fs/bcachefs/dirent.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0

 #include "bcachefs.h"
 #include "bkey_methods.h"
 #include "btree_update.h"
 #include "extents.h"
 #include "dirent.h"
 #include "fs.h"
 #include "keylist.h"
 #include "str_hash.h"
 #include "subvolume.h"

 #include <linux/dcache.h>

 unsigned bch2_dirent_name_bytes(struct bkey_s_c_dirent d)
 {
 	unsigned len = bkey_val_bytes(d.k) -
 		offsetof(struct bch_dirent, d_name);

 	return strnlen(d.v->d_name, len);
 }

 static u64 bch2_dirent_hash(const struct bch_hash_info *info,
 			    const struct qstr *name)
 {
 	struct bch_str_hash_ctx ctx;

 	bch2_str_hash_init(&ctx, info);
 	bch2_str_hash_update(&ctx, info, name->name, name->len);

 	/* [0,2) reserved for dots */
 	return max_t(u64, bch2_str_hash_end(&ctx, info), 2);
 }

 static u64 dirent_hash_key(const struct bch_hash_info *info, const void *key)
 {
 	return bch2_dirent_hash(info, key);
 }

 static u64 dirent_hash_bkey(const struct bch_hash_info *info, struct bkey_s_c k)
 {
 	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);
 	struct qstr name = QSTR_INIT(d.v->d_name, bch2_dirent_name_bytes(d));

 	return bch2_dirent_hash(info, &name);
 }

 static bool dirent_cmp_key(struct bkey_s_c _l, const void *_r)
 {
 	struct bkey_s_c_dirent l = bkey_s_c_to_dirent(_l);
 	int len = bch2_dirent_name_bytes(l);
 	const struct qstr *r = _r;

 	return len - r->len ?: memcmp(l.v->d_name, r->name, len);
 }

 static bool dirent_cmp_bkey(struct bkey_s_c _l, struct bkey_s_c _r)
 {
 	struct bkey_s_c_dirent l = bkey_s_c_to_dirent(_l);
 	struct bkey_s_c_dirent r = bkey_s_c_to_dirent(_r);
 	int l_len = bch2_dirent_name_bytes(l);
 	int r_len = bch2_dirent_name_bytes(r);

 	return l_len - r_len ?: memcmp(l.v->d_name, r.v->d_name, l_len);
 }

 static bool dirent_is_visible(subvol_inum inum, struct bkey_s_c k)
 {
 	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);

 	if (d.v->d_type == DT_SUBVOL)
 		return le32_to_cpu(d.v->d_parent_subvol) == inum.subvol;
 	return true;
 }

 const struct bch_hash_desc bch2_dirent_hash_desc = {
 	.btree_id	= BTREE_ID_dirents,
 	.key_type	= KEY_TYPE_dirent,
 	.hash_key	= dirent_hash_key,
 	.hash_bkey	= dirent_hash_bkey,
 	.cmp_key	= dirent_cmp_key,
 	.cmp_bkey	= dirent_cmp_bkey,
 	.is_visible	= dirent_is_visible,
 };

 int bch2_dirent_invalid(const struct bch_fs *c, struct bkey_s_c k,
 			unsigned flags, struct printbuf *err)
 {
 	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);
 	unsigned len;

 	if (bkey_val_bytes(k.k) < sizeof(struct bch_dirent)) {
 		prt_printf(err, "incorrect value size (%zu < %zu)",
 		       bkey_val_bytes(k.k), sizeof(*d.v));
 		return -BCH_ERR_invalid_bkey;
 	}

 	len = bch2_dirent_name_bytes(d);
 	if (!len) {
 		prt_printf(err, "empty name");
 		return -BCH_ERR_invalid_bkey;
 	}

 	if (bkey_val_u64s(k.k) > dirent_val_u64s(len)) {
 		prt_printf(err, "value too big (%zu > %u)",
 		       bkey_val_u64s(k.k), dirent_val_u64s(len));
 		return -BCH_ERR_invalid_bkey;
 	}

 	if (len > BCH_NAME_MAX) {
 		prt_printf(err, "dirent name too big (%u > %u)",
 		       len, BCH_NAME_MAX);
 		return -BCH_ERR_invalid_bkey;
 	}

 	if (len == 1 && !memcmp(d.v->d_name, ".", 1)) {
 		prt_printf(err, "invalid name");
 		return -BCH_ERR_invalid_bkey;
 	}

 	if (len == 2 && !memcmp(d.v->d_name, "..", 2)) {
 		prt_printf(err, "invalid name");
 		return -BCH_ERR_invalid_bkey;
 	}

 	if (memchr(d.v->d_name, '/', len)) {
 		prt_printf(err, "invalid name");
 		return -BCH_ERR_invalid_bkey;
 	}

