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SubjectRe: [f2fs-dev] [PATCH 2/6] f2fs: do not expose unwritten blocks to user by DIO
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On 2021/11/17 5:45, Jaegeuk Kim wrote:
> DIO preallocates physical blocks before writing data, but if an error occurrs
> or power-cut happens, we can see block contents from the disk. This patch tries
> to fix it by 1) turning to buffered writes for DIO into holes, 2) truncating
> unwritten blocks from error or power-cut.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
> fs/f2fs/data.c | 5 ++++-
> fs/f2fs/f2fs.h | 5 +++++
> fs/f2fs/file.c | 24 +++++++++++++++++++++++-
> 3 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 3b27fb7daa8b..7ac1a39fcad2 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1543,8 +1543,11 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
> flag != F2FS_GET_BLOCK_DIO);
> err = __allocate_data_block(&dn,
> map->m_seg_type);
> - if (!err)
> + if (!err) {
> + if (flag == F2FS_GET_BLOCK_PRE_DIO)
> + file_need_truncate(inode);

We will leave FADVISE_TRUNC_BIT flag in below call path, is this as expected?

- fallocate
- expand_inode_data
- f2fs_map_blocks(F2FS_GET_BLOCK_PRE_DIO)

Thanks,

> set_inode_flag(inode, FI_APPEND_WRITE);
> + }
> }
> if (err)
> goto sync_out;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index be871a79c634..14bea669f87e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -654,6 +654,7 @@ enum {
> #define FADVISE_KEEP_SIZE_BIT 0x10
> #define FADVISE_HOT_BIT 0x20
> #define FADVISE_VERITY_BIT 0x40
> +#define FADVISE_TRUNC_BIT 0x80
>
> #define FADVISE_MODIFIABLE_BITS (FADVISE_COLD_BIT | FADVISE_HOT_BIT)
>
> @@ -681,6 +682,10 @@ enum {
> #define file_is_verity(inode) is_file(inode, FADVISE_VERITY_BIT)
> #define file_set_verity(inode) set_file(inode, FADVISE_VERITY_BIT)
>
> +#define file_should_truncate(inode) is_file(inode, FADVISE_TRUNC_BIT)
> +#define file_need_truncate(inode) set_file(inode, FADVISE_TRUNC_BIT)
> +#define file_dont_truncate(inode) clear_file(inode, FADVISE_TRUNC_BIT)
> +
> #define DEF_DIR_LEVEL 0
>
> enum {
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 4bf77a5bf998..ec8de0662437 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -960,10 +960,21 @@ int f2fs_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
> down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> filemap_invalidate_lock(inode->i_mapping);
>
> + /*
> + * Truncate stale preallocated blocks used by the previous DIO.
> + */
> + if (file_should_truncate(inode)) {
> + err = f2fs_truncate(inode);
> + if (err)
> + goto out_unlock;
> + file_dont_truncate(inode);
> + }
> +
> truncate_setsize(inode, attr->ia_size);
>
> if (attr->ia_size <= old_size)
> err = f2fs_truncate(inode);
> +out_unlock:
> /*
> * do not trim all blocks after i_size if target size is
> * larger than i_size.
> @@ -4257,6 +4268,13 @@ static int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *iter)
> /* If it will be an out-of-place direct write, don't bother. */
> if (dio && f2fs_lfs_mode(sbi))
> return 0;
> + /*
> + * Don't preallocate holes aligned to DIO_SKIP_HOLES which turns into
> + * buffered IO, if DIO meets any holes.
> + */
> + if (dio && i_size_read(inode) &&
> + (F2FS_BYTES_TO_BLK(pos) < F2FS_BLK_ALIGN(i_size_read(inode))))
> + return 0;
>
> /* No-wait I/O can't allocate blocks. */
> if (iocb->ki_flags & IOCB_NOWAIT)
> @@ -4366,10 +4384,14 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> if (preallocated > 0 && i_size_read(inode) < target_size) {
> down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> filemap_invalidate_lock(inode->i_mapping);
> - f2fs_truncate(inode);
> + if (!f2fs_truncate(inode))
> + file_dont_truncate(inode);
> filemap_invalidate_unlock(inode->i_mapping);
> up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> + } else {
> + file_dont_truncate(inode);
> }
> +
> clear_inode_flag(inode, FI_PREALLOCATED_ALL);
>
> if (ret > 0)
>

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