/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * 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 version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/lustre/llite/rw26.c
 *
 * Lustre Lite I/O page cache routines for the 2.5/2.6 kernel version
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/unistd.h>
#include <linux/uaccess.h>

#include <linux/migrate.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>

#define DEBUG_SUBSYSTEM S_LLITE

#include "llite_internal.h"

/**
 * Implements Linux VM address_space::invalidatepage() method. This method is
 * called when the page is truncate from a file, either as a result of
 * explicit truncate, or when inode is removed from memory (as a result of
 * final iput(), umount, or memory pressure induced icache shrinking).
 *
 * [0, offset] bytes of the page remain valid (this is for a case of not-page
 * aligned truncate). Lustre leaves partially truncated page in the cache,
 * relying on struct inode::i_size to limit further accesses.
 */
static void ll_invalidatepage(struct page *vmpage, unsigned int offset,
                              unsigned int length)
{
        struct inode     *inode;
        struct lu_env    *env;
        struct cl_page   *page;
        struct cl_object *obj;

        int refcheck;

        LASSERT(PageLocked(vmpage));
        LASSERT(!PageWriteback(vmpage));

        /*
         * It is safe to not check anything in invalidatepage/releasepage
         * below because they are run with page locked and all our io is
         * happening with locked page too
         */
        if (offset == 0 && length == PAGE_SIZE) {
                env = cl_env_get(&refcheck);
                if (!IS_ERR(env)) {
                        inode = vmpage->mapping->host;
                        obj = ll_i2info(inode)->lli_clob;
                        if (obj) {
                                page = cl_vmpage_page(vmpage, obj);
                                if (page) {
                                        cl_page_delete(env, page);
                                        cl_page_put(env, page);
                                }
                        } else {
                                LASSERT(vmpage->private == 0);
                        }
                        cl_env_put(env, &refcheck);
                }
        }
}

static int ll_releasepage(struct page *vmpage, gfp_t gfp_mask)
{
        struct lu_env     *env;
        void                    *cookie;
        struct cl_object  *obj;
        struct cl_page    *page;
        struct address_space *mapping;
        int result = 0;

        LASSERT(PageLocked(vmpage));
        if (PageWriteback(vmpage) || PageDirty(vmpage))
                return 0;

        mapping = vmpage->mapping;
        if (!mapping)
                return 1;

        obj = ll_i2info(mapping->host)->lli_clob;
        if (!obj)
                return 1;

        /* 1 for caller, 1 for cl_page and 1 for page cache */
        if (page_count(vmpage) > 3)
                return 0;

        page = cl_vmpage_page(vmpage, obj);
        if (!page)
                return 1;

        cookie = cl_env_reenter();
        env = cl_env_percpu_get();
        LASSERT(!IS_ERR(env));

        if (!cl_page_in_use(page)) {
                result = 1;
                cl_page_delete(env, page);
        }

        /* To use percpu env array, the call path can not be rescheduled;
         * otherwise percpu array will be messed if ll_releaspage() called
         * again on the same CPU.
         *
         * If this page holds the last refc of cl_object, the following
         * call path may cause reschedule:
         *   cl_page_put -> cl_page_free -> cl_object_put ->
         *     lu_object_put -> lu_object_free -> lov_delete_raid0.
         *
         * However, the kernel can't get rid of this inode until all pages have
         * been cleaned up. Now that we hold page lock here, it's pretty safe
         * that we won't get into object delete path.
         */
        LASSERT(cl_object_refc(obj) > 1);
        cl_page_put(env, page);

        cl_env_percpu_put(env);
        cl_env_reexit(cookie);
        return result;
}

#define MAX_DIRECTIO_SIZE (2 * 1024 * 1024 * 1024UL)

static inline int ll_get_user_pages(int rw, unsigned long user_addr,
                                    size_t size, struct page ***pages,
                                    int *max_pages)
{
        int result = -ENOMEM;

        /* set an arbitrary limit to prevent arithmetic overflow */
        if (size > MAX_DIRECTIO_SIZE) {
                *pages = NULL;
                return -EFBIG;
        }

