patch-2.4.6 linux/fs/sysv/itree.c

• Lines: 441
• Date: Mon Jul 2 14:03:04 2001
• Orig file: v2.4.5/linux/fs/sysv/itree.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.5/linux/fs/sysv/itree.c linux/fs/sysv/itree.c
@@ -0,0 +1,440 @@
+/*
+ *  linux/fs/sysv/itree.c
+ *
+ *  Handling of indirect blocks' trees.
+ *  AV, Sep--Dec 2000
+ */
+
+#include <linux/fs.h>
+#include <linux/sysv_fs.h>
+#include <linux/locks.h>
+#include <linux/smp_lock.h>
+
+enum {DIRECT = 10, DEPTH = 4};	/* Have triple indirect */
+
+static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode)
+{
+	mark_buffer_dirty_inode(bh, inode);
+	if (IS_SYNC(inode)) {
+		ll_rw_block (WRITE, 1, &bh);
+		wait_on_buffer (bh);
+	}
+}
+
+static int block_to_path(struct inode *inode, long block, int offsets[DEPTH])
+{
+	struct super_block *sb = inode->i_sb;
+	int ptrs_bits = sb->sv_ind_per_block_bits;
+	unsigned long	indirect_blocks = sb->sv_ind_per_block,
+			double_blocks = sb->sv_ind_per_block_2;
+	int n = 0;
+
+	if (block < 0) {
+		printk("sysv_block_map: block < 0\n");
+	} else if (block < DIRECT) {
+		offsets[n++] = block;
+	} else if ( (block -= DIRECT) < indirect_blocks) {
+		offsets[n++] = DIRECT;
+		offsets[n++] = block;
+	} else if ((block -= indirect_blocks) < double_blocks) {
+		offsets[n++] = DIRECT+1;
+		offsets[n++] = block >> ptrs_bits;
+		offsets[n++] = block & (indirect_blocks - 1);
+	} else if (((block -= double_blocks) >> (ptrs_bits * 2)) < indirect_blocks) {
+		offsets[n++] = DIRECT+2;
+		offsets[n++] = block >> (ptrs_bits * 2);
+		offsets[n++] = (block >> ptrs_bits) & (indirect_blocks - 1);
+		offsets[n++] = block & (indirect_blocks - 1);
+	} else {
+		/* nothing */;
+	}
+	return n;
+}
+
+static inline int block_to_cpu(struct super_block *sb, u32 nr)
+{
+	return sb->sv_block_base + fs32_to_cpu(sb, nr);
+}
+
+typedef struct {
+	u32     *p;
+	u32     key;
+	struct buffer_head *bh;
+} Indirect;
+
+static inline void add_chain(Indirect *p, struct buffer_head *bh, u32 *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 u32 *block_end(struct buffer_head *bh)
+{
+	return (u32*)((char*)bh->b_data + bh->b_size);
+}
+
+static Indirect *get_branch(struct inode *inode,
+			    int depth,
+			    int offsets[],
+			    Indirect chain[],
+			    int *err)
+{
+	kdev_t dev = inode->i_dev;
+	int size = inode->i_sb->s_blocksize;
+	Indirect *p = chain;
+	struct buffer_head *bh;
+
+	*err = 0;
+	add_chain (chain, NULL, inode->u.sysv_i.i_data + *offsets);
+	if (!p->key)
+		goto no_block;
+	while (--depth) {
+		int block = block_to_cpu(inode->i_sb, p->key);
+		bh = bread(dev, block, size);
+		if (!bh)
+			goto failure;
+		if (!verify_chain(chain, p))
+			goto changed;
+		add_chain(++p, bh, (u32*)bh->b_data + *++offsets);
+		if (!p->key)
+		goto no_block;
+	}
+	return NULL;
+
+changed:
+	*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 blocksize = inode->i_sb->s_blocksize;
+	int n = 0;
+	int i;
+
+	branch[0].key = sysv_new_block(inode->i_sb);
+	if (branch[0].key) for (n = 1; n < num; n++) {
+		struct buffer_head *bh;
+		int parent;
+		/* Allocate the next block */
+		branch[n].key = sysv_new_block(inode->i_sb);
+		if (!branch[n].key)
+			break;
+		/*
+		 * Get buffer_head for parent block, zero it out and set 
+		 * the pointer to new one, then send parent to disk.