 	if (d.v->d_type != DT_SUBVOL &&
 	    le64_to_cpu(d.v->d_inum) == d.k->p.inode) {
 		prt_printf(err, "dirent points to own directory");
 		return -BCH_ERR_invalid_bkey;
 	}

 	return 0;
 }

 void bch2_dirent_to_text(struct printbuf *out, struct bch_fs *c,
 			 struct bkey_s_c k)
 {
 	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);

 	prt_printf(out, "%.*s -> %llu type %s",
 	       bch2_dirent_name_bytes(d),
 	       d.v->d_name,
 	       d.v->d_type != DT_SUBVOL
 	       ? le64_to_cpu(d.v->d_inum)
 	       : le32_to_cpu(d.v->d_child_subvol),
 	       bch2_d_type_str(d.v->d_type));
 }

 static struct bkey_i_dirent *dirent_create_key(struct btree_trans *trans,
 				subvol_inum dir, u8 type,
 				const struct qstr *name, u64 dst)
 {
 	struct bkey_i_dirent *dirent;
 	unsigned u64s = BKEY_U64s + dirent_val_u64s(name->len);

 	if (name->len > BCH_NAME_MAX)
 		return ERR_PTR(-ENAMETOOLONG);

 	BUG_ON(u64s > U8_MAX);

 	dirent = bch2_trans_kmalloc(trans, u64s * sizeof(u64));
 	if (IS_ERR(dirent))
 		return dirent;

 	bkey_dirent_init(&dirent->k_i);
 	dirent->k.u64s = u64s;

 	if (type != DT_SUBVOL) {
 		dirent->v.d_inum = cpu_to_le64(dst);
 	} else {
 		dirent->v.d_parent_subvol = cpu_to_le32(dir.subvol);
 		dirent->v.d_child_subvol = cpu_to_le32(dst);
 	}

 	dirent->v.d_type = type;

 	memcpy(dirent->v.d_name, name->name, name->len);
 	memset(dirent->v.d_name + name->len, 0,
 	       bkey_val_bytes(&dirent->k) -
 	       offsetof(struct bch_dirent, d_name) -
 	       name->len);

 	EBUG_ON(bch2_dirent_name_bytes(dirent_i_to_s_c(dirent)) != name->len);

 	return dirent;
 }

 int bch2_dirent_create(struct btree_trans *trans, subvol_inum dir,
 		       const struct bch_hash_info *hash_info,
 		       u8 type, const struct qstr *name, u64 dst_inum,
 		       u64 *dir_offset, int flags)
 {
 	struct bkey_i_dirent *dirent;
 	int ret;

 	dirent = dirent_create_key(trans, dir, type, name, dst_inum);
 	ret = PTR_ERR_OR_ZERO(dirent);
 	if (ret)
 		return ret;

 	ret = bch2_hash_set(trans, bch2_dirent_hash_desc, hash_info,
 			    dir, &dirent->k_i, flags);
 	*dir_offset = dirent->k.p.offset;

 	return ret;
 }

 static void dirent_copy_target(struct bkey_i_dirent *dst,
 			       struct bkey_s_c_dirent src)
 {
 	dst->v.d_inum = src.v->d_inum;
 	dst->v.d_type = src.v->d_type;
 }

 int bch2_dirent_read_target(struct btree_trans *trans, subvol_inum dir,
 			    struct bkey_s_c_dirent d, subvol_inum *target)
 {
 	struct bch_subvolume s;
 	int ret = 0;

 	if (d.v->d_type == DT_SUBVOL &&
 	    d.v->d_parent_subvol != dir.subvol)
 		return 1;

 	if (likely(d.v->d_type != DT_SUBVOL)) {
 		target->subvol	= dir.subvol;
 		target->inum	= le64_to_cpu(d.v->d_inum);
 	} else {
 		target->subvol	= le32_to_cpu(d.v->d_child_subvol);

 		ret = bch2_subvolume_get(trans, target->subvol, true, BTREE_ITER_CACHED, &s);

 		target->inum	= le64_to_cpu(s.inode);
 	}

 	return ret;
 }

 int bch2_dirent_rename(struct btree_trans *trans,
 		subvol_inum src_dir, struct bch_hash_info *src_hash,
 		subvol_inum dst_dir, struct bch_hash_info *dst_hash,
 		const struct qstr *src_name, subvol_inum *src_inum, u64 *src_offset,
 		const struct qstr *dst_name, subvol_inum *dst_inum, u64 *dst_offset,
 		enum bch_rename_mode mode)
 {
 	struct btree_iter src_iter = { NULL };
 	struct btree_iter dst_iter = { NULL };
 	struct bkey_s_c old_src, old_dst = bkey_s_c_null;
 	struct bkey_i_dirent *new_src = NULL, *new_dst = NULL;
 	struct bpos dst_pos =
 		POS(dst_dir.inum, bch2_dirent_hash(dst_hash, dst_name));
 	unsigned src_type = 0, dst_type = 0, src_update_flags = 0;
 	int ret = 0;

 	if (src_dir.subvol != dst_dir.subvol)
 		return -EXDEV;

 	memset(src_inum, 0, sizeof(*src_inum));
 	memset(dst_inum, 0, sizeof(*dst_inum));

