fs/ocfs2/buffer_head_io.c

   1 /* -*- mode: c; c-basic-offset: 8; -*-
   2  * vim: noexpandtab sw=8 ts=8 sts=0:
   3  *
   4  * io.c
   5  *
   6  * Buffer cache handling
   7  *
   8  * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 2 of the License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public
  21  * License along with this program; if not, write to the
  22  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23  * Boston, MA 021110-1307, USA.
  24  */
  25
  26 #include <linux/fs.h>
  27 #include <linux/types.h>
  28 #include <linux/slab.h>
  29 #include <linux/highmem.h>
  30
  31 #include <cluster/masklog.h>
  32
  33 #include "ocfs2.h"
  34
  35 #include "alloc.h"
  36 #include "inode.h"
  37 #include "journal.h"
  38 #include "uptodate.h"
  39
  40 #include "buffer_head_io.h"
  41
  42 int ocfs2_write_block(struct ocfs2_super *osb, struct buffer_head *bh,
  43                       struct inode *inode)
  44 {
  45         int ret = 0;
  46
  47         mlog_entry("(bh->b_blocknr = %llu, inode=%p)\n",
  48                    (unsigned long long)bh->b_blocknr, inode);
  49
  50         BUG_ON(bh->b_blocknr < OCFS2_SUPER_BLOCK_BLKNO);
  51         BUG_ON(buffer_jbd(bh));
  52
  53         /* No need to check for a soft readonly file system here. non
  54          * journalled writes are only ever done on system files which
  55          * can get modified during recovery even if read-only. */
  56         if (ocfs2_is_hard_readonly(osb)) {
  57                 ret = -EROFS;
  58                 goto out;
  59         }
  60
  61         mutex_lock(&OCFS2_I(inode)->ip_io_mutex);
  62
  63         lock_buffer(bh);
  64         set_buffer_uptodate(bh);
  65
  66         /* remove from dirty list before I/O. */
  67         clear_buffer_dirty(bh);
  68
  69         get_bh(bh); /* for end_buffer_write_sync() */
  70         bh->b_end_io = end_buffer_write_sync;
  71         submit_bh(WRITE, bh);
  72
  73         wait_on_buffer(bh);
  74
  75         if (buffer_uptodate(bh)) {
  76                 ocfs2_set_buffer_uptodate(inode, bh);
  77         } else {
  78                 /* We don't need to remove the clustered uptodate
  79                  * information for this bh as it's not marked locally
  80                  * uptodate. */
  81                 ret = -EIO;
  82                 put_bh(bh);
  83         }
  84
  85         mutex_unlock(&OCFS2_I(inode)->ip_io_mutex);
  86 out:
  87         mlog_exit(ret);
  88         return ret;
  89 }
  90
  91 int ocfs2_read_blocks(struct ocfs2_super *osb, u64 block, int nr,
  92                       struct buffer_head *bhs[], int flags,
  93                       struct inode *inode)
  94 {
  95         int status = 0;
  96         struct super_block *sb;
  97         int i, ignore_cache = 0;
  98         struct buffer_head *bh;
  99
 100         mlog_entry("(block=(%llu), nr=(%d), flags=%d, inode=%p)\n",
 101                    (unsigned long long)block, nr, flags, inode);
 102
 103         BUG_ON((flags & OCFS2_BH_READAHEAD) &&
 104                (!inode || !(flags & OCFS2_BH_CACHED)));
 105
 106         if (osb == NULL || osb->sb == NULL || bhs == NULL) {
 107                 status = -EINVAL;
 108                 mlog_errno(status);
 109                 goto bail;
 110         }
 111
 112         if (nr < 0) {
 113                 mlog(ML_ERROR, "asked to read %d blocks!\n", nr);
 114                 status = -EINVAL;
 115                 mlog_errno(status);
 116                 goto bail;
 117         }
 118
 119         if (nr == 0) {
 120                 mlog(ML_BH_IO, "No buffers will be read!\n");
 121                 status = 0;
 122                 goto bail;
 123         }
 124
 125         sb = osb->sb;
 126
 127         if (flags & OCFS2_BH_CACHED && !inode)
 128                 flags &= ~OCFS2_BH_CACHED;
 129
 130         if (inode)
 131                 mutex_lock(&OCFS2_I(inode)->ip_io_mutex);
 132         for (i = 0 ; i < nr ; i++) {
 133                 if (bhs[i] == NULL) {
 134                         bhs[i] = sb_getblk(sb, block++);
 135                         if (bhs[i] == NULL) {
 136                                 if (inode)
 137                                         mutex_unlock(&OCFS2_I(inode)->ip_io_mutex);
 138                                 status = -EIO;
 139                                 mlog_errno(status);
 140                                 goto bail;
 141                         }
 142                 }
 143                 bh = bhs[i];
 144                 ignore_cache = 0;
 145
 146                 /* There are three read-ahead cases here which we need to
 147                  * be concerned with. All three assume a buffer has
 148                  * previously been submitted with OCFS2_BH_READAHEAD
 149                  * and it hasn't yet completed I/O.
