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Commit 55bd725a authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Theodore Ts'o
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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: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarMingming Cao <cmm@us.ibm.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 642be6ec

fs/ext4/extents.c

+3 −7
Original line number Diff line number Diff line
@@ -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 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len) 
			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 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len) 
	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 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len) 
			 * 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;

}