bcachefs: Etyzinger cleanups

Pull out eytzinger.c and kill eytzinger_cmp_fn. We now provide
eytzinger0_sort and eytzinger0_sort_r, which use the standard cmp_func_t
and cmp_r_func_t callbacks.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

7 files changed, 285 insertions, 182 deletions

diff --git a/fs/bcachefs/Makefile b/fs/bcachefs/Makefile
index f6d86eb4b97652..0933493a322c41 100644
--- a/fs/bcachefs/Makefile
+++ b/fs/bcachefs/Makefile
@@ -37,6 +37,7 @@ bcachefs-y		:=	\
 	error.o			\
 	extents.o		\
 	extent_update.o		\
+	eytzinger.o		\
 	fs.o			\
 	fs-common.o		\
 	fs-ioctl.o		\
diff --git a/fs/bcachefs/eytzinger.c b/fs/bcachefs/eytzinger.c
new file mode 100644
index 00000000000000..4ce5e957a6e916
--- /dev/null
+++ b/fs/bcachefs/eytzinger.c
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "eytzinger.h"
+
+/**
+ * is_aligned - is this pointer & size okay for word-wide copying?
+ * @base: pointer to data
+ * @size: size of each element
+ * @align: required alignment (typically 4 or 8)
+ *
+ * Returns true if elements can be copied using word loads and stores.
+ * The size must be a multiple of the alignment, and the base address must
+ * be if we do not have CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
+ *
+ * For some reason, gcc doesn't know to optimize "if (a & mask || b & mask)"
+ * to "if ((a | b) & mask)", so we do that by hand.
+ */
+__attribute_const__ __always_inline
+static bool is_aligned(const void *base, size_t size, unsigned char align)
+{
+	unsigned char lsbits = (unsigned char)size;
+
+	(void)base;
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	lsbits |= (unsigned char)(uintptr_t)base;
+#endif
+	return (lsbits & (align - 1)) == 0;
+}
+
+/**
+ * swap_words_32 - swap two elements in 32-bit chunks
+ * @a: pointer to the first element to swap
+ * @b: pointer to the second element to swap
+ * @n: element size (must be a multiple of 4)
+ *
+ * Exchange the two objects in memory.  This exploits base+index addressing,
+ * which basically all CPUs have, to minimize loop overhead computations.
+ *
+ * For some reason, on x86 gcc 7.3.0 adds a redundant test of n at the
+ * bottom of the loop, even though the zero flag is still valid from the
+ * subtract (since the intervening mov instructions don't alter the flags).
+ * Gcc 8.1.0 doesn't have that problem.
+ */
+static void swap_words_32(void *a, void *b, size_t n)
+{
+	do {
+		u32 t = *(u32 *)(a + (n -= 4));
+		*(u32 *)(a + n) = *(u32 *)(b + n);
+		*(u32 *)(b + n) = t;
+	} while (n);
+}
+
+/**
+ * swap_words_64 - swap two elements in 64-bit chunks
+ * @a: pointer to the first element to swap
+ * @b: pointer to the second element to swap
+ * @n: element size (must be a multiple of 8)
+ *
+ * Exchange the two objects in memory.  This exploits base+index
+ * addressing, which basically all CPUs have, to minimize loop overhead
+ * computations.
+ *
+ * We'd like to use 64-bit loads if possible.  If they're not, emulating
+ * one requires base+index+4 addressing which x86 has but most other
+ * processors do not.  If CONFIG_64BIT, we definitely have 64-bit loads,
+ * but it's possible to have 64-bit loads without 64-bit pointers (e.g.
+ * x32 ABI).  Are there any cases the kernel needs to worry about?
+ */
+static void swap_words_64(void *a, void *b, size_t n)
+{
+	do {
+#ifdef CONFIG_64BIT
+		u64 t = *(u64 *)(a + (n -= 8));
+		*(u64 *)(a + n) = *(u64 *)(b + n);
+		*(u64 *)(b + n) = t;
+#else
+		/* Use two 32-bit transfers to avoid base+index+4 addressing */
+		u32 t = *(u32 *)(a + (n -= 4));
+		*(u32 *)(a + n) = *(u32 *)(b + n);
+		*(u32 *)(b + n) = t;
+
+		t = *(u32 *)(a + (n -= 4));
+		*(u32 *)(a + n) = *(u32 *)(b + n);
+		*(u32 *)(b + n) = t;
+#endif
+	} while (n);
+}
+
+/**
+ * swap_bytes - swap two elements a byte at a time
+ * @a: pointer to the first element to swap
+ * @b: pointer to the second element to swap
+ * @n: element size
