btrfs: zoned: prevent allocation from previous data relocation BG

After commit 5f0addf ("btrfs: zoned: use dedicated lock for data
relocation"), we observe IO errors on e.g, btrfs/232 like below.

  [09.0][T4038707] WARNING: CPU: 3 PID: 4038707 at fs/btrfs/extent-tree.c:2381 btrfs_cross_ref_exist+0xfc/0x120 [btrfs]
  <snip>
  [09.9][T4038707] Call Trace:
  [09.5][T4038707]  <TASK>
  [09.3][T4038707]  run_delalloc_nocow+0x7f1/0x11a0 [btrfs]
  [09.6][T4038707]  ? test_range_bit+0x174/0x320 [btrfs]
  [09.2][T4038707]  ? fallback_to_cow+0x980/0x980 [btrfs]
  [09.3][T4038707]  ? find_lock_delalloc_range+0x33e/0x3e0 [btrfs]
  [09.5][T4038707]  btrfs_run_delalloc_range+0x445/0x1320 [btrfs]
  [09.2][T4038707]  ? test_range_bit+0x320/0x320 [btrfs]
  [09.4][T4038707]  ? lock_downgrade+0x6a0/0x6a0
  [09.2][T4038707]  ? orc_find.part.0+0x1ed/0x300
  [09.5][T4038707]  ? __module_address.part.0+0x25/0x300
  [09.0][T4038707]  writepage_delalloc+0x159/0x310 [btrfs]
  <snip>
  [09.4][    C3] sd 10:0:1:0: [sde] tag#2620 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
  [09.5][    C3] sd 10:0:1:0: [sde] tag#2620 Sense Key : Illegal Request [current]
  [09.9][    C3] sd 10:0:1:0: [sde] tag#2620 Add. Sense: Unaligned write command
  [09.5][    C3] sd 10:0:1:0: [sde] tag#2620 CDB: Write(16) 8a 00 00 00 00 00 02 f3 63 87 00 00 00 2c 00 00
  [09.4][    C3] critical target error, dev sde, sector 396041272 op 0x1:(WRITE) flags 0x800 phys_seg 3 prio class 0
  [09.9][    C3] BTRFS error (device dm-1): bdev /dev/mapper/dml_102_2 errs: wr 1, rd 0, flush 0, corrupt 0, gen 0

The IO errors occur when we allocate a regular extent in previous data
relocation block group.

On zoned btrfs, we use a dedicated block group to relocate a data
extent. Thus, we allocate relocating data extents (pre-alloc) only from
the dedicated block group and vice versa. Once the free space in the
dedicated block group gets tight, a relocating extent may not fit into
the block group. In that case, we need to switch the dedicated block
group to the next one. Then, the previous one is now freed up for
allocating a regular extent. The BG is already not enough to allocate
the relocating extent, but there is still room to allocate a smaller
extent. Now the problem happens. By allocating a regular extent while
nocow IOs for the relocation is still on-going, we will issue WRITE IOs
(for relocation) and ZONE APPEND IOs (for the regular writes) at the
same time. That mixed IOs confuses the write pointer and arises the
unaligned write errors.

This commit introduces a new bit 'zoned_data_reloc_ongoing' to the
btrfs_block_group. We set this bit before releasing the dedicated block
group, and no extent are allocated from a block group having this bit
set. This bit is similar to setting block_group->ro, but is different from
it by allowing nocow writes to start.

Once all the nocow IO for relocation is done (hooked from
btrfs_finish_ordered_io), we reset the bit to release the block group for
further allocation.

Fixes: c2707a2 ("btrfs: zoned: add a dedicated data relocation block group")
CC: [email protected] # 5.16+
Signed-off-by: Naohiro Aota <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: naota

fs/btrfs/block-group.h

@@ -104,6 +104,7 @@ struct btrfs_block_group {
 	unsigned int relocating_repair:1;
 	unsigned int chunk_item_inserted:1;
 	unsigned int zone_is_active:1;
+	unsigned int zoned_data_reloc_ongoing:1;
 
 	int disk_cache_state;
 

fs/btrfs/extent-tree.c

@@ -3832,7 +3832,7 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
 	       block_group->start == fs_info->data_reloc_bg ||
 	       fs_info->data_reloc_bg == 0);
 
