Re: [PATCH -V2 2/2] ext4: truncate the file properly if we fail to copy data from userspace

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

On Mon, Jun 08, 2009 at 12:29:59PM -0400, Theodore Tso wrote:
> I had also already fixed this up in the patch queue.  This is what is
> currently there.
> 
> 						- Ted
> 
> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
> 
> ext4: truncate the file properly if we fail to copy data from userspace
> 
> In generic_perform_write if we fail to copy the user data we don't
> update the inode->i_size.  We should truncate the file in the above
> case so that we don't have blocks allocated outside inode->i_size.  Add
> the inode to orphan list in the same transaction as block allocation
> This ensures that if we crash in between the recovery would do the
> truncate.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> CC:  Jan Kara <jack@suse.cz>
> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 50ef1a2..8225f21 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1551,6 +1551,52 @@ static int write_end_fn(handle_t *handle, struct buffer_head *bh)
>  	return ext4_handle_dirty_metadata(handle, NULL, bh);
>  }
> 
> +static int ext4_generic_write_end(struct file *file,
> +				struct address_space *mapping,
> +				loff_t pos, unsigned len, unsigned copied,
> +				struct page *page, void *fsdata)
> +{
> +	int i_size_changed = 0;
> +	struct inode *inode = mapping->host;
> +	handle_t *handle = ext4_journal_current_handle();
> +
> +	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
> +
> +	/*
> +	 * No need to use i_size_read() here, the i_size
> +	 * cannot change under us because we hold i_mutex.
> +	 *
> +	 * But it's important to update i_size while still holding page lock:
> +	 * page writeout could otherwise come in and zero beyond i_size.
> +	 */
> +	if (pos + copied > inode->i_size) {
> +		i_size_write(inode, pos + copied);
> +		i_size_changed = 1;
> +	}
> +
> +	if (pos + copied >  EXT4_I(inode)->i_disksize) {
> +		/* We need to mark inode dirty even if
> +		 * new_i_size is less that inode->i_size
> +		 * bu greater than i_disksize.(hint delalloc)
> +		 */
> +		ext4_update_i_disksize(inode, (pos + copied));
> +		i_size_changed = 1;
> +	}
> +	unlock_page(page);
> +	page_cache_release(page);


You missed a block_unlock_hole_extend here. So you need to either fix
jan's patches or move this patch after jan's patch 


