the couple routines to find closest allocated blocks
to the left and to the right for given path.
thanks, Alex
Index: linux-2.6.19-rc6/include/linux/ext4_fs_extents.h
===================================================================
--- linux-2.6.19-rc6.orig/include/linux/ext4_fs_extents.h 2006-11-16 07:03:40.000000000 +0300
+++ linux-2.6.19-rc6/include/linux/ext4_fs_extents.h 2006-11-28 23:38:54.000000000 +0300
@@ -193,6 +193,8 @@ extern int ext4_ext_calc_credits_for_ins
extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *);
extern int ext4_ext_walk_space(struct inode *, unsigned long, unsigned long, ext_prepare_callback, void *);
extern struct ext4_ext_path * ext4_ext_find_extent(struct inode *, int, struct ext4_ext_path *);
+extern int ext4_ext_search_left(struct inode *, struct ext4_ext_path *, ext4_fsblk_t *, ext4_fsblk_t *);
+extern int ext4_ext_search_right(struct inode *, struct ext4_ext_path *, ext4_fsblk_t *, ext4_fsblk_t *);
#endif /* _LINUX_EXT4_EXTENTS */
Index: linux-2.6.19-rc6/fs/ext4/extents.c
===================================================================
--- linux-2.6.19-rc6.orig/fs/ext4/extents.c 2006-11-16 07:03:40.000000000 +0300
+++ linux-2.6.19-rc6/fs/ext4/extents.c 2006-11-28 23:40:25.000000000 +0300
@@ -974,6 +974,148 @@ out:
}
/*
+ * search the closest allocated block to the left for *logical
+ * and returns it at @logical + it's physical address at @phys
+ * if *logical is the smallest allocated block, the function
+ * returns 0 at @phys
+ * return value contains 0 (success) or error code
+ */
+int
+ext4_ext_search_left(struct inode *inode, struct ext4_ext_path *path,
+ ext4_fsblk_t *logical, ext4_fsblk_t *phys)
+{
+ struct ext4_extent_idx *ix;
+ struct ext4_extent *ex;
+ int depth;
+
+ BUG_ON(path == NULL);
+ depth = path->p_depth;
+ *phys = 0;
+
+ if (depth == 0 && path->p_ext == NULL)
+ return 0;
+
+ /* usually extent in the path covers blocks smaller
+ * then *logical, but it can be that extent is the
+ * first one in the file */
+
+ ex = path[depth].p_ext;
+ if (*logical < le32_to_cpu(ex->ee_block)) {
+ BUG_ON(EXT_FIRST_EXTENT(path[depth].p_hdr) != ex);
+ while (--depth >= 0) {
+ ix = path[depth].p_idx;
+ BUG_ON(ix != EXT_FIRST_INDEX(path[depth].p_hdr));
+ }
+ return 0;
+ }
+
+ BUG_ON(*logical < le32_to_cpu(ex->ee_block) + le16_to_cpu(ex->ee_len));
+
+ *logical = le32_to_cpu(ex->ee_block) + le16_to_cpu(ex->ee_len) - 1;
+ *phys = ext_pblock(ex) + le16_to_cpu(ex->ee_len) - 1;
+ return 0;
+}
+
+/*
+ * search the closest allocated block to the right for *logical
+ * and returns it at @logical + it's physical address at @phys
+ * if *logical is the smallest allocated block, the function
+ * returns 0 at @phys
+ * return value contains 0 (success) or error code
+ */
+int
+ext4_ext_search_right(struct inode *inode, struct ext4_ext_path *path,
+ ext4_fsblk_t *logical, ext4_fsblk_t *phys)
+{
+ struct buffer_head *bh = NULL;
+ struct ext4_extent_header *eh;
+ struct ext4_extent_idx *ix;
+ struct ext4_extent *ex;
+ ext4_fsblk_t block;
+ int depth;
+
+ BUG_ON(path == NULL);
+ depth = path->p_depth;
+ *phys = 0;
+
+ if (depth == 0 && path->p_ext == NULL)
+ return 0;
+
+ /* usually extent in the path covers blocks smaller
+ * then *logical, but it can be that extent is the
+ * first one in the file */
+
+ ex = path[depth].p_ext;
+ if (*logical < le32_to_cpu(ex->ee_block)) {
+ BUG_ON(EXT_FIRST_EXTENT(path[depth].p_hdr) != ex);
+ while (--depth >= 0) {
+ ix = path[depth].p_idx;
+ BUG_ON(ix != EXT_FIRST_INDEX(path[depth].p_hdr));
+ }
+ *logical = le32_to_cpu(ex->ee_block);
+ *phys = ext_pblock(ex);
+ return 0;
+ }
+
+ BUG_ON(*logical < le32_to_cpu(ex->ee_block) + le16_to_cpu(ex->ee_len));
+
+ if (ex != EXT_LAST_EXTENT(path[depth].p_hdr)) {
+ /* next allocated block in this leaf */
+ ex++;
+ *logical = le32_to_cpu(ex->ee_block);
+ *phys = ext_pblock(ex);
+ return 0;
+ }
+
+ /* go up and search for index to the right */
+ while (--depth >= 0) {
+ ix = path[depth].p_idx;
+ if (ix != EXT_LAST_INDEX(path[depth].p_hdr))
+ break;
+ }
+
+ if (depth < 0) {
+ /* we've gone up to the root and
+ * found no index to the right */
+ return 0;
+ }
+
+ /* we've found index to the right, let's
+ * follow it and find the closest allocated
+ * block to the right */
+ ix++;
+ block = idx_pblock(ix);
+ while (++depth < path->p_depth) {
+ bh = sb_bread(inode->i_sb, block);
+ if (bh == NULL)
+ return -EIO;
+ eh = ext_block_hdr(bh);
+ if (ext4_ext_check_header(__FUNCTION__, inode, eh)) {
+ brelse(bh);
+ return -EIO;
+ }
+ ix = EXT_FIRST_INDEX(eh);
+ block = idx_pblock(ix);
+ brelse(bh);
+ }
+
+ bh = sb_bread(inode->i_sb, block);
+ if (bh == NULL)
+ return -EIO;
+ eh = ext_block_hdr(bh);
+ if (ext4_ext_check_header(__FUNCTION__, inode, eh)) {
+ brelse(bh);
+ return -EIO;
+ }
+ ex = EXT_FIRST_EXTENT(eh);
+ *logical = le32_to_cpu(ex->ee_block);
+ *phys = ext_pblock(ex);
+ brelse(bh);
+ return 0;
+
+}
+
+/*
* ext4_ext_next_allocated_block:
* returns allocated block in subsequent extent or EXT_MAX_BLOCK.
* NOTE: it considers block number from index entry as