 	/* Lookup src: */
 	ret = bch2_hash_lookup(trans, &src_iter, bch2_dirent_hash_desc,
 			       src_hash, src_dir, src_name,
 			       BTREE_ITER_INTENT);
 	if (ret)
 		goto out;

 	old_src = bch2_btree_iter_peek_slot(&src_iter);
 	ret = bkey_err(old_src);
 	if (ret)
 		goto out;

 	ret = bch2_dirent_read_target(trans, src_dir,
 			bkey_s_c_to_dirent(old_src), src_inum);
 	if (ret)
 		goto out;

 	src_type = bkey_s_c_to_dirent(old_src).v->d_type;

 	if (src_type == DT_SUBVOL && mode == BCH_RENAME_EXCHANGE)
 		return -EOPNOTSUPP;


 	/* Lookup dst: */
 	if (mode == BCH_RENAME) {
 		/*
 		 * Note that we're _not_ checking if the target already exists -
 		 * we're relying on the VFS to do that check for us for
 		 * correctness:
 		 */
 		ret = bch2_hash_hole(trans, &dst_iter, bch2_dirent_hash_desc,
 				     dst_hash, dst_dir, dst_name);
 		if (ret)
 			goto out;
 	} else {
 		ret = bch2_hash_lookup(trans, &dst_iter, bch2_dirent_hash_desc,
 				       dst_hash, dst_dir, dst_name,
 				       BTREE_ITER_INTENT);
 		if (ret)
 			goto out;

 		old_dst = bch2_btree_iter_peek_slot(&dst_iter);
 		ret = bkey_err(old_dst);
 		if (ret)
 			goto out;

 		ret = bch2_dirent_read_target(trans, dst_dir,
 				bkey_s_c_to_dirent(old_dst), dst_inum);
 		if (ret)
 			goto out;

 		dst_type = bkey_s_c_to_dirent(old_dst).v->d_type;

 		if (dst_type == DT_SUBVOL)
 			return -EOPNOTSUPP;
 	}

 	if (mode != BCH_RENAME_EXCHANGE)
 		*src_offset = dst_iter.pos.offset;

 	/* Create new dst key: */
 	new_dst = dirent_create_key(trans, dst_dir, 0, dst_name, 0);
 	ret = PTR_ERR_OR_ZERO(new_dst);
 	if (ret)
 		goto out;

 	dirent_copy_target(new_dst, bkey_s_c_to_dirent(old_src));
 	new_dst->k.p = dst_iter.pos;

 	/* Create new src key: */
 	if (mode == BCH_RENAME_EXCHANGE) {
 		new_src = dirent_create_key(trans, src_dir, 0, src_name, 0);
 		ret = PTR_ERR_OR_ZERO(new_src);
 		if (ret)
 			goto out;

 		dirent_copy_target(new_src, bkey_s_c_to_dirent(old_dst));
 		new_src->k.p = src_iter.pos;
 	} else {
 		new_src = bch2_trans_kmalloc(trans, sizeof(struct bkey_i));
 		ret = PTR_ERR_OR_ZERO(new_src);
 		if (ret)
 			goto out;

 		bkey_init(&new_src->k);
 		new_src->k.p = src_iter.pos;

 		if (bkey_le(dst_pos, src_iter.pos) &&
 		    bkey_lt(src_iter.pos, dst_iter.pos)) {
 			/*
 			 * We have a hash collision for the new dst key,
 			 * and new_src - the key we're deleting - is between
 			 * new_dst's hashed slot and the slot we're going to be
 			 * inserting it into - oops.  This will break the hash
 			 * table if we don't deal with it:
 			 */
 			if (mode == BCH_RENAME) {
 				/*
 				 * If we're not overwriting, we can just insert
 				 * new_dst at the src position:
 				 */
 				new_src = new_dst;
 				new_src->k.p = src_iter.pos;
 				goto out_set_src;
 			} else {
 				/* If we're overwriting, we can't insert new_dst
 				 * at a different slot because it has to
 				 * overwrite old_dst - just make sure to use a
 				 * whiteout when deleting src:
 				 */
 				new_src->k.type = KEY_TYPE_hash_whiteout;
 			}
 		} else {
 			/* Check if we need a whiteout to delete src: */
 			ret = bch2_hash_needs_whiteout(trans, bch2_dirent_hash_desc,
 						       src_hash, &src_iter);
 			if (ret < 0)
 				goto out;

 			if (ret)
 				new_src->k.type = KEY_TYPE_hash_whiteout;
 		}
 	}

 	ret = bch2_trans_update(trans, &dst_iter, &new_dst->k_i, 0);
 	if (ret)
 		goto out;
 out_set_src:

