Namjae Jeon <namjae.jeon@xxxxxxxxxxx> writes:
> When running FSX with direct I/O mode, fsx resulted in DATA past EOF issues.
>
> fsx ./file2 -Z -r 4096 -w 4096
> ...
> ..
> truncating to largest ever: 0x907c
> fallocating to largest ever: 0x11137
> truncating to largest ever: 0x2c6fe
> truncating to largest ever: 0x2cfdf
> fallocating to largest ever: 0x40000
> Mapped Read: non-zero data past EOF (0x18628) page offset 0x629 is 0x2a4e
> ...
> ..
>
> The reason being, it is doing a truncate down, but the zeroing does
> not happen on the last block boundary when offset is not aligned.
> Even though it calls truncate_setsize()->truncate_inode_pages()->
> truncate_inode_pages_range() and considers the partial zeroout but it
> retrieves the page using find_lock_page() - which only looks the page in
> the cache. So, zeroing out does not happen in case of direct IO.
>
> Make a truncate page based around block_truncate_page for FAT filesystem and
> invoke that helper to zerout in case the offset is not aligned with
> the blocksize.
Acked-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Thanks.
> Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> Signed-off-by: Amit Sahrawat <a.sahrawat@xxxxxxxxxxx>
> ---
> fs/fat/fat.h | 1 +
> fs/fat/file.c | 3 +++
> fs/fat/inode.c | 12 ++++++++++++
> 3 files changed, 16 insertions(+)
>
> diff --git a/fs/fat/fat.h b/fs/fat/fat.h
> index eff027d..61801da 100644
> --- a/fs/fat/fat.h
> +++ b/fs/fat/fat.h
> @@ -374,6 +374,7 @@ extern int fat_file_fsync(struct file *file, loff_t start, loff_t end,
> int datasync);
>
> /* fat/inode.c */
> +extern int fat_block_truncate_page(struct inode *inode, loff_t from);
> extern void fat_attach(struct inode *inode, loff_t i_pos);
> extern void fat_detach(struct inode *inode);
> extern struct inode *fat_iget(struct super_block *sb, loff_t i_pos);
> diff --git a/fs/fat/file.c b/fs/fat/file.c
> index f2c73ae..757fc20 100644
> --- a/fs/fat/file.c
> +++ b/fs/fat/file.c
> @@ -523,6 +523,9 @@ int fat_setattr(struct dentry *dentry, struct iattr *attr)
> }
>
> if (attr->ia_valid & ATTR_SIZE) {
> + error = fat_block_truncate_page(inode, attr->ia_size);
> + if (error)
> + goto out;
> down_write(&MSDOS_I(inode)->truncate_lock);
> truncate_setsize(inode, attr->ia_size);
> fat_truncate_blocks(inode, attr->ia_size);
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index f362796..9bf44eb 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -339,6 +339,18 @@ static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
> return blocknr;
> }
>
> +/*
> + * fat_block_truncate_page() zeroes out a mapping from file offset `from'
> + * up to the end of the block which corresponds to `from'.
> + * This is required during truncate to physically zeroout the tail end
> + * of that block so it doesn't yield old data if the file is later grown.
> + * Also, avoid causing failure from fsx for cases of "data past EOF"
> + */
> +int fat_block_truncate_page(struct inode *inode, loff_t from)
> +{
> + return block_truncate_page(inode->i_mapping, from, fat_get_block);
> +}
> +
> static const struct address_space_operations fat_aops = {
> .readpage = fat_readpage,
> .readpages = fat_readpages,
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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