This series addresses a rare but real error condition when a CQE is dropped. Many applications rely on 1 SQE resulting in 1 CQE and may even block waiting for the CQE. In overflow conditions if the GFP_ATOMIC allocation fails, the CQE is dropped and a counter is incremented. However the application is not actively signalled that something bad has happened. We would like to indicate this error condition to the application but in a way that does not rely on the application doing invasive changes such as checking a flag before each wait. This series returns an error code to the application when the error hits, and then resets the error condition. If the application is ok with this error it can continue as is, or more likely it can clean up sanely. Patches 1&2 add tracing for overflows Patches 3&4 prep for adding this error Patch 5 is the main one returning an error Patch 6 allows liburing to test these conditions more easily with IOPOLL Dylan Yudaken (6): io_uring: add trace support for CQE overflow io_uring: trace cqe overflows io_uring: rework io_uring_enter to simplify return value io_uring: use constants for cq_overflow bitfield io_uring: return an error when cqe is dropped io_uring: allow NOP opcode in IOPOLL mode fs/io_uring.c | 89 ++++++++++++++++++++++----------- include/trace/events/io_uring.h | 42 +++++++++++++++- 2 files changed, 102 insertions(+), 29 deletions(-) base-commit: 7c648b7d6186c59ed3a0e0ae4b774aaf4b415ef2 -- 2.30.2
