linux-kernel - Re: [f2fs-dev] [PATCH v3] f2fs: prevent writing without fallocate() for pinned files

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Message-ID: <712f380c-68ef-4743-bd9b-7342e838ced7@kernel.org>
Date: Wed, 20 Mar 2024 17:38:47 +0800
From: Chao Yu <chao@...nel.org>
To: Daeho Jeong <daeho43@...il.com>, linux-kernel@...r.kernel.org,
 linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com
Cc: Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: prevent writing without fallocate()
 for pinned files

On 2024/3/20 5:23, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@...gle.com>
> 
> In a case writing without fallocate(), we can't guarantee it's allocated
> in the conventional area for zoned stroage.
> 
> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> ---
> v2: covered the direct io case
> v3: covered the mkwrite case
> ---
>   fs/f2fs/data.c | 14 ++++++++++++--
>   fs/f2fs/file.c | 16 ++++++++--------
>   2 files changed, 20 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index c21b92f18463..d3e5ab2736a6 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) && is_hole &&
> +		     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;
>   	}
> @@ -3407,6 +3412,11 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
>   
>   	if (!f2fs_lookup_read_extent_cache_block(inode, index,
>   						 &dn.data_blkaddr)) {
> +		if (f2fs_is_pinned_file(inode)) {
> +			err = -EIO;
> +			goto out;
> +		}
> +
>   		if (locked) {
>   			err = f2fs_reserve_block(&dn, index);
>   			goto out;
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 82277e95c88f..4db3b21c804b 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);

Will this check races w/ pinfile get|set?

Thanks,

>   	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);
>   	}
> -#endif
> +
>   	if (err) {
>   		unlock_page(page);
>   		goto out_sem;
> @@ -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);