+ *
+ * This is the fallback if alignment doesn't allow using larger chunks.
+ */
+static void swap_bytes(void *a, void *b, size_t n)
+{
+	do {
+		char t = ((char *)a)[--n];
+		((char *)a)[n] = ((char *)b)[n];
+		((char *)b)[n] = t;
+	} while (n);
+}
+
+/*
+ * The values are arbitrary as long as they can't be confused with
+ * a pointer, but small integers make for the smallest compare
+ * instructions.
+ */
+#define SWAP_WORDS_64 (swap_r_func_t)0
+#define SWAP_WORDS_32 (swap_r_func_t)1
+#define SWAP_BYTES    (swap_r_func_t)2
+#define SWAP_WRAPPER  (swap_r_func_t)3
+
+struct wrapper {
+	cmp_func_t cmp;
+	swap_func_t swap;
+};
+
+/*
+ * The function pointer is last to make tail calls most efficient if the
+ * compiler decides not to inline this function.
+ */
+static void do_swap(void *a, void *b, size_t size, swap_r_func_t swap_func, const void *priv)
+{
+	if (swap_func == SWAP_WRAPPER) {
+		((const struct wrapper *)priv)->swap(a, b, (int)size);
+		return;
+	}
+
+	if (swap_func == SWAP_WORDS_64)
+		swap_words_64(a, b, size);
+	else if (swap_func == SWAP_WORDS_32)
+		swap_words_32(a, b, size);
+	else if (swap_func == SWAP_BYTES)
+		swap_bytes(a, b, size);
+	else
+		swap_func(a, b, (int)size, priv);
+}
+
+#define _CMP_WRAPPER ((cmp_r_func_t)0L)
+
+static int do_cmp(const void *a, const void *b, cmp_r_func_t cmp, const void *priv)
+{
+	if (cmp == _CMP_WRAPPER)
+		return ((const struct wrapper *)priv)->cmp(a, b);
+	return cmp(a, b, priv);
+}
+
+static inline int eytzinger0_do_cmp(void *base, size_t n, size_t size,
+			 cmp_r_func_t cmp_func, const void *priv,
+			 size_t l, size_t r)
+{
+	return do_cmp(base + inorder_to_eytzinger0(l, n) * size,
+		      base + inorder_to_eytzinger0(r, n) * size,
+		      cmp_func, priv);
+}
+
+static inline void eytzinger0_do_swap(void *base, size_t n, size_t size,
+			   swap_r_func_t swap_func, const void *priv,
+			   size_t l, size_t r)
+{
+	do_swap(base + inorder_to_eytzinger0(l, n) * size,
+		base + inorder_to_eytzinger0(r, n) * size,
+		size, swap_func, priv);
+}
+
+void eytzinger0_sort_r(void *base, size_t n, size_t size,
+		       cmp_r_func_t cmp_func,
+		       swap_r_func_t swap_func,
+		       const void *priv)
+{
+	int i, c, r;
+
+	/* called from 'sort' without swap function, let's pick the default */
+	if (swap_func == SWAP_WRAPPER && !((struct wrapper *)priv)->swap)
+		swap_func = NULL;
+
+	if (!swap_func) {
+		if (is_aligned(base, size, 8))
+			swap_func = SWAP_WORDS_64;
+		else if (is_aligned(base, size, 4))
+			swap_func = SWAP_WORDS_32;
+		else
+			swap_func = SWAP_BYTES;
+	}
+
+	/* heapify */
+	for (i = n / 2 - 1; i >= 0; --i) {
+		for (r = i; r * 2 + 1 < n; r = c) {
+			c = r * 2 + 1;
+
+			if (c + 1 < n &&
+			    eytzinger0_do_cmp(base, n, size, cmp_func, priv, c, c + 1) < 0)
+				c++;
+
+			if (eytzinger0_do_cmp(base, n, size, cmp_func, priv, r, c) >= 0)
+				break;
+
+			eytzinger0_do_swap(base, n, size, swap_func, priv, r, c);
+		}
+	}
+
+	/* sort */
+	for (i = n - 1; i > 0; --i) {
+		eytzinger0_do_swap(base, n, size, swap_func, priv, 0, i);
+
+		for (r = 0; r * 2 + 1 < i; r = c) {
+			c = r * 2 + 1;
+
+			if (c + 1 < i &&
+			    eytzinger0_do_cmp(base, n, size, cmp_func, priv, c, c + 1) < 0)
+				c++;
+
+			if (eytzinger0_do_cmp(base, n, size, cmp_func, priv, r, c) >= 0)
+				break;
+
+			eytzinger0_do_swap(base, n, size, swap_func, priv, r, c);
+		}
+	}
+}
+
+void eytzinger0_sort(void *base, size_t n, size_t size,
+		     cmp_func_t cmp_func,
+		     swap_func_t swap_func)
+{
+	struct wrapper w = {
+		.cmp  = cmp_func,
+		.swap = swap_func,
+	};
+
+	return eytzinger0_sort_r(base, n, size, _CMP_WRAPPER, SWAP_WRAPPER, &w);
+}
diff --git a/fs/bcachefs/eytzinger.h b/fs/bcachefs/eytzinger.h
index b04750dbf870bc..ee0e2df33322d2 100644
--- a/fs/bcachefs/eytzinger.h
+++ b/fs/bcachefs/eytzinger.h
@@ -5,23 +5,33 @@
 #include <linux/bitops.h>
 #include <linux/log2.h>
 
