Commit 12659251 authored by Naohiro Aota's avatar Naohiro Aota Committed by David Sterba
Browse files

btrfs: implement log-structured superblock for ZONED mode 



Superblock (and its copies) is the only data structure in btrfs which
has a fixed location on a device. Since we cannot overwrite in a
sequential write required zone, we cannot place superblock in the zone.
One easy solution is limiting superblock and copies to be placed only in
conventional zones.  However, this method has two downsides: one is
reduced number of superblock copies. The location of the second copy of
superblock is 256GB, which is in a sequential write required zone on
typical devices in the market today.  So, the number of superblock and
copies is limited to be two.  Second downside is that we cannot support
devices which have no conventional zones at all.

To solve these two problems, we employ superblock log writing. It uses
two adjacent zones as a circular buffer to write updated superblocks.
Once the first zone is filled up, start writing into the second one.
Then, when both zones are filled up and before starting to write to the
first zone again, it reset the first zone.

We can determine the position of the latest superblock by reading write
pointer information from a device. One corner case is when both zones
are full. For this situation, we read out the last superblock of each
zone, and compare them to determine which zone is older.

The following zones are reserved as the circular buffer on ZONED btrfs.

- The primary superblock: zones 0 and 1
- The first copy: zones 16 and 17
- The second copy: zones 1024 or zone at 256GB which is minimum, and
  next to it

If these reserved zones are conventional, superblock is written fixed at
the start of the zone without logging.

Signed-off-by: default avatarNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent a589dde0

fs/btrfs/block-group.c

+9 −0
Original line number Diff line number Diff line
@@ -1679,6 +1679,7 @@ out: 
static int exclude_super_stripes(struct btrfs_block_group *cache)

{

	struct btrfs_fs_info *fs_info = cache->fs_info;

	const bool zoned = btrfs_is_zoned(fs_info);

	u64 bytenr;

	u64 *logical;

	int stripe_len;
@@ -1700,6 +1701,14 @@ static int exclude_super_stripes(struct btrfs_block_group *cache) 
		if (ret)

			return ret;



		/* Shouldn't have super stripes in sequential zones */

		if (zoned && nr) {

			btrfs_err(fs_info,

			"zoned: block group %llu must not contain super block",

				  cache->start);

			return -EUCLEAN;

		}



		while (nr--) {

			u64 len = min_t(u64, stripe_len,

				cache->start + cache->length - logical[nr]);

fs/btrfs/disk-io.c

+35 −7
Original line number Diff line number Diff line
@@ -3488,10 +3488,17 @@ struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev, 
{

	struct btrfs_super_block *super;

	struct page *page;

	u64 bytenr;

	u64 bytenr, bytenr_orig;

	struct address_space *mapping = bdev->bd_inode->i_mapping;

	int ret;



	bytenr_orig = btrfs_sb_offset(copy_num);

	ret = btrfs_sb_log_location_bdev(bdev, copy_num, READ, &bytenr);

	if (ret == -ENOENT)

		return ERR_PTR(-EINVAL);

	else if (ret)

		return ERR_PTR(ret);



	bytenr = btrfs_sb_offset(copy_num);

	if (bytenr + BTRFS_SUPER_INFO_SIZE >= i_size_read(bdev->bd_inode))

		return ERR_PTR(-EINVAL);
@@ -3505,7 +3512,7 @@ struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev, 
		return ERR_PTR(-ENODATA);

	}



	if (btrfs_super_bytenr(super) != bytenr) {

	if (btrfs_super_bytenr(super) != bytenr_orig) {

		btrfs_release_disk_super(super);

		return ERR_PTR(-EINVAL);

	}
@@ -3560,7 +3567,8 @@ static int write_dev_supers(struct btrfs_device *device, 
	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);

	int i;

	int errors = 0;

	u64 bytenr;

	int ret;

	u64 bytenr, bytenr_orig;



	if (max_mirrors == 0)

		max_mirrors = BTRFS_SUPER_MIRROR_MAX;
@@ -3572,12 +3580,22 @@ static int write_dev_supers(struct btrfs_device *device, 
		struct bio *bio;

		struct btrfs_super_block *disk_super;



		bytenr = btrfs_sb_offset(i);

		bytenr_orig = btrfs_sb_offset(i);

		ret = btrfs_sb_log_location(device, i, WRITE, &bytenr);

		if (ret == -ENOENT) {

			continue;

