/*
 * 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.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2008, 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.
 *
 * glimpse code shared between vvp and liblustre (and other Lustre clients in
 * the future).
 *
 *   Author: Nikita Danilov <nikita.danilov@sun.com>
 *   Author: Oleg Drokin <oleg.drokin@sun.com>
 */

#include "../../include/linux/libcfs/libcfs.h"
#include "../include/obd_class.h"
#include "../include/obd_support.h"
#include "../include/obd.h"

#include "../include/lustre_dlm.h"
#include "../include/lustre_lite.h"
#include "../include/lustre_mdc.h"
#include <linux/pagemap.h>
#include <linux/file.h>

#include "../include/cl_object.h"
#include "../include/lclient.h"
#include "../llite/llite_internal.h"

static const struct cl_lock_descr whole_file = {
        .cld_start = 0,
        .cld_end   = CL_PAGE_EOF,
        .cld_mode  = CLM_READ
};

/*
 * Check whether file has possible unwriten pages.
 *
 * \retval 1    file is mmap-ed or has dirty pages
 *       0    otherwise
 */
blkcnt_t dirty_cnt(struct inode *inode)
{
        blkcnt_t cnt = 0;
        struct ccc_object *vob = cl_inode2ccc(inode);
        void          *results[1];

        if (inode->i_mapping)
                cnt += radix_tree_gang_lookup_tag(&inode->i_mapping->page_tree,
                                                  results, 0, 1,
                                                  PAGECACHE_TAG_DIRTY);
        if (cnt == 0 && atomic_read(&vob->cob_mmap_cnt) > 0)
                cnt = 1;

        return (cnt > 0) ? 1 : 0;
}

int cl_glimpse_lock(const struct lu_env *env, struct cl_io *io,
                    struct inode *inode, struct cl_object *clob, int agl)
{
        struct cl_lock_descr *descr = &ccc_env_info(env)->cti_descr;
        struct cl_inode_info *lli   = cl_i2info(inode);
        const struct lu_fid  *fid   = lu_object_fid(&clob->co_lu);
        struct ccc_io   *cio   = ccc_env_io(env);
        struct cl_lock       *lock;
        int result;

        result = 0;
        if (!(lli->lli_flags & LLIF_MDS_SIZE_LOCK)) {
                CDEBUG(D_DLMTRACE, "Glimpsing inode "DFID"\n", PFID(fid));
                if (lli->lli_has_smd) {
                        /* NOTE: this looks like DLM lock request, but it may
                         *       not be one. Due to CEF_ASYNC flag (translated
                         *       to LDLM_FL_HAS_INTENT by osc), this is
                         *       glimpse request, that won't revoke any
                         *       conflicting DLM locks held. Instead,
                         *       ll_glimpse_callback() will be called on each
                         *       client holding a DLM lock against this file,
                         *       and resulting size will be returned for each
                         *       stripe. DLM lock on [0, EOF] is acquired only
                         *       if there were no conflicting locks. If there
                         *       were conflicting locks, enqueuing or waiting
                         *       fails with -ENAVAIL, but valid inode
                         *       attributes are returned anyway.
                         */
                        *descr = whole_file;
                        descr->cld_obj   = clob;
                        descr->cld_mode  = CLM_PHANTOM;
                        descr->cld_enq_flags = CEF_ASYNC | CEF_MUST;
                        if (agl)
                                descr->cld_enq_flags |= CEF_AGL;
                        cio->cui_glimpse = 1;
                        /*
                         * CEF_ASYNC is used because glimpse sub-locks cannot
                         * deadlock (because they never conflict with other
                         * locks) and, hence, can be enqueued out-of-order.
                         *
                         * CEF_MUST protects glimpse lock from conversion into
                         * a lockless mode.
                         */
                        lock = cl_lock_request(env, io, descr, "glimpse",
                                               current);
                        cio->cui_glimpse = 0;

                        if (!lock)
                                return 0;

                        if (IS_ERR(lock))
                                return PTR_ERR(lock);

