On 03/16/2017 08:08 AM, Matthew Wilcox wrote:

On Wed, Mar 15, 2017 at 04:51:02PM -0500, Goldwyn Rodrigues wrote:

quoted

This introduces a new function filemap_range_has_page() which
returns true if the file's mapping has a page within the range
mentioned.

I thought you were going to replace this patch with one that starts
writeback for these pages but does not wait for them?

As mentioned by Jan, Flags to filemap_write_and_wait_range are
unnecessarily complicated. The AIO-DIO API users who eye for performance
usually are careful with page writes/evictions. As a fallback, they can
(and should) go the wait route (without  IOCB_RW_FLAG_NOWAIT).

Finally, my take on this is that we don't want to perform tasks for a
following system call, which may or may not immediately follow the
current one. May not, because an application (DB) will offload the task
from the CPU thread to the I/O thread in case of -EAGAIN. A system call
should be complete in itself (and do the minimum, what is asked).


-- 
Goldwyn