ext4: modify block allocation algorithm for the last group

When a directory inode is allocated in the last group and the last group
contains less than s_blocks_per_group blocks, the initial block allocated
for the directory is not always allocated in the same group as the
directory inode, but in one of the first groups of the filesystem (group 1
for example).
Depending on the current process's pid, ext4_find_near() and
ext4_ext_find_goal() can return a block number greater than the maximum
blocks count in the filesystem and in that case the block will be not
allocated in the same group as the inode.

The following patch fixes the problem.

Should the modification also be done in ext2/3 code?

Signed-off-by: Valerie Clement <valerie.clement@bull.net>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c4d6f19faf379ef65637a700912d2d1fb84243c9..8a59f7ba30e6dfa09e37234629dd47eb2c262f20 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -148,6 +148,7 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
 {
        struct ext4_inode_info *ei = EXT4_I(inode);
        ext4_fsblk_t bg_start;
+       ext4_fsblk_t last_block;
        ext4_grpblk_t colour;
        int depth;
 
@@ -169,8 +170,13 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
        /* OK. use inode's group */
        bg_start = (ei->i_block_group * EXT4_BLOCKS_PER_GROUP(inode->i_sb)) +
                le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_first_data_block);
-       colour = (current->pid % 16) *
+       last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
+
+       if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
+               colour = (current->pid % 16) *
                        (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
+       else
+               colour = (current->pid % 16) * ((last_block - bg_start) / 16);
        return bg_start + colour + block;
 }
 

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d3c6f58a9def4184dc6b3de2e5dfec249a4bd788..34f3eb615fd5eaa0fdc077b4da6ad6d43a0bc3d8 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -403,6 +403,7 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
        __le32 *start = ind->bh ? (__le32*) ind->bh->b_data : ei->i_data;
        __le32 *p;
        ext4_fsblk_t bg_start;
+       ext4_fsblk_t last_block;
        ext4_grpblk_t colour;
 
        /* Try to find previous block */
@@ -420,8 +421,13 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
         * into the same cylinder group then.
         */
        bg_start = ext4_group_first_block_no(inode->i_sb, ei->i_block_group);
-       colour = (current->pid % 16) *
+       last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
+
+       if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
+               colour = (current->pid % 16) *
                        (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
+       else
+               colour = (current->pid % 16) * ((last_block - bg_start) / 16);
        return bg_start + colour;
 }