[PATCH] ext2: smarter block allocation startup

The same thing, for ext2.

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 7b876c242aba314c2da269e4e672e4702ec6bc7e..879944b4f1e3d786a2ded4c09060c46624ac340e 100644 (file)
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -303,14 +303,22 @@ no_block:
  *       + if there is a block to the left of our position - allocate near it.
  *       + if pointer will live in indirect block - allocate near that block.
  *       + if pointer will live in inode - allocate in the same cylinder group.
+ *
+ * In the latter case we colour the starting block by the callers PID to
+ * prevent it from clashing with concurrent allocations for a different inode
+ * in the same block group.   The PID is used here so that functionally related
+ * files will be close-by on-disk.
+ *
  *     Caller must make sure that @ind is valid and will stay that way.
  */
 
-static inline unsigned long ext2_find_near(struct inode *inode, Indirect *ind)
+static unsigned long ext2_find_near(struct inode *inode, Indirect *ind)
 {
        struct ext2_inode_info *ei = EXT2_I(inode);
        u32 *start = ind->bh ? (u32*) ind->bh->b_data : ei->i_data;
        u32 *p;
+       unsigned long bg_start;
+       unsigned long colour;
 
        /* Try to find previous block */
        for (p = ind->p - 1; p >= start; p--)
@@ -325,8 +333,11 @@ static inline unsigned long ext2_find_near(struct inode *inode, Indirect *ind)
         * It is going to be refered from inode itself? OK, just put it into
         * the same cylinder group then.
         */
-       return (ei->i_block_group * EXT2_BLOCKS_PER_GROUP(inode->i_sb)) +
-              le32_to_cpu(EXT2_SB(inode->i_sb)->s_es->s_first_data_block);
+       bg_start = (ei->i_block_group * EXT2_BLOCKS_PER_GROUP(inode->i_sb)) +
+               le32_to_cpu(EXT2_SB(inode->i_sb)->s_es->s_first_data_block);
+       colour = (current->pid % 16) *
+                       (EXT2_BLOCKS_PER_GROUP(inode->i_sb) / 16);
+       return bg_start + colour;
 }
 
 /**