dm thin: fix race between simultaneous io and discards to same block

[linux/fpc-iii.git] / drivers / base / dd.c

/*
 * drivers/base/dd.c - The core device/driver interactions.
 *
 * This file contains the (sometimes tricky) code that controls the
 * interactions between devices and drivers, which primarily includes
 * driver binding and unbinding.
 *
 * All of this code used to exist in drivers/base/bus.c, but was
 * relocated to here in the name of compartmentalization (since it wasn't
 * strictly code just for the 'struct bus_type'.
 *
 * Copyright (c) 2002-5 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2007-2009 Novell Inc.
 *
 * This file is released under the GPLv2
 */

#include <linux/device.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/async.h>
#include <linux/pm_runtime.h>

#include "base.h"
#include "power/power.h"

/*
 * Deferred Probe infrastructure.
 *
 * Sometimes driver probe order matters, but the kernel doesn't always have
 * dependency information which means some drivers will get probed before a
 * resource it depends on is available.  For example, an SDHCI driver may
 * first need a GPIO line from an i2c GPIO controller before it can be
 * initialized.  If a required resource is not available yet, a driver can
 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
 *
 * Deferred probe maintains two lists of devices, a pending list and an active
 * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
 * pending list.  A successful driver probe will trigger moving all devices
 * from the pending to the active list so that the workqueue will eventually
 * retry them.
 *
 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
 * of the (struct device*)->p->deferred_probe pointers are manipulated
 */
static DEFINE_MUTEX(deferred_probe_mutex);
static LIST_HEAD(deferred_probe_pending_list);
static LIST_HEAD(deferred_probe_active_list);
static struct workqueue_struct *deferred_wq;

/**
 * deferred_probe_work_func() - Retry probing devices in the active list.
 */
static void deferred_probe_work_func(struct work_struct *work)
{
        struct device *dev;
        struct device_private *private;
        /*
         * This block processes every device in the deferred 'active' list.
         * Each device is removed from the active list and passed to
         * bus_probe_device() to re-attempt the probe.  The loop continues
         * until every device in the active list is removed and retried.
         *
         * Note: Once the device is removed from the list and the mutex is
         * released, it is possible for the device get freed by another thread
         * and cause a illegal pointer dereference.  This code uses
         * get/put_device() to ensure the device structure cannot disappear
         * from under our feet.
         */
        mutex_lock(&deferred_probe_mutex);
        while (!list_empty(&deferred_probe_active_list)) {
                private = list_first_entry(&deferred_probe_active_list,
                                        typeof(*dev->p), deferred_probe);
                dev = private->device;
                list_del_init(&private->deferred_probe);

                get_device(dev);

                /*
                 * Drop the mutex while probing each device; the probe path may
                 * manipulate the deferred list
                 */
                mutex_unlock(&deferred_probe_mutex);

                /*
                 * Force the device to the end of the dpm_list since
                 * the PM code assumes that the order we add things to
                 * the list is a good order for suspend but deferred
                 * probe makes that very unsafe.
                 */
                device_pm_lock();
                device_pm_move_last(dev);
                device_pm_unlock();

                dev_dbg(dev, "Retrying from deferred list\n");
                bus_probe_device(dev);

                mutex_lock(&deferred_probe_mutex);

                put_device(dev);
        }
        mutex_unlock(&deferred_probe_mutex);
}
static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);

static void driver_deferred_probe_add(struct device *dev)
{
        mutex_lock(&deferred_probe_mutex);
        if (list_empty(&dev->p->deferred_probe)) {
                dev_dbg(dev, "Added to deferred list\n");
                list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
        }
        mutex_unlock(&deferred_probe_mutex);
}

void driver_deferred_probe_del(struct device *dev)
{
        mutex_lock(&deferred_probe_mutex);
        if (!list_empty(&dev->p->deferred_probe)) {
                dev_dbg(dev, "Removed from deferred list\n");
                list_del_init(&dev->p->deferred_probe);
        }
        mutex_unlock(&deferred_probe_mutex);
}

static bool driver_deferred_probe_enable = false;
/**
 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 *
 * This functions moves all devices from the pending list to the active
 * list and schedules the deferred probe workqueue to process them.  It
 * should be called anytime a driver is successfully bound to a device.
 */
static void driver_deferred_probe_trigger(void)
{
        if (!driver_deferred_probe_enable)
                return;