		} else if (ret < 0) {

			btrfs_err(device->fs_info,

				"couldn't get super block location for mirror %d",

				i);

			errors++;

			continue;

		}

		if (bytenr + BTRFS_SUPER_INFO_SIZE >=

		    device->commit_total_bytes)

			break;



		btrfs_set_super_bytenr(sb, bytenr);

		btrfs_set_super_bytenr(sb, bytenr_orig);



		crypto_shash_digest(shash, (const char *)sb + BTRFS_CSUM_SIZE,

				    BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE,
@@ -3622,6 +3640,7 @@ static int write_dev_supers(struct btrfs_device *device, 
			bio->bi_opf |= REQ_FUA;



		btrfsic_submit_bio(bio);

		btrfs_advance_sb_log(device, i);

	}

	return errors < i ? 0 : -1;

}
@@ -3638,6 +3657,7 @@ static int wait_dev_supers(struct btrfs_device *device, int max_mirrors) 
	int i;

	int errors = 0;

	bool primary_failed = false;

	int ret;

	u64 bytenr;



	if (max_mirrors == 0)
@@ -3646,7 +3666,15 @@ static int wait_dev_supers(struct btrfs_device *device, int max_mirrors) 
	for (i = 0; i < max_mirrors; i++) {

		struct page *page;



		bytenr = btrfs_sb_offset(i);

		ret = btrfs_sb_log_location(device, i, READ, &bytenr);

		if (ret == -ENOENT) {

			break;

		} else if (ret < 0) {

			errors++;

			if (i == 0)

				primary_failed = true;

			continue;

		}

		if (bytenr + BTRFS_SUPER_INFO_SIZE >=

		    device->commit_total_bytes)

			break;

fs/btrfs/scrub.c

+3 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include "rcu-string.h"

#include "raid56.h"

#include "block-group.h"

#include "zoned.h"



/*

 * This is only the first step towards a full-features scrub. It reads all
@@ -3732,6 +3733,8 @@ static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx, 
		if (bytenr + BTRFS_SUPER_INFO_SIZE >

		    scrub_dev->commit_total_bytes)

			break;

		if (!btrfs_check_super_location(scrub_dev, bytenr))

			continue;



		ret = scrub_pages(sctx, bytenr, BTRFS_SUPER_INFO_SIZE, bytenr,

				  scrub_dev, BTRFS_EXTENT_FLAG_SUPER, gen, i,

fs/btrfs/volumes.c

+15 −5
Original line number Diff line number Diff line
@@ -1276,7 +1276,7 @@ void btrfs_release_disk_super(struct btrfs_super_block *super) 
}



static struct btrfs_super_block *btrfs_read_disk_super(struct block_device *bdev,

						       u64 bytenr)

						       u64 bytenr, u64 bytenr_orig)

{

	struct btrfs_super_block *disk_super;

	struct page *page;
@@ -1307,7 +1307,7 @@ static struct btrfs_super_block *btrfs_read_disk_super(struct block_device *bdev 
	/* align our pointer to the offset of the super block */

	disk_super = p + offset_in_page(bytenr);



	if (btrfs_super_bytenr(disk_super) != bytenr ||

	if (btrfs_super_bytenr(disk_super) != bytenr_orig ||

	    btrfs_super_magic(disk_super) != BTRFS_MAGIC) {

		btrfs_release_disk_super(p);

		return ERR_PTR(-EINVAL);
@@ -1342,7 +1342,8 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags, 
	bool new_device_added = false;

	struct btrfs_device *device = NULL;

	struct block_device *bdev;

	u64 bytenr;

	u64 bytenr, bytenr_orig;

	int ret;



	lockdep_assert_held(&uuid_mutex);
@@ -1352,14 +1353,18 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags, 
	 * So, we need to add a special mount option to scan for

	 * later supers, using BTRFS_SUPER_MIRROR_MAX instead

	 */

	bytenr = btrfs_sb_offset(0);

	flags |= FMODE_EXCL;



	bdev = blkdev_get_by_path(path, flags, holder);

	if (IS_ERR(bdev))

		return ERR_CAST(bdev);



	disk_super = btrfs_read_disk_super(bdev, bytenr);

	bytenr_orig = btrfs_sb_offset(0);

	ret = btrfs_sb_log_location_bdev(bdev, 0, READ, &bytenr);

	if (ret)

		return ERR_PTR(ret);



	disk_super = btrfs_read_disk_super(bdev, bytenr, bytenr_orig);

	if (IS_ERR(disk_super)) {

		device = ERR_CAST(disk_super);

		goto error_bdev_put;
@@ -2023,6 +2028,11 @@ void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info, 
		if (IS_ERR(disk_super))

			continue;



		if (bdev_is_zoned(bdev)) {

			btrfs_reset_sb_log_zones(bdev, copy_num);

			continue;

