From e2c87f484190b12fedcea9c428906aafcb8783cf Mon Sep 17 00:00:00 2001 From: Takashi Sakamoto Date: Tue, 20 Aug 2024 22:21:32 +0900 Subject: [PATCH] firewire: core: update fw_device outside of device_find_child() When detecting updates of bus topology, the data of fw_device is newly allocated and caches the content of configuration ROM from the corresponding node. Then, the tree of device is sought to find the previous data of fw_device corresponding to the node. If found, the previous data is updated and reused and the data of fw_device newly allocated is going to be released. The above procedure is done in the call of device_find_child(), however it is a bit abusing against the intention of the helper function, since it is preferable to find only without updating. This commit splits the update outside of the call. Cc: Zijun Hu Link: https://lore.kernel.org/r/20240820132132.28839-1-o-takashi@sakamocchi.jp Signed-off-by: Takashi Sakamoto --- drivers/firewire/core-device.c | 116 +++++++++++++++++---------------- 1 file changed, 59 insertions(+), 57 deletions(-) diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c index f71e118ef60a..a99fe35f1f0d 100644 --- a/drivers/firewire/core-device.c +++ b/drivers/firewire/core-device.c @@ -928,56 +928,6 @@ static void fw_device_update(struct work_struct *work) device_for_each_child(&device->device, NULL, update_unit); } -/* - * If a device was pending for deletion because its node went away but its - * bus info block and root directory header matches that of a newly discovered - * device, revive the existing fw_device. - * The newly allocated fw_device becomes obsolete instead. - */ -static int lookup_existing_device(struct device *dev, void *data) -{ - struct fw_device *old = fw_device(dev); - struct fw_device *new = data; - struct fw_card *card = new->card; - int match = 0; - - if (!is_fw_device(dev)) - return 0; - - guard(rwsem_read)(&fw_device_rwsem); // serialize config_rom access - guard(spinlock_irq)(&card->lock); // serialize node access - - if (memcmp(old->config_rom, new->config_rom, 6 * 4) == 0 && - atomic_cmpxchg(&old->state, - FW_DEVICE_GONE, - FW_DEVICE_RUNNING) == FW_DEVICE_GONE) { - struct fw_node *current_node = new->node; - struct fw_node *obsolete_node = old->node; - - new->node = obsolete_node; - new->node->data = new; - old->node = current_node; - old->node->data = old; - - old->max_speed = new->max_speed; - old->node_id = current_node->node_id; - smp_wmb(); /* update node_id before generation */ - old->generation = card->generation; - old->config_rom_retries = 0; - fw_notice(card, "rediscovered device %s\n", dev_name(dev)); - - old->workfn = fw_device_update; - fw_schedule_device_work(old, 0); - - if (current_node == card->root_node) - fw_schedule_bm_work(card, 0); - - match = 1; - } - - return match; -} - enum { BC_UNKNOWN = 0, BC_UNIMPLEMENTED, BC_IMPLEMENTED, }; static void set_broadcast_channel(struct fw_device *device, int generation) @@ -1038,12 +988,24 @@ int fw_device_set_broadcast_channel(struct device *dev, void *gen) return 0; } +static int compare_configuration_rom(struct device *dev, void *data) +{ + const struct fw_device *old = fw_device(dev); + const u32 *config_rom = data; + + if (!is_fw_device(dev)) + return 0; + + // Compare the bus information block and root_length/root_crc. + return !memcmp(old->config_rom, config_rom, 6 * 4); +} + static void fw_device_init(struct work_struct *work) { struct fw_device *device = container_of(work, struct fw_device, work.work); struct fw_card *card = device->card; - struct device *revived_dev; + struct device *found; u32 minor; int ret; @@ -1071,13 +1033,53 @@ static void fw_device_init(struct work_struct *work) return; } - revived_dev = device_find_child(card->device, - device, lookup_existing_device); - if (revived_dev) { - put_device(revived_dev); - fw_device_release(&device->device); + // If a device was pending for deletion because its node went away but its bus info block + // and root directory header matches that of a newly discovered device, revive the + // existing fw_device. The newly allocated fw_device becomes obsolete instead. + // + // serialize config_rom access. + scoped_guard(rwsem_read, &fw_device_rwsem) { + found = device_find_child(card->device, (void *)device->config_rom, + compare_configuration_rom); + } + if (found) { + struct fw_device *reused = fw_device(found); - return; + if (atomic_cmpxchg(&reused->state, + FW_DEVICE_GONE, + FW_DEVICE_RUNNING) == FW_DEVICE_GONE) { + // serialize node access + scoped_guard(spinlock_irq, &card->lock) { + struct fw_node *current_node = device->node; + struct fw_node *obsolete_node = reused->node; + + device->node = obsolete_node; + device->node->data = device; + reused->node = current_node; + reused->node->data = reused; + + reused->max_speed = device->max_speed; + reused->node_id = current_node->node_id; + smp_wmb(); /* update node_id before generation */ + reused->generation = card->generation; + reused->config_rom_retries = 0; + fw_notice(card, "rediscovered device %s\n", + dev_name(found)); + + reused->workfn = fw_device_update; + fw_schedule_device_work(reused, 0); + + if (current_node == card->root_node) + fw_schedule_bm_work(card, 0); + } + + put_device(found); + fw_device_release(&device->device); + + return; + } + + put_device(found); } device_initialize(&device->device);