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

[Anand Jain <anand.jain@xxxxxxxxxx>]

On 8/16/19 10:19 PM, Damien Le Moal wrote:
> 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@xxxxxxx>
> > > Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
> > > ---
> > >    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@xxxxxxx>
> > > + *	Damien Le Moal	<damien.lemoal@xxxxxxx>
> > > + */
> > > +
> > > +#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.

 Agree that's pretty large.

> > 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 ?

 btrfs_get_dev_zones() allocates the memory for %zones_ret, and expects
 its parent function btrfs_get_dev_zone_info() to free, instead can we
 have alloc and free in the parent function btrfs_get_dev_zone_info().

Thanks, Anand

> > 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@xxxxxxx>
> > > + *	Damien Le Moal	<damien.lemoal@xxxxxxx>
> > > + */
> > > +
> > > +#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;
> > >