/*
 * Copyright(c) 2016 - 2017 Intel Corporation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */
#include <linux/pagemap.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/pfn_t.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/dax.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include "dax-private.h"
#include "dax.h"

static struct class *dax_class;

/*
 * Rely on the fact that drvdata is set before the attributes are
 * registered, and that the attributes are unregistered before drvdata
 * is cleared to assume that drvdata is always valid.
 */
static ssize_t id_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct dax_region *dax_region = dev_get_drvdata(dev);

        return sprintf(buf, "%d\n", dax_region->id);
}
static DEVICE_ATTR_RO(id);

static ssize_t region_size_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct dax_region *dax_region = dev_get_drvdata(dev);

        return sprintf(buf, "%llu\n", (unsigned long long)
                        resource_size(&dax_region->res));
}
static struct device_attribute dev_attr_region_size = __ATTR(size, 0444,
                region_size_show, NULL);

static ssize_t align_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct dax_region *dax_region = dev_get_drvdata(dev);

        return sprintf(buf, "%u\n", dax_region->align);
}
static DEVICE_ATTR_RO(align);

static struct attribute *dax_region_attributes[] = {
        &dev_attr_region_size.attr,
        &dev_attr_align.attr,
        &dev_attr_id.attr,
        NULL,
};

static const struct attribute_group dax_region_attribute_group = {
        .name = "dax_region",
        .attrs = dax_region_attributes,
};

static const struct attribute_group *dax_region_attribute_groups[] = {
        &dax_region_attribute_group,
        NULL,
};

static void dax_region_free(struct kref *kref)
{
        struct dax_region *dax_region;

        dax_region = container_of(kref, struct dax_region, kref);
        kfree(dax_region);
}

void dax_region_put(struct dax_region *dax_region)
{
        kref_put(&dax_region->kref, dax_region_free);
}
EXPORT_SYMBOL_GPL(dax_region_put);

static void dax_region_unregister(void *region)
{
        struct dax_region *dax_region = region;

        sysfs_remove_groups(&dax_region->dev->kobj,
                        dax_region_attribute_groups);
        dax_region_put(dax_region);
}

struct dax_region *alloc_dax_region(struct device *parent, int region_id,
                struct resource *res, unsigned int align, void *addr,
                unsigned long pfn_flags)
{
        struct dax_region *dax_region;

        /*
         * The DAX core assumes that it can store its private data in
         * parent->driver_data. This WARN is a reminder / safeguard for
         * developers of device-dax drivers.
         */
        if (dev_get_drvdata(parent)) {
                dev_WARN(parent, "dax core failed to setup private data\n");
                return NULL;
        }

        if (!IS_ALIGNED(res->start, align)
                        || !IS_ALIGNED(resource_size(res), align))
                return NULL;

        dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
        if (!dax_region)
                return NULL;

        dev_set_drvdata(parent, dax_region);
        memcpy(&dax_region->res, res, sizeof(*res));
        dax_region->pfn_flags = pfn_flags;
        kref_init(&dax_region->kref);
        dax_region->id = region_id;
        ida_init(&dax_region->ida);
        dax_region->align = align;
        dax_region->dev = parent;
        dax_region->base = addr;
        if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
                kfree(dax_region);
                return NULL;
        }

        kref_get(&dax_region->kref);
        if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region))
                return NULL;
        return dax_region;
}
EXPORT_SYMBOL_GPL(alloc_dax_region);

static struct dev_dax *to_dev_dax(struct device *dev)
{
        return container_of(dev, struct dev_dax, dev);
}

static ssize_t size_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct dev_dax *dev_dax = to_dev_dax(dev);
        unsigned long long size = 0;
        int i;

        for (i = 0; i < dev_dax->num_resources; i++)
                size += resource_size(&dev_dax->res[i]);

        return sprintf(buf, "%llu\n", size);
}
static DEVICE_ATTR_RO(size);

static struct attribute *dev_dax_attributes[] = {
        &dev_attr_size.attr,
        NULL,
};

static const struct attribute_group dev_dax_attribute_group = {
        .attrs = dev_dax_attributes,
};

static const struct attribute_group *dax_attribute_groups[] = {
        &dev_dax_attribute_group,
        NULL,
};

static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
                const char *func)
{
        struct dax_region *dax_region = dev_dax->region;
        struct device *dev = &dev_dax->dev;
        unsigned long mask;

        if (!dax_alive(dev_dax->dax_dev))
                return -ENXIO;