        *max_pages = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
        *max_pages -= user_addr >> PAGE_SHIFT;

        *pages = libcfs_kvzalloc(*max_pages * sizeof(**pages), GFP_NOFS);
        if (*pages) {
                result = get_user_pages_fast(user_addr, *max_pages,
                                             (rw == READ), *pages);
                if (unlikely(result <= 0))
                        kvfree(*pages);
        }

        return result;
}

/*  ll_free_user_pages - tear down page struct array
 *  @pages: array of page struct pointers underlying target buffer
 */
static void ll_free_user_pages(struct page **pages, int npages, int do_dirty)
{
        int i;

        for (i = 0; i < npages; i++) {
                if (do_dirty)
                        set_page_dirty_lock(pages[i]);
                put_page(pages[i]);
        }
        kvfree(pages);
}

ssize_t ll_direct_rw_pages(const struct lu_env *env, struct cl_io *io,
                           int rw, struct inode *inode,
                           struct ll_dio_pages *pv)
{
        struct cl_page    *clp;
        struct cl_2queue  *queue;
        struct cl_object  *obj = io->ci_obj;
        int i;
        ssize_t rc = 0;
        loff_t file_offset  = pv->ldp_start_offset;
        size_t size = pv->ldp_size;
        int page_count      = pv->ldp_nr;
        struct page **pages = pv->ldp_pages;
        size_t page_size = cl_page_size(obj);
        bool do_io;
        int  io_pages       = 0;

        queue = &io->ci_queue;
        cl_2queue_init(queue);
        for (i = 0; i < page_count; i++) {
                if (pv->ldp_offsets)
                        file_offset = pv->ldp_offsets[i];

                LASSERT(!(file_offset & (page_size - 1)));
                clp = cl_page_find(env, obj, cl_index(obj, file_offset),
                                   pv->ldp_pages[i], CPT_TRANSIENT);
                if (IS_ERR(clp)) {
                        rc = PTR_ERR(clp);
                        break;
                }

                rc = cl_page_own(env, io, clp);
                if (rc) {
                        LASSERT(clp->cp_state == CPS_FREEING);
                        cl_page_put(env, clp);
                        break;
                }

                do_io = true;

                /* check the page type: if the page is a host page, then do
                 * write directly
                 */
                if (clp->cp_type == CPT_CACHEABLE) {
                        struct page *vmpage = cl_page_vmpage(clp);
                        struct page *src_page;
                        struct page *dst_page;
                        void       *src;
                        void       *dst;

                        src_page = (rw == WRITE) ? pages[i] : vmpage;
                        dst_page = (rw == WRITE) ? vmpage : pages[i];

                        src = kmap_atomic(src_page);
                        dst = kmap_atomic(dst_page);
                        memcpy(dst, src, min(page_size, size));
                        kunmap_atomic(dst);
                        kunmap_atomic(src);

                        /* make sure page will be added to the transfer by
                         * cl_io_submit()->...->vvp_page_prep_write().
                         */
                        if (rw == WRITE)
                                set_page_dirty(vmpage);

                        if (rw == READ) {
                                /* do not issue the page for read, since it
                                 * may reread a ra page which has NOT uptodate
                                 * bit set.
                                 */
                                cl_page_disown(env, io, clp);
                                do_io = false;
                        }
                }

                if (likely(do_io)) {
                        /*
                         * Add a page to the incoming page list of 2-queue.
                         */
                        cl_page_list_add(&queue->c2_qin, clp);

                        /*
                         * Set page clip to tell transfer formation engine
                         * that page has to be sent even if it is beyond KMS.
                         */
                        cl_page_clip(env, clp, 0, min(size, page_size));

