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Date:	Wed, 18 Jul 2012 14:34:47 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Lukas Czerner <lczerner@...hat.com>
CC:	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tytso@....edu, achender@...ux.vnet.ibm.com
Subject: Re: [PATCH 02/12 v2] Revert "ext4: fix fsx truncate failure"

On 7/13/12 8:19 AM, Lukas Czerner wrote:
> This reverts commit 189e868fa8fdca702eb9db9d8afc46b5cb9144c9.
> 
> This commit reintroduces the use of ext4_block_truncate_page() in ext4
> truncate operation instead of ext4_discard_partial_page_buffers().

And I think commit 15291164b22a357cb211b618adfef4fa82fc0de3
jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer

fixed the fsx problem referenced in that commit more properly.

> The statement in the commit description that the truncate operation only
> zero block unaligned portion of the last page is not exactly right,
> since truncate_pagecache_range() also zeroes and invalidate the unaligned
> portion of the page. Then there is no need to zero and unmap it once more
> and ext4_block_truncate_page() was doing the right job, although we
> still need to update the buffer head containing the last block, which is
> exactly what ext4_block_truncate_page() is doing.
> 
> This was tested on ppc64 machine with block size of 1024 bytes without
> any problems.
> 
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> ---
>  fs/ext4/extents.c  |   13 ++-----------
>  fs/ext4/indirect.c |   13 ++-----------
>  2 files changed, 4 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 91341ec..ceab5f5 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4222,7 +4222,6 @@ void ext4_ext_truncate(struct inode *inode)
>  	struct super_block *sb = inode->i_sb;
>  	ext4_lblk_t last_block;
>  	handle_t *handle;
> -	loff_t page_len;
>  	int err = 0;
>  
>  	/*
> @@ -4239,16 +4238,8 @@ void ext4_ext_truncate(struct inode *inode)
>  	if (IS_ERR(handle))
>  		return;
>  
> -	if (inode->i_size % PAGE_CACHE_SIZE != 0) {
> -		page_len = PAGE_CACHE_SIZE -
> -			(inode->i_size & (PAGE_CACHE_SIZE - 1));
> -
> -		err = ext4_discard_partial_page_buffers(handle,
> -			mapping, inode->i_size, page_len, 0);
> -
> -		if (err)
> -			goto out_stop;
> -	}
> +	if (inode->i_size & (sb->s_blocksize - 1))
> +		ext4_block_truncate_page(handle, mapping, inode->i_size);
>  
>  	if (ext4_orphan_add(handle, inode))
>  		goto out_stop;
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 830e1b2..a082b30 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -1349,9 +1349,7 @@ void ext4_ind_truncate(struct inode *inode)
>  	__le32 nr = 0;
>  	int n = 0;
>  	ext4_lblk_t last_block, max_block;
> -	loff_t page_len;
>  	unsigned blocksize = inode->i_sb->s_blocksize;
> -	int err;
>  
>  	handle = start_transaction(inode);
>  	if (IS_ERR(handle))
> @@ -1362,16 +1360,9 @@ void ext4_ind_truncate(struct inode *inode)
>  	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
>  					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
>  
> -	if (inode->i_size % PAGE_CACHE_SIZE != 0) {
> -		page_len = PAGE_CACHE_SIZE -
> -			(inode->i_size & (PAGE_CACHE_SIZE - 1));
> -
> -		err = ext4_discard_partial_page_buffers(handle,
> -			mapping, inode->i_size, page_len, 0);
> -
> -		if (err)
> +	if (inode->i_size & (blocksize - 1))
> +		if (ext4_block_truncate_page(handle, mapping, inode->i_size))
>  			goto out_stop;
> -	}
>  
>  	if (last_block != max_block) {
>  		n = ext4_block_to_path(inode, last_block, offsets, NULL);
> 


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