Re: [PATCH v3 03/27] btrfs: Check and enable HMZONED mode

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

On 2019/08/15 22:46, Anand Jain wrote:
> On 8/8/19 5:30 PM, Naohiro Aota wrote:
>> HMZONED mode cannot be used together with the RAID5/6 profile for now.
>> Introduce the function btrfs_check_hmzoned_mode() to check this. This
>> function will also check if HMZONED flag is enabled on the file system and
>> if the file system consists of zoned devices with equal zone size.
>>
>> Additionally, as updates to the space cache are in-place, the space cache
>> cannot be located over sequential zones and there is no guarantees that the
>> device will have enough conventional zones to store this cache. Resolve
>> this problem by disabling completely the space cache.  This does not
>> introduces any problems with sequential block groups: all the free space is
>> located after the allocation pointer and no free space before the pointer.
>> There is no need to have such cache.
>>
>> For the same reason, NODATACOW is also disabled.
>>
>> Also INODE_MAP_CACHE is also disabled to avoid preallocation in the
>> INODE_MAP_CACHE inode.
> 
>   A list of incompatibility features with zoned devices. This need better
>   documentation, may be a table and its reason is better.

Are you referring to the format of the commit message itself ? Or would you like
to see a documentation added to Documentation/filesystems/btrfs.txt ?

