Sasha Levin
2023-Aug-29 13:31 UTC
[PATCH AUTOSEL 6.4 08/17] virtio-mem: keep retrying on offline_and_remove_memory() errors in Sub Block Mode (SBM)
From: David Hildenbrand <david at redhat.com> [ Upstream commit a31648fd4f96fbe0a4d0aeb16b57a2405c6943c0 ] In case offline_and_remove_memory() fails in SBM, we leave a completely unplugged Linux memory block stick around until we try plugging memory again. We won't try removing that memory block again. offline_and_remove_memory() may, for example, fail if we're racing with another alloc_contig_range() user, if allocating temporary memory fails, or if some memory notifier rejected the offlining request. Let's handle that case better, by simple retrying to offline and remove such memory. Tested using CONFIG_MEMORY_NOTIFIER_ERROR_INJECT. Signed-off-by: David Hildenbrand <david at redhat.com> Message-Id: <20230713145551.2824980-4-david at redhat.com> Signed-off-by: Michael S. Tsirkin <mst at redhat.com> Signed-off-by: Sasha Levin <sashal at kernel.org> --- drivers/virtio/virtio_mem.c | 92 +++++++++++++++++++++++++++++-------- 1 file changed, 73 insertions(+), 19 deletions(-) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 1a76ba2bc118c..a5cf92e3e5af2 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -168,6 +168,13 @@ struct virtio_mem { /* The number of subblocks per Linux memory block. */ uint32_t sbs_per_mb; + /* + * Some of the Linux memory blocks tracked as "partially + * plugged" are completely unplugged and can be offlined + * and removed -- which previously failed. + */ + bool have_unplugged_mb; + /* Summary of all memory block states. */ unsigned long mb_count[VIRTIO_MEM_SBM_MB_COUNT]; @@ -765,6 +772,34 @@ static int virtio_mem_sbm_offline_and_remove_mb(struct virtio_mem *vm, return virtio_mem_offline_and_remove_memory(vm, addr, size); } +/* + * Try (offlining and) removing memory from Linux in case all subblocks are + * unplugged. Can be called on online and offline memory blocks. + * + * May modify the state of memory blocks in virtio-mem. + */ +static int virtio_mem_sbm_try_remove_unplugged_mb(struct virtio_mem *vm, + unsigned long mb_id) +{ + int rc; + + /* + * Once all subblocks of a memory block were unplugged, offline and + * remove it. + */ + if (!virtio_mem_sbm_test_sb_unplugged(vm, mb_id, 0, vm->sbm.sbs_per_mb)) + return 0; + + /* offline_and_remove_memory() works for online and offline memory. */ + mutex_unlock(&vm->hotplug_mutex); + rc = virtio_mem_sbm_offline_and_remove_mb(vm, mb_id); + mutex_lock(&vm->hotplug_mutex); + if (!rc) + virtio_mem_sbm_set_mb_state(vm, mb_id, + VIRTIO_MEM_SBM_MB_UNUSED); + return rc; +} + /* * See virtio_mem_offline_and_remove_memory(): Try to offline and remove a * all Linux memory blocks covered by the big block. @@ -1988,20 +2023,10 @@ static int virtio_mem_sbm_unplug_any_sb_online(struct virtio_mem *vm, } unplugged: - /* - * Once all subblocks of a memory block were unplugged, offline and - * remove it. This will usually not fail, as no memory is in use - * anymore - however some other notifiers might NACK the request. - */ - if (virtio_mem_sbm_test_sb_unplugged(vm, mb_id, 0, vm->sbm.sbs_per_mb)) { - mutex_unlock(&vm->hotplug_mutex); - rc = virtio_mem_sbm_offline_and_remove_mb(vm, mb_id); - mutex_lock(&vm->hotplug_mutex); - if (!rc) - virtio_mem_sbm_set_mb_state(vm, mb_id, - VIRTIO_MEM_SBM_MB_UNUSED); - } - + rc = virtio_mem_sbm_try_remove_unplugged_mb(vm, mb_id); + if (rc) + vm->sbm.have_unplugged_mb = 1; + /* Ignore errors, this is not critical. We'll retry later. */ return 0; } @@ -2253,12 +2278,13 @@ static int virtio_mem_unplug_request(struct virtio_mem *vm, uint64_t diff) /* * Try to unplug all blocks that couldn't be unplugged before, for example, - * because the hypervisor was busy. + * because the hypervisor was busy. Further, offline and remove any memory + * blocks where we previously failed. */ -static int virtio_mem_unplug_pending_mb(struct virtio_mem *vm) +static int virtio_mem_cleanup_pending_mb(struct virtio_mem *vm) { unsigned long id; - int rc; + int rc = 0; if (!vm->in_sbm) { virtio_mem_bbm_for_each_bb(vm, id, @@ -2280,6 +2306,27 @@ static int virtio_mem_unplug_pending_mb(struct virtio_mem *vm) VIRTIO_MEM_SBM_MB_UNUSED); } + if (!vm->sbm.have_unplugged_mb) + return 0; + + /* + * Let's retry (offlining and) removing completely unplugged Linux + * memory blocks. + */ + vm->sbm.have_unplugged_mb = false; + + mutex_lock(&vm->hotplug_mutex); + virtio_mem_sbm_for_each_mb(vm, id, VIRTIO_MEM_SBM_MB_MOVABLE_PARTIAL) + rc |= virtio_mem_sbm_try_remove_unplugged_mb(vm, id); + virtio_mem_sbm_for_each_mb(vm, id, VIRTIO_MEM_SBM_MB_KERNEL_PARTIAL) + rc |= virtio_mem_sbm_try_remove_unplugged_mb(vm, id); + virtio_mem_sbm_for_each_mb(vm, id, VIRTIO_MEM_SBM_MB_OFFLINE_PARTIAL) + rc |= virtio_mem_sbm_try_remove_unplugged_mb(vm, id); + mutex_unlock(&vm->hotplug_mutex); + + if (rc) + vm->sbm.have_unplugged_mb = true; + /* Ignore errors, this is not critical. We'll retry later. */ return 0; } @@ -2361,9 +2408,9 @@ static void virtio_mem_run_wq(struct work_struct *work) virtio_mem_refresh_config(vm); } - /* Unplug any leftovers from previous runs */ + /* Cleanup any leftovers from previous runs */ if (!rc) - rc = virtio_mem_unplug_pending_mb(vm); + rc = virtio_mem_cleanup_pending_mb(vm); if (!rc && vm->requested_size != vm->plugged_size) { if (vm->requested_size > vm->plugged_size) { @@ -2375,6 +2422,13 @@ static void virtio_mem_run_wq(struct work_struct *work) } } + /* + * Keep retrying to offline and remove completely unplugged Linux + * memory blocks. + */ + if (!rc && vm->in_sbm && vm->sbm.have_unplugged_mb) + rc = -EBUSY; + switch (rc) { case 0: vm->retry_timer_ms = VIRTIO_MEM_RETRY_TIMER_MIN_MS; -- 2.40.1