ext4: Fix locking hierarchy violation in ext4_fallocate()

ext4_fallocate() was trying to acquire i_data_sem outside of
jbd2_start_transaction/jbd2_journal_stop, which violates ext4's locking
hierarchy.  So we take i_mutex to prevent writes and truncates during
the complete fallocate operation, and use ext4_get_block_wrap() which
acquires and releases i_data_sem for each block allocation.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 3 insertions, 7 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index bc7081f1fbe8..e856f660fc30 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2623,7 +2623,7 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
          * modify 1 super block, 1 block bitmap and 1 group descriptor.
          */
         credits = EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + 3;
-        down_write((&EXT4_I(inode)->i_data_sem));
+        mutex_lock(&inode->i_mutex);
 retry:
         while (ret >= 0 && ret < max_blocks) {
                 block = block + ret;
@@ -2634,7 +2634,7 @@ retry:
                         break;
                 }
 
-                ret = ext4_ext_get_blocks(handle, inode, block,
+                ret = ext4_get_blocks_wrap(handle, inode, block,
                                           max_blocks, &map_bh,
                                           EXT4_CREATE_UNINITIALIZED_EXT, 0);
                 WARN_ON(ret <= 0);
@@ -2680,7 +2680,6 @@ retry:
         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
                 goto retry;
 
-        up_write((&EXT4_I(inode)->i_data_sem));
         /*
          * Time to update the file size.
          * Update only when preallocation was requested beyond the file size.
@@ -2692,21 +2691,18 @@ retry:
                          * if no error, we assume preallocation succeeded
                          * completely
                          */
-                        mutex_lock(&inode->i_mutex);
                         i_size_write(inode, offset + len);
                         EXT4_I(inode)->i_disksize = i_size_read(inode);
-                        mutex_unlock(&inode->i_mutex);
                 } else if (ret < 0 && nblocks) {
                         /* Handle partial allocation scenario */
                         loff_t newsize;
 
-                        mutex_lock(&inode->i_mutex);
                         newsize  = (nblocks << blkbits) + i_size_read(inode);
                         i_size_write(inode, EXT4_BLOCK_ALIGN(newsize, blkbits));
                         EXT4_I(inode)->i_disksize = i_size_read(inode);
-                        mutex_unlock(&inode->i_mutex);
                 }
         }
 
+        mutex_unlock(&inode->i_mutex);
         return ret > 0 ? ret2 : ret;
 }