof(*zone_info->seq_zones),
>> +				       GFP_KERNEL);
>> +	if (!zone_info->seq_zones) {
>> +		ret = -ENOMEM;
>> +		goto out;
>> +	}
>> +
>> +	zone_info->empty_zones = kcalloc(BITS_TO_LONGS(zone_info->nr_zones),
>> +					 sizeof(*zone_info->empty_zones),
>> +					 GFP_KERNEL);
>> +	if (!zone_info->empty_zones) {
>> +		ret = -ENOMEM;
>> +		goto out;
>> +	}
>> +
>> +	/* Get zones type */
>> +	while (sector < nr_sectors) {
>> +		nr_zones = BTRFS_REPORT_NR_ZONES;
>> +		ret = btrfs_get_dev_zones(device, sector << SECTOR_SHIFT,
>> +					  &zones, &nr_zones, GFP_KERNEL);
> 
> 
> How many zones do we see in a disk? Not many I presume.

A 15 TB SMR drive with 256 MB zones (which is a failry common value for products
out there) has over 55,000 zones. "Not many" is subjective... I personally
consider 55000 a large number and that one should take care to write appropriate
code to manage that many objects.

> Here the allocation for %zones is inconsistent for each zone, unless
> there is substantial performance benefits, a consistent flow of
> alloc/free is fine as it makes the code easy to read and verify.

I do not understand your comment here. btrfs_get_dev_zones() will allocate and
fill the zones array with at most BTRFS_REPORT_NR_ZONES zones descriptors on the
first call. On subsequent calls, the same array is reused until information on
all zones of the disk is obtained. "the allocation for %zones is inconsistent
for each zone" does not makes much sense. What exactly do you mean ?

