[LU-12382] Deadloop on tiny write

Related — Wed, 9 Oct 2019 07:07:34 +0000

For a small write(<4K), we will use tiny write and __generic_file_write_iter() will be called to handle it. On newer kernel(4.14 etc), the function is exported and will do something like following:

    |->__generic_file_write_iter
      |->generic_write_perform()

If iov_iter_count() passed in is 0, generic_write_perform() will try go to forever loop as bytes copied is always calculated as 0.

The problem is VFS doesn't always skip IO count zero before it comes to lower layer read/write hook, and we should do it by ourselves.

Whamcloud Community JIRA

[LU-12382] Deadloop on tiny write