 	/*
 	 * If we're deleting a subvolume, we need to really delete the dirent,
 	 * not just emit a whiteout in the current snapshot:
 	 */
 	if (src_type == DT_SUBVOL) {
 		bch2_btree_iter_set_snapshot(&src_iter, old_src.k->p.snapshot);
 		ret = bch2_btree_iter_traverse(&src_iter);
 		if (ret)
 			goto out;

 		new_src->k.p = src_iter.pos;
 		src_update_flags |= BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE;
 	}

 	ret = bch2_trans_update(trans, &src_iter, &new_src->k_i, src_update_flags);
 	if (ret)
 		goto out;

 	if (mode == BCH_RENAME_EXCHANGE)
 		*src_offset = new_src->k.p.offset;
 	*dst_offset = new_dst->k.p.offset;
 out:
 	bch2_trans_iter_exit(trans, &src_iter);
 	bch2_trans_iter_exit(trans, &dst_iter);
 	return ret;
 }

 int __bch2_dirent_lookup_trans(struct btree_trans *trans,
 			       struct btree_iter *iter,
 			       subvol_inum dir,
 			       const struct bch_hash_info *hash_info,
 			       const struct qstr *name, subvol_inum *inum,
 			       unsigned flags)
 {
 	struct bkey_s_c k;
 	struct bkey_s_c_dirent d;
 	u32 snapshot;
 	int ret;

 	ret = bch2_subvolume_get_snapshot(trans, dir.subvol, &snapshot);
 	if (ret)
 		return ret;

 	ret = bch2_hash_lookup(trans, iter, bch2_dirent_hash_desc,
 			       hash_info, dir, name, flags);
 	if (ret)
 		return ret;

 	k = bch2_btree_iter_peek_slot(iter);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;

 	d = bkey_s_c_to_dirent(k);

 	ret = bch2_dirent_read_target(trans, dir, d, inum);
 	if (ret > 0)
 		ret = -ENOENT;
 err:
 	if (ret)
 		bch2_trans_iter_exit(trans, iter);

 	return ret;
 }

 u64 bch2_dirent_lookup(struct bch_fs *c, subvol_inum dir,
 		       const struct bch_hash_info *hash_info,
 		       const struct qstr *name, subvol_inum *inum)
 {
 	struct btree_trans trans;
 	struct btree_iter iter;
 	int ret;

 	bch2_trans_init(&trans, c, 0, 0);
 retry:
 	bch2_trans_begin(&trans);

 	ret = __bch2_dirent_lookup_trans(&trans, &iter, dir, hash_info,
 					  name, inum, 0);
 	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 		goto retry;
 	if (!ret)
 		bch2_trans_iter_exit(&trans, &iter);
 	bch2_trans_exit(&trans);
 	return ret;
 }

 int bch2_empty_dir_trans(struct btree_trans *trans, subvol_inum dir)
 {
 	struct btree_iter iter;
 	struct bkey_s_c k;
 	u32 snapshot;
 	int ret;

 	ret = bch2_subvolume_get_snapshot(trans, dir.subvol, &snapshot);
 	if (ret)
 		return ret;

 	for_each_btree_key_upto_norestart(trans, iter, BTREE_ID_dirents,
 			   SPOS(dir.inum, 0, snapshot),
 			   POS(dir.inum, U64_MAX), 0, k, ret)
 		if (k.k->type == KEY_TYPE_dirent) {
 			ret = -ENOTEMPTY;
 			break;
 		}
 	bch2_trans_iter_exit(trans, &iter);

 	return ret;
 }

 int bch2_readdir(struct bch_fs *c, subvol_inum inum, struct dir_context *ctx)
 {
 	struct btree_trans trans;
 	struct btree_iter iter;
 	struct bkey_s_c k;
 	struct bkey_s_c_dirent dirent;
 	subvol_inum target;
 	u32 snapshot;
 	int ret;

 	bch2_trans_init(&trans, c, 0, 0);
 retry:
 	bch2_trans_begin(&trans);

 	ret = bch2_subvolume_get_snapshot(&trans, inum.subvol, &snapshot);
 	if (ret)
 		goto err;

 	for_each_btree_key_upto_norestart(&trans, iter, BTREE_ID_dirents,
 			   SPOS(inum.inum, ctx->pos, snapshot),
 			   POS(inum.inum, U64_MAX), 0, k, ret) {
 		if (k.k->type != KEY_TYPE_dirent)
 			continue;

 		dirent = bkey_s_c_to_dirent(k);

 		ret = bch2_dirent_read_target(&trans, inum, dirent, &target);
 		if (ret < 0)
 			break;
 		if (ret)
 			continue;

 		/*
 		 * XXX: dir_emit() can fault and block, while we're holding
 		 * locks
 		 */
 		ctx->pos = dirent.k->p.offset;
 		if (!dir_emit(ctx, dirent.v->d_name,
 			      bch2_dirent_name_bytes(dirent),
 			      target.inum,
 			      vfs_d_type(dirent.v->d_type)))
 			break;
 		ctx->pos = dirent.k->p.offset + 1;

