Re: [net PATCH 1/2] ipv4: Restore fib_trie_flush_external function and fix call ordering

Tue, Nov 15, 2016 at 09:49:02PM CET, alexander.h.duyck@intel.com wrote:

On Tue, 2016-11-15 at 21:31 +0100, Jiri Pirko wrote:

quoted

Tue, Nov 15, 2016 at 09:29:09PM CET, alexander.h.duyck@intel.com wrote:

quoted

On Tue, 2016-11-15 at 20:51 +0100, Jiri Pirko wrote:

quoted

Tue, Nov 15, 2016 at 11:46:06AM CET, alexander.h.duyck@intel.com wrote:

quoted

The patch that removed the FIB offload infrastructure was a bit too
aggressive and also removed code needed to clean up us splitting the table
if additional rules were added.  Specifically the function
fib_trie_flush_external was called at the end of a new rule being added to
flush the foreign trie entries from the main trie.

I updated the code so that we only call fib_trie_flush_external on the main
table so that we flush the entries for local from main.  This way we don't
call it for every rule change which is what was happening previously.

Well, the function was introduced by:

commit 104616e74e0b464d449fdd2ee2f547d2fad71610
Author: Scott Feldman [off-list ref]
Date:   Thu Mar 5 21:21:16 2015 -0800

    switchdev: don't support custom ip rules, for now
    
    Keep switchdev FIB offload model simple for now and don't allow custom ip
    rules.

Why this was not needed before? What changed in between:
104616e74e0b464d449fdd2ee2f547d2fad71610 ("switchdev: don't support custom ip rules, for now")
and
347e3b28c1ba2 ("switchdev: remove FIB offload infrastructure")

We collapsed the two tables into one in commit 0ddcf43d5d4a ("ipv4: FIB
Local/MAIN table collapse") which was submitted the next day.  Scott
and I were working on things at the same time and the
fib_table_flush_external function was something we had worked out that
would allow him to take care of his use case and me to take care of
cleaning up the tables after unmerging.

Okay. But please name the fuction differently, as it does not flush
external. Thanks!

You and I have different meanings for "external".

In my case I am flushing entries that belong to a foreign "external"
table from the table specified. So by "external" I am referring to
entries that don't actually live in main, but actually reside in local.
If you take a look at fib_table_flush that gets rid of all entries,
fib_table_flush_external simply clears the foreign ones.

Also I'd rather maintain naming since it makes it easier if we need to
backport fixes.

Finally, the flag RTNH_F_EXTERNAL was renamed over a year ago in commit
36583eb54d46c ("rename RTNH_F_EXTERNAL to RTNH_F_OFFLOAD") so there
isn't too much likelihood of this being confused for something that
handles offloaded entries.  If you take a look in net/ipv4/* after your
patch there isn't actually anything that references the word external
so the likelihood for any confusion is extremely low.

Okay. But if you can, please put a comment to this function in order to
prevent future confusion. Thanks!