		}



		memset(&disk_super->magic, 0, sizeof(disk_super->magic));



		page = virt_to_page(disk_super);

fs/btrfs/zoned.c

+327 −0
Original line number Diff line number Diff line
@@ -10,6 +10,9 @@ 
/* Maximum number of zones to report per blkdev_report_zones() call */

#define BTRFS_REPORT_NR_ZONES   4096



/* Number of superblock log zones */

#define BTRFS_NR_SB_LOG_ZONES 2



static int copy_zone_info_cb(struct blk_zone *zone, unsigned int idx, void *data)

{

	struct blk_zone *zones = data;
@@ -19,6 +22,103 @@ static int copy_zone_info_cb(struct blk_zone *zone, unsigned int idx, void *data 
	return 0;

}



static int sb_write_pointer(struct block_device *bdev, struct blk_zone *zones,

			    u64 *wp_ret)

{

	bool empty[BTRFS_NR_SB_LOG_ZONES];

	bool full[BTRFS_NR_SB_LOG_ZONES];

	sector_t sector;



	ASSERT(zones[0].type != BLK_ZONE_TYPE_CONVENTIONAL &&

	       zones[1].type != BLK_ZONE_TYPE_CONVENTIONAL);



	empty[0] = (zones[0].cond == BLK_ZONE_COND_EMPTY);

	empty[1] = (zones[1].cond == BLK_ZONE_COND_EMPTY);

	full[0] = (zones[0].cond == BLK_ZONE_COND_FULL);

	full[1] = (zones[1].cond == BLK_ZONE_COND_FULL);



	/*

	 * Possible states of log buffer zones

	 *

	 *           Empty[0]  In use[0]  Full[0]

	 * Empty[1]         *          x        0

	 * In use[1]        0          x        0

	 * Full[1]          1          1        C

	 *

	 * Log position:

	 *   *: Special case, no superblock is written

	 *   0: Use write pointer of zones[0]

	 *   1: Use write pointer of zones[1]

	 *   C: Compare super blcoks from zones[0] and zones[1], use the latest

	 *      one determined by generation

	 *   x: Invalid state

	 */



	if (empty[0] && empty[1]) {

		/* Special case to distinguish no superblock to read */

		*wp_ret = zones[0].start << SECTOR_SHIFT;

		return -ENOENT;

	} else if (full[0] && full[1]) {

		/* Compare two super blocks */

		struct address_space *mapping = bdev->bd_inode->i_mapping;

		struct page *page[BTRFS_NR_SB_LOG_ZONES];

		struct btrfs_super_block *super[BTRFS_NR_SB_LOG_ZONES];

		int i;



		for (i = 0; i < BTRFS_NR_SB_LOG_ZONES; i++) {

			u64 bytenr;



			bytenr = ((zones[i].start + zones[i].len)

				   << SECTOR_SHIFT) - BTRFS_SUPER_INFO_SIZE;



			page[i] = read_cache_page_gfp(mapping,

					bytenr >> PAGE_SHIFT, GFP_NOFS);

			if (IS_ERR(page[i])) {

				if (i == 1)

					btrfs_release_disk_super(super[0]);

				return PTR_ERR(page[i]);

			}

			super[i] = page_address(page[i]);

		}



		if (super[0]->generation > super[1]->generation)

			sector = zones[1].start;

		else

			sector = zones[0].start;



		for (i = 0; i < BTRFS_NR_SB_LOG_ZONES; i++)

			btrfs_release_disk_super(super[i]);

	} else if (!full[0] && (empty[1] || full[1])) {

		sector = zones[0].wp;

	} else if (full[0]) {

		sector = zones[1].wp;

	} else {

		return -EUCLEAN;

	}

	*wp_ret = sector << SECTOR_SHIFT;

	return 0;

}



/*

 * The following zones are reserved as the circular buffer on ZONED btrfs.

