Date:	Wed, 20 Jan 2010 14:33:41 +0530
From:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Eric Sandeen <sandeen@...hat.com>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Add flag to files with blocks intentionally past EOF

On Tue, 19 Jan 2010 15:45:19 -0600, Eric Sandeen <sandeen@...hat.com> wrote:
> From: Jiaying Zhang <jiayingz@...gle.com>
> 
> fallocate() may potentially instantiate blocks past EOF, depending
> on the flags used when it is called.
> 
> e2fsck currently has a test for blocks past i_size, and it
> sometimes trips up - noticeably on xfstests 013 which runs fsstress.
> 
> This patch from Jiayang does fix it up for me - it (along with
> e2fsprogs updates and other patches recently from Aneesh) has
> survived many fsstress runs in a row.
> 
> The setattr interface may also be used to clear the flag and remove
> any blocks past EOF.
> 
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
> ---
> 
> (just resending this since it probably got lost in the previous
> thread - Jiaying didn't have a SOB line, but maybe that should
> be added.  I have included the proper From: line for authorship)
>

The patch i looked earlier was was early RFC and i didn't look the
full thread to find an updated patch was posted.(hmm getting used to
reading mails with notmuchmail.org)

http://article.gmane.org/gmane.comp.file-systems.ext4/15035

 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 874d169..4c7cd9b 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -284,10 +284,11 @@ struct flex_groups {
>  #define EXT4_TOPDIR_FL			0x00020000 /* Top of directory hierarchies*/
>  #define EXT4_HUGE_FILE_FL               0x00040000 /* Set to each huge file */
>  #define EXT4_EXTENTS_FL			0x00080000 /* Inode uses extents */
> +#define EXT4_EOFBLOCKS_FL		0x00400000 /* Blocks allocated beyond EOF (bit reserved in fs.h) */
>  #define EXT4_RESERVED_FL		0x80000000 /* reserved for ext4 lib */
> 
> -#define EXT4_FL_USER_VISIBLE		0x000BDFFF /* User visible flags */
> -#define EXT4_FL_USER_MODIFIABLE		0x000B80FF /* User modifiable flags */
> +#define EXT4_FL_USER_VISIBLE		0x004BDFFF /* User visible flags */
> +#define EXT4_FL_USER_MODIFIABLE		0x004B80FF /* User modifiable flags */
> 
>  /* Flags that should be inherited by new inodes from their parent. */
>  #define EXT4_FL_INHERITED (EXT4_SECRM_FL | EXT4_UNRM_FL | EXT4_COMPR_FL |\
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 765a482..e7d5ba2 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3185,7 +3185,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
>  {
>  	struct ext4_ext_path *path = NULL;
>  	struct ext4_extent_header *eh;
> -	struct ext4_extent newex, *ex;
> +	struct ext4_extent newex, *ex, *last_ex;
>  	ext4_fsblk_t newblock;
>  	int err = 0, depth, ret, cache_type;
>  	unsigned int allocated = 0;
> @@ -3366,6 +3366,14 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
>  					EXT4_STATE_DIO_UNWRITTEN;;
>  		}
>  	}
> +
> +	if (unlikely(inode->i_flags & EXT4_EOFBLOCKS_FL)) {
> +		BUG_ON(!eh->eh_entries);
> +		last_ex = EXT_LAST_EXTENT(eh);
> +		if (iblock + ar.len > le32_to_cpu(last_ex->ee_block)
> +					+ ext4_ext_get_actual_len(last_ex))
> +			inode->i_flags &= ~EXT4_EOFBLOCKS_FL;
> +	}


Why do we need to set inode->i_flag ? Can we make it Ext4 specific and
look at ext4_inode->i_flags . Also setting inode->i_flag with an EXT4
flag value is confusing.



