ext4: Add new functions for searching extent tree

Add the functions ext4_ext_search_left() and ext4_ext_search_right(),
which are used by mballoc during ext4_ext_get_blocks to decided whether
to merge extent information.

Signed-off-by: Alex Tomas <alex@clusterfs.com>
Signed-off-by: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: Johann Lombardi <johann@clusterfs.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 146 insertions, 0 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 01eda5c5281e..f5cf2a94b6fc 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1017,6 +1017,148 @@ 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_lblk_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_lblk_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(inode, eh, depth)) {
+                        put_bh(bh);
+                        return -EIO;
+                }
+                ix = EXT_FIRST_INDEX(eh);
+                block = idx_pblock(ix);
+                put_bh(bh);
+        }
+
+        bh = sb_bread(inode->i_sb, block);
+        if (bh == NULL)
+                return -EIO;
+        eh = ext_block_hdr(bh);
+        if (ext4_ext_check_header(inode, eh, path->p_depth - depth)) {
+                put_bh(bh);
+                return -EIO;
+        }
+        ex = EXT_FIRST_EXTENT(eh);
+        *logical = le32_to_cpu(ex->ee_block);
+        *phys = ext_pblock(ex);
+        put_bh(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
diff --git a/include/linux/ext4_fs_extents.h b/include/linux/ext4_fs_extents.h
index 1cfb4854c964..697da4bce6c5 100644
--- a/include/linux/ext4_fs_extents.h
+++ b/include/linux/ext4_fs_extents.h
@@ -223,5 +223,9 @@ extern unsigned int ext4_ext_check_overlap(struct inode *, struct ext4_extent *,
 extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *);
 extern struct ext4_ext_path *ext4_ext_find_extent(struct inode *, ext4_lblk_t,
                                                         struct ext4_ext_path *);
+extern int ext4_ext_search_left(struct inode *, struct ext4_ext_path *,
+                                                ext4_lblk_t *, ext4_fsblk_t *);
+extern int ext4_ext_search_right(struct inode *, struct ext4_ext_path *,
+                                                ext4_lblk_t *, ext4_fsblk_t *);
 #endif /* _LINUX_EXT4_EXTENTS */