> +
> +	/*
> +	 * Don't mark the inode dirty under page lock. First, it unnecessarily
> +	 * makes the holding time of page lock longer. Second, it forces lock
> +	 * ordering of page lock and transaction start for journaling
> +	 * filesystems.
> +	 */
> +	if (i_size_changed)
> +		ext4_mark_inode_dirty(handle, inode);
> +
> +	return copied;
> +}
> +
>  /*
>   * We need to pick up the new inode size which generic_commit_write gave us
>   * `file' can be NULL - eg, when called from page_symlink().
> @@ -1574,21 +1620,15 @@ static int ext4_ordered_write_end(struct file *file,
>  	ret = ext4_jbd2_file_inode(handle, inode);
> 
>  	if (ret == 0) {
> -		loff_t new_i_size;
> -
> -		new_i_size = pos + copied;
> -		if (new_i_size > EXT4_I(inode)->i_disksize) {
> -			ext4_update_i_disksize(inode, new_i_size);
> -			/* We need to mark inode dirty even if
> -			 * new_i_size is less that inode->i_size
> -			 * bu greater than i_disksize.(hint delalloc)
> -			 */
> -			ext4_mark_inode_dirty(handle, inode);
> -		}
> -
> -		ret2 = generic_write_end(file, mapping, pos, len, copied,
> +		ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
>  							page, fsdata);
>  		copied = ret2;
> +		if (pos + len > inode->i_size)
> +			/* if we have allocated more blocks and copied
> +			 * less. We will have blocks allocated outside
> +			 * inode->i_size. So truncate them
> +			 */
> +			ext4_orphan_add(handle, inode);
>  		if (ret2 < 0)
>  			ret = ret2;
>  	}
> @@ -1596,6 +1636,18 @@ static int ext4_ordered_write_end(struct file *file,
>  	if (!ret)
>  		ret = ret2;
> 
> +	if (pos + len > inode->i_size) {
> +		vmtruncate(inode, inode->i_size);
> +		/* 
> +		 * If vmtruncate failed early the inode might still be
> +		 * on the orphan list; we need to make sure the inode
> +		 * is removed from the orphan list in that case.
> +		 */
> +		if (inode->i_nlink)
> +			ext4_orphan_del(NULL, inode);
> +	}
> +
> +
>  	return ret ? ret : copied;
>  }
> 
> @@ -1607,25 +1659,21 @@ static int ext4_writeback_write_end(struct file *file,
>  	handle_t *handle = ext4_journal_current_handle();
>  	struct inode *inode = mapping->host;
>  	int ret = 0, ret2;
> -	loff_t new_i_size;
> 
>  	trace_mark(ext4_writeback_write_end,
>  		   "dev %s ino %lu pos %llu len %u copied %u",
>  		   inode->i_sb->s_id, inode->i_ino,
>  		   (unsigned long long) pos, len, copied);
> -	new_i_size = pos + copied;
> -	if (new_i_size > EXT4_I(inode)->i_disksize) {
> -		ext4_update_i_disksize(inode, new_i_size);
> -		/* We need to mark inode dirty even if
> -		 * new_i_size is less that inode->i_size
> -		 * bu greater than i_disksize.(hint delalloc)
> -		 */
> -		ext4_mark_inode_dirty(handle, inode);
> -	}
> -
> -	ret2 = generic_write_end(file, mapping, pos, len, copied,
> +	ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
>  							page, fsdata);
>  	copied = ret2;
> +	if (pos + len > inode->i_size)
> +		/* if we have allocated more blocks and copied
> +		 * less. We will have blocks allocated outside
> +		 * inode->i_size. So truncate them
> +		 */
> +		ext4_orphan_add(handle, inode);
> +
>  	if (ret2 < 0)
>  		ret = ret2;
> 
> @@ -1633,6 +1681,17 @@ static int ext4_writeback_write_end(struct file *file,
>  	if (!ret)
>  		ret = ret2;
> 
> +	if (pos + len > inode->i_size) {
> +		vmtruncate(inode, inode->i_size);
> +		/* 
> +		 * If vmtruncate failed early the inode might still be
> +		 * on the orphan list; we need to make sure the inode
> +		 * is removed from the orphan list in that case.
> +		 */
> +		if (inode->i_nlink)
> +			ext4_orphan_del(NULL, inode);
> +	}
> +
>  	return ret ? ret : copied;
>  }
> 
> @@ -1677,10 +1736,27 @@ static int ext4_journalled_write_end(struct file *file,
>  	}
> 
>  	unlock_page(page);
> +	page_cache_release(page);
> +	if (pos + len > inode->i_size)
> +		/* if we have allocated more blocks and copied
> +		 * less. We will have blocks allocated outside
> +		 * inode->i_size. So truncate them
> +		 */
> +		ext4_orphan_add(handle, inode);
> +
>  	ret2 = ext4_journal_stop(handle);
>  	if (!ret)
>  		ret = ret2;
> -	page_cache_release(page);
> +	if (pos + len > inode->i_size) {
> +		vmtruncate(inode, inode->i_size);
> +		/* 
> +		 * If vmtruncate failed early the inode might still be
> +		 * on the orphan list; we need to make sure the inode
> +		 * is removed from the orphan list in that case.
> +		 */
> +		if (inode->i_nlink)
> +			ext4_orphan_del(NULL, inode);
> +	}

Here also need special care with block_unlock_hole_extend. We need to do
a vmtruncate outside block_unlock_hole_extend.


> 
>  	return ret ? ret : copied;
>  }

I think i both the case Jan's patch
allocate-blocks-correctly-with-subpage-blocksize need an update ? Since you have put
the patch before Jan's changes.

-aneesh