1 files changed, 371 insertions, 0 deletions
diff --git a/fs/minix/itree_common.c b/fs/minix/itree_common.c
new file mode 100644
index 000000000..446148792
--- /dev/null
+++ b/fs/minix/itree_common.c
@@ -0,0 +1,371 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Generic part */
+
+typedef struct {
+	block_t	*p;
+	block_t	key;
+	struct buffer_head *bh;
+} Indirect;
+
+static DEFINE_RWLOCK(pointers_lock);
+
+static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v)
+{
+	p->key = *(p->p = v);
+	p->bh = bh;
+}
+
+static inline int verify_chain(Indirect *from, Indirect *to)
+{
+	while (from <= to && from->key == *from->p)
+		from++;
+	return (from > to);
+}
+
+static inline block_t *block_end(struct buffer_head *bh)
+{
+	return (block_t *)((char*)bh->b_data + bh->b_size);
+}
+
+static inline Indirect *get_branch(struct inode *inode,
+					int depth,
+					int *offsets,
+					Indirect chain[DEPTH],
+					int *err)
+{
+	struct super_block *sb = inode->i_sb;
+	Indirect *p = chain;
+	struct buffer_head *bh;
+
+	*err = 0;
+	/* i_data is not going away, no lock needed */
+	add_chain (chain, NULL, i_data(inode) + *offsets);
+	if (!p->key)
+		goto no_block;
+	while (--depth) {
+		bh = sb_bread(sb, block_to_cpu(p->key));
+		if (!bh)
+			goto failure;
+		read_lock(&pointers_lock);
+		if (!verify_chain(chain, p))
+			goto changed;
+		add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
+		read_unlock(&pointers_lock);
+		if (!p->key)
+			goto no_block;
+	}
+	return NULL;
+
+changed:
+	read_unlock(&pointers_lock);
+	brelse(bh);
+	*err = -EAGAIN;
+	goto no_block;
+failure:
+	*err = -EIO;
+no_block:
+	return p;
+}
+
+static int alloc_branch(struct inode *inode,
+			     int num,
+			     int *offsets,
+			     Indirect *branch)
+{
+	int n = 0;
+	int i;
+	int parent = minix_new_block(inode);
+	int err = -ENOSPC;
+
+	branch[0].key = cpu_to_block(parent);
+	if (parent) for (n = 1; n < num; n++) {
+		struct buffer_head *bh;
+		/* Allocate the next block */
+		int nr = minix_new_block(inode);
+		if (!nr)
+			break;
+		branch[n].key = cpu_to_block(nr);
+		bh = sb_getblk(inode->i_sb, parent);
+		if (!bh) {
+			minix_free_block(inode, nr);
+			err = -ENOMEM;
+			break;
+		}
+		lock_buffer(bh);
+		memset(bh->b_data, 0, bh->b_size);
+		branch[n].bh = bh;
+		branch[n].p = (block_t*) bh->b_data + offsets[n];
+		*branch[n].p = branch[n].key;
+		set_buffer_uptodate(bh);
+		unlock_buffer(bh);
+		mark_buffer_dirty_inode(bh, inode);
+		parent = nr;
+	}
+	if (n == num)
+		return 0;
+
+	/* Allocation failed, free what we already allocated */
+	for (i = 1; i < n; i++)
+		bforget(branch[i].bh);
+	for (i = 0; i < n; i++)
+		minix_free_block(inode, block_to_cpu(branch[i].key));
+	return err;
+}
+
+static inline int splice_branch(struct inode *inode,
+				     Indirect chain[DEPTH],
+				     Indirect *where,
+				     int num)
+{
+	int i;
+
+	write_lock(&pointers_lock);
+
+	/* Verify that place we are splicing to is still there and vacant */
+	if (!verify_chain(chain, where-1) || *where->p)
+		goto changed;
+
+	*where->p = where->key;
+
+	write_unlock(&pointers_lock);
+
+	/* We are done with atomic stuff, now do the rest of housekeeping */
+
+	inode->i_ctime = current_time(inode);
+
+	/* had we spliced it onto indirect block? */
+	if (where->bh)
+		mark_buffer_dirty_inode(where->bh, inode);
+
+	mark_inode_dirty(inode);
+	return 0;
+
+changed:
+	write_unlock(&pointers_lock);
+	for (i = 1; i < num; i++)
+		bforget(where[i].bh);
+	for (i = 0; i < num; i++)
+		minix_free_block(inode, block_to_cpu(where[i].key));
+	return -EAGAIN;
+}
+
+static int get_block(struct inode * inode, sector_t block,
+			struct buffer_head *bh, int create)
+{
+	int err = -EIO;
+	int offsets[DEPTH];
+	Indirect chain[DEPTH];
+	Indirect *partial;
+	int left;
+	int depth = block_to_path(inode, block, offsets);
+
+	if (depth == 0)
+		goto out;
+
+reread:
+	partial = get_branch(inode, depth, offsets, chain, &err);
+
+	/* Simplest case - block found, no allocation needed */
+	if (!partial) {
+got_it:
+		map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
+		/* Clean up and exit */
+		partial = chain+depth-1; /* the whole chain */
+		goto cleanup;
+	}
+
+	/* Next simple case - plain lookup or failed read of indirect block */
+	if (!create || err == -EIO) {
+cleanup:
+		while (partial > chain) {
+			brelse(partial->bh);
+			partial--;
+		}
+out:
+		return err;
+	}
+
+	/*
+	 * Indirect block might be removed by truncate while we were
+	 * reading it. Handling of that case (forget what we've got and
+	 * reread) is taken out of the main path.
