Re: [f2fs-dev] [PATCH v5] f2fs: prevent writing without fallocate() for pinned files

[Chao Yu <chao@kernel.org>]

On 2024/3/27 4:31, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@google.com>
> 
> In a case writing without fallocate(), we can't guarantee it's allocated
> in the conventional area for zoned stroage. To make it consistent across
> storage devices, we disallow it regardless of storage device types.
> 
> Signed-off-by: Daeho Jeong <daehojeong@google.com>
> ---
> v2: covered the direct io case
> v3: covered the mkwrite case
> v4: moved pin file check position in prepare_write_begin()
> v5: removed unnecessary condition in f2fs_map_blocks() and disallowed
>      pre-written inodes for file pinning
> ---
>   fs/f2fs/data.c | 20 ++++++++++++++++----
>   fs/f2fs/file.c | 18 +++++++++---------
>   2 files changed, 25 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index c21b92f18463..1b02a9291176 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1584,8 +1584,11 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
>   
>   	/* use out-place-update for direct IO under LFS mode */
>   	if (map->m_may_create &&
> -	    (is_hole || (f2fs_lfs_mode(sbi) && flag == F2FS_GET_BLOCK_DIO))) {
> -		if (unlikely(f2fs_cp_error(sbi))) {
> +	    (is_hole || (f2fs_lfs_mode(sbi) && flag == F2FS_GET_BLOCK_DIO &&
> +			 !f2fs_is_pinned_file(inode)))) {
> +		if (unlikely(f2fs_cp_error(sbi)) ||
> +		    (f2fs_is_pinned_file(inode) &&
> +		     flag != F2FS_GET_BLOCK_PRE_DIO)) {
>   			err = -EIO;
>   			goto sync_out;
>   		}
> @@ -3378,6 +3381,8 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
>   		f2fs_map_lock(sbi, flag);
>   		locked = true;
>   	} else if ((pos & PAGE_MASK) >= i_size_read(inode)) {
> +		if (f2fs_is_pinned_file(inode))
> +			return -EIO;
>   		f2fs_map_lock(sbi, flag);
>   		locked = true;
>   	}
> @@ -3414,8 +3419,15 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
>   
>   		/* hole case */
>   		err = f2fs_get_dnode_of_data(&dn, index, LOOKUP_NODE);
> -		if (!err && dn.data_blkaddr != NULL_ADDR)
> -			goto out;
> +		if (!err) {
> +			if (dn.data_blkaddr != NULL_ADDR) {
> +				goto out;
> +			} else if (f2fs_is_pinned_file(inode)) {
> +				err = -EIO;
> +				goto out;
> +			}
> +		}
> +
>   		f2fs_put_dnode(&dn);
>   		f2fs_map_lock(sbi, F2FS_GET_BLOCK_PRE_AIO);
>   		WARN_ON(flag != F2FS_GET_BLOCK_PRE_AIO);
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 82277e95c88f..7aa53cf553a1 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -57,7 +57,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>   	struct inode *inode = file_inode(vmf->vma->vm_file);
>   	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>   	struct dnode_of_data dn;
> -	bool need_alloc = true;
> +	bool need_alloc = !f2fs_is_pinned_file(inode);
>   	int err = 0;
>   	vm_fault_t ret;
>   
> @@ -114,19 +114,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>   		goto out_sem;
>   	}
>   
> +	set_new_dnode(&dn, inode, NULL, NULL, 0);
>   	if (need_alloc) {
>   		/* block allocation */
> -		set_new_dnode(&dn, inode, NULL, NULL, 0);
>   		err = f2fs_get_block_locked(&dn, page->index);
> -	}
> -
> -#ifdef CONFIG_F2FS_FS_COMPRESSION
> -	if (!need_alloc) {
> -		set_new_dnode(&dn, inode, NULL, NULL, 0);
> +	} else {
>   		err = f2fs_get_dnode_of_data(&dn, page->index, LOOKUP_NODE);
>   		f2fs_put_dnode(&dn);
>   	}

It needs to check dn.data_blkaddr for pinfile? return EIO if it hits a hole?

Thanks,

> -#endif
> +
>   	if (err) {
>   		unlock_page(page);
>   		goto out_sem;
> @@ -3235,7 +3231,7 @@ static int f2fs_ioc_set_pin_file(struct file *filp, unsigned long arg)
>   		goto done;
>   	}
>   
> -	if (f2fs_sb_has_blkzoned(sbi) && F2FS_HAS_BLOCKS(inode)) {
> +	if (F2FS_HAS_BLOCKS(inode)) {
>   		ret = -EFBIG;
>   		goto out;
>   	}
> @@ -4611,6 +4607,10 @@ static int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *iter,
>   			return ret;
>   	}
>   
> +	/* For pinned files, it should be fallocate()-ed in advance. */
> +	if (f2fs_is_pinned_file(inode))
> +		return 0;
> +
>   	/* Do not preallocate blocks that will be written partially in 4KB. */
>   	map.m_lblk = F2FS_BLK_ALIGN(pos);
>   	map.m_len = F2FS_BYTES_TO_BLK(pos + count);