xref: /openbmc/linux/fs/ocfs2/buffer_head_io.c (revision 64c70b1c)
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 		brelse(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 				brelse(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