        /* prevent private mappings from being established */
        if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
                dev_info(dev, "%s: %s: fail, attempted private mapping\n",
                                current->comm, func);
                return -EINVAL;
        }

        mask = dax_region->align - 1;
        if (vma->vm_start & mask || vma->vm_end & mask) {
                dev_info(dev, "%s: %s: fail, unaligned vma (%#lx - %#lx, %#lx)\n",
                                current->comm, func, vma->vm_start, vma->vm_end,
                                mask);
                return -EINVAL;
        }

        if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) == PFN_DEV
                        && (vma->vm_flags & VM_DONTCOPY) == 0) {
                dev_info(dev, "%s: %s: fail, dax range requires MADV_DONTFORK\n",
                                current->comm, func);
                return -EINVAL;
        }

        if (!vma_is_dax(vma)) {
                dev_info(dev, "%s: %s: fail, vma is not DAX capable\n",
                                current->comm, func);
                return -EINVAL;
        }

        return 0;
}

/* see "strong" declaration in tools/testing/nvdimm/dax-dev.c */
__weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
                unsigned long size)
{
        struct resource *res;
        /* gcc-4.6.3-nolibc for i386 complains that this is uninitialized */
        phys_addr_t uninitialized_var(phys);
        int i;

        for (i = 0; i < dev_dax->num_resources; i++) {
                res = &dev_dax->res[i];
                phys = pgoff * PAGE_SIZE + res->start;
                if (phys >= res->start && phys <= res->end)
                        break;
                pgoff -= PHYS_PFN(resource_size(res));
        }

        if (i < dev_dax->num_resources) {
                res = &dev_dax->res[i];
                if (phys + size - 1 <= res->end)
                        return phys;
        }

        return -1;
}

static int __dev_dax_pte_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
{
        struct device *dev = &dev_dax->dev;
        struct dax_region *dax_region;
        int rc = VM_FAULT_SIGBUS;
        phys_addr_t phys;
        pfn_t pfn;
        unsigned int fault_size = PAGE_SIZE;

        if (check_vma(dev_dax, vmf->vma, __func__))
                return VM_FAULT_SIGBUS;

        dax_region = dev_dax->region;
        if (dax_region->align > PAGE_SIZE) {
                dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
                        dax_region->align, fault_size);
                return VM_FAULT_SIGBUS;
        }

        if (fault_size != dax_region->align)
                return VM_FAULT_SIGBUS;

        phys = dax_pgoff_to_phys(dev_dax, vmf->pgoff, PAGE_SIZE);
        if (phys == -1) {
                dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", vmf->pgoff);
                return VM_FAULT_SIGBUS;
        }

        pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

        rc = vm_insert_mixed(vmf->vma, vmf->address, pfn);

        if (rc == -ENOMEM)
                return VM_FAULT_OOM;
        if (rc < 0 && rc != -EBUSY)
                return VM_FAULT_SIGBUS;

        return VM_FAULT_NOPAGE;
}

static int __dev_dax_pmd_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
{
        unsigned long pmd_addr = vmf->address & PMD_MASK;
        struct device *dev = &dev_dax->dev;
        struct dax_region *dax_region;
        phys_addr_t phys;
        pgoff_t pgoff;
        pfn_t pfn;
        unsigned int fault_size = PMD_SIZE;

        if (check_vma(dev_dax, vmf->vma, __func__))
                return VM_FAULT_SIGBUS;

        dax_region = dev_dax->region;
        if (dax_region->align > PMD_SIZE) {
                dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
                        dax_region->align, fault_size);
                return VM_FAULT_SIGBUS;
        }

