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

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Message-ID: <6d8df20e-d99a-0f80-f3e1-3c661351759c@redhat.com>
Date:   Wed, 6 Apr 2022 18:57:02 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Luís Henriques <lhenriques@...e.de>
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


On 4/6/22 6:50 PM, Luís Henriques wrote:
> 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);
>>> @@ -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);
>>> +		}
>> Shouldn't we fail it if the 'invalidate_inode_pages2_range()' fails here ?
> Yeah, I'm not really sure.  I'm simply following the usual pattern where
> an invalidate_inode_pages2_range() failure is logged and ignored.  And
> this is not ceph-specific, other filesystems seem to do the same thing.

I think it should be they are using this to invalidate the range only, 
do not depend on it to writeback the dirty pages.

Such as they may will call 'filemap_fdatawrite_range()', etc.

I saw in the beginning of the 'ceph_sync_write()', it will do 
'filemap_write_and_wait_range()' too. So the dirty pages should have 
already flushed.

-- Xiubo



> Cheers,