linux-ext4 - Re: [PATCH 3/3] ext4: unmap the underlying metadata when allocating blocks via fallocate

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Message-ID: <4B44F090.4020609@redhat.com>
Date:	Wed, 06 Jan 2010 14:20:32 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
CC:	cmm@...ibm.com, tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 3/3] ext4: unmap the underlying metadata when allocating
 blocks via fallocate

Aneesh Kumar K.V wrote:
> This become important when we are running with nojournal mode. We
> may end up allocating recently freed metablocks for fallocate. We
> want to make sure we unmap the old mapping so that when we convert
> the fallocated uninitialized extent to initialized extent we don't
> have the old mapping around. Leaving the old mapping can cause
> file system corruption

if you could devise a testcase for that, it'd be great - it should
go into the test suite ...

-Eric

> Now that we unmap old metadata blocks we need not return blocks
> allocated from fallocate area as new.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  fs/ext4/ext4.h    |   14 ++++++++++++++
>  fs/ext4/extents.c |   18 ++++--------------
>  fs/ext4/inode.c   |   18 +-----------------
>  3 files changed, 19 insertions(+), 31 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 874d169..110a31f 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1773,6 +1773,20 @@ static inline void set_bitmap_uptodate(struct buffer_head *bh)
>  	set_bit(BH_BITMAP_UPTODATE, &(bh)->b_state);
>  }
>  
> +/*
> + * __unmap_underlying_bh_blocks - just a helper function to unmap
> + * set of blocks described by @bh
> + */
> +static inline void __unmap_underlying_bh_blocks(struct inode *inode,
> +					     struct buffer_head *bh)
> +{
> +	struct block_device *bdev = inode->i_sb->s_bdev;
> +	int blocks, i;
> +
> +	blocks = bh->b_size >> inode->i_blkbits;
> +	for (i = 0; i < blocks; i++)
> +		unmap_underlying_metadata(bdev, bh->b_blocknr + i);
> +}
>  #endif	/* __KERNEL__ */
>  
>  #endif	/* _EXT4_H */
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 765a482..7b4f4cc 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3120,21 +3120,9 @@ out:
>  		goto out2;
>  	} else
>  		allocated = ret;
> -	set_buffer_new(bh_result);
> -	/*
> -	 * if we allocated more blocks than requested
> -	 * we need to make sure we unmap the extra block
> -	 * allocated. The actual needed block will get
> -	 * unmapped later when we find the buffer_head marked
> -	 * new.
> -	 */
> -	if (allocated > max_blocks) {
> -		unmap_underlying_metadata_blocks(inode->i_sb->s_bdev,
> -					newblock + max_blocks,
> -					allocated - max_blocks);
> -		allocated = max_blocks;
> -	}
>  
> +	if (allocated > max_blocks)
> +		allocated = max_blocks;
>  	/*
>  	 * If we have done fallocate with the offset that is already
>  	 * delayed allocated, we would have block reservation
> @@ -3570,6 +3558,8 @@ retry:
>  			ret2 = ext4_journal_stop(handle);
>  			break;
>  		}
> +		if (buffer_new(&map_bh))
> +			__unmap_underlying_bh_blocks(inode, &map_bh);
>  		if ((block + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
>  						blkbits) >> blkbits))
>  			new_size = offset + len;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index fec4ea1..831c7cd 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2104,22 +2104,6 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
>  	}
>  }
>  
> -
> -/*
> - * __unmap_underlying_blocks - just a helper function to unmap
> - * set of blocks described by @bh
> - */
> -static inline void __unmap_underlying_blocks(struct inode *inode,
> -					     struct buffer_head *bh)
> -{
> -	struct block_device *bdev = inode->i_sb->s_bdev;
> -	int blocks, i;
> -
> -	blocks = bh->b_size >> inode->i_blkbits;
> -	for (i = 0; i < blocks; i++)
> -		unmap_underlying_metadata(bdev, bh->b_blocknr + i);
> -}
> -
>  static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
>  					sector_t logical, long blk_cnt)
>  {
> @@ -2274,7 +2258,7 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
>  	new.b_size = (blks << mpd->inode->i_blkbits);
>  
>  	if (buffer_new(&new))
> -		__unmap_underlying_blocks(mpd->inode, &new);
> +		__unmap_underlying_bh_blocks(mpd->inode, &new);
>  
>  	/*
>  	 * If blocks are delayed marked, we need to

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