        /* dax pmd mappings require pfn_t_devmap() */
        if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) != (PFN_DEV|PFN_MAP)) {
                dev_dbg(dev, "region lacks devmap flags\n");
                return VM_FAULT_SIGBUS;
        }

        if (fault_size < dax_region->align)
                return VM_FAULT_SIGBUS;
        else if (fault_size > dax_region->align)
                return VM_FAULT_FALLBACK;

        /* if we are outside of the VMA */
        if (pmd_addr < vmf->vma->vm_start ||
                        (pmd_addr + PMD_SIZE) > vmf->vma->vm_end)
                return VM_FAULT_SIGBUS;

        pgoff = linear_page_index(vmf->vma, pmd_addr);
        phys = dax_pgoff_to_phys(dev_dax, pgoff, PMD_SIZE);
        if (phys == -1) {
                dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
                return VM_FAULT_SIGBUS;
        }

        pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

        return vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd, pfn,
                        vmf->flags & FAULT_FLAG_WRITE);
}

#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
static int __dev_dax_pud_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
{
        unsigned long pud_addr = vmf->address & PUD_MASK;
        struct device *dev = &dev_dax->dev;
        struct dax_region *dax_region;
        phys_addr_t phys;
        pgoff_t pgoff;
        pfn_t pfn;
        unsigned int fault_size = PUD_SIZE;


        if (check_vma(dev_dax, vmf->vma, __func__))
                return VM_FAULT_SIGBUS;

        dax_region = dev_dax->region;
        if (dax_region->align > PUD_SIZE) {
                dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
                        dax_region->align, fault_size);
                return VM_FAULT_SIGBUS;
        }

        /* dax pud mappings require pfn_t_devmap() */
        if ((dax_region->pfn_flags & (PFN_DEV|PFN_MAP)) != (PFN_DEV|PFN_MAP)) {
                dev_dbg(dev, "region lacks devmap flags\n");
                return VM_FAULT_SIGBUS;
        }

        if (fault_size < dax_region->align)
                return VM_FAULT_SIGBUS;
        else if (fault_size > dax_region->align)
                return VM_FAULT_FALLBACK;

        /* if we are outside of the VMA */
        if (pud_addr < vmf->vma->vm_start ||
                        (pud_addr + PUD_SIZE) > vmf->vma->vm_end)
                return VM_FAULT_SIGBUS;

        pgoff = linear_page_index(vmf->vma, pud_addr);
        phys = dax_pgoff_to_phys(dev_dax, pgoff, PUD_SIZE);
        if (phys == -1) {
                dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
                return VM_FAULT_SIGBUS;
        }

        pfn = phys_to_pfn_t(phys, dax_region->pfn_flags);

        return vmf_insert_pfn_pud(vmf->vma, vmf->address, vmf->pud, pfn,
                        vmf->flags & FAULT_FLAG_WRITE);
}
#else
static int __dev_dax_pud_fault(struct dev_dax *dev_dax, struct vm_fault *vmf)
{
        return VM_FAULT_FALLBACK;
}
#endif /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */

static int dev_dax_huge_fault(struct vm_fault *vmf,
                enum page_entry_size pe_size)
{
        int rc, id;
        struct file *filp = vmf->vma->vm_file;
        struct dev_dax *dev_dax = filp->private_data;

        dev_dbg(&dev_dax->dev, "%s: %s (%#lx - %#lx) size = %d\n", current->comm,
                        (vmf->flags & FAULT_FLAG_WRITE) ? "write" : "read",
                        vmf->vma->vm_start, vmf->vma->vm_end, pe_size);

        id = dax_read_lock();
        switch (pe_size) {
        case PE_SIZE_PTE:
                rc = __dev_dax_pte_fault(dev_dax, vmf);
                break;
        case PE_SIZE_PMD:
                rc = __dev_dax_pmd_fault(dev_dax, vmf);
                break;
        case PE_SIZE_PUD:
                rc = __dev_dax_pud_fault(dev_dax, vmf);
                break;
        default:
                rc = VM_FAULT_SIGBUS;
        }
        dax_read_unlock(id);

