xfs: implement masked btree key comparisons for _has_records scans

For keyspace fullness scans, we want to be able to mask off the parts of
the key that we don't care about.  For most btree types we /do/ want the
full keyspace, but for checking that a given space usage also has a full
complement of rmapbt records (even if different/multiple owners) we need
this masking so that we only track sparseness of rm_startblock, not the
whole keyspace (which is extremely sparse).

Augment the ->diff_two_keys and ->keys_contiguous helpers to take a
third union xfs_btree_key argument, and wire up xfs_rmap_has_records to
pass this through.  This third "mask" argument should contain a nonzero
value in each structure field that should be used in the key comparisons
done during the scan.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Author: Darrick J. Wong

fs/xfs/libxfs/xfs_alloc.c

@@ -3764,7 +3764,7 @@ xfs_alloc_has_records(
 	memset(&high, 0xFF, sizeof(high));
 	high.a.ar_startblock = bno + len - 1;
 
-	return xfs_btree_has_records(cur, &low, &high, outcome);
+	return xfs_btree_has_records(cur, &low, &high, NULL, outcome);
 }
 
 /*

fs/xfs/libxfs/xfs_alloc_btree.c

@@ -260,20 +260,27 @@ STATIC int64_t
 xfs_bnobt_diff_two_keys(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*k1,
-	const union xfs_btree_key	*k2)
+	const union xfs_btree_key	*k2,
+	const union xfs_btree_key	*mask)
 {
+	ASSERT(!mask || mask->alloc.ar_startblock);
+
 	return (int64_t)be32_to_cpu(k1->alloc.ar_startblock) -
-			  be32_to_cpu(k2->alloc.ar_startblock);
+			be32_to_cpu(k2->alloc.ar_startblock);
 }
 
 STATIC int64_t
 xfs_cntbt_diff_two_keys(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*k1,
-	const union xfs_btree_key	*k2)
+	const union xfs_btree_key	*k2,
+	const union xfs_btree_key	*mask)
 {
 	int64_t				diff;
 
+	ASSERT(!mask || (mask->alloc.ar_blockcount &&
+			 mask->alloc.ar_startblock));
+
 	diff =  be32_to_cpu(k1->alloc.ar_blockcount) -
 		be32_to_cpu(k2->alloc.ar_blockcount);
 	if (diff)
@@ -427,8 +434,11 @@ STATIC enum xbtree_key_contig
 xfs_allocbt_keys_contiguous(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*key1,
-	const union xfs_btree_key	*key2)
+	const union xfs_btree_key	*key2,
+	const union xfs_btree_key	*mask)
 {
+	ASSERT(!mask || mask->alloc.ar_startblock);
+
 	return xbtree_key_contig(be32_to_cpu(key1->alloc.ar_startblock),
 				 be32_to_cpu(key2->alloc.ar_startblock));
 }

fs/xfs/libxfs/xfs_bmap_btree.c

@@ -382,11 +382,14 @@ STATIC int64_t
 xfs_bmbt_diff_two_keys(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*k1,
-	const union xfs_btree_key	*k2)
+	const union xfs_btree_key	*k2,
+	const union xfs_btree_key	*mask)
 {
 	uint64_t			a = be64_to_cpu(k1->bmbt.br_startoff);
 	uint64_t			b = be64_to_cpu(k2->bmbt.br_startoff);
 
+	ASSERT(!mask || mask->bmbt.br_startoff);
+
 	/*
 	 * Note: This routine previously casted a and b to int64 and subtracted
 	 * them to generate a result.  This lead to problems if b was the
@@ -504,8 +507,11 @@ STATIC enum xbtree_key_contig
 xfs_bmbt_keys_contiguous(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*key1,
-	const union xfs_btree_key	*key2)
+	const union xfs_btree_key	*key2,
+	const union xfs_btree_key	*mask)
 {
+	ASSERT(!mask || mask->bmbt.br_startoff);
+
 	return xbtree_key_contig(be64_to_cpu(key1->bmbt.br_startoff),
 				 be64_to_cpu(key2->bmbt.br_startoff));
 }

fs/xfs/libxfs/xfs_btree.c

@@ -5030,6 +5030,9 @@ struct xfs_btree_has_records {
 	union xfs_btree_key		start_key;
 	union xfs_btree_key		end_key;
 
