LXR linux/drivers/staging/lustre/lustre/llite/glimpse.c

   1/*
   2 * GPL HEADER START
   3 *
   4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 only,
   8 * as published by the Free Software Foundation.
   9 *
  10 * This program is distributed in the hope that it will be useful, but
  11 * WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 * General Public License version 2 for more details (a copy is included
  14 * in the LICENSE file that accompanied this code).
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * version 2 along with this program; If not, see
  18 * http://www.gnu.org/licenses/gpl-2.0.html
  19 *
  20 * GPL HEADER END
  21 */
  22/*
  23 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  24 * Use is subject to license terms.
  25 *
  26 * Copyright (c) 2011, 2012, Intel Corporation.
  27 */
  28/*
  29 * This file is part of Lustre, http://www.lustre.org/
  30 * Lustre is a trademark of Sun Microsystems, Inc.
  31 *
  32 * glimpse code shared between vvp and liblustre (and other Lustre clients in
  33 * the future).
  34 *
  35 *   Author: Nikita Danilov <nikita.danilov@sun.com>
  36 *   Author: Oleg Drokin <oleg.drokin@sun.com>
  37 */
  38
  39#include "../../include/linux/libcfs/libcfs.h"
  40#include "../include/obd_class.h"
  41#include "../include/obd_support.h"
  42#include "../include/obd.h"
  43
  44#include "../include/lustre_dlm.h"
  45#include "../include/lustre_mdc.h"
  46#include <linux/pagemap.h>
  47#include <linux/file.h>
  48
  49#include "../include/cl_object.h"
  50#include "../llite/llite_internal.h"
  51
  52static const struct cl_lock_descr whole_file = {
  53        .cld_start = 0,
  54        .cld_end   = CL_PAGE_EOF,
  55        .cld_mode  = CLM_READ
  56};
  57
  58/*
  59 * Check whether file has possible unwriten pages.
  60 *
  61 * \retval 1    file is mmap-ed or has dirty pages
  62 *       0    otherwise
  63 */
  64blkcnt_t dirty_cnt(struct inode *inode)
  65{
  66        blkcnt_t cnt = 0;
  67        struct vvp_object *vob = cl_inode2vvp(inode);
  68        void          *results[1];
  69
  70        if (inode->i_mapping)
  71                cnt += radix_tree_gang_lookup_tag(&inode->i_mapping->page_tree,
  72                                                  results, 0, 1,
  73                                                  PAGECACHE_TAG_DIRTY);
  74        if (cnt == 0 && atomic_read(&vob->vob_mmap_cnt) > 0)
  75                cnt = 1;
  76
  77        return (cnt > 0) ? 1 : 0;
  78}
  79
  80int cl_glimpse_lock(const struct lu_env *env, struct cl_io *io,
  81                    struct inode *inode, struct cl_object *clob, int agl)
  82{
  83        const struct lu_fid  *fid   = lu_object_fid(&clob->co_lu);
  84        struct cl_lock *lock = vvp_env_lock(env);
  85        struct cl_lock_descr *descr = &lock->cll_descr;
  86        int result = 0;
  87
  88        CDEBUG(D_DLMTRACE, "Glimpsing inode " DFID "\n", PFID(fid));
  89
  90        /* NOTE: this looks like DLM lock request, but it may
  91         *       not be one. Due to CEF_ASYNC flag (translated
  92         *       to LDLM_FL_HAS_INTENT by osc), this is
  93         *       glimpse request, that won't revoke any
  94         *       conflicting DLM locks held. Instead,
  95         *       ll_glimpse_callback() will be called on each
  96         *       client holding a DLM lock against this file,
  97         *       and resulting size will be returned for each
  98         *       stripe. DLM lock on [0, EOF] is acquired only
  99         *       if there were no conflicting locks. If there
 100         *       were conflicting locks, enqueuing or waiting
 101         *       fails with -ENAVAIL, but valid inode
 102         *       attributes are returned anyway.
 103         */
 104        *descr = whole_file;
 105        descr->cld_obj = clob;
 106        descr->cld_mode = CLM_READ;
 107        descr->cld_enq_flags = CEF_ASYNC | CEF_MUST;
 108        if (agl)
 109                descr->cld_enq_flags |= CEF_AGL;
 110        /*
 111         * CEF_ASYNC is used because glimpse sub-locks cannot
 112         * deadlock (because they never conflict with other
 113         * locks) and, hence, can be enqueued out-of-order.
 114         *
 115         * CEF_MUST protects glimpse lock from conversion into
 116         * a lockless mode.
 117         */
 118        result = cl_lock_request(env, io, lock);
 119        if (result < 0)
 120                return result;
 121
 122        if (!agl) {
 123                ll_merge_attr(env, inode);
 124                if (i_size_read(inode) > 0 && !inode->i_blocks) {
 125                        /*
 126                         * LU-417: Add dirty pages block count
 127                         * lest i_blocks reports 0, some "cp" or
 128                         * "tar" may think it's a completely
 129                         * sparse file and skip it.
 130                         */
 131                        inode->i_blocks = dirty_cnt(inode);
 132                }
 133        }
 134
 135        cl_lock_release(env, lock);
 136
 137        return result;
 138}
 139
 140static int cl_io_get(struct inode *inode, struct lu_env **envout,
 141                     struct cl_io **ioout, u16 *refcheck)
 142{
 143        struct lu_env     *env;
 144        struct cl_io       *io;
 145        struct ll_inode_info    *lli = ll_i2info(inode);
 146        struct cl_object       *clob = lli->lli_clob;
 147        int result;
 148
 149        if (S_ISREG(inode->i_mode)) {
 150                env = cl_env_get(refcheck);
 151                if (!IS_ERR(env)) {
 152                        io = vvp_env_thread_io(env);
 153                        io->ci_obj = clob;
 154                        *envout = env;
 155                        *ioout  = io;
 156                        result = 1;
 157                } else {
 158                        result = PTR_ERR(env);
 159                }
 160        } else {
 161                result = 0;
 162        }
 163        return result;
 164}
 165
 166int cl_glimpse_size0(struct inode *inode, int agl)
 167{
 168        /*
 169         * We don't need ast_flags argument to cl_glimpse_size(), because
 170         * osc_lock_enqueue() takes care of the possible deadlock that said
 171         * argument was introduced to avoid.
 172         */
 173        /*
 174         * XXX but note that ll_file_seek() passes LDLM_FL_BLOCK_NOWAIT to
 175         * cl_glimpse_size(), which doesn't make sense: glimpse locks are not
 176         * blocking anyway.
 177         */
 178        struct lu_env     *env = NULL;
 179        struct cl_io       *io  = NULL;
 180        int                  result;
 181        u16 refcheck;
 182
 183        result = cl_io_get(inode, &env, &io, &refcheck);
 184        if (result > 0) {
 185again:
 186                io->ci_verify_layout = 1;
 187                result = cl_io_init(env, io, CIT_MISC, io->ci_obj);
 188                if (result > 0)
 189                        /*
 190                         * nothing to do for this io. This currently happens
 191                         * when stripe sub-object's are not yet created.
 192                         */
 193                        result = io->ci_result;
 194                else if (result == 0)
 195                        result = cl_glimpse_lock(env, io, inode, io->ci_obj,
 196                                                 agl);
 197
 198                OBD_FAIL_TIMEOUT(OBD_FAIL_GLIMPSE_DELAY, 2);
 199                cl_io_fini(env, io);
 200                if (unlikely(io->ci_need_restart))
 201                        goto again;
 202                cl_env_put(env, &refcheck);
 203        }
 204        return result;
 205}
 206