On Wed, May 18, 2011 at 6:59 AM, Jiaying Zhang <jiayingz@xxxxxxxxxx> wrote:
> There is a bug in commit c8d46e41 "ext4: Add flag to files with blocks
> intentionally past EOF" that if we fallocate a file with FALLOC_FL_KEEP_SIZE
> flag and then ftruncate the file to a size larger than the file's i_size,
> any allocated but unwritten blocks will be freed but the file size is set
> to the size that ftruncate specifies.
>
> Here is a simple test to reproduce the problem:
> 1. fallocate a 12k size file with KEEP_SIZE flag
> 2. write the first 4k
> 3. ftruncate the file to 8k
> Then 'ls -l' shows that the i_size of the file becomes 8k but debugfs
> shows the file has only the first written block left.
>
> Below is the proposed patch to fix the bug:
>
> ext4: use vmtruncate() instead of ext4_truncate() in ext4_setattr().
>
> Change ext4_setattr() to use vmtruncate(inode, attr->ia_size) instead
> of ext4_truncate(inode) when it needs to truncate an inode so that
> if the inode has EXT4_EOFBLOCKS_FL flag set and we are trying to truncate
> to a size larger than the inode's i_size, we will only truncate the blocks
> beyond the specified truncate size instead of all of blocks beyond i_size.
>
> Signed-off-by: Jiaying Zhang <jiayingz@xxxxxxxxxx>
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 3424e82..3bfad57 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5347,8 +5347,11 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
> }
> }
> /* ext4_truncate will clear the flag */
> - if ((ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS)))
> - ext4_truncate(inode);
> + if ((ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS))) {
> + rc = vmtruncate(inode, attr->ia_size);
> + if (rc)
> + goto err_out;
> + }
Hi there,
It seems that the error handling has problems. 1)We should handle
error as the below code does. or 2) we can add a OR condition to the
if statement below so that it can handle case here. I prefer the 2nd
solution. it looks like:
- /* ext4_truncate will clear the flag */
- if ((ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS)))
- ext4_truncate(inode);
- if ((attr->ia_valid & ATTR_SIZE) &&
- attr->ia_size != i_size_read(inode))
+ if (((attr->ia_valid & ATTR_SIZE) &&
+ attr->ia_size != i_size_read(inode)) ||
+ ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS))
rc = vmtruncate(inode, attr->ia_size);
Yongqiang.
> }
>
> if ((attr->ia_valid & ATTR_SIZE) &&
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
Best Wishes
Yongqiang Yang
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
