ext4: Allow indirect-block file to grow the file size to max file size

We can create 4402345721856 byte file with indirect block mapping.
However, if we grow an indirect-block file to the size with ftruncate(),
we can see an ext4 warning. The following patch fixes this problem.

How to reproduce:
# dd if=/dev/zero of=/mnt/mp1/hoge bs=1 count=0 seek=4402345721856
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000221428 s, 0.0 kB/s
# tail -n 1 /var/log/messages
Nov 25 15:10:27 test kernel: EXT4-fs warning (device sda8): ext4_block_to_path:345: block 1074791436 > max in inode 12

Signed-off-by: Kazuya Mio <k-mio@sx.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 17 insertions, 6 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7d11e02ad01d..5560f78690ac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4429,8 +4429,8 @@ void ext4_truncate(struct inode *inode)
         Indirect chain[4];
         Indirect *partial;
         __le32 nr = 0;
-        int n;
-        ext4_lblk_t last_block;
+        int n = 0;
+        ext4_lblk_t last_block, max_block;
         unsigned blocksize = inode->i_sb->s_blocksize;
 
         trace_ext4_truncate_enter(inode);
@@ -4455,14 +4455,18 @@ void ext4_truncate(struct inode *inode)
 
         last_block = (inode->i_size + blocksize-1)
                                         >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
+        max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
+                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
 
         if (inode->i_size & (blocksize - 1))
                 if (ext4_block_truncate_page(handle, mapping, inode->i_size))
                         goto out_stop;
 
-        n = ext4_block_to_path(inode, last_block, offsets, NULL);
-        if (n == 0)
-                goto out_stop;  /* error */
+        if (last_block != max_block) {
+                n = ext4_block_to_path(inode, last_block, offsets, NULL);
+                if (n == 0)
+                        goto out_stop;  /* error */
+        }
 
         /*
          * OK.  This truncate is going to happen.  We add the inode to the
@@ -4493,7 +4497,13 @@ void ext4_truncate(struct inode *inode)
          */
         ei->i_disksize = inode->i_size;
 
-        if (n == 1) {           /* direct blocks */
+        if (last_block == max_block) {
+                /*
+                 * It is unnecessary to free any data blocks if last_block is
+                 * equal to the indirect block limit.
+                 */
+                goto out_unlock;
+        } else if (n == 1) {            /* direct blocks */
                 ext4_free_data(handle, inode, NULL, i_data+offsets[0],
                                i_data + EXT4_NDIR_BLOCKS);
                 goto do_indirects;
@@ -4553,6 +4563,7 @@ do_indirects:
                 ;
         }
 
+out_unlock:
         up_write(&ei->i_data_sem);
         inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
         ext4_mark_inode_dirty(handle, inode);