Re: [PATCH V18 00/18] Allow I/O on blocks whose size is less than page size

[Chandan Rajendra <chandan@linux.vnet.ibm.com>]

On Tuesday 26 Apr 2016 14:54:46 Filipe Manana wrote:

> Hi Chandan,
> 
> What does it mean the tests don't pass? Is there absolutely no code
> changes for scrub and compression, or there is but still needs more
> working, or what?
>

Hi Filipe,

The patches that have been sent have no changes made with respect to either
scrub or compression.

> What happens if, when one is using block size < page size, and enables
> compression on a single file (i.e. fs not mounted with -o compress or
> force-compress), we start writing and read to the file? Does it result
> in the syscalls failing with -EIO or some other error, does it result
> in crashes (BUG_ON(), etc), dues it result in transparently falling
> back to non compression mode, or what happens exactly?

With the current patchset, reading/writing to a compressed file in
(block size == page size) scenario works fine. However reading/writing to a
compressed file in (block size < page size) results in crashes.

> 
> Same kind of question regarding scrub.
>

Scrub works fine for (block size == page size) scenario. However, Scrub ioctl
returns -EINVAL for the case where block size != page size. Without the block
size check, scrub might result in crashes.

-- 
chandan