-#include "util.h"
+#ifdef EYTZINGER_DEBUG
+#define EYTZINGER_BUG_ON(cond)		BUG_ON(cond)
+#else
+#define EYTZINGER_BUG_ON(cond)
+#endif
 
 /*
  * Traversal for trees in eytzinger layout - a full binary tree layed out in an
- * array
- */
-
-/*
- * One based indexing version:
+ * array.
  *
- * With one based indexing each level of the tree starts at a power of two -
- * good for cacheline alignment:
+ * Consider using an eytzinger tree any time you would otherwise be doing binary
+ * search over an array. Binary search is a worst case scenario for branch
+ * prediction and prefetching, but in an eytzinger tree every node's children
+ * are adjacent in memory, thus we can prefetch children before knowing the
+ * result of the comparison, assuming multiple nodes fit on a cacheline.
+ *
+ * Two variants are provided, for one based indexing and zero based indexing.
+ *
+ * Zero based indexing is more convenient, but one based indexing has better
+ * alignment and thus better performance because each new level of the tree
+ * starts at a power of two, and thus if element 0 was cacheline aligned, each
+ * new level will be as well.
  */
 
 static inline unsigned eytzinger1_child(unsigned i, unsigned child)
 {
-	EBUG_ON(child > 1);
+	EYTZINGER_BUG_ON(child > 1);
 
 	return (i << 1) + child;
 }
@@ -58,7 +68,7 @@ static inline unsigned eytzinger1_last(unsigned size)
 
 static inline unsigned eytzinger1_next(unsigned i, unsigned size)
 {
-	EBUG_ON(i > size);
+	EYTZINGER_BUG_ON(i > size);
 
 	if (eytzinger1_right_child(i) <= size) {
 		i = eytzinger1_right_child(i);
@@ -74,7 +84,7 @@ static inline unsigned eytzinger1_next(unsigned i, unsigned size)
 
 static inline unsigned eytzinger1_prev(unsigned i, unsigned size)
 {
-	EBUG_ON(i > size);
+	EYTZINGER_BUG_ON(i > size);
 
 	if (eytzinger1_left_child(i) <= size) {
 		i = eytzinger1_left_child(i) + 1;
@@ -101,7 +111,7 @@ static inline unsigned __eytzinger1_to_inorder(unsigned i, unsigned size,
 	unsigned shift = __fls(size) - b;
 	int s;
 