 		/*
 		 * read_target looks up subvolumes, we can overflow paths if the
 		 * directory has many subvolumes in it
 		 */
 		ret = btree_trans_too_many_iters(&trans);
 		if (ret)
 			break;
 	}
 	bch2_trans_iter_exit(&trans, &iter);
 err:
 	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 		goto retry;

 	bch2_trans_exit(&trans);

 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0

	#include "bcachefs.h"
	#include "bkey_methods.h"
	#include "btree_update.h"
	#include "extents.h"
	#include "dirent.h"
	#include "fs.h"
	#include "keylist.h"
	#include "str_hash.h"
	#include "subvolume.h"

	#include <linux/dcache.h>

	unsigned bch2_dirent_name_bytes(struct bkey_s_c_dirent d)
	{
	unsigned len = bkey_val_bytes(d.k) -
	offsetof(struct bch_dirent, d_name);

	return strnlen(d.v->d_name, len);
	}

	static u64 bch2_dirent_hash(const struct bch_hash_info *info,
	const struct qstr *name)
	{
	struct bch_str_hash_ctx ctx;

	bch2_str_hash_init(&ctx, info);
	bch2_str_hash_update(&ctx, info, name->name, name->len);

	/* [0,2) reserved for dots */
	return max_t(u64, bch2_str_hash_end(&ctx, info), 2);
	}

	static u64 dirent_hash_key(const struct bch_hash_info info, const void key)
	{
	return bch2_dirent_hash(info, key);
	}

	static u64 dirent_hash_bkey(const struct bch_hash_info *info, struct bkey_s_c k)
	{
	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);
	struct qstr name = QSTR_INIT(d.v->d_name, bch2_dirent_name_bytes(d));

	return bch2_dirent_hash(info, &name);
	}

	static bool dirent_cmp_key(struct bkey_s_c _l, const void *_r)
	{
	struct bkey_s_c_dirent l = bkey_s_c_to_dirent(_l);
	int len = bch2_dirent_name_bytes(l);
	const struct qstr *r = _r;

	return len - r->len ?: memcmp(l.v->d_name, r->name, len);
	}

	static bool dirent_cmp_bkey(struct bkey_s_c _l, struct bkey_s_c _r)
	{
	struct bkey_s_c_dirent l = bkey_s_c_to_dirent(_l);
	struct bkey_s_c_dirent r = bkey_s_c_to_dirent(_r);
	int l_len = bch2_dirent_name_bytes(l);
	int r_len = bch2_dirent_name_bytes(r);

	return l_len - r_len ?: memcmp(l.v->d_name, r.v->d_name, l_len);
	}

	static bool dirent_is_visible(subvol_inum inum, struct bkey_s_c k)
	{
	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);

	if (d.v->d_type == DT_SUBVOL)
	return le32_to_cpu(d.v->d_parent_subvol) == inum.subvol;
	return true;
	}

	const struct bch_hash_desc bch2_dirent_hash_desc = {
	.btree_id = BTREE_ID_dirents,
	.key_type = KEY_TYPE_dirent,
	.hash_key = dirent_hash_key,
	.hash_bkey = dirent_hash_bkey,
	.cmp_key = dirent_cmp_key,
	.cmp_bkey = dirent_cmp_bkey,
	.is_visible = dirent_is_visible,
	};

	int bch2_dirent_invalid(const struct bch_fs *c, struct bkey_s_c k,
	unsigned flags, struct printbuf *err)
	{
	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);
	unsigned len;

	if (bkey_val_bytes(k.k) < sizeof(struct bch_dirent)) {
	prt_printf(err, "incorrect value size (%zu < %zu)",
	bkey_val_bytes(k.k), sizeof(*d.v));
	return -BCH_ERR_invalid_bkey;
	}

	len = bch2_dirent_name_bytes(d);
	if (!len) {
	prt_printf(err, "empty name");
	return -BCH_ERR_invalid_bkey;
	}

	if (bkey_val_u64s(k.k) > dirent_val_u64s(len)) {
	prt_printf(err, "value too big (%zu > %u)",
	bkey_val_u64s(k.k), dirent_val_u64s(len));
	return -BCH_ERR_invalid_bkey;
	}

	if (len > BCH_NAME_MAX) {
	prt_printf(err, "dirent name too big (%u > %u)",
	len, BCH_NAME_MAX);
	return -BCH_ERR_invalid_bkey;
	}

	if (len == 1 && !memcmp(d.v->d_name, ".", 1)) {
	prt_printf(err, "invalid name");
	return -BCH_ERR_invalid_bkey;
	}

	if (len == 2 && !memcmp(d.v->d_name, "..", 2)) {
	prt_printf(err, "invalid name");
	return -BCH_ERR_invalid_bkey;
	}