                        LASSERT(agl == 0);
                        result = cl_wait(env, lock);
                        if (result == 0) {
                                cl_merge_lvb(env, inode);
                                if (cl_isize_read(inode) > 0 &&
                                    inode->i_blocks == 0) {
                                        /*
                                         * LU-417: Add dirty pages block count
                                         * lest i_blocks reports 0, some "cp" or
                                         * "tar" may think it's a completely
                                         * sparse file and skip it.
                                         */
                                        inode->i_blocks = dirty_cnt(inode);
                                }
                                cl_unuse(env, lock);
                        }
                        cl_lock_release(env, lock, "glimpse", current);
                } else {
                        CDEBUG(D_DLMTRACE, "No objects for inode\n");
                        cl_merge_lvb(env, inode);
                }
        }

        return result;
}

static int cl_io_get(struct inode *inode, struct lu_env **envout,
                     struct cl_io **ioout, int *refcheck)
{
        struct lu_env     *env;
        struct cl_io       *io;
        struct cl_inode_info   *lli = cl_i2info(inode);
        struct cl_object       *clob = lli->lli_clob;
        int result;

        if (S_ISREG(cl_inode_mode(inode))) {
                env = cl_env_get(refcheck);
                if (!IS_ERR(env)) {
                        io = ccc_env_thread_io(env);
                        io->ci_obj = clob;
                        *envout = env;
                        *ioout  = io;
                        result = 1;
                } else
                        result = PTR_ERR(env);
        } else
                result = 0;
        return result;
}

int cl_glimpse_size0(struct inode *inode, int agl)
{
        /*
         * We don't need ast_flags argument to cl_glimpse_size(), because
         * osc_lock_enqueue() takes care of the possible deadlock that said
         * argument was introduced to avoid.
         */
        /*
         * XXX but note that ll_file_seek() passes LDLM_FL_BLOCK_NOWAIT to
         * cl_glimpse_size(), which doesn't make sense: glimpse locks are not
         * blocking anyway.
         */
        struct lu_env     *env = NULL;
        struct cl_io       *io  = NULL;
        int                  result;
        int                  refcheck;

        result = cl_io_get(inode, &env, &io, &refcheck);
        if (result > 0) {
again:
                io->ci_verify_layout = 1;
                result = cl_io_init(env, io, CIT_MISC, io->ci_obj);
                if (result > 0)
                        /*
                         * nothing to do for this io. This currently happens
                         * when stripe sub-object's are not yet created.
                         */
                        result = io->ci_result;
                else if (result == 0)
                        result = cl_glimpse_lock(env, io, inode, io->ci_obj,
                                                 agl);

                OBD_FAIL_TIMEOUT(OBD_FAIL_GLIMPSE_DELAY, 2);
                cl_io_fini(env, io);
                if (unlikely(io->ci_need_restart))
                        goto again;
                cl_env_put(env, &refcheck);
        }
        return result;
}

int cl_local_size(struct inode *inode)
{
        struct lu_env      *env = NULL;
        struct cl_io        *io  = NULL;
        struct ccc_thread_info  *cti;
        struct cl_object        *clob;
        struct cl_lock_descr    *descr;
        struct cl_lock    *lock;
        int                   result;
        int                   refcheck;

        if (!cl_i2info(inode)->lli_has_smd)
                return 0;

        result = cl_io_get(inode, &env, &io, &refcheck);
        if (result <= 0)
                return result;

        clob = io->ci_obj;
        result = cl_io_init(env, io, CIT_MISC, clob);
        if (result > 0)
                result = io->ci_result;
        else if (result == 0) {
                cti = ccc_env_info(env);
                descr = &cti->cti_descr;

                *descr = whole_file;
                descr->cld_obj = clob;
                lock = cl_lock_peek(env, io, descr, "localsize", current);
                if (lock) {
                        cl_merge_lvb(env, inode);
                        cl_unuse(env, lock);
                        cl_lock_release(env, lock, "localsize", current);
                        result = 0;
                } else
                        result = -ENODATA;
        }
        cl_io_fini(env, io);
        cl_env_put(env, &refcheck);
        return result;
}