-	EBUG_ON(!i || i > size);
+	EYTZINGER_BUG_ON(!i || i > size);
 
 	i  ^= 1U << b;
 	i <<= 1;
@@ -126,7 +136,7 @@ static inline unsigned __inorder_to_eytzinger1(unsigned i, unsigned size,
 	unsigned shift;
 	int s;
 
-	EBUG_ON(!i || i > size);
+	EYTZINGER_BUG_ON(!i || i > size);
 
 	/*
 	 * sign bit trick:
@@ -164,7 +174,7 @@ static inline unsigned inorder_to_eytzinger1(unsigned i, unsigned size)
 
 static inline unsigned eytzinger0_child(unsigned i, unsigned child)
 {
-	EBUG_ON(child > 1);
+	EYTZINGER_BUG_ON(child > 1);
 
 	return (i << 1) + 1 + child;
 }
@@ -231,11 +241,9 @@ static inline unsigned inorder_to_eytzinger0(unsigned i, unsigned size)
 	     (_i) != -1;				\
 	     (_i) = eytzinger0_next((_i), (_size)))
 
-typedef int (*eytzinger_cmp_fn)(const void *l, const void *r, size_t size);
-
 /* return greatest node <= @search, or -1 if not found */
 static inline ssize_t eytzinger0_find_le(void *base, size_t nr, size_t size,
-					 eytzinger_cmp_fn cmp, const void *search)
+					 cmp_func_t cmp, const void *search)
 {
 	unsigned i, n = 0;
 
@@ -244,21 +252,24 @@ static inline ssize_t eytzinger0_find_le(void *base, size_t nr, size_t size,
 
 	do {
 		i = n;
-		n = eytzinger0_child(i, cmp(search, base + i * size, size) >= 0);
+		n = eytzinger0_child(i, cmp(base + i * size, search) <= 0);
 	} while (n < nr);
 
 	if (n & 1) {
 		/* @i was greater than @search, return previous node: */
-
-		if (i == eytzinger0_first(nr))
-			return -1;
-
 		return eytzinger0_prev(i, nr);
 	} else {
 		return i;
 	}
 }
 
+static inline ssize_t eytzinger0_find_gt(void *base, size_t nr, size_t size,
+					 cmp_func_t cmp, const void *search)
+{
+	ssize_t idx = eytzinger0_find_le(base, nr, size, cmp, search);
+	return eytzinger0_next(idx, size);
+}
+
 #define eytzinger0_find(base, nr, size, _cmp, search)			\
 ({									\
 	void *_base		= (base);				\
@@ -269,13 +280,13 @@ static inline ssize_t eytzinger0_find_le(void *base, size_t nr, size_t size,
 	int _res;							\
 									\
 	while (_i < _nr &&						\
-	       (_res = _cmp(_search, _base + _i * _size, _size)))	\
+	       (_res = _cmp(_search, _base + _i * _size)))		\
 		_i = eytzinger0_child(_i, _res > 0);			\
 	_i;								\
 })
 
-void eytzinger0_sort(void *, size_t, size_t,
-		    int (*cmp_func)(const void *, const void *, size_t),
-		    void (*swap_func)(void *, void *, size_t));
+void eytzinger0_sort_r(void *, size_t, size_t,
+		       cmp_r_func_t, swap_r_func_t, const void *);
+void eytzinger0_sort(void *, size_t, size_t, cmp_func_t, swap_func_t);
 
 #endif /* _EYTZINGER_H */
diff --git a/fs/bcachefs/journal_seq_blacklist.c b/fs/bcachefs/journal_seq_blacklist.c
index b5303874fc35b3..37a024e034d495 100644
--- a/fs/bcachefs/journal_seq_blacklist.c
+++ b/fs/bcachefs/journal_seq_blacklist.c
@@ -95,8 +95,7 @@ out:
 	return ret ?: bch2_blacklist_table_initialize(c);
 }
 
-static int journal_seq_blacklist_table_cmp(const void *_l,
-					   const void *_r, size_t size)
+static int journal_seq_blacklist_table_cmp(const void *_l, const void *_r)
 {
 	const struct journal_seq_blacklist_table_entry *l = _l;
 	const struct journal_seq_blacklist_table_entry *r = _r;
diff --git a/fs/bcachefs/replicas.c b/fs/bcachefs/replicas.c
index cc2672c120312c..678b9c20e2514b 100644
--- a/fs/bcachefs/replicas.c
+++ b/fs/bcachefs/replicas.c
@@ -6,12 +6,15 @@
 #include "replicas.h"
 #include "super-io.h"
 
