/* AFS filesystem file handling
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/gfp.h>
#include <linux/task_io_accounting_ops.h>
#include "internal.h"

static int afs_readpage(struct file *file, struct page *page);
static void afs_invalidatepage(struct page *page, unsigned int offset,
                               unsigned int length);
static int afs_releasepage(struct page *page, gfp_t gfp_flags);
static int afs_launder_page(struct page *page);

static int afs_readpages(struct file *filp, struct address_space *mapping,
                         struct list_head *pages, unsigned nr_pages);

const struct file_operations afs_file_operations = {
        .open           = afs_open,
        .flush          = afs_flush,
        .release        = afs_release,
        .llseek         = generic_file_llseek,
        .read_iter      = generic_file_read_iter,
        .write_iter     = afs_file_write,
        .mmap           = generic_file_readonly_mmap,
        .splice_read    = generic_file_splice_read,
        .fsync          = afs_fsync,
        .lock           = afs_lock,
        .flock          = afs_flock,
};

const struct inode_operations afs_file_inode_operations = {
        .getattr        = afs_getattr,
        .setattr        = afs_setattr,
        .permission     = afs_permission,
        .listxattr      = afs_listxattr,
};

const struct address_space_operations afs_fs_aops = {
        .readpage       = afs_readpage,
        .readpages      = afs_readpages,
        .set_page_dirty = afs_set_page_dirty,
        .launder_page   = afs_launder_page,
        .releasepage    = afs_releasepage,
        .invalidatepage = afs_invalidatepage,
        .write_begin    = afs_write_begin,
        .write_end      = afs_write_end,
        .writepage      = afs_writepage,
        .writepages     = afs_writepages,
};

/*
 * open an AFS file or directory and attach a key to it
 */
int afs_open(struct inode *inode, struct file *file)
{
        struct afs_vnode *vnode = AFS_FS_I(inode);
        struct key *key;
        int ret;

        _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);

        key = afs_request_key(vnode->volume->cell);
        if (IS_ERR(key)) {
                _leave(" = %ld [key]", PTR_ERR(key));
                return PTR_ERR(key);
        }

        ret = afs_validate(vnode, key);
        if (ret < 0) {
                _leave(" = %d [val]", ret);
                return ret;
        }

        file->private_data = key;
        _leave(" = 0");
        return 0;
}

/*
 * release an AFS file or directory and discard its key
 */
int afs_release(struct inode *inode, struct file *file)
{
        struct afs_vnode *vnode = AFS_FS_I(inode);

        _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);

        key_put(file->private_data);
        _leave(" = 0");
        return 0;
}

/*
 * Dispose of a ref to a read record.
 */
void afs_put_read(struct afs_read *req)
{
        int i;

        if (atomic_dec_and_test(&req->usage)) {
                for (i = 0; i < req->nr_pages; i++)
                        if (req->pages[i])
                                put_page(req->pages[i]);
                kfree(req);
        }
}

#ifdef CONFIG_AFS_FSCACHE
/*
 * deal with notification that a page was read from the cache
 */
static void afs_file_readpage_read_complete(struct page *page,
                                            void *data,
                                            int error)
{
        _enter("%p,%p,%d", page, data, error);

        /* if the read completes with an error, we just unlock the page and let
         * the VM reissue the readpage */
        if (!error)
                SetPageUptodate(page);
        unlock_page(page);
}
#endif

/*
 * read page from file, directory or symlink, given a key to use
 */
int afs_page_filler(void *data, struct page *page)
{
        struct inode *inode = page->mapping->host;
        struct afs_vnode *vnode = AFS_FS_I(inode);
        struct afs_read *req;
        struct key *key = data;
        int ret;

        _enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);

        BUG_ON(!PageLocked(page));

        ret = -ESTALE;
        if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
                goto error;

        /* is it cached? */
#ifdef CONFIG_AFS_FSCACHE
        ret = fscache_read_or_alloc_page(vnode->cache,
                                         page,
                                         afs_file_readpage_read_complete,
                                         NULL,
                                         GFP_KERNEL);
#else
        ret = -ENOBUFS;
#endif
        switch (ret) {
                /* read BIO submitted (page in cache) */
        case 0:
                break;

                /* page not yet cached */
        case -ENODATA:
                _debug("cache said ENODATA");
                goto go_on;

                /* page will not be cached */
        case -ENOBUFS:
                _debug("cache said ENOBUFS");
        default:
        go_on:
                req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
                              GFP_KERNEL);
                if (!req)
                        goto enomem;

                /* We request a full page.  If the page is a partial one at the
                 * end of the file, the server will return a short read and the
                 * unmarshalling code will clear the unfilled space.
                 */
                atomic_set(&req->usage, 1);
                req->pos = (loff_t)page->index << PAGE_SHIFT;
                req->len = PAGE_SIZE;
                req->nr_pages = 1;
                req->pages[0] = page;
                get_page(page);