+		 */
+		parent = block_to_cpu(inode->i_sb, branch[n-1].key);
+		bh = getblk(inode->i_dev, parent, blocksize);
+		lock_buffer(bh);
+		memset(bh->b_data, 0, blocksize);
+		branch[n].bh = bh;
+		branch[n].p = (u32*) bh->b_data + offsets[n];
+		*branch[n].p = branch[n].key;
+		mark_buffer_uptodate(bh, 1);
+		unlock_buffer(bh);
+		dirty_indirect(bh, inode);
+	}
+	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++)
+		sysv_free_block(inode->i_sb, branch[i].key);
+	return -ENOSPC;
+}
+
+static inline int splice_branch(struct inode *inode,
+				Indirect chain[],
+				Indirect *where,
+				int num)
+{
+	int i;
+	/* 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;
+	inode->i_ctime = CURRENT_TIME;
+
+	/* had we spliced it onto indirect block? */
+	if (where->bh)
+		dirty_indirect(where->bh, inode);
+
+	if (IS_SYNC(inode))
+		sysv_sync_inode(inode);
+	else
+		mark_inode_dirty(inode);
+	return 0;
+
+changed:
+	for (i = 1; i < num; i++)
+		bforget(where[i].bh);
+	for (i = 0; i < num; i++)
+		sysv_free_block(inode->i_sb, where[i].key);
+	return -EAGAIN;
+}
+
+static int get_block(struct inode *inode, long iblock, struct buffer_head *bh_result, int create)
+{
+	int err = -EIO;
+	int offsets[DEPTH];
+	Indirect chain[DEPTH];
+	struct super_block *sb = inode->i_sb;
+	Indirect *partial;
+	int left;
+	int depth = block_to_path(inode, iblock, offsets);
+
+	if (depth == 0)
+		goto out;
+
+	lock_kernel();
+reread:
+	partial = get_branch(inode, depth, offsets, chain, &err);
+
+	/* Simplest case - block found, no allocation needed */
+	if (!partial) {
+got_it:
+		bh_result->b_dev = sb->s_dev;
+		bh_result->b_blocknr = block_to_cpu(sb, chain[depth-1].key);
+		bh_result->b_state |= (1UL << BH_Mapped);
+		/* 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--;
+		}
+		unlock_kernel();
+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;
+
+	bh_result->b_state |= (1UL << BH_New);
+	goto got_it;
+
+changed:
+	while (partial > chain) {
+		brelse(partial->bh);
+		partial--;
+	}
+	goto reread;
+}
+
+static inline int all_zeroes(u32 *p, u32 *q)
+{
+	while (p < q)
+		if (*p++)
+			return 0;
+	return 1;
+}
+
+static Indirect *find_shared(struct inode *inode,
+				int depth,
+				int offsets[],
+				Indirect chain[],
+				u32 *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);
+	if (!partial)
+		partial = chain + k-1;
+	/*
+	 * If the branch acquired continuation since we've looked at it -
+	 * fine, it should all survive and (new) top doesn't belong to us.
+	 */
+	if (!partial->key && *partial->p)
+		goto no_top;
+	for (p=partial; p>chain && all_zeroes((u32*)p->bh->b_data,p->p); p--)
+		;
+	/*
+	 * OK, we've found the last block that must survive. The rest of our
+	 * branch should be detached before unlocking. However, if that rest
+	 * of branch is all ours and does not grow immediately from the inode
+	 * it's easier to cheat and just decrement partial->p.