> 
> 
> Thanks, Anand
> 
>> +		if (ret)
>> +			goto out;
>> +
>> +		for (i = 0; i < nr_zones; i++) {
>> +			if (zones[i].type == BLK_ZONE_TYPE_SEQWRITE_REQ)
>> +				set_bit(nreported, zone_info->seq_zones);
>> +			if (zones[i].cond == BLK_ZONE_COND_EMPTY)
>> +				set_bit(nreported, zone_info->empty_zones);
>> +			nreported++;
>> +		}
>> +		sector = zones[nr_zones - 1].start + zones[nr_zones - 1].len;
>> +	}
>> +
>> +	if (nreported != zone_info->nr_zones) {
>> +		btrfs_err_in_rcu(device->fs_info,
>> +				 "inconsistent number of zones on %s (%u / %u)",
>> +				 rcu_str_deref(device->name), nreported,
>> +				 zone_info->nr_zones);
>> +		ret = -EIO;
>> +		goto out;
>> +	}
>> +
>> +	device->zone_info = zone_info;
>> +
>> +	btrfs_info_in_rcu(
>> +		device->fs_info,
>> +		"host-%s zoned block device %s, %u zones of %llu sectors",
>> +		bdev_zoned_model(bdev) == BLK_ZONED_HM ? "managed" : "aware",
>> +		rcu_str_deref(device->name), zone_info->nr_zones,
>> +		zone_info->zone_size >> SECTOR_SHIFT);
>> +
>> +out:
>> +	kfree(zones);
>> +
>> +	if (ret) {
>> +		kfree(zone_info->seq_zones);
>> +		kfree(zone_info->empty_zones);
>> +		kfree(zone_info);
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +void btrfs_destroy_dev_zone_info(struct btrfs_device *device)
>> +{
>> +	struct btrfs_zoned_device_info *zone_info = device->zone_info;
>> +
>> +	if (!zone_info)
>> +		return;
>> +
>> +	kfree(zone_info->seq_zones);
>> +	kfree(zone_info->empty_zones);
>> +	kfree(zone_info);
>> +	device->zone_info = NULL;
>> +}
>> +
>> +int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>> +		       struct blk_zone *zone, gfp_t gfp_mask)
>> +{
>> +	unsigned int nr_zones = 1;
>> +	int ret;
>> +
>> +	ret = btrfs_get_dev_zones(device, pos, &zone, &nr_zones, gfp_mask);
>> +	if (ret != 0 || !nr_zones)
>> +		return ret ? ret : -EIO;
>> +
>> +	return 0;
>> +}
>> diff --git a/fs/btrfs/hmzoned.h b/fs/btrfs/hmzoned.h
>> new file mode 100644
>> index 000000000000..ffc70842135e
>> --- /dev/null
>> +++ b/fs/btrfs/hmzoned.h
>> @@ -0,0 +1,79 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Copyright (C) 2019 Western Digital Corporation or its affiliates.
>> + * Authors:
>> + *	Naohiro Aota	<naohiro.aota@wdc.com>
>> + *	Damien Le Moal	<damien.lemoal@wdc.com>
>> + */
>> +
>> +#ifndef BTRFS_HMZONED_H
>> +#define BTRFS_HMZONED_H
>> +
>> +struct btrfs_zoned_device_info {
>> +	/*
>> +	 * Number of zones, zone size and types of zones if bdev is a
>> +	 * zoned block device.
>> +	 */
>> +	u64 zone_size;
>> +	u8  zone_size_shift;
>> +	u32 nr_zones;
>> +	unsigned long *seq_zones;
>> +	unsigned long *empty_zones;
>> +};
>> +
>> +int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>> +		       struct blk_zone *zone, gfp_t gfp_mask);
>> +int btrfs_get_dev_zone_info(struct btrfs_device *device);
>> +void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
>> +
>> +static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)
>> +{
>> +	struct btrfs_zoned_device_info *zone_info = device->zone_info;
>> +
>> +	if (!zone_info)
>> +		return false;
>> +
>> +	return test_bit(pos >> zone_info->zone_size_shift,
>> +			zone_info->seq_zones);
>> +}
>> +
>> +static inline bool btrfs_dev_is_empty_zone(struct btrfs_device *device, u64 pos)
>> +{
>> +	struct btrfs_zoned_device_info *zone_info = device->zone_info;
>> +
>> +	if (!zone_info)
>> +		return true;
>> +
>> +	return test_bit(pos >> zone_info->zone_size_shift,
>> +			zone_info->empty_zones);
>> +}
>> +
>> +static inline void btrfs_dev_set_empty_zone_bit(struct btrfs_device *device,
>> +						u64 pos, bool set)
>> +{
>> +	struct btrfs_zoned_device_info *zone_info = device->zone_info;
>> +	unsigned int zno;
>> +
>> +	if (!zone_info)
>> +		return;
>> +
>> +	zno = pos >> zone_info->zone_size_shift;
>> +	if (set)
>> +		set_bit(zno, zone_info->empty_zones);
>> +	else
>> +		clear_bit(zno, zone_info->empty_zones);
>> +}
>> +
>> +static inline void btrfs_dev_set_zone_empty(struct btrfs_device *device,
>> +					    u64 pos)
>> +{
>> +	btrfs_dev_set_empty_zone_bit(device, pos, true);
>> +}
>> +
>> +static inline void btrfs_dev_clear_zone_empty(struct btrfs_device *device,
>> +					      u64 pos)
>> +{
>> +	btrfs_dev_set_empty_zone_bit(device, pos, false);
>> +}
>> +
>> +#endif
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index d74b74ca07af..8e5a894e7bde 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -29,6 +29,7 @@
>>   #include "sysfs.h"
>>   #include "tree-checker.h"
>>   #include "space-info.h"
>> +#include "hmzoned.h"
>>   
>>   const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
>>   	[BTRFS_RAID_RAID10] = {
>> @@ -342,6 +343,7 @@ void btrfs_free_device(struct btrfs_device *device)
>>   	rcu_string_free(device->name);
>>   	extent_io_tree_release(&device->alloc_state);
>>   	bio_put(device->flush_bio);
>> +	btrfs_destroy_dev_zone_info(device);
>>   	kfree(device);
>>   }
>>   
>> @@ -847,6 +849,11 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
>>   	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
>>   	device->mode = flags;
>>   
>> +	/* Get zone type information of zoned block devices */
>> +	ret = btrfs_get_dev_zone_info(device);
>> +	if (ret != 0)
>> +		goto error_brelse;
>> +
>>   	fs_devices->open_devices++;
>>   	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
>>   	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
>> @@ -2598,6 +2605,14 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>>   	}
>>   	rcu_assign_pointer(device->name, name);
>>   
>> +	device->fs_info = fs_info;
>> +	device->bdev = bdev;
>> +
>> +	/* Get zone type information of zoned block devices */
>> +	ret = btrfs_get_dev_zone_info(device);
>> +	if (ret)
>> +		goto error_free_device;
>> +
>>   	trans = btrfs_start_transaction(root, 0);
>>   	if (IS_ERR(trans)) {
>>   		ret = PTR_ERR(trans);
>> @@ -2614,8 +2629,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>>   					 fs_info->sectorsize);
>>   	device->disk_total_bytes = device->total_bytes;
>>   	device->commit_total_bytes = device->total_bytes;
>> -	device->fs_info = fs_info;
>> -	device->bdev = bdev;
>>   	set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
>>   	clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
>>   	device->mode = FMODE_EXCL;
>> @@ -2756,6 +2769,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>>   		sb->s_flags |= SB_RDONLY;
>>   	if (trans)
>>   		btrfs_end_transaction(trans);
>> +	btrfs_destroy_dev_zone_info(device);
>>   error_free_device:
>>   	btrfs_free_device(device);
>>   error:
>> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
>> index 7f6aa1816409..5da1f354db93 100644
>> --- a/fs/btrfs/volumes.h
>> +++ b/fs/btrfs/volumes.h
>> @@ -57,6 +57,8 @@ struct btrfs_io_geometry {
>>   #define BTRFS_DEV_STATE_REPLACE_TGT	(3)
>>   #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
>>   
>> +struct btrfs_zoned_device_info;
>> +
>>   struct btrfs_device {
>>   	struct list_head dev_list; /* device_list_mutex */
>>   	struct list_head dev_alloc_list; /* chunk mutex */
>> @@ -77,6 +79,8 @@ struct btrfs_device {
>>   
>>   	struct block_device *bdev;
>>   
>> +	struct btrfs_zoned_device_info *zone_info;
>> +
>>   	/* the mode sent to blkdev_get */
>>   	fmode_t mode;
>>   
>>
> 
> 


-- 
Damien Le Moal
Western Digital Research