+	/* Mask for key comparisons, if desired. */
+	const union xfs_btree_key	*key_mask;
+
 	/* Highest record key we've seen so far. */
 	union xfs_btree_key		high_key;
 
@@ -5057,7 +5060,8 @@ xfs_btree_has_records_helper(
 		 * then there is a hole at the start of the search range.
 		 * Classify this as sparse and stop immediately.
 		 */
-		if (xfs_btree_keycmp_lt(cur, &info->start_key, &rec_key))
+		if (xfs_btree_masked_keycmp_lt(cur, &info->start_key, &rec_key,
+					info->key_mask))
 			return -ECANCELED;
 	} else {
 		/*
@@ -5068,7 +5072,7 @@ xfs_btree_has_records_helper(
 		 * signal corruption.
 		 */
 		key_contig = cur->bc_ops->keys_contiguous(cur, &info->high_key,
-					&rec_key);
+					&rec_key, info->key_mask);
 		if (key_contig == XBTREE_KEY_OVERLAP &&
 				!(cur->bc_flags & XFS_BTREE_OVERLAPPING))
 			return -EFSCORRUPTED;
@@ -5081,7 +5085,8 @@ xfs_btree_has_records_helper(
 	 * remember it for later.
 	 */
 	cur->bc_ops->init_high_key_from_rec(&rec_high_key, rec);
-	if (xfs_btree_keycmp_gt(cur, &rec_high_key, &info->high_key))
+	if (xfs_btree_masked_keycmp_gt(cur, &rec_high_key, &info->high_key,
+				info->key_mask))
 		info->high_key = rec_high_key; /* struct copy */
 
 	return 0;
@@ -5092,16 +5097,26 @@ xfs_btree_has_records_helper(
  * map to any records; is fully mapped to records; or is partially mapped to
  * records.  This is the btree record equivalent to determining if a file is
  * sparse.
+ *
+ * For most btree types, the record scan should use all available btree key
+ * fields to compare the keys encountered.  These callers should pass NULL for
+ * @mask.  However, some callers (e.g.  scanning physical space in the rmapbt)
+ * want to ignore some part of the btree record keyspace when performing the
+ * comparison.  These callers should pass in a union xfs_btree_key object with
+ * the fields that *should* be a part of the comparison set to any nonzero
+ * value, and the rest zeroed.
  */
 int
 xfs_btree_has_records(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_irec	*low,
 	const union xfs_btree_irec	*high,
+	const union xfs_btree_key	*mask,
 	enum xbtree_recpacking		*outcome)
 {
 	struct xfs_btree_has_records	info = {
 		.outcome		= XBTREE_RECPACKING_EMPTY,
+		.key_mask		= mask,
 	};
 	int				error;
 
@@ -5129,7 +5144,8 @@ xfs_btree_has_records(
 	 * the end of the search range, classify this as full.  Otherwise,
 	 * there is a hole at the end of the search range.
 	 */
-	if (xfs_btree_keycmp_ge(cur, &info.high_key, &info.end_key))
+	if (xfs_btree_masked_keycmp_ge(cur, &info.high_key, &info.end_key,
+				mask))
 		info.outcome = XBTREE_RECPACKING_FULL;
 
 out:

fs/xfs/libxfs/xfs_btree.h

@@ -161,11 +161,14 @@ struct xfs_btree_ops {
 
 	/*
 	 * Difference between key2 and key1 -- positive if key1 > key2,
-	 * negative if key1 < key2, and zero if equal.
+	 * negative if key1 < key2, and zero if equal.  If the @mask parameter
+	 * is non NULL, each key field to be used in the comparison must
+	 * contain a nonzero value.
 	 */
 	int64_t (*diff_two_keys)(struct xfs_btree_cur *cur,
 				 const union xfs_btree_key *key1,
-				 const union xfs_btree_key *key2);
+				 const union xfs_btree_key *key2,
+				 const union xfs_btree_key *mask);
 
 	const struct xfs_buf_ops	*buf_ops;
 