+	 */
+	if (p == chain + k - 1 && p > chain) {
+		p->p--;
+	} else {
+		*top = *p->p;
+		*p->p = 0;
+	}
+
+	while(partial > p) {
+		brelse(partial->bh);
+		partial--;
+	}
+no_top:
+	return partial;
+}
+
+static inline void free_data(struct inode *inode, u32 *p, u32 *q)
+{
+	for ( ; p < q ; p++) {
+		u32 nr = *p;
+		if (nr) {
+			*p = 0;
+			sysv_free_block(inode->i_sb, nr);
+			mark_inode_dirty(inode);
+		}
+	}
+}
+
+static void free_branches(struct inode *inode, u32 *p, u32 *q, int depth)
+{
+	struct buffer_head * bh;
+	struct super_block *sb = inode->i_sb;
+
+	if (depth--) {
+		for ( ; p < q ; p++) {
+			int block;
+			u32 nr = *p;
+			if (!nr)
+				continue;
+			*p = 0;
+			block = block_to_cpu(sb, nr);
+			bh = bread(inode->i_dev, block, sb->s_blocksize);
+			if (!bh)
+				continue;
+			free_branches(inode, (u32*)bh->b_data,
+					block_end(bh), depth);
+			bforget(bh);
+			sysv_free_block(sb, nr);
+			mark_inode_dirty(inode);
+		}
+	} else
+		free_data(inode, p, q);
+}
+
+void sysv_truncate (struct inode * inode)
+{
+	u32 *i_data = inode->u.sysv_i.i_data;
+	int offsets[DEPTH];
+	Indirect chain[DEPTH];
+	Indirect *partial;
+	int nr = 0;
+	int n;
+	long iblock;
+	unsigned blocksize;
+
+	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+	    S_ISLNK(inode->i_mode)))
+		return;
+
+	blocksize = inode->i_sb->s_blocksize;
+	iblock = (inode->i_size + blocksize-1)
+					>> inode->i_sb->s_blocksize_bits;
+
+	block_truncate_page(inode->i_mapping, inode->i_size, get_block);
+
+	n = block_to_path(inode, iblock, offsets);
+	if (n == 0)
+		return;
+
+	if (n == 1) {
+		free_data(inode, i_data+offsets[0], i_data + DIRECT);
+		goto do_indirects;
+	}
+
+	partial = find_shared(inode, n, offsets, chain, &nr);
+	/* Kill the top of shared branch (already detached) */
+	if (nr) {
+		if (partial == chain)
+			mark_inode_dirty(inode);
+		else
+			dirty_indirect(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);
+		dirty_indirect(partial->bh, inode);
+		brelse (partial->bh);
+		partial--;
+	}
+do_indirects:
+	/* Kill the remaining (whole) subtrees (== subtrees deeper than...) */
+	while (n < DEPTH) {
+		nr = i_data[DIRECT + n - 1];
+		if (nr) {
+			i_data[DIRECT + n - 1] = 0;
+			mark_inode_dirty(inode);
+			free_branches(inode, &nr, &nr+1, n);
+		}
+		n++;
+	}
+	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	if (IS_SYNC(inode))
+		sysv_sync_inode (inode);
+	else
+		mark_inode_dirty(inode);
+}
+
+static int sysv_writepage(struct page *page)
+{
+	return block_write_full_page(page,get_block);
+}
+static int sysv_readpage(struct file *file, struct page *page)
+{
+	return block_read_full_page(page,get_block);
+}
+static int sysv_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to)
+{
+	return block_prepare_write(page,from,to,get_block);
+}
+static int sysv_bmap(struct address_space *mapping, long block)
+{
+	return generic_block_bmap(mapping,block,get_block);
+}
+struct address_space_operations sysv_aops = {
+	readpage: sysv_readpage,
+	writepage: sysv_writepage,
+	sync_page: block_sync_page,
+	prepare_write: sysv_prepare_write,
+	commit_write: generic_commit_write,
+	bmap: sysv_bmap
+};