        /*
         * A successful probe means that all the devices in the pending list
         * should be triggered to be reprobed.  Move all the deferred devices
         * into the active list so they can be retried by the workqueue
         */
        mutex_lock(&deferred_probe_mutex);
        list_splice_tail_init(&deferred_probe_pending_list,
                              &deferred_probe_active_list);
        mutex_unlock(&deferred_probe_mutex);

        /*
         * Kick the re-probe thread.  It may already be scheduled, but it is
         * safe to kick it again.
         */
        queue_work(deferred_wq, &deferred_probe_work);
}

/**
 * deferred_probe_initcall() - Enable probing of deferred devices
 *
 * We don't want to get in the way when the bulk of drivers are getting probed.
 * Instead, this initcall makes sure that deferred probing is delayed until
 * late_initcall time.
 */
static int deferred_probe_initcall(void)
{
        deferred_wq = create_singlethread_workqueue("deferwq");
        if (WARN_ON(!deferred_wq))
                return -ENOMEM;

        driver_deferred_probe_enable = true;
        driver_deferred_probe_trigger();
        return 0;
}
late_initcall(deferred_probe_initcall);

static void driver_bound(struct device *dev)
{
        if (klist_node_attached(&dev->p->knode_driver)) {
                printk(KERN_WARNING "%s: device %s already bound\n",
                        __func__, kobject_name(&dev->kobj));
                return;
        }

        pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
                 __func__, dev->driver->name);

        klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);

        /*
         * Make sure the device is no longer in one of the deferred lists and
         * kick off retrying all pending devices
         */
        driver_deferred_probe_del(dev);
        driver_deferred_probe_trigger();

        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_BOUND_DRIVER, dev);
}

static int driver_sysfs_add(struct device *dev)
{
        int ret;

        if (dev->bus)
                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                             BUS_NOTIFY_BIND_DRIVER, dev);

        ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
                          kobject_name(&dev->kobj));
        if (ret == 0) {
                ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
                                        "driver");
                if (ret)
                        sysfs_remove_link(&dev->driver->p->kobj,
                                        kobject_name(&dev->kobj));
        }
        return ret;
}

static void driver_sysfs_remove(struct device *dev)
{
        struct device_driver *drv = dev->driver;

        if (drv) {
                sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
                sysfs_remove_link(&dev->kobj, "driver");
        }
}

/**
 * device_bind_driver - bind a driver to one device.
 * @dev: device.
 *
 * Allow manual attachment of a driver to a device.
 * Caller must have already set @dev->driver.
 *
 * Note that this does not modify the bus reference count
 * nor take the bus's rwsem. Please verify those are accounted
 * for before calling this. (It is ok to call with no other effort
 * from a driver's probe() method.)
 *
 * This function must be called with the device lock held.
 */
int device_bind_driver(struct device *dev)
{
        int ret;

        ret = driver_sysfs_add(dev);
        if (!ret)
                driver_bound(dev);
        return ret;
}
EXPORT_SYMBOL_GPL(device_bind_driver);

static atomic_t probe_count = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);

static int really_probe(struct device *dev, struct device_driver *drv)
{
        int ret = 0;

        atomic_inc(&probe_count);
        pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
                 drv->bus->name, __func__, drv->name, dev_name(dev));
        WARN_ON(!list_empty(&dev->devres_head));

        dev->driver = drv;
        if (driver_sysfs_add(dev)) {
                printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
                        __func__, dev_name(dev));
                goto probe_failed;
        }

