#include <linux/ceph/ceph_debug.h>

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/namei.h>
#include <linux/writeback.h>

#include <linux/ceph/libceph.h>

/*
 * build a vector of user pages
 */
struct page **ceph_get_direct_page_vector(const void __user *data,
                                          int num_pages, bool write_page)
{
        struct page **pages;
        int got = 0;
        int rc = 0;

        pages = kmalloc(sizeof(*pages) * num_pages, GFP_NOFS);
        if (!pages)
                return ERR_PTR(-ENOMEM);

        while (got < num_pages) {
                rc = get_user_pages_unlocked(
                    (unsigned long)data + ((unsigned long)got * PAGE_SIZE),
                    num_pages - got, pages + got, write_page ? FOLL_WRITE : 0);
                if (rc < 0)
                        break;
                BUG_ON(rc == 0);
                got += rc;
        }
        if (rc < 0)
                goto fail;
        return pages;

fail:
        ceph_put_page_vector(pages, got, false);
        return ERR_PTR(rc);
}
EXPORT_SYMBOL(ceph_get_direct_page_vector);

void ceph_put_page_vector(struct page **pages, int num_pages, bool dirty)
{
        int i;

        for (i = 0; i < num_pages; i++) {
                if (dirty)
                        set_page_dirty_lock(pages[i]);
                put_page(pages[i]);
        }
        kvfree(pages);
}
EXPORT_SYMBOL(ceph_put_page_vector);

void ceph_release_page_vector(struct page **pages, int num_pages)
{
        int i;

        for (i = 0; i < num_pages; i++)
                __free_pages(pages[i], 0);
        kfree(pages);
}
EXPORT_SYMBOL(ceph_release_page_vector);

/*
 * allocate a vector new pages
 */
struct page **ceph_alloc_page_vector(int num_pages, gfp_t flags)
{
        struct page **pages;
        int i;

        pages = kmalloc(sizeof(*pages) * num_pages, flags);
        if (!pages)
                return ERR_PTR(-ENOMEM);
        for (i = 0; i < num_pages; i++) {
                pages[i] = __page_cache_alloc(flags);
                if (pages[i] == NULL) {
                        ceph_release_page_vector(pages, i);
                        return ERR_PTR(-ENOMEM);
                }
        }
        return pages;
}
EXPORT_SYMBOL(ceph_alloc_page_vector);

/*
 * copy user data into a page vector
 */
int ceph_copy_user_to_page_vector(struct page **pages,
                                         const void __user *data,
                                         loff_t off, size_t len)
{
        int i = 0;
        int po = off & ~PAGE_MASK;
        int left = len;
        int l, bad;

        while (left > 0) {
                l = min_t(int, PAGE_SIZE-po, left);
                bad = copy_from_user(page_address(pages[i]) + po, data, l);
                if (bad == l)
                        return -EFAULT;
                data += l - bad;
                left -= l - bad;
                po += l - bad;
                if (po == PAGE_SIZE) {
                        po = 0;
                        i++;
                }
        }
        return len;
}
EXPORT_SYMBOL(ceph_copy_user_to_page_vector);

void ceph_copy_to_page_vector(struct page **pages,
                                    const void *data,
                                    loff_t off, size_t len)
{
        int i = 0;
        size_t po = off & ~PAGE_MASK;
        size_t left = len;

        while (left > 0) {
                size_t l = min_t(size_t, PAGE_SIZE-po, left);

                memcpy(page_address(pages[i]) + po, data, l);
                data += l;
                left -= l;
                po += l;
                if (po == PAGE_SIZE) {
                        po = 0;
                        i++;
                }
        }
}
EXPORT_SYMBOL(ceph_copy_to_page_vector);

void ceph_copy_from_page_vector(struct page **pages,
                                    void *data,
                                    loff_t off, size_t len)
{
        int i = 0;
        size_t po = off & ~PAGE_MASK;
        size_t left = len;

        while (left > 0) {
                size_t l = min_t(size_t, PAGE_SIZE-po, left);

                memcpy(data, page_address(pages[i]) + po, l);
                data += l;
                left -= l;
                po += l;
                if (po == PAGE_SIZE) {
                        po = 0;
                        i++;
                }
        }
}
EXPORT_SYMBOL(ceph_copy_from_page_vector);

/*
 * Zero an extent within a page vector.  Offset is relative to the
 * start of the first page.
 */
void ceph_zero_page_vector_range(int off, int len, struct page **pages)
{
        int i = off >> PAGE_SHIFT;

        off &= ~PAGE_MASK;

        dout("zero_page_vector_page %u~%u\n", off, len);

        /* leading partial page? */
        if (off) {
                int end = min((int)PAGE_SIZE, off + len);
                dout("zeroing %d %p head from %d\n", i, pages[i],
                     (int)off);
                zero_user_segment(pages[i], off, end);
                len -= (end - off);
                i++;
        }
        while (len >= PAGE_SIZE) {
                dout("zeroing %d %p len=%d\n", i, pages[i], len);
                zero_user_segment(pages[i], 0, PAGE_SIZE);
                len -= PAGE_SIZE;
                i++;
        }
        /* trailing partial page? */
        if (len) {
                dout("zeroing %d %p tail to %d\n", i, pages[i], (int)len);
                zero_user_segment(pages[i], 0, len);
        }
}
EXPORT_SYMBOL(ceph_zero_page_vector_range);