f2fs: support zone capacity less than zone size

NVMe Zoned Namespace devices can have zone-capacity less than zone-size.
Zone-capacity indicates the maximum number of sectors that are usable in
a zone beginning from the first sector of the zone. This makes the sectors
sectors after the zone-capacity till zone-size to be unusable.
This patch set tracks zone-size and zone-capacity in zoned devices and
calculate the usable blocks per segment and usable segments per section.

If zone-capacity is less than zone-size mark only those segments which
start before zone-capacity as free segments. All segments at and beyond
zone-capacity are treated as permanently used segments. In cases where
zone-capacity does not align with segment size the last segment will start
before zone-capacity and end beyond the zone-capacity of the zone. For
such spanning segments only sectors within the zone-capacity are used.

During writes and GC manage the usable segments in a section and usable
blocks per segment. Segments which are beyond zone-capacity are never
allocated, and do not need to be garbage collected, only the segments
which are before zone-capacity needs to garbage collected.
For spanning segments based on the number of usable blocks in that
segment, write to blocks only up to zone-capacity.

Zone-capacity is device specific and cannot be configured by the user.
Since NVMe ZNS device zones are sequentially write only, a block device
with conventional zones or any normal block device is needed along with
the ZNS device for the metadata operations of F2fs.

A typical nvme-cli output of a zoned device shows zone start and capacity
and write pointer as below:

SLBA: 0x0     WP: 0x0     Cap: 0x18800 State: EMPTY Type: SEQWRITE_REQ
SLBA: 0x20000 WP: 0x20000 Cap: 0x18800 State: EMPTY Type: SEQWRITE_REQ
SLBA: 0x40000 WP: 0x40000 Cap: 0x18800 State: EMPTY Type: SEQWRITE_REQ

Here zone size is 64MB, capacity is 49MB, WP is at zone start as the zones
are in EMPTY state. For each zone, only zone start + 49MB is usable area,
any lba/sector after 49MB cannot be read or written to, the drive will fail
any attempts to read/write. So, the second zone starts at 64MB and is
usable till 113MB (64 + 49) and the range between 113 and 128MB is
again unusable. The next zone starts at 128MB, and so on.

Signed-off-by: Aravind Ramesh <aravind.ramesh@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 40 insertions, 4 deletions

diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index db3c61046aa4..ee5d7f30a1f8 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -44,13 +44,49 @@ struct gc_inode_list {
 /*
  * inline functions
  */
+
+/*
+ * On a Zoned device zone-capacity can be less than zone-size and if
+ * zone-capacity is not aligned to f2fs segment size(2MB), then the segment
+ * starting just before zone-capacity has some blocks spanning across the
+ * zone-capacity, these blocks are not usable.
+ * Such spanning segments can be in free list so calculate the sum of usable
+ * blocks in currently free segments including normal and spanning segments.
+ */
+static inline block_t free_segs_blk_count_zoned(struct f2fs_sb_info *sbi)
+{
+	block_t free_seg_blks = 0;
+	struct free_segmap_info *free_i = FREE_I(sbi);
+	int j;
+
+	spin_lock(&free_i->segmap_lock);
+	for (j = 0; j < MAIN_SEGS(sbi); j++)
+		if (!test_bit(j, free_i->free_segmap))
+			free_seg_blks += f2fs_usable_blks_in_seg(sbi, j);
+	spin_unlock(&free_i->segmap_lock);
+
+	return free_seg_blks;
+}
+
+static inline block_t free_segs_blk_count(struct f2fs_sb_info *sbi)
+{
+	if (f2fs_sb_has_blkzoned(sbi))
+		return free_segs_blk_count_zoned(sbi);
+
+	return free_segments(sbi) << sbi->log_blocks_per_seg;
+}
+
 static inline block_t free_user_blocks(struct f2fs_sb_info *sbi)
 {
-	if (free_segments(sbi) < overprovision_segments(sbi))
+	block_t free_blks, ovp_blks;
+
+	free_blks = free_segs_blk_count(sbi);
+	ovp_blks = overprovision_segments(sbi) << sbi->log_blocks_per_seg;
+
+	if (free_blks < ovp_blks)
 		return 0;
-	else
-		return (free_segments(sbi) - overprovision_segments(sbi))
-			<< sbi->log_blocks_per_seg;
+
+	return free_blks - ovp_blks;
 }
 
 static inline block_t limit_invalid_user_blocks(struct f2fs_sb_info *sbi)