                        ++io_pages;
                }

                /* drop the reference count for cl_page_find */
                cl_page_put(env, clp);
                size -= page_size;
                file_offset += page_size;
        }

        if (rc == 0 && io_pages) {
                rc = cl_io_submit_sync(env, io,
                                       rw == READ ? CRT_READ : CRT_WRITE,
                                       queue, 0);
        }
        if (rc == 0)
                rc = pv->ldp_size;

        cl_2queue_discard(env, io, queue);
        cl_2queue_disown(env, io, queue);
        cl_2queue_fini(env, queue);
        return rc;
}
EXPORT_SYMBOL(ll_direct_rw_pages);

static ssize_t ll_direct_IO_26_seg(const struct lu_env *env, struct cl_io *io,
                                   int rw, struct inode *inode,
                                   struct address_space *mapping,
                                   size_t size, loff_t file_offset,
                                   struct page **pages, int page_count)
{
        struct ll_dio_pages pvec = {
                .ldp_pages      = pages,
                .ldp_nr         = page_count,
                .ldp_size       = size,
                .ldp_offsets    = NULL,
                .ldp_start_offset = file_offset
        };

        return ll_direct_rw_pages(env, io, rw, inode, &pvec);
}

/* This is the maximum size of a single O_DIRECT request, based on the
 * kmalloc limit.  We need to fit all of the brw_page structs, each one
 * representing PAGE_SIZE worth of user data, into a single buffer, and
 * then truncate this to be a full-sized RPC.  For 4kB PAGE_SIZE this is
 * up to 22MB for 128kB kmalloc and up to 682MB for 4MB kmalloc.
 */
#define MAX_DIO_SIZE ((KMALLOC_MAX_SIZE / sizeof(struct brw_page) *       \
                       PAGE_SIZE) & ~(DT_MAX_BRW_SIZE - 1))
static ssize_t ll_direct_IO_26(struct kiocb *iocb, struct iov_iter *iter)
{
        struct lu_env *env;
        struct cl_io *io;
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        loff_t file_offset = iocb->ki_pos;
        ssize_t count = iov_iter_count(iter);
        ssize_t tot_bytes = 0, result = 0;
        struct ll_inode_info *lli = ll_i2info(inode);
        long size = MAX_DIO_SIZE;
        int refcheck;

        if (!lli->lli_has_smd)
                return -EBADF;

        /* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
        if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
                return -EINVAL;

        CDEBUG(D_VFSTRACE, "VFS Op:inode="DFID"(%p), size=%zd (max %lu), offset=%lld=%llx, pages %zd (max %lu)\n",
               PFID(ll_inode2fid(inode)), inode, count, MAX_DIO_SIZE,
               file_offset, file_offset, count >> PAGE_SHIFT,
               MAX_DIO_SIZE >> PAGE_SHIFT);

        /* Check that all user buffers are aligned as well */
        if (iov_iter_alignment(iter) & ~PAGE_MASK)
                return -EINVAL;

        env = cl_env_get(&refcheck);
        LASSERT(!IS_ERR(env));
        io = vvp_env_io(env)->vui_cl.cis_io;
        LASSERT(io);

        while (iov_iter_count(iter)) {
                struct page **pages;
                size_t offs;

                count = min_t(size_t, iov_iter_count(iter), size);
                if (iov_iter_rw(iter) == READ) {
                        if (file_offset >= i_size_read(inode))
                                break;
                        if (file_offset + count > i_size_read(inode))
                                count = i_size_read(inode) - file_offset;
                }

                result = iov_iter_get_pages_alloc(iter, &pages, count, &offs);
                if (likely(result > 0)) {
                        int n = DIV_ROUND_UP(result + offs, PAGE_SIZE);

                        result = ll_direct_IO_26_seg(env, io, iov_iter_rw(iter),
                                                     inode, file->f_mapping,
                                                     result, file_offset, pages,
                                                     n);
                        ll_free_user_pages(pages, n, iov_iter_rw(iter) == READ);
                }
                if (unlikely(result <= 0)) {
                        /* If we can't allocate a large enough buffer
                         * for the request, shrink it to a smaller
                         * PAGE_SIZE multiple and try again.
                         * We should always be able to kmalloc for a
                         * page worth of page pointers = 4MB on i386.
                         */
                        if (result == -ENOMEM &&
                            size > (PAGE_SIZE / sizeof(*pages)) *
                            PAGE_SIZE) {
                                size = ((((size / 2) - 1) |
                                         ~PAGE_MASK) + 1) &
                                        PAGE_MASK;
                                CDEBUG(D_VFSTRACE, "DIO size now %lu\n",
                                       size);
                                continue;
                        }

