linux-kernel - Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid non-section-aligned size pinned file generation

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Message-ID: <e6a2233f-5f32-4e1a-87b3-4ecb935e3997@kernel.org>
Date: Tue, 17 Jun 2025 17:30:43 +0800
From: Chao Yu <chao@...nel.org>
To: wangzijie <wangzijie1@...or.com>, linux-f2fs-devel@...ts.sourceforge.net
Cc: chao@...nel.org, feng.han@...or.com, jaegeuk@...nel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid non-section-aligned size
 pinned file generation

On 6/17/25 15:36, wangzijie wrote:
>> On 6/17/25 11:57, wangzijie wrote:
>>> To prevent non-section-aligned size pinned file generated from truncation,
>>> add check condition in setattr.
>>>
>>> Signed-off-by: wangzijie <wangzijie1@...or.com>
>>> ---
>>>  fs/f2fs/file.c | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 6bd3de64f..72f7d1b4a 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -1026,6 +1026,7 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
>>>  {
>>>  	struct inode *inode = d_inode(dentry);
>>>  	struct f2fs_inode_info *fi = F2FS_I(inode);
>>> +	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>  	int err;
>>>  
>>>  	if (unlikely(f2fs_cp_error(F2FS_I_SB(inode))))
>>> @@ -1047,6 +1048,11 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
>>>  			!IS_ALIGNED(attr->ia_size,
>>>  			F2FS_BLK_TO_BYTES(fi->i_cluster_size)))
>>>  			return -EINVAL;
>>> +		if (f2fs_is_pinned_file(inode) &&
>>> +			attr->ia_size < i_size_read(inode) &&
>>
>> Do we need to consider attr->ia_size > i_size case?
>>
>> Thanks,
> 
> Hi, Chao
> After commit 3fdd89b452c2("f2fs: prevent writing without fallocate() for pinned
> files"), when we want to write data to pinned file, we need to use pin+fallocate, 
> and we did CAP_BLKS_PER_SEC roundup align when fallocate pinned file:
> 
> block_t sec_len = roundup(map.m_len, sec_blks);
> 
> Even if we truncate the file to a larger size(maybe larger than sec_len, section
> align or not), and write data to offset beyond sec_len, the write will fail(commit
> 3fdd89b452c2 prevent it). The scattered pin block cannot be generated by this way,
> so I did not consider attr->ia_size > i_size case.
> Do you have some suggestions?

Ah, correct, so what about adding comments here to describe why we don't
need consider attr->ia_size > i_size case?

> 
>>> +			!IS_ALIGNED(attr->ia_size,
>>> +			F2FS_BLK_TO_BYTES(CAP_BLKS_PER_SEC(sbi))))
>>> +			return -EINVAL;
>>>  	}
>>>  
>>>  	err = setattr_prepare(idmap, dentry, attr);
> 
> 
>