 *  - The primary superblock: zones 0 and 1

 *  - The first copy: zones 16 and 17

 *  - The second copy: zones 1024 or zone at 256GB which is minimum, and

 *                     the following one

 */

static inline u32 sb_zone_number(int shift, int mirror)

{

	ASSERT(mirror < BTRFS_SUPER_MIRROR_MAX);



	switch (mirror) {

	case 0: return 0;

	case 1: return 16;

	case 2: return min_t(u64, btrfs_sb_offset(mirror) >> shift, 1024);

	}



	return 0;

}



static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,

			       struct blk_zone *zones, unsigned int *nr_zones)

{
@@ -122,6 +222,52 @@ int btrfs_get_dev_zone_info(struct btrfs_device *device) 
		goto out;

	}



	/* Validate superblock log */

	nr_zones = BTRFS_NR_SB_LOG_ZONES;

	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {

		u32 sb_zone;

		u64 sb_wp;

		int sb_pos = BTRFS_NR_SB_LOG_ZONES * i;



		sb_zone = sb_zone_number(zone_info->zone_size_shift, i);

		if (sb_zone + 1 >= zone_info->nr_zones)

			continue;



		sector = sb_zone << (zone_info->zone_size_shift - SECTOR_SHIFT);

		ret = btrfs_get_dev_zones(device, sector << SECTOR_SHIFT,

					  &zone_info->sb_zones[sb_pos],

					  &nr_zones);

		if (ret)

			goto out;



		if (nr_zones != BTRFS_NR_SB_LOG_ZONES) {

			btrfs_err_in_rcu(device->fs_info,

	"zoned: failed to read super block log zone info at devid %llu zone %u",

					 device->devid, sb_zone);

			ret = -EUCLEAN;

			goto out;

		}



		/*

		 * If zones[0] is conventional, always use the beggining of the

		 * zone to record superblock. No need to validate in that case.

		 */

		if (zone_info->sb_zones[BTRFS_NR_SB_LOG_ZONES * i].type ==

		    BLK_ZONE_TYPE_CONVENTIONAL)

			continue;



		ret = sb_write_pointer(device->bdev,

				       &zone_info->sb_zones[sb_pos], &sb_wp);

		if (ret != -ENOENT && ret) {

			btrfs_err_in_rcu(device->fs_info,

			"zoned: super block log zone corrupted devid %llu zone %u",

					 device->devid, sb_zone);

			ret = -EUCLEAN;

			goto out;

		}

	}





	kfree(zones);



	device->zone_info = zone_info;
@@ -287,3 +433,184 @@ int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info) 


	return 0;

}



static int sb_log_location(struct block_device *bdev, struct blk_zone *zones,

			   int rw, u64 *bytenr_ret)

{

	u64 wp;

	int ret;



	if (zones[0].type == BLK_ZONE_TYPE_CONVENTIONAL) {

		*bytenr_ret = zones[0].start << SECTOR_SHIFT;

		return 0;

	}



	ret = sb_write_pointer(bdev, zones, &wp);

	if (ret != -ENOENT && ret < 0)

		return ret;



	if (rw == WRITE) {

		struct blk_zone *reset = NULL;



		if (wp == zones[0].start << SECTOR_SHIFT)

			reset = &zones[0];

		else if (wp == zones[1].start << SECTOR_SHIFT)

			reset = &zones[1];



		if (reset && reset->cond != BLK_ZONE_COND_EMPTY) {

			ASSERT(reset->cond == BLK_ZONE_COND_FULL);



			ret = blkdev_zone_mgmt(bdev, REQ_OP_ZONE_RESET,

					       reset->start, reset->len,

					       GFP_NOFS);

			if (ret)

				return ret;



			reset->cond = BLK_ZONE_COND_EMPTY;

			reset->wp = reset->start;

		}

	} else if (ret != -ENOENT) {

		/* For READ, we want the precious one */

		if (wp == zones[0].start << SECTOR_SHIFT)

			wp = (zones[1].start + zones[1].len) << SECTOR_SHIFT;

		wp -= BTRFS_SUPER_INFO_SIZE;

	}



	*bytenr_ret = wp;

	return 0;



}



int btrfs_sb_log_location_bdev(struct block_device *bdev, int mirror, int rw,

			       u64 *bytenr_ret)

{

	struct blk_zone zones[BTRFS_NR_SB_LOG_ZONES];

	unsigned int zone_sectors;

	u32 sb_zone;

	int ret;

	u64 zone_size;

	u8 zone_sectors_shift;

	sector_t nr_sectors;

	u32 nr_zones;



	if (!bdev_is_zoned(bdev)) {

		*bytenr_ret = btrfs_sb_offset(mirror);

		return 0;