                        goto out;
                }
                iov_iter_advance(iter, result);
                tot_bytes += result;
                file_offset += result;
        }
out:
        if (tot_bytes > 0) {
                struct vvp_io *vio = vvp_env_io(env);

                /* no commit async for direct IO */
                vio->u.write.vui_written += tot_bytes;
        }

        cl_env_put(env, &refcheck);
        return tot_bytes ? tot_bytes : result;
}

/**
 * Prepare partially written-to page for a write.
 */
static int ll_prepare_partial_page(const struct lu_env *env, struct cl_io *io,
                                   struct cl_page *pg)
{
        struct cl_attr *attr   = vvp_env_thread_attr(env);
        struct cl_object *obj  = io->ci_obj;
        struct vvp_page *vpg   = cl_object_page_slice(obj, pg);
        loff_t          offset = cl_offset(obj, vvp_index(vpg));
        int             result;

        cl_object_attr_lock(obj);
        result = cl_object_attr_get(env, obj, attr);
        cl_object_attr_unlock(obj);
        if (result == 0) {
                /*
                 * If are writing to a new page, no need to read old data.
                 * The extent locking will have updated the KMS, and for our
                 * purposes here we can treat it like i_size.
                 */
                if (attr->cat_kms <= offset) {
                        char *kaddr = kmap_atomic(vpg->vpg_page);

                        memset(kaddr, 0, cl_page_size(obj));
                        kunmap_atomic(kaddr);
                } else if (vpg->vpg_defer_uptodate) {
                        vpg->vpg_ra_used = 1;
                } else {
                        result = ll_page_sync_io(env, io, pg, CRT_READ);
                }
        }
        return result;
}

static int ll_write_begin(struct file *file, struct address_space *mapping,
                          loff_t pos, unsigned len, unsigned flags,
                          struct page **pagep, void **fsdata)
{
        struct ll_cl_context *lcc;
        const struct lu_env  *env;
        struct cl_io   *io;
        struct cl_page *page;
        struct cl_object *clob = ll_i2info(mapping->host)->lli_clob;
        pgoff_t index = pos >> PAGE_SHIFT;
        struct page *vmpage = NULL;
        unsigned int from = pos & (PAGE_SIZE - 1);
        unsigned int to = from + len;
        int result = 0;

        CDEBUG(D_VFSTRACE, "Writing %lu of %d to %d bytes\n", index, from, len);

        lcc = ll_cl_find(file);
        if (!lcc) {
                result = -EIO;
                goto out;
        }

        env = lcc->lcc_env;
        io  = lcc->lcc_io;

        /* To avoid deadlock, try to lock page first. */
        vmpage = grab_cache_page_nowait(mapping, index);
        if (unlikely(!vmpage || PageDirty(vmpage) || PageWriteback(vmpage))) {
                struct vvp_io *vio = vvp_env_io(env);
                struct cl_page_list *plist = &vio->u.write.vui_queue;

                /* if the page is already in dirty cache, we have to commit
                 * the pages right now; otherwise, it may cause deadlock
                 * because it holds page lock of a dirty page and request for
                 * more grants. It's okay for the dirty page to be the first
                 * one in commit page list, though.
                 */
                if (vmpage && plist->pl_nr > 0) {
                        unlock_page(vmpage);
                        put_page(vmpage);
                        vmpage = NULL;
                }

