[PATCH 0/2] test/link-timeout: add regression tests for link timeout chains

This series adds liburing regression tests for read -> link timeout -> nop
chains on pipes.  The tests complement two independent io_uring kernel
changes submitted separately:

  - io_uring/rw: fix link failure on successful pipe short reads
  - io_uring/timeout: cancel pending link timeouts from ltimeout_list

Without the kernel fixes, short pipe reads can incorrectly fail the link
chain and cancel subsequent requests, and TIMEOUT_REMOVE against a pending
link timeout returns -ENOENT because only timeout_list was scanned.

Patch summary
-------------

 1/2 test/link-timeout: add natural disarm chain with short pipe read
 2/2 test/link-timeout: add link timeout remove tests

Test cases
----------

  - test_link_timeout_natural_disarm_chain (patch 1)
    read(LINK) -> link timeout(LINK) -> nop, with a 1-byte pipe write.
    Expect read=1, link timeout=-ECANCELED, nop=0 after natural disarm.
    Requires the kernel short read completion fix.

  - test_link_timeout_remove (patch 2)
    read(LINK) -> link timeout, then TIMEOUT_REMOVE by user_data.
    Expect remove=0 and link timeout=-ECANCELED.
    Requires the kernel link timeout cancel fix.

  - test_link_timeout_remove_chain (patch 2)
    read(LINK) -> link timeout(LINK) -> nop, then TIMEOUT_REMOVE, then
    complete the read with a 1-byte write.
    Expect remove=0, link timeout=-ECANCELED, read=1, nop=0.
    Requires both kernel fixes.

Test plan
---------

With both kernel patches applied:

  $ make -C test link-timeout.t
  $ ./test/link-timeout.t

Without the kernel patches, the new tests are expected to fail on current
upstream kernels.

test/link-timeout: add natural disarm chain with short pipe read
test/link-timeout: add link timeout remove tests
--
2.25.1

Signed-off-by: Yang Xiuwei <[email protected]>