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Date:	Mon, 8 Jun 2009 21:23:57 +0200
From:	Jan Kara <jack@...e.cz>
To:	Theodore Tso <tytso@....edu>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	cmm@...ibm.com, sandeen@...hat.com, linux-ext4@...r.kernel.org,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH -V2 2/2] ext4: truncate the file properly if we fail to
	copy data from userspace

  Hi,

On Mon 08-06-09 15:14:20, Theodore Tso wrote:
> On Mon, Jun 08, 2009 at 10:13:57PM +0530, Aneesh Kumar K.V wrote:
> > 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.
> 
> OK, here's how I updated Jan's patch.  I'm going to assume that we'll
> submit the ext4 patch queue immediately as soon as the merge window
> opens, since my impression is Jan is still waiting for some mm
> developers to review his patch set.
  Yes, no review yet :( So put my patches to the end so that they don't
block other fixes in the patch queue.

> Annesh, does this look good to you?
> 
> Jan, if we go down this path, you'll need to update your ext4 patch
> with this updated one, to take into account the changes from Aneesh's
> patch.
  Thanks for the patch.

								Honza

> ext4: Make sure blocks are properly allocated under mmaped page even when blocksize < pagesize
> 
> From: Jan Kara <jack@...e.cz>
> 
> In a situation like:
>   truncate(f, 1024);
>   a = mmap(f, 0, 4096);
>   a[0] = 'a';
>   truncate(f, 4096);
> 
> we end up with a dirty page which does not have all blocks allocated /
> reserved.  Fix the problem by using new VFS infrastructure.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/extents.c |    2 +-
>  fs/ext4/inode.c   |   22 ++++++++++++++++++++--
>  2 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 9c35a7b..f2a2591 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3069,7 +3069,7 @@ static void ext4_falloc_update_inode(struct inode *inode,
>  	 */
>  	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
>  		if (new_size > i_size_read(inode))
> -			i_size_write(inode, new_size);
> +			block_extend_i_size(inode, new_size, 0);
>  		if (new_size > EXT4_I(inode)->i_disksize)
>  			ext4_update_i_disksize(inode, new_size);
>  	}
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index f4cf46e..6450b55 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1491,7 +1491,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
>   	index = pos >> PAGE_CACHE_SHIFT;
>  	from = pos & (PAGE_CACHE_SIZE - 1);
>  	to = from + len;
> -
> +	block_lock_hole_extend(inode, pos);
>  retry:
>  	handle = ext4_journal_start(inode, needed_blocks);
>  	if (IS_ERR(handle)) {
> @@ -1550,6 +1550,8 @@ retry:
>  	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
>  		goto retry;
>  out:
> +	if (ret)
> +		block_unlock_hole_extend(inode);
>  	return ret;
>  }
>  
> @@ -1595,6 +1597,7 @@ static int ext4_generic_write_end(struct file *file,
>  	}
>  	unlock_page(page);
>  	page_cache_release(page);
> +	block_unlock_hole_extend(inode);
>  
>  	/*
>  	 * Don't mark the inode dirty under page lock. First, it unnecessarily
> @@ -1739,6 +1742,8 @@ static int ext4_journalled_write_end(struct file *file,
>  
>  	unlock_page(page);
>  	page_cache_release(page);
> +	block_unlock_hole_extend(inode);
> +
>  	if (pos + len > inode->i_size)
>  		/* if we have allocated more blocks and copied
>  		 * less. We will have blocks allocated outside
> @@ -2888,6 +2893,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
>  	}
>  	*fsdata = (void *)0;
>  	trace_ext4_da_write_begin(inode, pos, len, flags);
> +	block_lock_hole_extend(inode, pos);
>  retry:
>  	/*
>  	 * With delayed allocation, we don't log the i_disksize update
> @@ -2930,6 +2936,8 @@ retry:
>  	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
>  		goto retry;
>  out:
> +	if (ret)
> +		block_unlock_hole_extend(inode);
>  	return ret;
>  }
>  
> @@ -3468,7 +3476,7 @@ static ssize_t ext4_direct_IO(int rw, struct kiocb *iocb,
>  			loff_t end = offset + ret;
>  			if (end > inode->i_size) {
>  				ei->i_disksize = end;
> -				i_size_write(inode, end);
> +				block_extend_i_size(inode, offset, ret);
>  				/*
>  				 * We're going to return a positive `ret'
>  				 * here due to non-zero-length I/O, so there's
> @@ -3513,6 +3521,7 @@ static const struct address_space_operations ext4_ordered_aops = {
>  	.sync_page		= block_sync_page,
>  	.write_begin		= ext4_write_begin,
>  	.write_end		= ext4_ordered_write_end,
> +	.extend_i_size		= block_extend_i_size,
>  	.bmap			= ext4_bmap,
>  	.invalidatepage		= ext4_invalidatepage,
>  	.releasepage		= ext4_releasepage,
> @@ -3528,6 +3537,7 @@ static const struct address_space_operations ext4_writeback_aops = {
>  	.sync_page		= block_sync_page,
>  	.write_begin		= ext4_write_begin,
>  	.write_end		= ext4_writeback_write_end,
> +	.extend_i_size		= block_extend_i_size,
>  	.bmap			= ext4_bmap,
>  	.invalidatepage		= ext4_invalidatepage,
>  	.releasepage		= ext4_releasepage,
> @@ -3543,6 +3553,7 @@ static const struct address_space_operations ext4_journalled_aops = {
>  	.sync_page		= block_sync_page,
>  	.write_begin		= ext4_write_begin,
>  	.write_end		= ext4_journalled_write_end,
> +	.extend_i_size		= block_extend_i_size,
>  	.set_page_dirty		= ext4_journalled_set_page_dirty,
>  	.bmap			= ext4_bmap,
>  	.invalidatepage		= ext4_invalidatepage,
> @@ -3558,6 +3569,7 @@ static const struct address_space_operations ext4_da_aops = {
>  	.sync_page		= block_sync_page,
>  	.write_begin		= ext4_da_write_begin,
>  	.write_end		= ext4_da_write_end,
> +	.extend_i_size		= block_extend_i_size,
>  	.bmap			= ext4_bmap,
>  	.invalidatepage		= ext4_da_invalidatepage,
>  	.releasepage		= ext4_releasepage,
> @@ -5404,6 +5416,12 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
>  	struct address_space *mapping = inode->i_mapping;
>  
>  	/*
> +	 * Wait for extending of i_size, after this moment, next truncate /
> +	 * write can create holes under us but they writeprotect our page so
> +	 * we'll be called again to fill the hole.
> +	 */
> +	block_wait_on_hole_extend(inode, page_offset(page));
> +	/*
>  	 * Get i_alloc_sem to stop truncates messing with the inode. We cannot
>  	 * get i_mutex because we are already holding mmap_sem.
>  	 */
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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