ocfs2: clean up bh null checks
[linux-3.10.git] / 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 }