On Sunday, August 18, 2019 7:15:42 PM IST Chao Yu wrote:
> Hi Chandan,
> On 2019-8-16 14:18, Chandan Rajendra wrote:
> > F2FS has a copy of "post read processing" code using which encrypted
> > file data is decrypted. This commit replaces it to make use of the
> > generic read_callbacks facility.
> I remember that previously Jaegeuk had mentioned f2fs will support compression
> later, and it needs to reuse 'post read processing' fwk.
> There is very initial version of compression feature in below link:
> https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git/log/?h=compression
> So my concern is how can we uplift the most common parts of this fwk into vfs,
> and meanwhile keeping the ability and flexibility when introducing private
> feature/step in specified filesytem(now f2fs)?
> According to current f2fs compression's requirement, maybe we can expand to
> - support callback to let filesystem set the function for the flow in
> decompression/verity/decryption step.
> - support to use individual/common workqueue according the parameter.
> Any thoughts?


F2FS can be made to use fscrypt's queue for decryption and hence can reuse
"read callbacks" code for decrypting data.

For decompression, we could have a STEP_MISC where we invoke a FS provided
callback function for FS specific post read processing? 

Something like the following can be implemented in read_callbacks(),
          case STEP_MISC:
                  if (ctx->enabled_steps & (1 << STEP_MISC)) {
                            ctx->fs_misc() must process bio in a workqueue
                            and later invoke read_callbacks() with
                            bio->bi_private's value as an argument.

The fs_misc() callback can be passed in by the filesystem when invoking


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