 150                  *
 151                  * 1) The current request is sync to disk. This rarely
 152                  *    happens these days, and never when performance
 153                  *    matters - the code can just wait on the buffer
 154                  *    lock and re-submit.
 155                  *
 156                  * 2) The current request is cached, but not
 157                  *    readahead. ocfs2_buffer_uptodate() will return
 158                  *    false anyway, so we'll wind up waiting on the
 159                  *    buffer lock to do I/O. We re-check the request
 160                  *    with after getting the lock to avoid a re-submit.
 161                  *
 162                  * 3) The current request is readahead (and so must
 163                  *    also be a caching one). We short circuit if the
 164                  *    buffer is locked (under I/O) and if it's in the
 165                  *    uptodate cache. The re-check from #2 catches the
 166                  *    case that the previous read-ahead completes just
 167                  *    before our is-it-in-flight check.
 168                  */
 169
 170                 if (flags & OCFS2_BH_CACHED &&
 171                     !ocfs2_buffer_uptodate(inode, bh)) {
 172                         mlog(ML_UPTODATE,
 173                              "bh (%llu), inode %llu not uptodate\n",
 174                              (unsigned long long)bh->b_blocknr,
 175                              (unsigned long long)OCFS2_I(inode)->ip_blkno);
 176                         ignore_cache = 1;
 177                 }
 178
 179                 /* XXX: Can we ever get this and *not* have the cached
 180                  * flag set? */
 181                 if (buffer_jbd(bh)) {
 182                         if (!(flags & OCFS2_BH_CACHED) || ignore_cache)
 183                                 mlog(ML_BH_IO, "trying to sync read a jbd "
 184                                                "managed bh (blocknr = %llu)\n",
 185                                      (unsigned long long)bh->b_blocknr);
 186                         continue;
 187                 }
 188
 189                 if (!(flags & OCFS2_BH_CACHED) || ignore_cache) {
 190                         if (buffer_dirty(bh)) {
 191                                 /* This should probably be a BUG, or
 192                                  * at least return an error. */
 193                                 mlog(ML_BH_IO, "asking me to sync read a dirty "
 194                                                "buffer! (blocknr = %llu)\n",
 195                                      (unsigned long long)bh->b_blocknr);
 196                                 continue;
 197                         }
 198
 199                         /* A read-ahead request was made - if the
 200                          * buffer is already under read-ahead from a
 201                          * previously submitted request than we are
 202                          * done here. */
 203                         if ((flags & OCFS2_BH_READAHEAD)
 204                             && ocfs2_buffer_read_ahead(inode, bh))
 205                                 continue;
 206
 207                         lock_buffer(bh);
 208                         if (buffer_jbd(bh)) {
 209 #ifdef CATCH_BH_JBD_RACES
 210                                 mlog(ML_ERROR, "block %llu had the JBD bit set "
 211                                                "while I was in lock_buffer!",
 212                                      (unsigned long long)bh->b_blocknr);
 213                                 BUG();
 214 #else
 215                                 unlock_buffer(bh);
 216                                 continue;
 217 #endif
 218                         }
 219
 220                         /* Re-check ocfs2_buffer_uptodate() as a
 221                          * previously read-ahead buffer may have
 222                          * completed I/O while we were waiting for the
 223                          * buffer lock. */
 224                         if ((flags & OCFS2_BH_CACHED)
 225                             && !(flags & OCFS2_BH_READAHEAD)
 226                             && ocfs2_buffer_uptodate(inode, bh)) {
