Hello Jens, This patch series reworks blk-mq timeout handling by introducing a state machine per request. Please consider this patch series for inclusion in the upstream kernel. Bart. Changes compared to v10: - In patch 1/2, added "default y if 64BIT" to the "config ARCH_HAVE_CMPXCHG64" entry in arch/Kconfig. Left out the "select ARCH_HAVE_CMPXCHG64" statements that became superfluous due to this change (alpha, arm64, powerpc and s390). - Also in patch 1/2, only select ARCH_HAVE_CMPXCHG64 if X86_CMPXCHG64 has been selected. - In patch 2/2, moved blk_mq_change_rq_state() from blk-mq.h to blk-mq.c. - Added a comment header above __blk_mq_requeue_request() and blk_mq_requeue_request(). - Documented the MQ_RQ_* state transitions in block/blk-mq.h. - Left out the fourth argument of blk_mq_rq_set_deadline(). Changes compared to v9: - Addressed multiple comments related to patch 1/2: added CONFIG_ARCH_HAVE_CMPXCHG64 for riscv, modified features/locking/cmpxchg64/arch-support.txt as requested and made the order of the symbols in the arch/*/Kconfig alphabetical where possible. Changes compared to v8: - Split into two patches. - Moved the spin_lock_init() call from blk_mq_rq_ctx_init() into blk_mq_init_request(). - Fixed the deadline set by blk_add_timer(). - Surrounded the das_lock member with #ifndef CONFIG_ARCH_HAVE_CMPXCHG64 / #endif. Changes compared to v7: - Fixed the generation number mechanism. Note: with this patch applied the behavior of the block layer does not depend on the generation number. - Added more 32-bit architectures to the list of architectures on which cmpxchg64() should not be used. Changes compared to v6: - Used a union instead of bit manipulations to store multiple values into a single 64-bit field. - Reduced the size of the timeout field from 64 to 32 bits. - Made sure that the block layer still builds with this patch applied for the sh and mips architectures. - Fixed two sparse warnings that were introduced by this patch in the WRITE_ONCE() calls. Changes compared to v5: - Restored the synchronize_rcu() call between marking a request for timeout handling and the actual timeout handling to avoid that timeout handling starts while .queue_rq() is still in progress if the timeout is very short. - Only use cmpxchg() if another context could attempt to change the request state concurrently. Use WRITE_ONCE() otherwise. Changes compared to v4: - Addressed multiple review comments from Christoph. The most important are that atomic_long_cmpxchg() has been changed into cmpxchg() and also that there is now a nice and clean split between the legacy and blk-mq versions of blk_add_timer(). - Changed the patch name and modified the patch description because there is disagreement about whether or not the v4.16 blk-mq core can complete a single request twice. Kept the "Cc: stable" tag because of https://bugzilla.kernel.org/show_bug.cgi?id=199077. Changes compared to v3 (see also https://www.mail-archive.com/linux-block@xxxxxxxxxxxxxxx/msg20073.html): - Removed the spinlock again that was introduced to protect the request state. v4 uses atomic_long_cmpxchg() instead. - Split __deadline into two variables - one for the legacy block layer and one for blk-mq. Changes compared to v2 (https://www.mail-archive.com/linux-block@xxxxxxxxxxxxxxx/msg18338.html): - Rebased and retested on top of kernel v4.16. Changes compared to v1 (https://www.mail-archive.com/linux-block@xxxxxxxxxxxxxxx/msg18089.html): - Removed the gstate and aborted_gstate members of struct request and used the __deadline member to encode both the generation and state information. Bart Van Assche (2): arch/*: Add CONFIG_ARCH_HAVE_CMPXCHG64 blk-mq: Rework blk-mq timeout handling again .../features/locking/cmpxchg64/arch-support.txt | 33 +++ arch/Kconfig | 4 + arch/arm/Kconfig | 1 + arch/ia64/Kconfig | 1 + arch/m68k/Kconfig | 1 + arch/mips/Kconfig | 1 + arch/parisc/Kconfig | 1 + arch/riscv/Kconfig | 1 + arch/sparc/Kconfig | 1 + arch/x86/Kconfig | 1 + arch/xtensa/Kconfig | 1 + block/blk-core.c | 6 - block/blk-mq-debugfs.c | 1 - block/blk-mq.c | 238 ++++++++++----------- block/blk-mq.h | 64 +++--- block/blk-timeout.c | 133 ++++++++---- block/blk.h | 11 +- include/linux/blkdev.h | 47 ++-- 18 files changed, 308 insertions(+), 238 deletions(-) create mode 100644 Documentation/features/locking/cmpxchg64/arch-support.txt -- 2.16.3