                /* read the contents of the file from the server into the
                 * page */
                ret = afs_vnode_fetch_data(vnode, key, req);
                afs_put_read(req);
                if (ret < 0) {
                        if (ret == -ENOENT) {
                                _debug("got NOENT from server"
                                       " - marking file deleted and stale");
                                set_bit(AFS_VNODE_DELETED, &vnode->flags);
                                ret = -ESTALE;
                        }

#ifdef CONFIG_AFS_FSCACHE
                        fscache_uncache_page(vnode->cache, page);
#endif
                        BUG_ON(PageFsCache(page));

                        if (ret == -EINTR ||
                            ret == -ENOMEM ||
                            ret == -ERESTARTSYS ||
                            ret == -EAGAIN)
                                goto error;
                        goto io_error;
                }

                SetPageUptodate(page);

                /* send the page to the cache */
#ifdef CONFIG_AFS_FSCACHE
                if (PageFsCache(page) &&
                    fscache_write_page(vnode->cache, page, GFP_KERNEL) != 0) {
                        fscache_uncache_page(vnode->cache, page);
                        BUG_ON(PageFsCache(page));
                }
#endif
                unlock_page(page);
        }

        _leave(" = 0");
        return 0;

io_error:
        SetPageError(page);
        goto error;
enomem:
        ret = -ENOMEM;
error:
        unlock_page(page);
        _leave(" = %d", ret);
        return ret;
}

/*
 * read page from file, directory or symlink, given a file to nominate the key
 * to be used
 */
static int afs_readpage(struct file *file, struct page *page)
{
        struct key *key;
        int ret;

        if (file) {
                key = file->private_data;
                ASSERT(key != NULL);
                ret = afs_page_filler(key, page);
        } else {
                struct inode *inode = page->mapping->host;
                key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
                if (IS_ERR(key)) {
                        ret = PTR_ERR(key);
                } else {
                        ret = afs_page_filler(key, page);
                        key_put(key);
                }
        }
        return ret;
}

/*
 * Make pages available as they're filled.
 */
static void afs_readpages_page_done(struct afs_call *call, struct afs_read *req)
{
#ifdef CONFIG_AFS_FSCACHE
        struct afs_vnode *vnode = call->reply;
#endif
        struct page *page = req->pages[req->index];

        req->pages[req->index] = NULL;
        SetPageUptodate(page);

        /* send the page to the cache */
#ifdef CONFIG_AFS_FSCACHE
        if (PageFsCache(page) &&
            fscache_write_page(vnode->cache, page, GFP_KERNEL) != 0) {
                fscache_uncache_page(vnode->cache, page);
                BUG_ON(PageFsCache(page));
        }
#endif
        unlock_page(page);
        put_page(page);
}

/*
 * Read a contiguous set of pages.
 */
static int afs_readpages_one(struct file *file, struct address_space *mapping,
                             struct list_head *pages)
{
        struct afs_vnode *vnode = AFS_FS_I(mapping->host);
        struct afs_read *req;
        struct list_head *p;
        struct page *first, *page;
        struct key *key = file->private_data;
        pgoff_t index;
        int ret, n, i;

        /* Count the number of contiguous pages at the front of the list.  Note
         * that the list goes prev-wards rather than next-wards.
         */
        first = list_entry(pages->prev, struct page, lru);
        index = first->index + 1;
        n = 1;
        for (p = first->lru.prev; p != pages; p = p->prev) {
                page = list_entry(p, struct page, lru);
                if (page->index != index)
                        break;
                index++;
                n++;
        }

        req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *) * n,
                      GFP_NOFS);
        if (!req)
                return -ENOMEM;

        atomic_set(&req->usage, 1);
        req->page_done = afs_readpages_page_done;
        req->pos = first->index;
        req->pos <<= PAGE_SHIFT;

        /* Transfer the pages to the request.  We add them in until one fails
         * to add to the LRU and then we stop (as that'll make a hole in the
         * contiguous run.
         *
         * Note that it's possible for the file size to change whilst we're
         * doing this, but we rely on the server returning less than we asked
         * for if the file shrank.  We also rely on this to deal with a partial
         * page at the end of the file.
         */
        do {
                page = list_entry(pages->prev, struct page, lru);
                list_del(&page->lru);
                index = page->index;
                if (add_to_page_cache_lru(page, mapping, index,
                                          readahead_gfp_mask(mapping))) {
#ifdef CONFIG_AFS_FSCACHE
                        fscache_uncache_page(vnode->cache, page);
#endif
                        put_page(page);
                        break;
                }