 227                                 unlock_buffer(bh);
 228                                 continue;
 229                         }
 230
 231                         clear_buffer_uptodate(bh);
 232                         get_bh(bh); /* for end_buffer_read_sync() */
 233                         bh->b_end_io = end_buffer_read_sync;
 234                         submit_bh(READ, bh);
 235                         continue;
 236                 }
 237         }
 238
 239         status = 0;
 240
 241         for (i = (nr - 1); i >= 0; i--) {
 242                 bh = bhs[i];
 243
 244                 if (!(flags & OCFS2_BH_READAHEAD)) {
 245                         /* We know this can't have changed as we hold the
 246                          * inode sem. Avoid doing any work on the bh if the
 247                          * journal has it. */
 248                         if (!buffer_jbd(bh))
 249                                 wait_on_buffer(bh);
 250
 251                         if (!buffer_uptodate(bh)) {
 252                                 /* Status won't be cleared from here on out,
 253                                  * so we can safely record this and loop back
 254                                  * to cleanup the other buffers. Don't need to
 255                                  * remove the clustered uptodate information
 256                                  * for this bh as it's not marked locally
 257                                  * uptodate. */
 258                                 status = -EIO;
 259                                 put_bh(bh);
 260                                 bhs[i] = NULL;
 261                                 continue;
 262                         }
 263                 }
 264
 265                 /* Always set the buffer in the cache, even if it was
 266                  * a forced read, or read-ahead which hasn't yet
 267                  * completed. */
 268                 if (inode)
 269                         ocfs2_set_buffer_uptodate(inode, bh);
 270         }
 271         if (inode)
 272                 mutex_unlock(&OCFS2_I(inode)->ip_io_mutex);
 273
 274         mlog(ML_BH_IO, "block=(%llu), nr=(%d), cached=%s, flags=0x%x\n",
 275              (unsigned long long)block, nr,
 276              (!(flags & OCFS2_BH_CACHED) || ignore_cache) ? "no" : "yes", flags);
 277
 278 bail:
 279
 280         mlog_exit(status);
 281         return status;
 282 }
 283
 284 /* Check whether the blkno is the super block or one of the backups. */
 285 static void ocfs2_check_super_or_backup(struct super_block *sb,
 286                                         sector_t blkno)
 287 {
 288         int i;
 289         u64 backup_blkno;
 290
 291         if (blkno == OCFS2_SUPER_BLOCK_BLKNO)
 292                 return;
 293
 294         for (i = 0; i < OCFS2_MAX_BACKUP_SUPERBLOCKS; i++) {
 295                 backup_blkno = ocfs2_backup_super_blkno(sb, i);
 296                 if (backup_blkno == blkno)
 297                         return;
 298         }
 299
 300         BUG();
 301 }
 302
 303 /*
 304  * Write super block and backups doesn't need to collaborate with journal,
 305  * so we don't need to lock ip_io_mutex and inode doesn't need to bea passed
 306  * into this function.
 307  */
 308 int ocfs2_write_super_or_backup(struct ocfs2_super *osb,
 309                                 struct buffer_head *bh)
 310 {
 311         int ret = 0;
 312
 313         mlog_entry_void();
 314
 315         BUG_ON(buffer_jbd(bh));
 316         ocfs2_check_super_or_backup(osb->sb, bh->b_blocknr);
 317
 318         if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb)) {
 319                 ret = -EROFS;
 320                 goto out;
 321         }
 322
 323         lock_buffer(bh);
 324         set_buffer_uptodate(bh);
 325
 326         /* remove from dirty list before I/O. */
 327         clear_buffer_dirty(bh);
 328
 329         get_bh(bh); /* for end_buffer_write_sync() */
 330         bh->b_end_io = end_buffer_write_sync;
 331         submit_bh(WRITE, bh);
 332
 333         wait_on_buffer(bh);
 334
 335         if (!buffer_uptodate(bh)) {
 336                 ret = -EIO;
 337                 put_bh(bh);
 338         }
 339
 340 out:
 341         mlog_exit(ret);
 342         return ret;
 343 }