Merge branch 'bpf-support-atomic-update-for-htab-of-maps'

Hou Tao says:

====================
bpf: Support atomic update for htab of maps

From: Hou Tao <[email protected]>

Hi,

The motivation for the patch set comes from the question raised by Cody
Haas [1]. When trying to concurrently lookup and update an existing
element in a htab of maps, the lookup procedure may return -ENOENT
unexpectedly. The first revision of the patch set tried to resolve the
problem by making the insertion of the new element and the deletion of
the old element being atomic from the perspective of the lookup process.
While the solution would benefit all hash maps, it does not fully
resolved the problem due to the immediate reuse issue. Therefore, in v2
of the patch set, it only fixes the problem for fd htab.

Please see individual patches for details. Comments are always welcome.

v3:
 * rebase on bpf_next/for-next
 * add Acked-by tags

v2: https://lore.kernel.org/bpf/[email protected]/
  * only support atomic update for fd htab

v1: https://lore.kernel.org/bpf/[email protected]

[1]: https://lore.kernel.org/xdp-newbies/CAH7f-ULFTwKdoH_t2SFc5rWCVYLEg-14d1fBYWH2eekudsnTRg@mail.gmail.com/
====================

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: Alexei Starovoitov