+	 */
+	if (err == -EAGAIN)
+		goto changed;
+
+	left = (chain + depth) - partial;
+	err = alloc_branch(inode, left, offsets+(partial-chain), partial);
+	if (err)
+		goto cleanup;
+
+	if (splice_branch(inode, chain, partial, left) < 0)
+		goto changed;
+
+	set_buffer_new(bh);
+	goto got_it;
+
+changed:
+	while (partial > chain) {
+		brelse(partial->bh);
+		partial--;
+	}
+	goto reread;
+}
+
+static inline int all_zeroes(block_t *p, block_t *q)
+{
+	while (p < q)
+		if (*p++)
+			return 0;
+	return 1;
+}
+
+static Indirect *find_shared(struct inode *inode,
+				int depth,
+				int offsets[DEPTH],
+				Indirect chain[DEPTH],
+				block_t *top)
+{
+	Indirect *partial, *p;
+	int k, err;
+
+	*top = 0;
+	for (k = depth; k > 1 && !offsets[k-1]; k--)
+		;
+	partial = get_branch(inode, k, offsets, chain, &err);
+
+	write_lock(&pointers_lock);
+	if (!partial)
+		partial = chain + k-1;
+	if (!partial->key && *partial->p) {
+		write_unlock(&pointers_lock);
+		goto no_top;
+	}
+	for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
+		;
+	if (p == chain + k - 1 && p > chain) {
+		p->p--;
+	} else {
+		*top = *p->p;
+		*p->p = 0;
+	}
+	write_unlock(&pointers_lock);
+
+	while(partial > p)
+	{
+		brelse(partial->bh);
+		partial--;
+	}
+no_top:
+	return partial;
+}
+
+static inline void free_data(struct inode *inode, block_t *p, block_t *q)
+{
+	unsigned long nr;
+
+	for ( ; p < q ; p++) {
+		nr = block_to_cpu(*p);
+		if (nr) {
+			*p = 0;
+			minix_free_block(inode, nr);
+		}
+	}
+}
+
+static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
+{
+	struct buffer_head * bh;
+	unsigned long nr;
+
+	if (depth--) {
+		for ( ; p < q ; p++) {
+			nr = block_to_cpu(*p);
+			if (!nr)
+				continue;
+			*p = 0;
+			bh = sb_bread(inode->i_sb, nr);
+			if (!bh)
+				continue;
+			free_branches(inode, (block_t*)bh->b_data,
+				      block_end(bh), depth);
+			bforget(bh);
+			minix_free_block(inode, nr);
+			mark_inode_dirty(inode);
+		}
+	} else
+		free_data(inode, p, q);
+}
+
+static inline void truncate (struct inode * inode)
+{
+	struct super_block *sb = inode->i_sb;
+	block_t *idata = i_data(inode);
+	int offsets[DEPTH];
+	Indirect chain[DEPTH];
+	Indirect *partial;
+	block_t nr = 0;
+	int n;
+	int first_whole;
+	long iblock;
+
+	iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits;
+	block_truncate_page(inode->i_mapping, inode->i_size, get_block);
+
+	n = block_to_path(inode, iblock, offsets);
+	if (!n)
+		return;
+
+	if (n == 1) {
+		free_data(inode, idata+offsets[0], idata + DIRECT);
+		first_whole = 0;
+		goto do_indirects;
+	}
+
+	first_whole = offsets[0] + 1 - DIRECT;
+	partial = find_shared(inode, n, offsets, chain, &nr);
+	if (nr) {
+		if (partial == chain)
+			mark_inode_dirty(inode);
+		else
+			mark_buffer_dirty_inode(partial->bh, inode);
+		free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
+	}
+	/* Clear the ends of indirect blocks on the shared branch */
+	while (partial > chain) {
+		free_branches(inode, partial->p + 1, block_end(partial->bh),
+				(chain+n-1) - partial);
+		mark_buffer_dirty_inode(partial->bh, inode);
+		brelse (partial->bh);
+		partial--;
+	}
+do_indirects:
+	/* Kill the remaining (whole) subtrees */
+	while (first_whole < DEPTH-1) {
+		nr = idata[DIRECT+first_whole];
+		if (nr) {
+			idata[DIRECT+first_whole] = 0;
+			mark_inode_dirty(inode);
+			free_branches(inode, &nr, &nr+1, first_whole+1);
+		}
+		first_whole++;
+	}
+	inode->i_mtime = inode->i_ctime = current_time(inode);
+	mark_inode_dirty(inode);
+}
+
+static inline unsigned nblocks(loff_t size, struct super_block *sb)
+{
+	int k = sb->s_blocksize_bits - 10;
+	unsigned blocks, res, direct = DIRECT, i = DEPTH;
+	blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k);
+	res = blocks;
+	while (--i && blocks > direct) {
+		blocks -= direct;
+		blocks += sb->s_blocksize/sizeof(block_t) - 1;
+		blocks /= sb->s_blocksize/sizeof(block_t);
+		res += blocks;
+		direct = 1;
+	}
+	return res;
+}