        if (dev->bus->probe) {
                ret = dev->bus->probe(dev);
                if (ret)
                        goto probe_failed;
        } else if (drv->probe) {
                ret = drv->probe(dev);
                if (ret)
                        goto probe_failed;
        }

        driver_bound(dev);
        ret = 1;
        pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
                 drv->bus->name, __func__, dev_name(dev), drv->name);
        goto done;

probe_failed:
        devres_release_all(dev);
        driver_sysfs_remove(dev);
        dev->driver = NULL;
        dev_set_drvdata(dev, NULL);

        if (ret == -EPROBE_DEFER) {
                /* Driver requested deferred probing */
                dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
                driver_deferred_probe_add(dev);
        } else if (ret != -ENODEV && ret != -ENXIO) {
                /* driver matched but the probe failed */
                printk(KERN_WARNING
                       "%s: probe of %s failed with error %d\n",
                       drv->name, dev_name(dev), ret);
        } else {
                pr_debug("%s: probe of %s rejects match %d\n",
                       drv->name, dev_name(dev), ret);
        }
        /*
         * Ignore errors returned by ->probe so that the next driver can try
         * its luck.
         */
        ret = 0;
done:
        atomic_dec(&probe_count);
        wake_up(&probe_waitqueue);
        return ret;
}

/**
 * driver_probe_done
 * Determine if the probe sequence is finished or not.
 *
 * Should somehow figure out how to use a semaphore, not an atomic variable...
 */
int driver_probe_done(void)
{
        pr_debug("%s: probe_count = %d\n", __func__,
                 atomic_read(&probe_count));
        if (atomic_read(&probe_count))
                return -EBUSY;
        return 0;
}

/**
 * wait_for_device_probe
 * Wait for device probing to be completed.
 */
void wait_for_device_probe(void)
{
        /* wait for the known devices to complete their probing */
        wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
        async_synchronize_full();
}
EXPORT_SYMBOL_GPL(wait_for_device_probe);

/**
 * driver_probe_device - attempt to bind device & driver together
 * @drv: driver to bind a device to
 * @dev: device to try to bind to the driver
 *
 * This function returns -ENODEV if the device is not registered,
 * 1 if the device is bound successfully and 0 otherwise.
 *
 * This function must be called with @dev lock held.  When called for a
 * USB interface, @dev->parent lock must be held as well.
 */
int driver_probe_device(struct device_driver *drv, struct device *dev)
{
        int ret = 0;

        if (!device_is_registered(dev))
                return -ENODEV;

        pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
                 drv->bus->name, __func__, dev_name(dev), drv->name);

        pm_runtime_barrier(dev);
        ret = really_probe(dev, drv);
        pm_runtime_idle(dev);

        return ret;
}

static int __device_attach(struct device_driver *drv, void *data)
{
        struct device *dev = data;

        if (!driver_match_device(drv, dev))
                return 0;

        return driver_probe_device(drv, dev);
}

/**
 * device_attach - try to attach device to a driver.
 * @dev: device.
 *
 * Walk the list of drivers that the bus has and call
 * driver_probe_device() for each pair. If a compatible
 * pair is found, break out and return.
 *
 * Returns 1 if the device was bound to a driver;
 * 0 if no matching driver was found;
 * -ENODEV if the device is not registered.
 *
 * When called for a USB interface, @dev->parent lock must be held.
 */
int device_attach(struct device *dev)
{
        int ret = 0;

        device_lock(dev);
        if (dev->driver) {
                if (klist_node_attached(&dev->p->knode_driver)) {
                        ret = 1;
                        goto out_unlock;
                }
                ret = device_bind_driver(dev);
                if (ret == 0)
                        ret = 1;
                else {
                        dev->driver = NULL;
                        ret = 0;
                }
        } else {
                ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
                pm_runtime_idle(dev);
        }
out_unlock:
        device_unlock(dev);
        return ret;
}
EXPORT_SYMBOL_GPL(device_attach);

static int __driver_attach(struct device *dev, void *data)
{
        struct device_driver *drv = data;