>  	err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
>  	if (err) {
>  		/* free data blocks we just allocated */
> @@ -3499,6 +3507,13 @@ static void ext4_falloc_update_inode(struct inode *inode,
>  			i_size_write(inode, new_size);
>  		if (new_size > EXT4_I(inode)->i_disksize)
>  			ext4_update_i_disksize(inode, new_size);
> +	} else {
> +		/*
> +		 * Mark that we allocate beyond EOF so the subsequent truncate
> +		 * can proceed even if the new size is the same as i_size.
> +		 */
> +		if (new_size > i_size_read(inode))
> +			inode->i_flags |= EXT4_EOFBLOCKS_FL;
>  	}
> 
>  }
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index cbf56da..bc31ea6 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4429,6 +4429,8 @@ void ext4_truncate(struct inode *inode)
>  	if (!ext4_can_truncate(inode))
>  		return;
> 
> +	inode->i_flags &= ~EXT4_EOFBLOCKS_FL;
> +
>  	if (inode->i_size == 0 && !test_opt(inode->i_sb, NO_AUTO_DA_ALLOC))
>  		ei->i_state |= EXT4_STATE_DA_ALLOC_CLOSE;
> 
> @@ -4741,8 +4743,8 @@ void ext4_get_inode_flags(struct ext4_inode_info *ei)
>  {
>  	unsigned int flags = ei->vfs_inode.i_flags;
> 
> -	ei->i_flags &= ~(EXT4_SYNC_FL|EXT4_APPEND_FL|
> -			EXT4_IMMUTABLE_FL|EXT4_NOATIME_FL|EXT4_DIRSYNC_FL);
> +	ei->i_flags &= ~(EXT4_SYNC_FL|EXT4_APPEND_FL|EXT4_IMMUTABLE_FL|
> +
> EXT4_NOATIME_FL|EXT4_DIRSYNC_FL|EXT4_EOFBLOCKS_FL);


Do we really need to allow the get and set of this flag. IMHO a truncate
should be the only API and the flag should be remove implicitly for that.


>  	if (flags & S_SYNC)
>  		ei->i_flags |= EXT4_SYNC_FL;
>  	if (flags & S_APPEND)
> @@ -4753,6 +4755,8 @@ void ext4_get_inode_flags(struct ext4_inode_info *ei)
>  		ei->i_flags |= EXT4_NOATIME_FL;
>  	if (flags & S_DIRSYNC)
>  		ei->i_flags |= EXT4_DIRSYNC_FL;
> +	if (flags & FS_EOFBLOCKS_FL)
> +		ei->i_flags |= EXT4_EOFBLOCKS_FL;
>  }
> 
>  static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
> @@ -5284,7 +5288,9 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
>  	}
> 
>  	if (S_ISREG(inode->i_mode) &&
> -	    attr->ia_valid & ATTR_SIZE && attr->ia_size < inode->i_size) {
> +	    attr->ia_valid & ATTR_SIZE &&
> +	    (attr->ia_size < inode->i_size ||
> +	     (inode->i_flags & EXT4_EOFBLOCKS_FL))) {
>  		handle_t *handle;
> 
>  		handle = ext4_journal_start(inode, 3);
> @@ -5315,6 +5321,11 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
>  				goto err_out;
>  			}
>  		}
> +		if ((inode->i_flags & EXT4_EOFBLOCKS_FL)) {
> +			rc = vmtruncate(inode, attr->ia_size);
> +			if (rc)
> +				goto err_out;
> +		}
>  	}
> 
>  	rc = inode_setattr(inode, attr);
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index b63d193..71f578e 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -92,6 +92,16 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  			flags &= ~EXT4_EXTENTS_FL;
>  		}
> 
> +		if (flags & EXT4_EOFBLOCKS_FL) {
> +			/* we don't support adding EOFBLOCKS flag */
> +			if (!(oldflags & EXT4_EOFBLOCKS_FL)) {
> +				err = -EOPNOTSUPP;
> +				goto flags_out;
> +			}
> +		} else if (oldflags & EXT4_EOFBLOCKS_FL)
> +			/* free the space reserved with fallocate KEEPSIZE */
> +			vmtruncate(inode, inode->i_size);
> +
>  		handle = ext4_journal_start(inode, 1);
>  		if (IS_ERR(handle)) {
>  			err = PTR_ERR(handle);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9147ca8..db3ffb6 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -349,10 +349,11 @@ struct inodes_stat_t {
>  #define FS_TOPDIR_FL			0x00020000 /* Top of directory hierarchies*/
>  #define FS_EXTENT_FL			0x00080000 /* Extents */
>  #define FS_DIRECTIO_FL			0x00100000 /* Use direct i/o */
> +#define FS_EOFBLOCKS_FL			0x00400000 /* Blocks allocated beyond EOF */
>  #define FS_RESERVED_FL			0x80000000 /* reserved for ext2 lib */
> 
> -#define FS_FL_USER_VISIBLE		0x0003DFFF /* User visible flags */
> -#define FS_FL_USER_MODIFIABLE		0x000380FF /* User modifiable flags */
> +#define FS_FL_USER_VISIBLE		0x0043DFFF /* User visible flags */
> +#define FS_FL_USER_MODIFIABLE		0x004380FF /* User modifiable flags */
> 
> 
>  #define SYNC_FILE_RANGE_WAIT_BEFORE	1
> 

If we remove ext4_ioctl support i guess that patch can become much
simpler. 

-aneesh
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