/* 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_file_mmap(struct file *file, struct vm_area_struct *vma);
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_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           = afs_file_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,
};

static const struct vm_operations_struct afs_vm_ops = {
        .fault          = filemap_fault,
        .map_pages      = filemap_map_pages,
        .page_mkwrite   = afs_page_mkwrite,
};

/*
 * Discard a pin on a writeback key.
 */
void afs_put_wb_key(struct afs_wb_key *wbk)
{
        if (refcount_dec_and_test(&wbk->usage)) {
                key_put(wbk->key);
                kfree(wbk);
        }
}

/*
 * Cache key for writeback.
 */
int afs_cache_wb_key(struct afs_vnode *vnode, struct afs_file *af)
{
        struct afs_wb_key *wbk, *p;

        wbk = kzalloc(sizeof(struct afs_wb_key), GFP_KERNEL);
        if (!wbk)
                return -ENOMEM;
        refcount_set(&wbk->usage, 2);
        wbk->key = af->key;

        spin_lock(&vnode->wb_lock);
        list_for_each_entry(p, &vnode->wb_keys, vnode_link) {
                if (p->key == wbk->key)
                        goto found;
        }

        key_get(wbk->key);
        list_add_tail(&wbk->vnode_link, &vnode->wb_keys);
        spin_unlock(&vnode->wb_lock);
        af->wb = wbk;
        return 0;

found:
        refcount_inc(&p->usage);
        spin_unlock(&vnode->wb_lock);
        af->wb = p;
        kfree(wbk);
        return 0;
}

/*
 * 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 afs_file *af;
        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)) {
                ret = PTR_ERR(key);
                goto error;
        }

        af = kzalloc(sizeof(*af), GFP_KERNEL);
        if (!af) {
                ret = -ENOMEM;
                goto error_key;
        }
        af->key = key;

        ret = afs_validate(vnode, key);
        if (ret < 0)
                goto error_af;

        if (file->f_mode & FMODE_WRITE) {
                ret = afs_cache_wb_key(vnode, af);
                if (ret < 0)
                        goto error_af;
        }
        
        file->private_data = af;
        _leave(" = 0");
        return 0;

error_af:
        kfree(af);
error_key:
        key_put(key);
error:
        _leave(" = %d", ret);
        return ret;
}

/*
 * 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);
        struct afs_file *af = file->private_data;

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

        file->private_data = NULL;
        if (af->wb)
                afs_put_wb_key(af->wb);
        key_put(af->key);
        kfree(af);
        afs_prune_wb_keys(vnode);
        _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

/*
 * Fetch file data from the volume.
 */
int afs_fetch_data(struct afs_vnode *vnode, struct key *key, struct afs_read *desc)
{
        struct afs_fs_cursor fc;
        int ret;

        _enter("%s{%x:%u.%u},%x,,,",
               vnode->volume->name,
               vnode->fid.vid,
               vnode->fid.vnode,
               vnode->fid.unique,
               key_serial(key));

        ret = -ERESTARTSYS;
        if (afs_begin_vnode_operation(&fc, vnode, key)) {
                while (afs_select_fileserver(&fc)) {
                        fc.cb_break = vnode->cb_break + vnode->cb_s_break;
                        afs_fs_fetch_data(&fc, desc);
                }

                afs_check_for_remote_deletion(&fc, fc.vnode);
                afs_vnode_commit_status(&fc, vnode, fc.cb_break);
                ret = afs_end_vnode_operation(&fc);
        }

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

/*
 * 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_fetch_data(vnode, key, req);
                afs_put_read(req);

                if (ret >= 0 && S_ISDIR(inode->i_mode) &&
                    !afs_dir_check_page(inode, page))
                        ret = -EIO;

                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 = afs_file_key(file);
                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)->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[0];
#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 = afs_file_key(file);
        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_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 = afs_file_key(file);
        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;
}

/*
 * 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_vnode *vnode = AFS_FS_I(page->mapping->host);
        unsigned long priv;

        _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)) {
                        priv = page_private(page);
                        trace_afs_page_dirty(vnode, tracepoint_string("inval"),
                                             page->index, priv);
                        set_page_private(page, 0);
                        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_vnode *vnode = AFS_FS_I(page->mapping->host);
        unsigned long priv;

        _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)) {
                priv = page_private(page);
                trace_afs_page_dirty(vnode, tracepoint_string("rel"),
                                     page->index, priv);
                set_page_private(page, 0);
                ClearPagePrivate(page);
        }

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

/*
 * Handle setting up a memory mapping on an AFS file.
 */
static int afs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
        int ret;

        ret = generic_file_mmap(file, vma);
        if (ret == 0)
                vma->vm_ops = &afs_vm_ops;
        return ret;
}