fs/sysv/itree.c - pub/scm/linux/kernel/git/joro/linux - Git at Google

 /*
  *  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
 };
	/*
	* 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
	};