	}



	ASSERT(rw == READ || rw == WRITE);



	zone_sectors = bdev_zone_sectors(bdev);

	if (!is_power_of_2(zone_sectors))

		return -EINVAL;

	zone_size = zone_sectors << SECTOR_SHIFT;

	zone_sectors_shift = ilog2(zone_sectors);

	nr_sectors = bdev->bd_part->nr_sects;

	nr_zones = nr_sectors >> zone_sectors_shift;



	sb_zone = sb_zone_number(zone_sectors_shift + SECTOR_SHIFT, mirror);

	if (sb_zone + 1 >= nr_zones)

		return -ENOENT;



	ret = blkdev_report_zones(bdev, sb_zone << zone_sectors_shift,

				  BTRFS_NR_SB_LOG_ZONES, copy_zone_info_cb,

				  zones);

	if (ret < 0)

		return ret;

	if (ret != BTRFS_NR_SB_LOG_ZONES)

		return -EIO;



	return sb_log_location(bdev, zones, rw, bytenr_ret);

}



int btrfs_sb_log_location(struct btrfs_device *device, int mirror, int rw,

			  u64 *bytenr_ret)

{

	struct btrfs_zoned_device_info *zinfo = device->zone_info;

	u32 zone_num;



	if (!zinfo) {

		*bytenr_ret = btrfs_sb_offset(mirror);

		return 0;

	}



	zone_num = sb_zone_number(zinfo->zone_size_shift, mirror);

	if (zone_num + 1 >= zinfo->nr_zones)

		return -ENOENT;



	return sb_log_location(device->bdev,

			       &zinfo->sb_zones[BTRFS_NR_SB_LOG_ZONES * mirror],

			       rw, bytenr_ret);

}



static inline bool is_sb_log_zone(struct btrfs_zoned_device_info *zinfo,

				  int mirror)

{

	u32 zone_num;



	if (!zinfo)

		return false;



	zone_num = sb_zone_number(zinfo->zone_size_shift, mirror);

	if (zone_num + 1 >= zinfo->nr_zones)

		return false;



	if (!test_bit(zone_num, zinfo->seq_zones))

		return false;



	return true;

}



void btrfs_advance_sb_log(struct btrfs_device *device, int mirror)

{

	struct btrfs_zoned_device_info *zinfo = device->zone_info;

	struct blk_zone *zone;



	if (!is_sb_log_zone(zinfo, mirror))

		return;



	zone = &zinfo->sb_zones[BTRFS_NR_SB_LOG_ZONES * mirror];

	if (zone->cond != BLK_ZONE_COND_FULL) {

		if (zone->cond == BLK_ZONE_COND_EMPTY)

			zone->cond = BLK_ZONE_COND_IMP_OPEN;



		zone->wp += (BTRFS_SUPER_INFO_SIZE >> SECTOR_SHIFT);



		if (zone->wp == zone->start + zone->len)

			zone->cond = BLK_ZONE_COND_FULL;



		return;

	}



	zone++;

	ASSERT(zone->cond != BLK_ZONE_COND_FULL);

	if (zone->cond == BLK_ZONE_COND_EMPTY)

		zone->cond = BLK_ZONE_COND_IMP_OPEN;



	zone->wp += (BTRFS_SUPER_INFO_SIZE >> SECTOR_SHIFT);



	if (zone->wp == zone->start + zone->len)

		zone->cond = BLK_ZONE_COND_FULL;

}



int btrfs_reset_sb_log_zones(struct block_device *bdev, int mirror)

{

	sector_t zone_sectors;

	sector_t nr_sectors;

	u8 zone_sectors_shift;

	u32 sb_zone;

	u32 nr_zones;



	zone_sectors = bdev_zone_sectors(bdev);

	zone_sectors_shift = ilog2(zone_sectors);

	nr_sectors = bdev->bd_part->nr_sects;

	nr_zones = nr_sectors >> zone_sectors_shift;



	sb_zone = sb_zone_number(zone_sectors_shift + SECTOR_SHIFT, mirror);

	if (sb_zone + 1 >= nr_zones)

		return -ENOENT;



	return blkdev_zone_mgmt(bdev, REQ_OP_ZONE_RESET,

				sb_zone << zone_sectors_shift,

				zone_sectors * BTRFS_NR_SB_LOG_ZONES, GFP_NOFS);

}

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