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Subject[PATCH 27/48] [GFS2] Add a function to interate over an extent
Date
From: Steven Whitehouse <swhiteho@redhat.com>

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: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 7f72564..6780aa5 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -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);
@@ -499,26 +535,26 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
goto out_fail;
boundary = error;

+ if (new) {
+ map_bh(bh_map, inode->i_sb, dblock);
+ if (boundary)
+ set_buffer_boundary(bh_map);
+ 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;
+ }
+
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);
- 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 (boundary)
- set_buffer_boundary(bh_map);
- }
}
out_ok:
error = 0;
--
1.5.1.2


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