+#include <linux/sort.h>
+
 static int bch2_cpu_replicas_to_sb_replicas(struct bch_fs *,
 					    struct bch_replicas_cpu *);
 
 /* Some (buggy!) compilers don't allow memcmp to be passed as a pointer */
-static int bch2_memcmp(const void *l, const void *r, size_t size)
+static int bch2_memcmp(const void *l, const void *r,  const void *priv)
 {
+	size_t size = (size_t) priv;
 	return memcmp(l, r, size);
 }
 
@@ -39,7 +42,8 @@ void bch2_replicas_entry_sort(struct bch_replicas_entry_v1 *e)
 
 static void bch2_cpu_replicas_sort(struct bch_replicas_cpu *r)
 {
-	eytzinger0_sort(r->entries, r->nr, r->entry_size, bch2_memcmp, NULL);
+	eytzinger0_sort_r(r->entries, r->nr, r->entry_size,
+			  bch2_memcmp, NULL, (void *)(size_t)r->entry_size);
 }
 
 static void bch2_replicas_entry_v0_to_text(struct printbuf *out,
@@ -228,7 +232,7 @@ static inline int __replicas_entry_idx(struct bch_replicas_cpu *r,
 
 	verify_replicas_entry(search);
 
-#define entry_cmp(_l, _r, size)	memcmp(_l, _r, entry_size)
+#define entry_cmp(_l, _r)	memcmp(_l, _r, entry_size)
 	idx = eytzinger0_find(r->entries, r->nr, r->entry_size,
 			      entry_cmp, search);
 #undef entry_cmp
@@ -824,10 +828,11 @@ static int bch2_cpu_replicas_validate(struct bch_replicas_cpu *cpu_r,
 {
 	unsigned i;
 
-	sort_cmp_size(cpu_r->entries,
-		      cpu_r->nr,
-		      cpu_r->entry_size,
-		      bch2_memcmp, NULL);
+	sort_r(cpu_r->entries,
+	       cpu_r->nr,
+	       cpu_r->entry_size,
+	       bch2_memcmp, NULL,
+	       (void *)(size_t)cpu_r->entry_size);
 
 	for (i = 0; i < cpu_r->nr; i++) {
 		struct bch_replicas_entry_v1 *e =
diff --git a/fs/bcachefs/util.c b/fs/bcachefs/util.c
index 216fadf16928b9..92c6ad75e702ab 100644
--- a/fs/bcachefs/util.c
+++ b/fs/bcachefs/util.c
@@ -707,149 +707,6 @@ void memcpy_from_bio(void *dst, struct bio *src, struct bvec_iter src_iter)
 	}
 }
 
