linux-kernel - Re: [f2fs-dev] [PATCH v4 2/2] f2fs: don't allow unaligned truncation to smaller/equal size on pinned file

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Message-ID: <3c0d3d19-58b2-4702-b42b-1df7985def74@kernel.org>
Date: Mon, 30 Jun 2025 11:41:39 +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 v4 2/2] f2fs: don't allow unaligned truncation
 to smaller/equal size on pinned file

On 6/30/25 10:50, wangzijie wrote:
>> On 6/24/25 11:59, wangzijie wrote:
>>> To prevent scattered pin block generation, don't allow non-section aligned truncation
>>> to smaller or equal size on pinned file. But for truncation to larger size, after
>>> commit 3fdd89b452c2("f2fs: prevent writing without fallocate() for pinned files"),
>>> we only support overwrite IO to pinned file, so we don't need to consider
>>> attr->ia_size > i_size case.
>>
>> Zijie, can you take a look generic/494? suspect that it is caused by this change.
>>
>> generic/494 3s ... - output mismatch (see /share/git/fstests/results//generic/494.out.bad)
>>    --- tests/generic/494.out   2025-01-12 21:57:40.279440664 +0800
>>    +++ /share/git/fstests/results//generic/494.out.bad 2025-06-30 10:01:37.000000000 +0800
>>    @@ -2,7 +2,7 @@
>>     Format and mount
>>     Initialize file
>>     Try to truncate
>>    -ftruncate: Text file busy
>>    +ftruncate: Invalid argument
>>     Try to punch hole
>>     fallocate: Text file busy
>>    ...
>>    (Run 'diff -u /share/git/fstests/tests/generic/494.out /share/git/fstests/results//generic/494.out.bad'  to see the entire diff)
>> Ran: generic/494
>> Failures: generic/494
>> Failed 1 of 1 tests
>>
>> Thanks,
> 
> Hi, Chao
> generic/494 swapon file and try to ftruncate.
> 
> Before this change
> swap_acticate:
> set_inode_flag(inode, FI_PIN_FILE)
> 
> ftruncate:
> setattr_prepare
> -inode_newsize_ok
> --return -ETXTBSY for SWAPFILE
> 
> After this change:
> swap_acticate:
> set_inode_flag(inode, FI_PIN_FILE)
> 
> ftruncate: 
> prevent unaligned truncation before setattr_prepare()
> return -EINVAL
> 
> Sorry for this. Maybe I should apply this check after setattr_prepare()? Or do

Check after setattr_prepare() looks fine to me, in addition, can you please add
more comments for the reason why we relocate code there?

Thanks,

> you have some suggestions?
> 
> 
>>>
>>> Signed-off-by: wangzijie <wangzijie1@...or.com>
>>> ---
>>> v4:
>>> - convert sbi first and apply change
>>> ---
>>>  fs/f2fs/file.c | 11 +++++++++++
>>>  1 file changed, 11 insertions(+)
>>>
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 209f43653..4809f0fd6 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -1048,6 +1048,17 @@ 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;
>>> +		/*
>>> +		 * To prevent scattered pin block generation, we don't allow
>>> +		 * smaller/equal size unaligned truncation for pinned file.
>>> +		 * We only support overwrite IO to pinned file, so don't
>>> +		 * care about larger size truncation.
>>> +		 */
>>> +		if (f2fs_is_pinned_file(inode) &&
>>> +			attr->ia_size <= i_size_read(inode) &&
>>> +			!IS_ALIGNED(attr->ia_size,
>>> +			F2FS_BLK_TO_BYTES(CAP_BLKS_PER_SEC(sbi))))
>>> +			return -EINVAL;
>>>  	}
>>>  
>>>  	err = setattr_prepare(idmap, dentry, attr);
>