        return rc;
}

static int dev_dax_fault(struct vm_fault *vmf)
{
        return dev_dax_huge_fault(vmf, PE_SIZE_PTE);
}

static int dev_dax_split(struct vm_area_struct *vma, unsigned long addr)
{
        struct file *filp = vma->vm_file;
        struct dev_dax *dev_dax = filp->private_data;
        struct dax_region *dax_region = dev_dax->region;

        if (!IS_ALIGNED(addr, dax_region->align))
                return -EINVAL;
        return 0;
}

static unsigned long dev_dax_pagesize(struct vm_area_struct *vma)
{
        struct file *filp = vma->vm_file;
        struct dev_dax *dev_dax = filp->private_data;
        struct dax_region *dax_region = dev_dax->region;

        return dax_region->align;
}

static const struct vm_operations_struct dax_vm_ops = {
        .fault = dev_dax_fault,
        .huge_fault = dev_dax_huge_fault,
        .split = dev_dax_split,
        .pagesize = dev_dax_pagesize,
};

static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct dev_dax *dev_dax = filp->private_data;
        int rc, id;

        dev_dbg(&dev_dax->dev, "trace\n");

        /*
         * We lock to check dax_dev liveness and will re-check at
         * fault time.
         */
        id = dax_read_lock();
        rc = check_vma(dev_dax, vma, __func__);
        dax_read_unlock(id);
        if (rc)
                return rc;

        vma->vm_ops = &dax_vm_ops;
        vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
        return 0;
}

/* return an unmapped area aligned to the dax region specified alignment */
static unsigned long dax_get_unmapped_area(struct file *filp,
                unsigned long addr, unsigned long len, unsigned long pgoff,
                unsigned long flags)
{
        unsigned long off, off_end, off_align, len_align, addr_align, align;
        struct dev_dax *dev_dax = filp ? filp->private_data : NULL;
        struct dax_region *dax_region;

        if (!dev_dax || addr)
                goto out;

        dax_region = dev_dax->region;
        align = dax_region->align;
        off = pgoff << PAGE_SHIFT;
        off_end = off + len;
        off_align = round_up(off, align);

        if ((off_end <= off_align) || ((off_end - off_align) < align))
                goto out;

        len_align = len + align;
        if ((off + len_align) < off)
                goto out;

        addr_align = current->mm->get_unmapped_area(filp, addr, len_align,
                        pgoff, flags);
        if (!IS_ERR_VALUE(addr_align)) {
                addr_align += (off - addr_align) & (align - 1);
                return addr_align;
        }
 out:
        return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
}

static int dax_open(struct inode *inode, struct file *filp)
{
        struct dax_device *dax_dev = inode_dax(inode);
        struct inode *__dax_inode = dax_inode(dax_dev);
        struct dev_dax *dev_dax = dax_get_private(dax_dev);

        dev_dbg(&dev_dax->dev, "trace\n");
        inode->i_mapping = __dax_inode->i_mapping;
        inode->i_mapping->host = __dax_inode;
        filp->f_mapping = inode->i_mapping;
        filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
        filp->private_data = dev_dax;
        inode->i_flags = S_DAX;

        return 0;
}

static int dax_release(struct inode *inode, struct file *filp)
{
        struct dev_dax *dev_dax = filp->private_data;

        dev_dbg(&dev_dax->dev, "trace\n");
        return 0;
}

static const struct file_operations dax_fops = {
        .llseek = noop_llseek,
        .owner = THIS_MODULE,
        .open = dax_open,
        .release = dax_release,
        .get_unmapped_area = dax_get_unmapped_area,
        .mmap = dax_mmap,
        .mmap_supported_flags = MAP_SYNC,
};

static void dev_dax_release(struct device *dev)
{
        struct dev_dax *dev_dax = to_dev_dax(dev);
        struct dax_region *dax_region = dev_dax->region;
        struct dax_device *dax_dev = dev_dax->dax_dev;

        if (dev_dax->id >= 0)
                ida_simple_remove(&dax_region->ida, dev_dax->id);
        dax_region_put(dax_region);
        put_dax(dax_dev);
        kfree(dev_dax);
}