> 
> 
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
>> ---
>>   fs/btrfs/ctree.h       |  3 ++
>>   fs/btrfs/dev-replace.c |  8 +++++
>>   fs/btrfs/disk-io.c     |  8 +++++
>>   fs/btrfs/hmzoned.c     | 67 ++++++++++++++++++++++++++++++++++++++++++
>>   fs/btrfs/hmzoned.h     | 18 ++++++++++++
>>   fs/btrfs/super.c       |  1 +
>>   fs/btrfs/volumes.c     |  5 ++++
>>   7 files changed, 110 insertions(+)
>>
>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
>> index 299e11e6c554..a00ce8c4d678 100644
>> --- a/fs/btrfs/ctree.h
>> +++ b/fs/btrfs/ctree.h
>> @@ -713,6 +713,9 @@ struct btrfs_fs_info {
>>   	struct btrfs_root *uuid_root;
>>   	struct btrfs_root *free_space_root;
>>   
>> +	/* Zone size when in HMZONED mode */
>> +	u64 zone_size;
>> +
>>   	/* the log root tree is a directory of all the other log roots */
>>   	struct btrfs_root *log_root_tree;
>>   
>> diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
>> index 6b2e9aa83ffa..2cc3ac4d101d 100644
>> --- a/fs/btrfs/dev-replace.c
>> +++ b/fs/btrfs/dev-replace.c
>> @@ -20,6 +20,7 @@
>>   #include "rcu-string.h"
>>   #include "dev-replace.h"
>>   #include "sysfs.h"
>> +#include "hmzoned.h"
>>   
>>   static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
>>   				       int scrub_ret);
>> @@ -201,6 +202,13 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
>>   		return PTR_ERR(bdev);
>>   	}
>>   
>> +	if (!btrfs_check_device_zone_type(fs_info, bdev)) {
>> +		btrfs_err(fs_info,
>> +			  "zone type of target device mismatch with the filesystem!");
>> +		ret = -EINVAL;
>> +		goto error;
>> +	}
>> +
>>   	sync_blockdev(bdev);
>>   
>>   	devices = &fs_info->fs_devices->devices;
>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
>> index 5f7ee70b3d1a..8854ff2e5fa5 100644
>> --- a/fs/btrfs/disk-io.c
>> +++ b/fs/btrfs/disk-io.c
>> @@ -40,6 +40,7 @@
>>   #include "compression.h"
>>   #include "tree-checker.h"
>>   #include "ref-verify.h"
>> +#include "hmzoned.h"
>>   
>>   #define BTRFS_SUPER_FLAG_SUPP	(BTRFS_HEADER_FLAG_WRITTEN |\
>>   				 BTRFS_HEADER_FLAG_RELOC |\
>> @@ -3123,6 +3124,13 @@ int open_ctree(struct super_block *sb,
>>   
>>   	btrfs_free_extra_devids(fs_devices, 1);
>>   
>> +	ret = btrfs_check_hmzoned_mode(fs_info);
>> +	if (ret) {
>> +		btrfs_err(fs_info, "failed to init hmzoned mode: %d",
>> +				ret);
>> +		goto fail_block_groups;
>> +	}
>> +
>>   	ret = btrfs_sysfs_add_fsid(fs_devices, NULL);
>>   	if (ret) {
>>   		btrfs_err(fs_info, "failed to init sysfs fsid interface: %d",
>> diff --git a/fs/btrfs/hmzoned.c b/fs/btrfs/hmzoned.c
>> index bfd04792dd62..512674d8f488 100644
>> --- a/fs/btrfs/hmzoned.c
>> +++ b/fs/btrfs/hmzoned.c
>> @@ -160,3 +160,70 @@ int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>>   
>>   	return 0;
>>   }
>> +
>> +int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
>> +{
>> +	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
>> +	struct btrfs_device *device;
>> +	u64 hmzoned_devices = 0;
>> +	u64 nr_devices = 0;
>> +	u64 zone_size = 0;
>> +	int incompat_hmzoned = btrfs_fs_incompat(fs_info, HMZONED);
>> +	int ret = 0;
>> +
>> +	/* Count zoned devices */
>> +	list_for_each_entry(device, &fs_devices->devices, dev_list) {
>> +		if (!device->bdev)
>> +			continue;
>> +		if (bdev_zoned_model(device->bdev) == BLK_ZONED_HM ||
>> +		    (bdev_zoned_model(device->bdev) == BLK_ZONED_HA &&
>> +		     incompat_hmzoned)) {
>> +			hmzoned_devices++;
>> +			if (!zone_size) {
>> +				zone_size = device->zone_info->zone_size;
>> +			} else if (device->zone_info->zone_size != zone_size) {
>> +				btrfs_err(fs_info,
>> +					  "Zoned block devices must have equal zone sizes");
>> +				ret = -EINVAL;
>> +				goto out;
>> +			}
>> +		}
>> +		nr_devices++;
>> +	}
>> +
>> +	if (!hmzoned_devices && incompat_hmzoned) {
>> +		/* No zoned block device found on HMZONED FS */
>> +		btrfs_err(fs_info, "HMZONED enabled file system should have zoned devices");
>> +		ret = -EINVAL;
>> +		goto out;
> 
> 
>   When does the HMZONED gets enabled? I presume during mkfs. Where are
>   the related btrfs-progs patches? Searching for the related btrfs-progs
>   patches doesn't show up anything in the ML. Looks like I am missing
>   something, nor the cover letter said anything about the progs part.
> 
> Thanks, Anand
> 
>> +	}
>> +
>> +	if (!hmzoned_devices && !incompat_hmzoned)
>> +		goto out;
>> +
>> +	fs_info->zone_size = zone_size;
>> +
>> +	if (hmzoned_devices != nr_devices) {
>> +		btrfs_err(fs_info,
>> +			  "zoned devices cannot be mixed with regular devices");
>> +		ret = -EINVAL;
>> +		goto out;
>> +	}
>> +
>> +	/*
>> +	 * stripe_size is always aligned to BTRFS_STRIPE_LEN in
>> +	 * __btrfs_alloc_chunk(). Since we want stripe_len == zone_size,
>> +	 * check the alignment here.
>> +	 */
>> +	if (!IS_ALIGNED(zone_size, BTRFS_STRIPE_LEN)) {
>> +		btrfs_err(fs_info,
>> +			  "zone size is not aligned to BTRFS_STRIPE_LEN");
>> +		ret = -EINVAL;
>> +		goto out;
>> +	}
>> +
>> +	btrfs_info(fs_info, "HMZONED mode enabled, zone size %llu B",
>> +		   fs_info->zone_size);
>> +out:
>> +	return ret;
>> +}
>> diff --git a/fs/btrfs/hmzoned.h b/fs/btrfs/hmzoned.h
>> index ffc70842135e..29cfdcabff2f 100644
>> --- a/fs/btrfs/hmzoned.h
>> +++ b/fs/btrfs/hmzoned.h
>> @@ -9,6 +9,8 @@
>>   #ifndef BTRFS_HMZONED_H
>>   #define BTRFS_HMZONED_H
>>   
>> +#include <linux/blkdev.h>
>> +
>>   struct btrfs_zoned_device_info {
>>   	/*
>>   	 * Number of zones, zone size and types of zones if bdev is a
>> @@ -25,6 +27,7 @@ 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);
>> +int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info);
>>   
>>   static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)
>>   {
>> @@ -76,4 +79,19 @@ static inline void btrfs_dev_clear_zone_empty(struct btrfs_device *device,
>>   	btrfs_dev_set_empty_zone_bit(device, pos, false);
>>   }
>>   
>> +static inline bool btrfs_check_device_zone_type(struct btrfs_fs_info *fs_info,
>> +						struct block_device *bdev)
>> +{
>> +	u64 zone_size;
>> +
>> +	if (btrfs_fs_incompat(fs_info, HMZONED)) {
>> +		zone_size = (u64)bdev_zone_sectors(bdev) << SECTOR_SHIFT;
>> +		/* Do not allow non-zoned device */
>> +		return bdev_is_zoned(bdev) && fs_info->zone_size == zone_size;
>> +	}
>> +
>> +	/* Do not allow Host Manged zoned device */
>> +	return bdev_zoned_model(bdev) != BLK_ZONED_HM;
>> +}
>> +
>>   #endif
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index 78de9d5d80c6..d7879a5a2536 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -43,6 +43,7 @@
>>   #include "free-space-cache.h"
>>   #include "backref.h"
>>   #include "space-info.h"
>> +#include "hmzoned.h"
>>   #include "tests/btrfs-tests.h"
>>   
>>   #include "qgroup.h"
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index 8e5a894e7bde..755b2ec1e0de 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -2572,6 +2572,11 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>>   	if (IS_ERR(bdev))
>>   		return PTR_ERR(bdev);
>>   
>> +	if (!btrfs_check_device_zone_type(fs_info, bdev)) {
>> +		ret = -EINVAL;
>> +		goto error;
>> +	}
>> +
>>   	if (fs_devices->seeding) {
>>   		seeding_dev = 1;
>>   		down_write(&sb->s_umount);
>>
> 
> 


-- 
Damien Le Moal
Western Digital Research