Commit 30cbf189 authored by Steven Whitehouse's avatar Steven Whitehouse
Browse files

[GFS2] Add a function to interate over an extent 



This adds a function (currently the only use is during mapping
of already allocated blocks, but watch this space) which iterates
over a number of pointers in a block and returns the extent length.

If the initial pointer is 0 (i.e. unallocated) it will return the
number of unallocated blocks in the extent. If the initial pointer
is allocated, then it returns the number of contiguously allocated
blocks in the extent.

Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent c85a665f

fs/gfs2/bmap.c

+52 −16
Original line number Diff line number Diff line
@@ -422,6 +422,42 @@ static void release_metapath(struct metapath *mp) 
			brelse(mp->mp_bh[i]);

}



/**

 * gfs2_extent_length - Returns length of an extent of blocks

 * @start: Start of the buffer

 * @len: Length of the buffer in bytes

 * @ptr: Current position in the buffer

 * @limit: Max extent length to return (0 = unlimited)

 * @eob: Set to 1 if we hit "end of block"

 *

 * If the first block is zero (unallocated) it will return the number of

 * unallocated blocks in the extent, otherwise it will return the number

 * of contiguous blocks in the extent.

 *

 * Returns: The length of the extent (minimum of one block)

 */



static inline unsigned int gfs2_extent_length(void *start, unsigned int len, __be64 *ptr, unsigned limit, int *eob)

{

	const __be64 *end = (start + len);

	const __be64 *first = ptr;

	u64 d = be64_to_cpu(*ptr);



	*eob = 0;

	do {

		ptr++;

		if (ptr >= end)

			break;

		if (limit && --limit == 0)

			break;

		if (d)

			d++;

	} while(be64_to_cpu(*ptr) == d);

	if (ptr >= end)

		*eob = 1;

	return (ptr - first);

}



static inline void bmap_lock(struct inode *inode, int create)

{

	struct gfs2_inode *ip = GFS2_I(inode);
@@ -499,27 +535,27 @@ int gfs2_block_map(struct inode *inode, sector_t lblock, 
		goto out_fail;

	boundary = error;



	if (dblock) {

	if (new) {

		map_bh(bh_map, inode->i_sb, dblock);

		if (boundary)

			set_buffer_boundary(bh_map);

		if (new) {

		gfs2_trans_add_bh(ip->i_gl, mp.mp_bh[0], 1);

		gfs2_dinode_out(ip, mp.mp_bh[0]->b_data);

		set_buffer_new(bh_map);

		goto out_ok;

	}

		while(--maxlen && !buffer_boundary(bh_map)) {

			u64 eblock;

			mp.mp_list[ip->i_height - 1]++;

			boundary = lookup_block(ip, ip->i_height - 1, &mp, 0, &new, &eblock);

			if (eblock != ++dblock)

				break;

			bh_map->b_size += (1 << inode->i_blkbits);



	if (dblock) {

		unsigned int len;

		struct buffer_head *bh = mp.mp_bh[ip->i_height - 1];

		__be64 *ptr = metapointer(&boundary, ip->i_height - 1, &mp);

		map_bh(bh_map, inode->i_sb, dblock);

		len = gfs2_extent_length(bh->b_data, bh->b_size, ptr, maxlen,

					 &boundary);

		bh_map->b_size = (len << inode->i_blkbits);

		if (boundary)

			set_buffer_boundary(bh_map);

	}

	}

out_ok:

	error = 0;

out_fail:

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