	if (memchr(d.v->d_name, '/', len)) {
	prt_printf(err, "invalid name");
	return -BCH_ERR_invalid_bkey;
	}

	if (d.v->d_type != DT_SUBVOL &&
	le64_to_cpu(d.v->d_inum) == d.k->p.inode) {
	prt_printf(err, "dirent points to own directory");
	return -BCH_ERR_invalid_bkey;
	}

	return 0;
	}

	void bch2_dirent_to_text(struct printbuf out, struct bch_fs c,
	struct bkey_s_c k)
	{
	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);

	prt_printf(out, "%.*s -> %llu type %s",
	bch2_dirent_name_bytes(d),
	d.v->d_name,
	d.v->d_type != DT_SUBVOL
	? le64_to_cpu(d.v->d_inum)
	: le32_to_cpu(d.v->d_child_subvol),
	bch2_d_type_str(d.v->d_type));
	}

	static struct bkey_i_dirent dirent_create_key(struct btree_trans trans,
	subvol_inum dir, u8 type,
	const struct qstr *name, u64 dst)
	{
	struct bkey_i_dirent *dirent;
	unsigned u64s = BKEY_U64s + dirent_val_u64s(name->len);

	if (name->len > BCH_NAME_MAX)
	return ERR_PTR(-ENAMETOOLONG);

	BUG_ON(u64s > U8_MAX);

	dirent = bch2_trans_kmalloc(trans, u64s * sizeof(u64));
	if (IS_ERR(dirent))
	return dirent;

	bkey_dirent_init(&dirent->k_i);
	dirent->k.u64s = u64s;

	if (type != DT_SUBVOL) {
	dirent->v.d_inum = cpu_to_le64(dst);
	} else {
	dirent->v.d_parent_subvol = cpu_to_le32(dir.subvol);
	dirent->v.d_child_subvol = cpu_to_le32(dst);
	}

	dirent->v.d_type = type;

	memcpy(dirent->v.d_name, name->name, name->len);
	memset(dirent->v.d_name + name->len, 0,
	bkey_val_bytes(&dirent->k) -
	offsetof(struct bch_dirent, d_name) -
	name->len);

	EBUG_ON(bch2_dirent_name_bytes(dirent_i_to_s_c(dirent)) != name->len);

	return dirent;
	}

	int bch2_dirent_create(struct btree_trans *trans, subvol_inum dir,
	const struct bch_hash_info *hash_info,
	u8 type, const struct qstr *name, u64 dst_inum,
	u64 *dir_offset, int flags)
	{
	struct bkey_i_dirent *dirent;
	int ret;

	dirent = dirent_create_key(trans, dir, type, name, dst_inum);
	ret = PTR_ERR_OR_ZERO(dirent);
	if (ret)
	return ret;

	ret = bch2_hash_set(trans, bch2_dirent_hash_desc, hash_info,
	dir, &dirent->k_i, flags);
	*dir_offset = dirent->k.p.offset;

	return ret;
	}

	static void dirent_copy_target(struct bkey_i_dirent *dst,
	struct bkey_s_c_dirent src)
	{
	dst->v.d_inum = src.v->d_inum;
	dst->v.d_type = src.v->d_type;
	}

	int bch2_dirent_read_target(struct btree_trans *trans, subvol_inum dir,
	struct bkey_s_c_dirent d, subvol_inum *target)
	{
	struct bch_subvolume s;
	int ret = 0;

	if (d.v->d_type == DT_SUBVOL &&
	d.v->d_parent_subvol != dir.subvol)
	return 1;

	if (likely(d.v->d_type != DT_SUBVOL)) {
	target->subvol = dir.subvol;
	target->inum = le64_to_cpu(d.v->d_inum);
	} else {
	target->subvol = le32_to_cpu(d.v->d_child_subvol);

	ret = bch2_subvolume_get(trans, target->subvol, true, BTREE_ITER_CACHED, &s);

	target->inum = le64_to_cpu(s.inode);
	}

	return ret;
	}

	int bch2_dirent_rename(struct btree_trans *trans,
	subvol_inum src_dir, struct bch_hash_info *src_hash,
	subvol_inum dst_dir, struct bch_hash_info *dst_hash,
	const struct qstr src_name, subvol_inum src_inum, u64 *src_offset,
	const struct qstr dst_name, subvol_inum dst_inum, u64 *dst_offset,
	enum bch_rename_mode mode)
	{
	struct btree_iter src_iter = { NULL };
	struct btree_iter dst_iter = { NULL };
	struct bkey_s_c old_src, old_dst = bkey_s_c_null;
	struct bkey_i_dirent new_src = NULL, new_dst = NULL;
	struct bpos dst_pos =
	POS(dst_dir.inum, bch2_dirent_hash(dst_hash, dst_name));
	unsigned src_type = 0, dst_type = 0, src_update_flags = 0;
	int ret = 0;

	if (src_dir.subvol != dst_dir.subvol)
	return -EXDEV;

	memset(src_inum, 0, sizeof(*src_inum));
	memset(dst_inum, 0, sizeof(*dst_inum));