static void kill_dev_dax(struct dev_dax *dev_dax)
{
        struct dax_device *dax_dev = dev_dax->dax_dev;
        struct inode *inode = dax_inode(dax_dev);

        kill_dax(dax_dev);
        unmap_mapping_range(inode->i_mapping, 0, 0, 1);
}

static void unregister_dev_dax(void *dev)
{
        struct dev_dax *dev_dax = to_dev_dax(dev);
        struct dax_device *dax_dev = dev_dax->dax_dev;
        struct inode *inode = dax_inode(dax_dev);
        struct cdev *cdev = inode->i_cdev;

        dev_dbg(dev, "trace\n");

        kill_dev_dax(dev_dax);
        cdev_device_del(cdev, dev);
        put_device(dev);
}

struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
                int id, struct resource *res, int count)
{
        struct device *parent = dax_region->dev;
        struct dax_device *dax_dev;
        struct dev_dax *dev_dax;
        struct inode *inode;
        struct device *dev;
        struct cdev *cdev;
        int rc, i;

        if (!count)
                return ERR_PTR(-EINVAL);

        dev_dax = kzalloc(sizeof(*dev_dax) + sizeof(*res) * count, GFP_KERNEL);
        if (!dev_dax)
                return ERR_PTR(-ENOMEM);

        for (i = 0; i < count; i++) {
                if (!IS_ALIGNED(res[i].start, dax_region->align)
                                || !IS_ALIGNED(resource_size(&res[i]),
                                        dax_region->align)) {
                        rc = -EINVAL;
                        break;
                }
                dev_dax->res[i].start = res[i].start;
                dev_dax->res[i].end = res[i].end;
        }

        if (i < count)
                goto err_id;

        if (id < 0) {
                id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
                dev_dax->id = id;
                if (id < 0) {
                        rc = id;
                        goto err_id;
                }
        } else {
                /* region provider owns @id lifetime */
                dev_dax->id = -1;
        }

        /*
         * No 'host' or dax_operations since there is no access to this
         * device outside of mmap of the resulting character device.
         */
        dax_dev = alloc_dax(dev_dax, NULL, NULL);
        if (!dax_dev) {
                rc = -ENOMEM;
                goto err_dax;
        }

        /* from here on we're committed to teardown via dax_dev_release() */
        dev = &dev_dax->dev;
        device_initialize(dev);

        inode = dax_inode(dax_dev);
        cdev = inode->i_cdev;
        cdev_init(cdev, &dax_fops);
        cdev->owner = parent->driver->owner;

        dev_dax->num_resources = count;
        dev_dax->dax_dev = dax_dev;
        dev_dax->region = dax_region;
        kref_get(&dax_region->kref);

        dev->devt = inode->i_rdev;
        dev->class = dax_class;
        dev->parent = parent;
        dev->groups = dax_attribute_groups;
        dev->release = dev_dax_release;
        dev_set_name(dev, "dax%d.%d", dax_region->id, id);

        rc = cdev_device_add(cdev, dev);
        if (rc) {
                kill_dev_dax(dev_dax);
                put_device(dev);
                return ERR_PTR(rc);
        }

        rc = devm_add_action_or_reset(dax_region->dev, unregister_dev_dax, dev);
        if (rc)
                return ERR_PTR(rc);

        return dev_dax;

 err_dax:
        if (dev_dax->id >= 0)
                ida_simple_remove(&dax_region->ida, dev_dax->id);
 err_id:
        kfree(dev_dax);

        return ERR_PTR(rc);
}
EXPORT_SYMBOL_GPL(devm_create_dev_dax);

static int __init dax_init(void)
{
        dax_class = class_create(THIS_MODULE, "dax");
        return PTR_ERR_OR_ZERO(dax_class);
}

static void __exit dax_exit(void)
{
        class_destroy(dax_class);
}

MODULE_AUTHOR("Intel Corporation");
MODULE_LICENSE("GPL v2");
subsys_initcall(dax_init);
module_exit(dax_exit);