        /*
         * Lock device and try to bind to it. We drop the error
         * here and always return 0, because we need to keep trying
         * to bind to devices and some drivers will return an error
         * simply if it didn't support the device.
         *
         * driver_probe_device() will spit a warning if there
         * is an error.
         */

        if (!driver_match_device(drv, dev))
                return 0;

        if (dev->parent)        /* Needed for USB */
                device_lock(dev->parent);
        device_lock(dev);
        if (!dev->driver)
                driver_probe_device(drv, dev);
        device_unlock(dev);
        if (dev->parent)
                device_unlock(dev->parent);

        return 0;
}

/**
 * driver_attach - try to bind driver to devices.
 * @drv: driver.
 *
 * Walk the list of devices that the bus has on it and try to
 * match the driver with each one.  If driver_probe_device()
 * returns 0 and the @dev->driver is set, we've found a
 * compatible pair.
 */
int driver_attach(struct device_driver *drv)
{
        return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
}
EXPORT_SYMBOL_GPL(driver_attach);

/*
 * __device_release_driver() must be called with @dev lock held.
 * When called for a USB interface, @dev->parent lock must be held as well.
 */
static void __device_release_driver(struct device *dev)
{
        struct device_driver *drv;

        drv = dev->driver;
        if (drv) {
                pm_runtime_get_sync(dev);

                driver_sysfs_remove(dev);

                if (dev->bus)
                        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                                     BUS_NOTIFY_UNBIND_DRIVER,
                                                     dev);

                pm_runtime_put_sync(dev);

                if (dev->bus && dev->bus->remove)
                        dev->bus->remove(dev);
                else if (drv->remove)
                        drv->remove(dev);
                devres_release_all(dev);
                dev->driver = NULL;
                dev_set_drvdata(dev, NULL);
                klist_remove(&dev->p->knode_driver);
                if (dev->bus)
                        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
                                                     BUS_NOTIFY_UNBOUND_DRIVER,
                                                     dev);

        }
}

/**
 * device_release_driver - manually detach device from driver.
 * @dev: device.
 *
 * Manually detach device from driver.
 * When called for a USB interface, @dev->parent lock must be held.
 */
void device_release_driver(struct device *dev)
{
        /*
         * If anyone calls device_release_driver() recursively from
         * within their ->remove callback for the same device, they
         * will deadlock right here.
         */
        device_lock(dev);
        __device_release_driver(dev);
        device_unlock(dev);
}
EXPORT_SYMBOL_GPL(device_release_driver);

/**
 * driver_detach - detach driver from all devices it controls.
 * @drv: driver.
 */
void driver_detach(struct device_driver *drv)
{
        struct device_private *dev_prv;
        struct device *dev;

        for (;;) {
                spin_lock(&drv->p->klist_devices.k_lock);
                if (list_empty(&drv->p->klist_devices.k_list)) {
                        spin_unlock(&drv->p->klist_devices.k_lock);
                        break;
                }
                dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
                                     struct device_private,
                                     knode_driver.n_node);
                dev = dev_prv->device;
                get_device(dev);
                spin_unlock(&drv->p->klist_devices.k_lock);

                if (dev->parent)        /* Needed for USB */
                        device_lock(dev->parent);
                device_lock(dev);
                if (dev->driver == drv)
                        __device_release_driver(dev);
                device_unlock(dev);
                if (dev->parent)
                        device_unlock(dev->parent);
                put_device(dev);
        }
}

/*
 * These exports can't be _GPL due to .h files using this within them, and it
 * might break something that was previously working...
 */
void *dev_get_drvdata(const struct device *dev)
{
        if (dev && dev->p)
                return dev->p->driver_data;
        return NULL;
}
EXPORT_SYMBOL(dev_get_drvdata);

int dev_set_drvdata(struct device *dev, void *data)
{
        int error;

        if (!dev->p) {
                error = device_private_init(dev);
                if (error)
                        return error;
        }
        dev->p->driver_data = data;
        return 0;
}
EXPORT_SYMBOL(dev_set_drvdata);