@@ -187,10 +190,13 @@ struct xfs_btree_ops {
 	 * @key1 < K < @key2.  To determine if two btree records are
 	 * immediately adjacent, @key1 should be the high key of the first
 	 * record and @key2 should be the low key of the second record.
+	 * If the @mask parameter is non NULL, each key field to be used in the
+	 * comparison must contain a nonzero value.
 	 */
 	enum xbtree_key_contig (*keys_contiguous)(struct xfs_btree_cur *cur,
 			       const union xfs_btree_key *key1,
-			       const union xfs_btree_key *key2);
+			       const union xfs_btree_key *key2,
+			       const union xfs_btree_key *mask);
 };
 
 /*
@@ -581,6 +587,7 @@ typedef bool (*xfs_btree_key_gap_fn)(struct xfs_btree_cur *cur,
 int xfs_btree_has_records(struct xfs_btree_cur *cur,
 		const union xfs_btree_irec *low,
 		const union xfs_btree_irec *high,
+		const union xfs_btree_key *mask,
 		enum xbtree_recpacking *outcome);
 
 bool xfs_btree_has_more_records(struct xfs_btree_cur *cur);
@@ -593,7 +600,7 @@ xfs_btree_keycmp_lt(
 	const union xfs_btree_key	*key1,
 	const union xfs_btree_key	*key2)
 {
-	return cur->bc_ops->diff_two_keys(cur, key1, key2) < 0;
+	return cur->bc_ops->diff_two_keys(cur, key1, key2, NULL) < 0;
 }
 
 static inline bool
@@ -602,7 +609,7 @@ xfs_btree_keycmp_gt(
 	const union xfs_btree_key	*key1,
 	const union xfs_btree_key	*key2)
 {
-	return cur->bc_ops->diff_two_keys(cur, key1, key2) > 0;
+	return cur->bc_ops->diff_two_keys(cur, key1, key2, NULL) > 0;
 }
 
 static inline bool
@@ -611,7 +618,7 @@ xfs_btree_keycmp_eq(
 	const union xfs_btree_key	*key1,
 	const union xfs_btree_key	*key2)
 {
-	return cur->bc_ops->diff_two_keys(cur, key1, key2) == 0;
+	return cur->bc_ops->diff_two_keys(cur, key1, key2, NULL) == 0;
 }
 
 static inline bool
@@ -641,6 +648,37 @@ xfs_btree_keycmp_ne(
 	return !xfs_btree_keycmp_eq(cur, key1, key2);
 }
 
+/* Masked key comparison helpers */
+static inline bool
+xfs_btree_masked_keycmp_lt(
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_key	*key1,
+	const union xfs_btree_key	*key2,
+	const union xfs_btree_key	*mask)
+{
+	return cur->bc_ops->diff_two_keys(cur, key1, key2, mask) < 0;
+}
+
+static inline bool
+xfs_btree_masked_keycmp_gt(
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_key	*key1,
+	const union xfs_btree_key	*key2,
+	const union xfs_btree_key	*mask)
+{
+	return cur->bc_ops->diff_two_keys(cur, key1, key2, mask) > 0;
+}
+
+static inline bool
+xfs_btree_masked_keycmp_ge(
+	struct xfs_btree_cur		*cur,
+	const union xfs_btree_key	*key1,
+	const union xfs_btree_key	*key2,
+	const union xfs_btree_key	*mask)
+{
+	return !xfs_btree_masked_keycmp_lt(cur, key1, key2, mask);
+}
+
 /* Does this cursor point to the last block in the given level? */
 static inline bool
 xfs_btree_islastblock(