                req->pages[req->nr_pages++] = page;
                req->len += PAGE_SIZE;
        } while (req->nr_pages < n);

        if (req->nr_pages == 0) {
                kfree(req);
                return 0;
        }

        ret = afs_vnode_fetch_data(vnode, key, req);
        if (ret < 0)
                goto error;

        task_io_account_read(PAGE_SIZE * req->nr_pages);
        afs_put_read(req);
        return 0;

error:
        if (ret == -ENOENT) {
                _debug("got NOENT from server"
                       " - marking file deleted and stale");
                set_bit(AFS_VNODE_DELETED, &vnode->flags);
                ret = -ESTALE;
        }

        for (i = 0; i < req->nr_pages; i++) {
                page = req->pages[i];
                if (page) {
#ifdef CONFIG_AFS_FSCACHE
                        fscache_uncache_page(vnode->cache, page);
#endif
                        SetPageError(page);
                        unlock_page(page);
                }
        }

        afs_put_read(req);
        return ret;
}

/*
 * read a set of pages
 */
static int afs_readpages(struct file *file, struct address_space *mapping,
                         struct list_head *pages, unsigned nr_pages)
{
        struct key *key = file->private_data;
        struct afs_vnode *vnode;
        int ret = 0;

        _enter("{%d},{%lu},,%d",
               key_serial(key), mapping->host->i_ino, nr_pages);

        ASSERT(key != NULL);

        vnode = AFS_FS_I(mapping->host);
        if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
                _leave(" = -ESTALE");
                return -ESTALE;
        }

        /* attempt to read as many of the pages as possible */
#ifdef CONFIG_AFS_FSCACHE
        ret = fscache_read_or_alloc_pages(vnode->cache,
                                          mapping,
                                          pages,
                                          &nr_pages,
                                          afs_file_readpage_read_complete,
                                          NULL,
                                          mapping_gfp_mask(mapping));
#else
        ret = -ENOBUFS;
#endif

        switch (ret) {
                /* all pages are being read from the cache */
        case 0:
                BUG_ON(!list_empty(pages));
                BUG_ON(nr_pages != 0);
                _leave(" = 0 [reading all]");
                return 0;

                /* there were pages that couldn't be read from the cache */
        case -ENODATA:
        case -ENOBUFS:
                break;

                /* other error */
        default:
                _leave(" = %d", ret);
                return ret;
        }

        while (!list_empty(pages)) {
                ret = afs_readpages_one(file, mapping, pages);
                if (ret < 0)
                        break;
        }

        _leave(" = %d [netting]", ret);
        return ret;
}

/*
 * write back a dirty page
 */
static int afs_launder_page(struct page *page)
{
        _enter("{%lu}", page->index);

        return 0;
}

/*
 * invalidate part or all of a page
 * - release a page and clean up its private data if offset is 0 (indicating
 *   the entire page)
 */
static void afs_invalidatepage(struct page *page, unsigned int offset,
                               unsigned int length)
{
        struct afs_writeback *wb = (struct afs_writeback *) page_private(page);

        _enter("{%lu},%u,%u", page->index, offset, length);

        BUG_ON(!PageLocked(page));

        /* we clean up only if the entire page is being invalidated */
        if (offset == 0 && length == PAGE_SIZE) {
#ifdef CONFIG_AFS_FSCACHE
                if (PageFsCache(page)) {
                        struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
                        fscache_wait_on_page_write(vnode->cache, page);
                        fscache_uncache_page(vnode->cache, page);
                }
#endif

                if (PagePrivate(page)) {
                        if (wb && !PageWriteback(page)) {
                                set_page_private(page, 0);
                                afs_put_writeback(wb);
                        }

                        if (!page_private(page))
                                ClearPagePrivate(page);
                }
        }

        _leave("");
}

/*
 * release a page and clean up its private state if it's not busy
 * - return true if the page can now be released, false if not
 */
static int afs_releasepage(struct page *page, gfp_t gfp_flags)
{
        struct afs_writeback *wb = (struct afs_writeback *) page_private(page);
        struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);

        _enter("{{%x:%u}[%lu],%lx},%x",
               vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
               gfp_flags);

        /* deny if page is being written to the cache and the caller hasn't
         * elected to wait */
#ifdef CONFIG_AFS_FSCACHE
        if (!fscache_maybe_release_page(vnode->cache, page, gfp_flags)) {
                _leave(" = F [cache busy]");
                return 0;
        }
#endif

        if (PagePrivate(page)) {
                if (wb) {
                        set_page_private(page, 0);
                        afs_put_writeback(wb);
                }
                ClearPagePrivate(page);
        }

        /* indicate that the page can be released */
        _leave(" = T");
        return 1;
}