-static int alignment_ok(const void *base, size_t align)
-{
-	return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
-		((unsigned long)base & (align - 1)) == 0;
-}
-
-static void u32_swap(void *a, void *b, size_t size)
-{
-	u32 t = *(u32 *)a;
-	*(u32 *)a = *(u32 *)b;
-	*(u32 *)b = t;
-}
-
-static void u64_swap(void *a, void *b, size_t size)
-{
-	u64 t = *(u64 *)a;
-	*(u64 *)a = *(u64 *)b;
-	*(u64 *)b = t;
-}
-
-static void generic_swap(void *a, void *b, size_t size)
-{
-	char t;
-
-	do {
-		t = *(char *)a;
-		*(char *)a++ = *(char *)b;
-		*(char *)b++ = t;
-	} while (--size > 0);
-}
-
-static inline int do_cmp(void *base, size_t n, size_t size,
-			 int (*cmp_func)(const void *, const void *, size_t),
-			 size_t l, size_t r)
-{
-	return cmp_func(base + inorder_to_eytzinger0(l, n) * size,
-			base + inorder_to_eytzinger0(r, n) * size,
-			size);
-}
-
-static inline void do_swap(void *base, size_t n, size_t size,
-			   void (*swap_func)(void *, void *, size_t),
-			   size_t l, size_t r)
-{
-	swap_func(base + inorder_to_eytzinger0(l, n) * size,
-		  base + inorder_to_eytzinger0(r, n) * size,
-		  size);
-}
-
-void eytzinger0_sort(void *base, size_t n, size_t size,
-		     int (*cmp_func)(const void *, const void *, size_t),
-		     void (*swap_func)(void *, void *, size_t))
-{
-	int i, c, r;
-
-	if (!swap_func) {
-		if (size == 4 && alignment_ok(base, 4))
-			swap_func = u32_swap;
-		else if (size == 8 && alignment_ok(base, 8))
-			swap_func = u64_swap;
-		else
-			swap_func = generic_swap;
-	}
-
-	/* heapify */
-	for (i = n / 2 - 1; i >= 0; --i) {
-		for (r = i; r * 2 + 1 < n; r = c) {
-			c = r * 2 + 1;
-
-			if (c + 1 < n &&
-			    do_cmp(base, n, size, cmp_func, c, c + 1) < 0)
-				c++;
-
-			if (do_cmp(base, n, size, cmp_func, r, c) >= 0)
-				break;
-
-			do_swap(base, n, size, swap_func, r, c);
-		}
-	}
-
-	/* sort */
-	for (i = n - 1; i > 0; --i) {
-		do_swap(base, n, size, swap_func, 0, i);
-
-		for (r = 0; r * 2 + 1 < i; r = c) {
-			c = r * 2 + 1;
-
-			if (c + 1 < i &&
-			    do_cmp(base, n, size, cmp_func, c, c + 1) < 0)
-				c++;
-
-			if (do_cmp(base, n, size, cmp_func, r, c) >= 0)
-				break;
-
-			do_swap(base, n, size, swap_func, r, c);
-		}
-	}
-}
-
-void sort_cmp_size(void *base, size_t num, size_t size,
-	  int (*cmp_func)(const void *, const void *, size_t),
-	  void (*swap_func)(void *, void *, size_t size))
-{
-	/* pre-scale counters for performance */
-	int i = (num/2 - 1) * size, n = num * size, c, r;
-
-	if (!swap_func) {
-		if (size == 4 && alignment_ok(base, 4))
-			swap_func = u32_swap;
-		else if (size == 8 && alignment_ok(base, 8))
-			swap_func = u64_swap;
-		else
-			swap_func = generic_swap;
-	}
-
-	/* heapify */
-	for ( ; i >= 0; i -= size) {
-		for (r = i; r * 2 + size < n; r  = c) {
-			c = r * 2 + size;
-			if (c < n - size &&
-			    cmp_func(base + c, base + c + size, size) < 0)
-				c += size;
-			if (cmp_func(base + r, base + c, size) >= 0)
-				break;
-			swap_func(base + r, base + c, size);
-		}
-	}
-
-	/* sort */
-	for (i = n - size; i > 0; i -= size) {
-		swap_func(base, base + i, size);
-		for (r = 0; r * 2 + size < i; r = c) {
-			c = r * 2 + size;
-			if (c < i - size &&
-			    cmp_func(base + c, base + c + size, size) < 0)
-				c += size;
-			if (cmp_func(base + r, base + c, size) >= 0)
-				break;
-			swap_func(base + r, base + c, size);
-		}
-	}
-}
-
 #if 0
 void eytzinger1_test(void)
 {
diff --git a/fs/bcachefs/util.h b/fs/bcachefs/util.h
index 4577c0789a3a7f..b7e7c29278fc05 100644
--- a/fs/bcachefs/util.h
+++ b/fs/bcachefs/util.h
@@ -631,10 +631,6 @@ static inline void memset_u64s_tail(void *s, int c, unsigned bytes)
 	memset(s + bytes, c, rem);
 }
 
-void sort_cmp_size(void *base, size_t num, size_t size,
-	  int (*cmp_func)(const void *, const void *, size_t),
-	  void (*swap_func)(void *, void *, size_t));
-
 /* just the memmove, doesn't update @_nr */
 #define __array_insert_item(_array, _nr, _pos)				\
 	memmove(&(_array)[(_pos) + 1],					\