3 files changed, 47 insertions, 6 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8fab233cb05f..24a2604dde7b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -985,6 +985,16 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
         } else {
                 retval = ext4_get_blocks_handle(handle, inode, block,
                                 max_blocks, bh, create, extend_disksize);
+
+                if (retval > 0 && buffer_new(bh)) {
+                        /*
+                         * We allocated new blocks which will result in
+                         * i_data's format changing.  Force the migrate
+                         * to fail by clearing migrate flags
+                         */
+                        EXT4_I(inode)->i_flags = EXT4_I(inode)->i_flags &
+                                                        ~EXT4_EXT_MIGRATE;
+                }
         }
         up_write((&EXT4_I(inode)->i_data_sem));
         return retval;
@@ -2976,7 +2986,8 @@ static int ext4_do_update_inode(handle_t *handle,
         if (ext4_inode_blocks_set(handle, raw_inode, ei))
                 goto out_brelse;
         raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
-        raw_inode->i_flags = cpu_to_le32(ei->i_flags);
+        /* clear the migrate flag in the raw_inode */
+        raw_inode->i_flags = cpu_to_le32(ei->i_flags & ~EXT4_EXT_MIGRATE);
         if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
             cpu_to_le32(EXT4_OS_HURD))
                 raw_inode->i_file_acl_high =
diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index 5c1e27de7755..9b4fb07d192c 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -327,7 +327,7 @@ static int free_ind_block(handle_t *handle, struct inode *inode, __le32 *i_data)
 }
 
 static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
-                                struct inode *tmp_inode)
+                                                struct inode *tmp_inode)
 {
         int retval;
         __le32  i_data[3];
@@ -339,7 +339,7 @@ static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
          * i_data field of the original inode
          */
         retval = ext4_journal_extend(handle, 1);
-        if (retval != 0) {
+        if (retval) {
                 retval = ext4_journal_restart(handle, 1);
                 if (retval)
                         goto err_out;
@@ -351,6 +351,18 @@ static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
 
         down_write(&EXT4_I(inode)->i_data_sem);
         /*
+         * if EXT4_EXT_MIGRATE is cleared a block allocation
+         * happened after we started the migrate. We need to
+         * fail the migrate
+         */
+        if (!(EXT4_I(inode)->i_flags & EXT4_EXT_MIGRATE)) {
+                retval = -EAGAIN;
+                up_write(&EXT4_I(inode)->i_data_sem);
+                goto err_out;
+        } else
+                EXT4_I(inode)->i_flags = EXT4_I(inode)->i_flags &
+                                                        ~EXT4_EXT_MIGRATE;
+        /*
          * We have the extent map build with the tmp inode.
          * Now copy the i_data across
          */
@@ -508,6 +520,17 @@ int ext4_ext_migrate(struct inode *inode, struct file *filp,
          * switch the inode format to prevent read.
          */
         mutex_lock(&(inode->i_mutex));
+        /*
+         * Even though we take i_mutex we can still cause block allocation
+         * via mmap write to holes. If we have allocated new blocks we fail
+         * migrate.  New block allocation will clear EXT4_EXT_MIGRATE flag.
+         * The flag is updated with i_data_sem held to prevent racing with
+         * block allocation.
+         */
+        down_read((&EXT4_I(inode)->i_data_sem));
+        EXT4_I(inode)->i_flags = EXT4_I(inode)->i_flags | EXT4_EXT_MIGRATE;
+        up_read((&EXT4_I(inode)->i_data_sem));
+
         handle = ext4_journal_start(inode, 1);
 
         ei = EXT4_I(inode);
@@ -559,9 +582,15 @@ err_out:
                  * tmp_inode
                  */
                 free_ext_block(handle, tmp_inode);
-        else
-                retval = ext4_ext_swap_inode_data(handle, inode,
-                                                        tmp_inode);
+        else {
+                retval = ext4_ext_swap_inode_data(handle, inode, tmp_inode);
+                if (retval)
+                        /*
+                         * if we fail to swap inode data free the extent
+                         * details of the tmp inode
+                         */
+                        free_ext_block(handle, tmp_inode);
+        }
 
         /* We mark the tmp_inode dirty via ext4_ext_tree_init. */
         if (ext4_journal_extend(handle, 1) != 0)
diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 250032548597..105337ca9ed0 100644
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -231,6 +231,7 @@ struct ext4_group_desc
 #define EXT4_TOPDIR_FL                  0x00020000 /* Top of directory hierarchies*/
 #define EXT4_HUGE_FILE_FL               0x00040000 /* Set to each huge file */
 #define EXT4_EXTENTS_FL                 0x00080000 /* Inode uses extents */
+#define EXT4_EXT_MIGRATE                0x00100000 /* Inode is migrating */
 #define EXT4_RESERVED_FL                0x80000000 /* reserved for ext4 lib */
 
 #define EXT4_FL_USER_VISIBLE            0x000BDFFF /* User visible flags */