-	if (block_group->ro) {
+	if (block_group->ro || block_group->zoned_data_reloc_ongoing) {
 		ret = 1;
 		goto out;
 	}
@@ -3894,8 +3894,24 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
 out:
 	if (ret && ffe_ctl->for_treelog)
 		fs_info->treelog_bg = 0;
-	if (ret && ffe_ctl->for_data_reloc)
+	if (ret && ffe_ctl->for_data_reloc &&
+	    fs_info->data_reloc_bg == block_group->start) {
+		/*
+		 * Do not allow further allocations from this block group.
+		 * Compared to increasing the ->ro, setting the
+		 * ->zoned_data_reloc_ongoing flag still allows nocow
+		 *  writers to come in. See btrfs_inc_nocow_writers().
+		 *
+		 * We need to disable an allocation to avoid an allocation of
+		 * regular (non-relocation data) extent. With mix of relocation
+		 * extents and regular extents, we can dispatch WRITE commands
+		 * (for relocation extents) and ZONE APPEND commands (for
+		 * regular extents) at the same time to the same zone, which
+		 * easily break the write pointer.
+		 */
+		block_group->zoned_data_reloc_ongoing = 1;
 		fs_info->data_reloc_bg = 0;
+	}
 	spin_unlock(&fs_info->relocation_bg_lock);
 	spin_unlock(&fs_info->treelog_bg_lock);
 	spin_unlock(&block_group->lock);

fs/btrfs/inode.c

@@ -3195,6 +3195,8 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 						ordered_extent->file_offset,
 						ordered_extent->file_offset +
 						logical_len);
+		btrfs_zoned_release_data_reloc_bg(fs_info, ordered_extent->disk_bytenr,
+						  ordered_extent->disk_num_bytes);
 	} else {
 		BUG_ON(root == fs_info->tree_root);
 		ret = insert_ordered_extent_file_extent(trans, ordered_extent);

fs/btrfs/zoned.c

@@ -2140,3 +2140,30 @@ bool btrfs_zoned_should_reclaim(struct btrfs_fs_info *fs_info)
 	factor = div64_u64(used * 100, total);
 	return factor >= fs_info->bg_reclaim_threshold;
 }
+
+void btrfs_zoned_release_data_reloc_bg(struct btrfs_fs_info *fs_info, u64 logical,
+				       u64 length)
+{
+	struct btrfs_block_group *block_group;
+
+	if (!btrfs_is_zoned(fs_info))
+		return;
+
+	block_group = btrfs_lookup_block_group(fs_info, logical);
+	/* It should be called on a previous data relocation block group. */
+	ASSERT(block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA));
+
+	spin_lock(&block_group->lock);
+	if (!block_group->zoned_data_reloc_ongoing)
+		goto out;
+
+	/* All relocation extents are written. */
+	if (block_group->start + block_group->alloc_offset == logical + length) {
+		/* Now, release this block group for further allocations. */
+		block_group->zoned_data_reloc_ongoing = 0;
+	}
+
+out:
+	spin_unlock(&block_group->lock);
+	btrfs_put_block_group(block_group);
+}

fs/btrfs/zoned.h

@@ -77,6 +77,8 @@ void btrfs_schedule_zone_finish_bg(struct btrfs_block_group *bg,
 void btrfs_clear_data_reloc_bg(struct btrfs_block_group *bg);
 void btrfs_free_zone_cache(struct btrfs_fs_info *fs_info);
 bool btrfs_zoned_should_reclaim(struct btrfs_fs_info *fs_info);
+void btrfs_zoned_release_data_reloc_bg(struct btrfs_fs_info *fs_info, u64 logical,
+				       u64 length);
 #else /* CONFIG_BLK_DEV_ZONED */
 static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
 				     struct blk_zone *zone)
@@ -243,6 +245,9 @@ static inline bool btrfs_zoned_should_reclaim(struct btrfs_fs_info *fs_info)
 {
 	return false;
 }
+
+static inline void btrfs_zoned_release_data_reloc_bg(struct btrfs_fs_info *fs_info,
+						     u64 logical, u64 length) { }
 #endif
 
 static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)