	/* Lookup src: */
	ret = bch2_hash_lookup(trans, &src_iter, bch2_dirent_hash_desc,
	src_hash, src_dir, src_name,
	BTREE_ITER_INTENT);
	if (ret)
	goto out;

	old_src = bch2_btree_iter_peek_slot(&src_iter);
	ret = bkey_err(old_src);
	if (ret)
	goto out;

	ret = bch2_dirent_read_target(trans, src_dir,
	bkey_s_c_to_dirent(old_src), src_inum);
	if (ret)
	goto out;

	src_type = bkey_s_c_to_dirent(old_src).v->d_type;

	if (src_type == DT_SUBVOL && mode == BCH_RENAME_EXCHANGE)
	return -EOPNOTSUPP;


	/* Lookup dst: */
	if (mode == BCH_RENAME) {
	/*
	* Note that we're _not_ checking if the target already exists -
	* we're relying on the VFS to do that check for us for
	* correctness:
	*/
	ret = bch2_hash_hole(trans, &dst_iter, bch2_dirent_hash_desc,
	dst_hash, dst_dir, dst_name);
	if (ret)
	goto out;
	} else {
	ret = bch2_hash_lookup(trans, &dst_iter, bch2_dirent_hash_desc,
	dst_hash, dst_dir, dst_name,
	BTREE_ITER_INTENT);
	if (ret)
	goto out;

	old_dst = bch2_btree_iter_peek_slot(&dst_iter);
	ret = bkey_err(old_dst);
	if (ret)
	goto out;

	ret = bch2_dirent_read_target(trans, dst_dir,
	bkey_s_c_to_dirent(old_dst), dst_inum);
	if (ret)
	goto out;

	dst_type = bkey_s_c_to_dirent(old_dst).v->d_type;

	if (dst_type == DT_SUBVOL)
	return -EOPNOTSUPP;
	}

	if (mode != BCH_RENAME_EXCHANGE)
	*src_offset = dst_iter.pos.offset;

	/* Create new dst key: */
	new_dst = dirent_create_key(trans, dst_dir, 0, dst_name, 0);
	ret = PTR_ERR_OR_ZERO(new_dst);
	if (ret)
	goto out;

	dirent_copy_target(new_dst, bkey_s_c_to_dirent(old_src));
	new_dst->k.p = dst_iter.pos;

	/* Create new src key: */
	if (mode == BCH_RENAME_EXCHANGE) {
	new_src = dirent_create_key(trans, src_dir, 0, src_name, 0);
	ret = PTR_ERR_OR_ZERO(new_src);
	if (ret)
	goto out;

	dirent_copy_target(new_src, bkey_s_c_to_dirent(old_dst));
	new_src->k.p = src_iter.pos;
	} else {
	new_src = bch2_trans_kmalloc(trans, sizeof(struct bkey_i));
	ret = PTR_ERR_OR_ZERO(new_src);
	if (ret)
	goto out;

	bkey_init(&new_src->k);
	new_src->k.p = src_iter.pos;

	if (bkey_le(dst_pos, src_iter.pos) &&
	bkey_lt(src_iter.pos, dst_iter.pos)) {
	/*
	* We have a hash collision for the new dst key,
	* and new_src - the key we're deleting - is between
	* new_dst's hashed slot and the slot we're going to be
	* inserting it into - oops. This will break the hash
	* table if we don't deal with it:
	*/
	if (mode == BCH_RENAME) {
	/*
	* If we're not overwriting, we can just insert
	* new_dst at the src position:
	*/
	new_src = new_dst;
	new_src->k.p = src_iter.pos;
	goto out_set_src;
	} else {
	/* If we're overwriting, we can't insert new_dst
	* at a different slot because it has to
	* overwrite old_dst - just make sure to use a
	* whiteout when deleting src:
	*/
	new_src->k.type = KEY_TYPE_hash_whiteout;
	}
	} else {
	/* Check if we need a whiteout to delete src: */
	ret = bch2_hash_needs_whiteout(trans, bch2_dirent_hash_desc,
	src_hash, &src_iter);
	if (ret < 0)
	goto out;

	if (ret)
	new_src->k.type = KEY_TYPE_hash_whiteout;
	}
	}

	ret = bch2_trans_update(trans, &dst_iter, &new_dst->k_i, 0);
	if (ret)
	goto out;
	out_set_src:

	/*
	* If we're deleting a subvolume, we need to really delete the dirent,
	* not just emit a whiteout in the current snapshot:
	*/
	if (src_type == DT_SUBVOL) {
	bch2_btree_iter_set_snapshot(&src_iter, old_src.k->p.snapshot);
	ret = bch2_btree_iter_traverse(&src_iter);
	if (ret)
	goto out;

	new_src->k.p = src_iter.pos;
	src_update_flags \|= BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE;
	}

	ret = bch2_trans_update(trans, &src_iter, &new_src->k_i, src_update_flags);
	if (ret)
	goto out;

	if (mode == BCH_RENAME_EXCHANGE)
	*src_offset = new_src->k.p.offset;
	*dst_offset = new_dst->k.p.offset;
	out:
	bch2_trans_iter_exit(trans, &src_iter);
	bch2_trans_iter_exit(trans, &dst_iter);
	return ret;
	}

	int __bch2_dirent_lookup_trans(struct btree_trans *trans,
	struct btree_iter *iter,
	subvol_inum dir,
	const struct bch_hash_info *hash_info,
	const struct qstr name, subvol_inum inum,
	unsigned flags)
	{
	struct bkey_s_c k;
	struct bkey_s_c_dirent d;
	u32 snapshot;
	int ret;

	ret = bch2_subvolume_get_snapshot(trans, dir.subvol, &snapshot);
	if (ret)
	return ret;

	ret = bch2_hash_lookup(trans, iter, bch2_dirent_hash_desc,
	hash_info, dir, name, flags);
	if (ret)
	return ret;

	k = bch2_btree_iter_peek_slot(iter);
	ret = bkey_err(k);
	if (ret)
	goto err;

	d = bkey_s_c_to_dirent(k);

	ret = bch2_dirent_read_target(trans, dir, d, inum);
	if (ret > 0)
	ret = -ENOENT;
	err:
	if (ret)
	bch2_trans_iter_exit(trans, iter);

	return ret;
	}

	u64 bch2_dirent_lookup(struct bch_fs *c, subvol_inum dir,
	const struct bch_hash_info *hash_info,
	const struct qstr name, subvol_inum inum)
	{
	struct btree_trans trans;
	struct btree_iter iter;
	int ret;

	bch2_trans_init(&trans, c, 0, 0);
	retry:
	bch2_trans_begin(&trans);

	ret = __bch2_dirent_lookup_trans(&trans, &iter, dir, hash_info,
	name, inum, 0);
	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
	goto retry;
	if (!ret)
	bch2_trans_iter_exit(&trans, &iter);
	bch2_trans_exit(&trans);
	return ret;
	}

	int bch2_empty_dir_trans(struct btree_trans *trans, subvol_inum dir)
	{
	struct btree_iter iter;
	struct bkey_s_c k;
	u32 snapshot;
	int ret;

	ret = bch2_subvolume_get_snapshot(trans, dir.subvol, &snapshot);
	if (ret)
	return ret;

	for_each_btree_key_upto_norestart(trans, iter, BTREE_ID_dirents,
	SPOS(dir.inum, 0, snapshot),
	POS(dir.inum, U64_MAX), 0, k, ret)
	if (k.k->type == KEY_TYPE_dirent) {
	ret = -ENOTEMPTY;
	break;
	}
	bch2_trans_iter_exit(trans, &iter);

	return ret;
	}

	int bch2_readdir(struct bch_fs c, subvol_inum inum, struct dir_context ctx)
	{
	struct btree_trans trans;
	struct btree_iter iter;
	struct bkey_s_c k;
	struct bkey_s_c_dirent dirent;
	subvol_inum target;
	u32 snapshot;
	int ret;

	bch2_trans_init(&trans, c, 0, 0);
	retry:
	bch2_trans_begin(&trans);

	ret = bch2_subvolume_get_snapshot(&trans, inum.subvol, &snapshot);
	if (ret)
	goto err;

	for_each_btree_key_upto_norestart(&trans, iter, BTREE_ID_dirents,
	SPOS(inum.inum, ctx->pos, snapshot),
	POS(inum.inum, U64_MAX), 0, k, ret) {
	if (k.k->type != KEY_TYPE_dirent)
	continue;

	dirent = bkey_s_c_to_dirent(k);

	ret = bch2_dirent_read_target(&trans, inum, dirent, &target);
	if (ret < 0)
	break;
	if (ret)
	continue;

	/*
	* XXX: dir_emit() can fault and block, while we're holding
	* locks
	*/
	ctx->pos = dirent.k->p.offset;
	if (!dir_emit(ctx, dirent.v->d_name,
	bch2_dirent_name_bytes(dirent),
	target.inum,
	vfs_d_type(dirent.v->d_type)))
	break;
	ctx->pos = dirent.k->p.offset + 1;

	/*
	* read_target looks up subvolumes, we can overflow paths if the
	* directory has many subvolumes in it
	*/
	ret = btree_trans_too_many_iters(&trans);
	if (ret)
	break;
	}
	bch2_trans_iter_exit(&trans, &iter);
	err:
	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
	goto retry;

	bch2_trans_exit(&trans);

	return ret;
	}