fs/xfs/libxfs/xfs_ialloc_btree.c

@@ -269,10 +269,13 @@ STATIC int64_t
 xfs_inobt_diff_two_keys(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*k1,
-	const union xfs_btree_key	*k2)
+	const union xfs_btree_key	*k2,
+	const union xfs_btree_key	*mask)
 {
+	ASSERT(!mask || mask->inobt.ir_startino);
+
 	return (int64_t)be32_to_cpu(k1->inobt.ir_startino) -
-			  be32_to_cpu(k2->inobt.ir_startino);
+			be32_to_cpu(k2->inobt.ir_startino);
 }
 
 static xfs_failaddr_t
@@ -387,8 +390,11 @@ STATIC enum xbtree_key_contig
 xfs_inobt_keys_contiguous(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*key1,
-	const union xfs_btree_key	*key2)
+	const union xfs_btree_key	*key2,
+	const union xfs_btree_key	*mask)
 {
+	ASSERT(!mask || mask->inobt.ir_startino);
+
 	return xbtree_key_contig(be32_to_cpu(key1->inobt.ir_startino),
 				 be32_to_cpu(key2->inobt.ir_startino));
 }

fs/xfs/libxfs/xfs_refcount.c

@@ -2019,7 +2019,7 @@ xfs_refcount_has_records(
 	high.rc.rc_startblock = bno + len - 1;
 	low.rc.rc_domain = high.rc.rc_domain = domain;
 
-	return xfs_btree_has_records(cur, &low, &high, outcome);
+	return xfs_btree_has_records(cur, &low, &high, NULL, outcome);
 }
 
 int __init

fs/xfs/libxfs/xfs_refcount_btree.c

@@ -202,10 +202,13 @@ STATIC int64_t
 xfs_refcountbt_diff_two_keys(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*k1,
-	const union xfs_btree_key	*k2)
+	const union xfs_btree_key	*k2,
+	const union xfs_btree_key	*mask)
 {
+	ASSERT(!mask || mask->refc.rc_startblock);
+
 	return (int64_t)be32_to_cpu(k1->refc.rc_startblock) -
-			  be32_to_cpu(k2->refc.rc_startblock);
+			be32_to_cpu(k2->refc.rc_startblock);
 }
 
 STATIC xfs_failaddr_t
@@ -304,8 +307,11 @@ STATIC enum xbtree_key_contig
 xfs_refcountbt_keys_contiguous(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_key	*key1,
-	const union xfs_btree_key	*key2)
+	const union xfs_btree_key	*key2,
+	const union xfs_btree_key	*mask)
 {
+	ASSERT(!mask || mask->refc.rc_startblock);
+
 	return xbtree_key_contig(be32_to_cpu(key1->refc.rc_startblock),
 				 be32_to_cpu(key2->refc.rc_startblock));
 }

fs/xfs/libxfs/xfs_rmap.c

@@ -2721,6 +2721,9 @@ xfs_rmap_has_records(
 	xfs_extlen_t		len,
 	enum xbtree_recpacking	*outcome)
 {
+	union xfs_btree_key	mask = {
+		.rmap.rm_startblock = cpu_to_be32(-1U),
+	};
 	union xfs_btree_irec	low;
 	union xfs_btree_irec	high;
 
@@ -2729,7 +2732,7 @@ xfs_rmap_has_records(
 	memset(&high, 0xFF, sizeof(high));
 	high.r.rm_startblock = bno + len - 1;
 
-	return xfs_btree_has_records(cur, &low, &high, outcome);
+	return xfs_btree_has_records(cur, &low, &high, &mask, outcome);
 }
 
 /*