Re: [PATCH RFC 0/2] ceph: size handling for the fscrypt

[Xiubo Li <xiubli@redhat.com>]

On 9/7/21 8:35 PM, Jeff Layton wrote:
> On Fri, 2021-09-03 at 16:15 +0800, xiubli@redhat.com wrote:
>> From: Xiubo Li <xiubli@redhat.com>
>>
>> This patch series is based Jeff's ceph-fscrypt-size-experimental
>> branch in https://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux.git.
>>
>> This is just a draft patch and need to rebase or recode after Jeff
>> finished his huge patch set.
>>
>> Post the patch out for advices and ideas. Thanks.
>>
> I'll take a look. Going forward though, it'd probably be best for you to
> just take over development of the entire ceph-fscrypt-size series
> instead of trying to develop on top of my branch.
>
> That branch is _very_ rough anyway. Just clone the branch into your tree
> and then you can drop or change patches in it as you see fit.

Sure.


>> ====
>>
>> This approach will not do the rmw immediately after the file is
>> truncated. If the truncate size is aligned to the BLOCK SIZE, so
>> there no need to do the rmw and only in unaligned case will the
>> rmw is needed.
>>
>> And the 'fscrypt_file' field will be cleared after the rmw is done.
>> If the 'fscrypt_file' is none zero that means after the kclient
>> reading that block to local buffer or pagecache it needs to do the
>> zeroing of that block in range of [fscrypt_file, round_up(fscrypt_file,
>> BLOCK SIZE)).
>>
>> Once any kclient has dirty that block and write it back to ceph, the
>> 'fscrypt_file' field will be cleared and set to 0. More detail please
>> see the commit comments in the second patch.
>>
> That sounds odd. How do you know where the file ends once you zero out
> fscrypt_file?
>
> /me goes to look at the patches...

The code in the ceph_fill_inode() is not handling well for multiple 
ftruncates case, need to be fixed.

Maybe we need to change the 'fscrypt_file' field's logic and make it 
opaqueness for MDS, then the MDS will use it to do the truncate instead 
as I mentioned in the previous reply in your patch set.

Then we can do the defer rmw in any kclient when necessary as this patch 
does.

>
>> There also need on small work in Jeff's MDS PR in cap flushing code
>> to clear the 'fscrypt_file'.
>>
>>
>> Xiubo Li (2):
>>    Revert "ceph: make client zero partial trailing block on truncate"
>>    ceph: truncate the file contents when needed when file scrypted
>>
>>   fs/ceph/addr.c  | 19 ++++++++++++++-
>>   fs/ceph/caps.c  | 24 ++++++++++++++++++
>>   fs/ceph/file.c  | 65 ++++++++++++++++++++++++++++++++++++++++++++++---
>>   fs/ceph/inode.c | 48 +++++++++++++++++++-----------------
>>   fs/ceph/super.h | 13 +++++++---
>>   5 files changed, 138 insertions(+), 31 deletions(-)
>>