On 6/1/18 12:27 AM, Ladvine D Almeida wrote: > On Thursday 31 May 2018 04:46 PM, Jens Axboe wrote: >> On 5/31/18 1:47 AM, Ladvine D Almeida wrote: >>> On Monday 28 May 2018 04:54 PM, Jens Axboe wrote: >>>> On 5/28/18 7:43 AM, Ladvine D Almeida wrote: >>>>> This patch introduces new variable under bio structure to >>>>> facilitate inline encryption. This variable is used to >>>>> associate I/O requests to crypto information. >>>> Hard no on this, for two reasons: >>>> >>>> 1) Any additions to struct bio are scrutinized heavily and >>>> need strong justification. >>> Thanks for sharing your feedback on the patch. >>> I am providing reference to an earlier article related to inline encryption support below: >>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lwn.net_Articles_717754_&d=DwICaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=z00zRD9ARrwHpe-XSl1OtUp1uNKGYoXI1G2DhOaDDBI&m=m8U0bg9QiswO2oVJgJKq3MmJpqPPK_tN667XwsjojcM&s=9VPcl80YTKwbf8T-oCxWTRahYzS2xNDHZMexpFbuepY&e= >> Took a quick look, and this looks like a classic case of something >> that should just be a cloned bio. If you clone, you own the bi_private >> field, which is what you need. > > Cloning the bio gives ownership of the bi_private variable which i can > use to refer to the crypto context. But i have the following problem > here: > 1. In the dm-crypt subsystem, we clone the bio and assign the > bi_private variable. Afterwards, generic_make_request() is done to > submit I/O request to block device. > 2. The bio will be cloned further in the below layers. The reference > in the bi_private variable is now lost as the bio_clone function will > not copy the bi_private variable. > > Also, the bi_private variable is already used in the dm-crypt layer > for storing its private data. This prevents me from using the same. If you clone or allocate a bio, you are the owner of bi_private. If someone further down the stack clones it again, then they own the NEW bi_private of the newly returned cloned. Nobody will mess with yours, that would be a layering violation. That is the way to store data on a per bio basis, not by adding a new random field to the bio structure. -- Jens Axboe
