bcachefs: Reduce/kill BKEY_PADDED use

With various newer key types - stripe keys, inline data extents - the
old approach of calculating the maximum size of the value is becoming
more and more error prone. Better to switch to bkey_on_stack, which can
dynamically allocate if necessary to handle any size bkey.

In particular we also want to get rid of BKEY_EXTENT_VAL_U64s_MAX.

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

1 files changed, 60 insertions, 0 deletions

diff --git a/fs/bcachefs/bkey_buf.h b/fs/bcachefs/bkey_buf.h
new file mode 100644
index 000000000000..0d7c67a959af
--- /dev/null
+++ b/fs/bcachefs/bkey_buf.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_BKEY_BUF_H
+#define _BCACHEFS_BKEY_BUF_H
+
+#include "bcachefs.h"
+
+struct bkey_buf {
+	struct bkey_i	*k;
+	u64		onstack[12];
+};
+
+static inline void bch2_bkey_buf_realloc(struct bkey_buf *s,
+					 struct bch_fs *c, unsigned u64s)
+{
+	if (s->k == (void *) s->onstack &&
+	    u64s > ARRAY_SIZE(s->onstack)) {
+		s->k = mempool_alloc(&c->large_bkey_pool, GFP_NOFS);
+		memcpy(s->k, s->onstack, sizeof(s->onstack));
+	}
+}
+
+static inline void bch2_bkey_buf_reassemble(struct bkey_buf *s,
+					    struct bch_fs *c,
+					    struct bkey_s_c k)
+{
+	bch2_bkey_buf_realloc(s, c, k.k->u64s);
+	bkey_reassemble(s->k, k);
+}
+
+static inline void bch2_bkey_buf_copy(struct bkey_buf *s,
+				      struct bch_fs *c,
+				      struct bkey_i *src)
+{
+	bch2_bkey_buf_realloc(s, c, src->k.u64s);
+	bkey_copy(s->k, src);
+}
+
+static inline void bch2_bkey_buf_unpack(struct bkey_buf *s,
+					struct bch_fs *c,
+					struct btree *b,
+					struct bkey_packed *src)
+{
+	bch2_bkey_buf_realloc(s, c, BKEY_U64s +
+			      bkeyp_val_u64s(&b->format, src));
+	bch2_bkey_unpack(b, s->k, src);
+}
+
+static inline void bch2_bkey_buf_init(struct bkey_buf *s)
+{
+	s->k = (void *) s->onstack;
+}
+
+static inline void bch2_bkey_buf_exit(struct bkey_buf *s, struct bch_fs *c)
+{
+	if (s->k != (void *) s->onstack)
+		mempool_free(s->k, &c->large_bkey_pool);
+	s->k = NULL;
+}
+
+#endif /* _BCACHEFS_BKEY_BUF_H */