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Ocfs2/move_extents: helper to probe a proper region to move in an alloc group. 

Before doing the movement of extents, we'd better probe the alloc group from
'goal_blk' for searching a contiguous region to fit the wanted movement, we
even will have a best-effort try by compromising to a threshold around the
given goal.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
This commit is contained in:
Tristan Ye 2011-03-18 14:35:37 +08:00
parent 99e4c75041
commit e6b5859ccc
1 changed files with 39 additions and 0 deletions
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39
fs/ocfs2/move_extents.c
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@ -516,3 +516,42 @@ out:
return ret;
}
static void ocfs2_probe_alloc_group(struct inode *inode, struct buffer_head *bh,
int *goal_bit, u32 move_len, u32 max_hop,
u32 *phys_cpos)
{
int i, used, last_free_bits = 0, base_bit = *goal_bit;
struct ocfs2_group_desc *gd = (struct ocfs2_group_desc *)bh->b_data;
u32 base_cpos = ocfs2_blocks_to_clusters(inode->i_sb,
le64_to_cpu(gd->bg_blkno));
for (i = base_bit; i < le16_to_cpu(gd->bg_bits); i++) {
used = ocfs2_test_bit(i, (unsigned long *)gd->bg_bitmap);
if (used) {
/*
* we even tried searching the free chunk by jumping
* a 'max_hop' distance, but still failed.
*/
if ((i - base_bit) > max_hop) {
*phys_cpos = 0;
break;
}
if (last_free_bits)
last_free_bits = 0;
continue;
} else
last_free_bits++;
if (last_free_bits == move_len) {
*goal_bit = i;
*phys_cpos = base_cpos + i;
break;
}
}
mlog(0, "found phys_cpos: %u to fit the wanted moving.\n", *phys_cpos);
}