                /* commit pages and then wait for page lock */
                result = vvp_io_write_commit(env, io);
                if (result < 0)
                        goto out;

                if (!vmpage) {
                        vmpage = grab_cache_page_write_begin(mapping, index,
                                                             flags);
                        if (!vmpage) {
                                result = -ENOMEM;
                                goto out;
                        }
                }
        }

        page = cl_page_find(env, clob, vmpage->index, vmpage, CPT_CACHEABLE);
        if (IS_ERR(page)) {
                result = PTR_ERR(page);
                goto out;
        }

        lcc->lcc_page = page;
        lu_ref_add(&page->cp_reference, "cl_io", io);

        cl_page_assume(env, io, page);
        if (!PageUptodate(vmpage)) {
                /*
                 * We're completely overwriting an existing page,
                 * so _don't_ set it up to date until commit_write
                 */
                if (from == 0 && to == PAGE_SIZE) {
                        CL_PAGE_HEADER(D_PAGE, env, page, "full page write\n");
                        POISON_PAGE(vmpage, 0x11);
                } else {
                        /* TODO: can be optimized at OSC layer to check if it
                         * is a lockless IO. In that case, it's not necessary
                         * to read the data.
                         */
                        result = ll_prepare_partial_page(env, io, page);
                        if (result == 0)
                                SetPageUptodate(vmpage);
                }
        }
        if (result < 0)
                cl_page_unassume(env, io, page);
out:
        if (result < 0) {
                if (vmpage) {
                        unlock_page(vmpage);
                        put_page(vmpage);
                }
        } else {
                *pagep = vmpage;
                *fsdata = lcc;
        }
        return result;
}

static int ll_write_end(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *vmpage, void *fsdata)
{
        struct ll_cl_context *lcc = fsdata;
        const struct lu_env *env;
        struct cl_io *io;
        struct vvp_io *vio;
        struct cl_page *page;
        unsigned from = pos & (PAGE_SIZE - 1);
        bool unplug = false;
        int result = 0;

        put_page(vmpage);

        env  = lcc->lcc_env;
        page = lcc->lcc_page;
        io   = lcc->lcc_io;
        vio  = vvp_env_io(env);

        LASSERT(cl_page_is_owned(page, io));
        if (copied > 0) {
                struct cl_page_list *plist = &vio->u.write.vui_queue;

                lcc->lcc_page = NULL; /* page will be queued */

                /* Add it into write queue */
                cl_page_list_add(plist, page);
                if (plist->pl_nr == 1) /* first page */
                        vio->u.write.vui_from = from;
                else
                        LASSERT(from == 0);
                vio->u.write.vui_to = from + copied;

                /*
                 * To address the deadlock in balance_dirty_pages() where
                 * this dirty page may be written back in the same thread.
                 */
                if (PageDirty(vmpage))
                        unplug = true;

                /* We may have one full RPC, commit it soon */
                if (plist->pl_nr >= PTLRPC_MAX_BRW_PAGES)
                        unplug = true;

                CL_PAGE_DEBUG(D_VFSTRACE, env, page,
                              "queued page: %d.\n", plist->pl_nr);
        } else {
                cl_page_disown(env, io, page);

                lcc->lcc_page = NULL;
                lu_ref_del(&page->cp_reference, "cl_io", io);
                cl_page_put(env, page);

                /* page list is not contiguous now, commit it now */
                unplug = true;
        }

        if (unplug ||
            file->f_flags & O_SYNC || IS_SYNC(file_inode(file)))
                result = vvp_io_write_commit(env, io);

        return result >= 0 ? copied : result;
}

#ifdef CONFIG_MIGRATION
static int ll_migratepage(struct address_space *mapping,
                          struct page *newpage, struct page *page,
                          enum migrate_mode mode
                )
{
        /* Always fail page migration until we have a proper implementation */
        return -EIO;
}
#endif

const struct address_space_operations ll_aops = {
        .readpage       = ll_readpage,
        .direct_IO      = ll_direct_IO_26,
        .writepage      = ll_writepage,
        .writepages     = ll_writepages,
        .set_page_dirty = __set_page_dirty_nobuffers,
        .write_begin    = ll_write_begin,
        .write_end      = ll_write_end,
        .invalidatepage = ll_invalidatepage,
        .releasepage    = (void *)ll_releasepage,
#ifdef CONFIG_MIGRATION
        .migratepage    = ll_migratepage,
#endif
};