linux-kernel - Re: [PATCH v2] ceph: invalidate pages when doing DIO in encrypted inodes

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Date:   Wed, 06 Apr 2022 11:57:14 +0100
From:   Luís Henriques <lhenriques@...e.de>
To:     Xiubo Li <xiubli@...hat.com>
Cc:     Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ceph: invalidate pages when doing DIO in encrypted
 inodes

Xiubo Li <xiubli@...hat.com> writes:

> On 4/1/22 9:32 PM, Luís Henriques wrote:
>> When doing DIO on an encrypted node, we need to invalidate the page cache in
>> the range being written to, otherwise the cache will include invalid data.
>>
>> Signed-off-by: Luís Henriques <lhenriques@...e.de>
>> ---
>>   fs/ceph/file.c | 11 ++++++++++-
>>   1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> Changes since v1:
>> - Replaced truncate_inode_pages_range() by invalidate_inode_pages2_range
>> - Call fscache_invalidate with FSCACHE_INVAL_DIO_WRITE if we're doing DIO
>>
>> Note: I'm not really sure this last change is required, it doesn't really
>> affect generic/647 result, but seems to be the most correct.
>>
>> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
>> index 5072570c2203..b2743c342305 100644
>> --- a/fs/ceph/file.c
>> +++ b/fs/ceph/file.c
>> @@ -1605,7 +1605,7 @@ ceph_sync_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos,
>>   	if (ret < 0)
>>   		return ret;
>>   -	ceph_fscache_invalidate(inode, false);
>> +	ceph_fscache_invalidate(inode, (iocb->ki_flags & IOCB_DIRECT));
>>   	ret = invalidate_inode_pages2_range(inode->i_mapping,
>>   					    pos >> PAGE_SHIFT,
>>   					    (pos + count - 1) >> PAGE_SHIFT);
>
> The above has already invalidated the pages, why doesn't it work ?

I suspect the reason is because later on we loop through the number of
pages, call copy_page_from_iter() and then ceph_fscrypt_encrypt_pages().

Cheers,
-- 
Luís

>
> -- Xiubo
>
>> @@ -1895,6 +1895,15 @@ ceph_sync_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos,
>>   		req->r_inode = inode;
>>   		req->r_mtime = mtime;
>>   +		if (IS_ENCRYPTED(inode) && (iocb->ki_flags & IOCB_DIRECT)) {
>> +			ret = invalidate_inode_pages2_range(
>> +				inode->i_mapping,
>> +				write_pos >> PAGE_SHIFT,
>> +				(write_pos + write_len - 1) >> PAGE_SHIFT);
>> +			if (ret < 0)
>> +				dout("invalidate_inode_pages2_range returned %d\n", ret);
>> +		}
>> +
>>   		/* Set up the assertion */
>>   		if (rmw) {
>>   			/*
>>
>