Added ASCII art to make this clearer.
[tprouty/samba.git] / source / smbd / fileio.c
1 /* 
2    Unix SMB/Netbios implementation.
3    Version 1.9.
4    read/write to a files_struct
5    Copyright (C) Andrew Tridgell 1992-1998
6    Copyright (C) Jeremy Allison 2000-2002. - write cache.
7    
8    This program is free software; you can redistribute it and/or modify
9    it under the terms of the GNU General Public License as published by
10    the Free Software Foundation; either version 2 of the License, or
11    (at your option) any later version.
12    
13    This program is distributed in the hope that it will be useful,
14    but WITHOUT ANY WARRANTY; without even the implied warranty of
15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16    GNU General Public License for more details.
17    
18    You should have received a copy of the GNU General Public License
19    along with this program; if not, write to the Free Software
20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 */
22
23 #include "includes.h"
24
25 static BOOL setup_write_cache(files_struct *, SMB_OFF_T);
26
27 /****************************************************************************
28  Seek a file. Try to avoid the seek if possible.
29 ****************************************************************************/
30
31 static SMB_OFF_T seek_file(files_struct *fsp,SMB_OFF_T pos)
32 {
33         SMB_OFF_T offset = 0;
34         SMB_OFF_T seek_ret;
35
36         if (fsp->print_file && lp_postscript(fsp->conn->service))
37                 offset = 3;
38
39         seek_ret = fsp->conn->vfs_ops.lseek(fsp,fsp->fd,pos+offset,SEEK_SET);
40
41         if(seek_ret == -1) {
42                 DEBUG(0,("seek_file: (%s) sys_lseek failed. Error was %s\n",
43                         fsp->fsp_name, strerror(errno) ));
44                 fsp->pos = -1;
45                 return -1;
46         }
47
48         fsp->pos = seek_ret - offset;
49
50         DEBUG(10,("seek_file (%s): requested pos = %.0f, new pos = %.0f\n",
51                 fsp->fsp_name, (double)(pos+offset), (double)fsp->pos ));
52
53         return(fsp->pos);
54 }
55
56 /****************************************************************************
57  Read from write cache if we can.
58 ****************************************************************************/
59
60
61 static BOOL read_from_write_cache(files_struct *fsp,char *data,SMB_OFF_T pos,size_t n)
62 {
63         write_cache *wcp = fsp->wcp;
64
65         if(!wcp)
66                 return False;
67
68         if(n > wcp->data_size || pos < wcp->offset || pos + n > wcp->offset + wcp->data_size)
69                 return False;
70
71         memcpy(data, wcp->data + (pos - wcp->offset), n);
72
73         DO_PROFILE_INC(writecache_read_hits);
74
75         return True;
76 }
77
78 /****************************************************************************
79  Read from a file.
80 ****************************************************************************/
81
82 ssize_t read_file(files_struct *fsp,char *data,SMB_OFF_T pos,size_t n)
83 {
84         ssize_t ret=0,readret;
85
86         /* you can't read from print files */
87         if (fsp->print_file)
88                 return -1;
89
90         /*
91          * Serve from write cache if we can.
92          */
93
94         if(read_from_write_cache(fsp, data, pos, n))
95                 return n;
96
97         flush_write_cache(fsp, READ_FLUSH);
98
99         if (seek_file(fsp,pos) == -1) {
100                 DEBUG(3,("read_file: Failed to seek to %.0f\n",(double)pos));
101                 return(ret);
102         }
103   
104         if (n > 0) {
105 #ifdef DMF_FIX
106                 int numretries = 3;
107 tryagain:
108                 readret = fsp->conn->vfs_ops.read(fsp,fsp->fd,data,n);
109                 if (readret == -1) {
110                         if ((errno == EAGAIN) && numretries) {
111                                 DEBUG(3,("read_file EAGAIN retry in 10 seconds\n"));
112                                 (void)sleep(10);
113                                 --numretries;
114                                 goto tryagain;
115                         }
116                         return -1;
117                 }
118 #else /* NO DMF fix. */
119                 readret = fsp->conn->vfs_ops.read(fsp,fsp->fd,data,n);
120                 if (readret == -1)
121                         return -1;
122 #endif
123                 if (readret > 0)
124                         ret += readret;
125         }
126
127         DEBUG(10,("read_file (%s): pos = %.0f, size = %lu, returned %lu\n",
128                 fsp->fsp_name, (double)pos, (unsigned long)n, (long)ret ));
129
130         return(ret);
131 }
132
133 /* how many write cache buffers have been allocated */
134 static unsigned int allocated_write_caches;
135
136 /****************************************************************************
137  *Really* write to a file.
138 ****************************************************************************/
139
140 static ssize_t real_write_file(files_struct *fsp,char *data,SMB_OFF_T pos, size_t n)
141 {
142         ssize_t ret;
143
144         if ((pos != -1) && (seek_file(fsp,pos) == -1))
145                 return -1;
146
147         ret = vfs_write_data(fsp,data,n);
148
149         DEBUG(10,("real_write_file (%s): pos = %.0f, size = %lu, returned %ld\n",
150                 fsp->fsp_name, (double)pos, (unsigned long)n, (long)ret ));
151
152         return ret;
153 }
154
155 /****************************************************************************
156 write to a file
157 ****************************************************************************/
158
159 ssize_t write_file(files_struct *fsp, char *data, SMB_OFF_T pos, size_t n)
160 {
161         write_cache *wcp = fsp->wcp;
162         ssize_t total_written = 0;
163         int write_path = -1; 
164
165         if (fsp->print_file)
166                 return print_job_write(SNUM(fsp->conn), fsp->print_jobid, data, n);
167
168         if (!fsp->can_write) {
169                 errno = EPERM;
170                 return(0);
171         }
172
173         if (!fsp->modified) {
174                 SMB_STRUCT_STAT st;
175                 fsp->modified = True;
176
177                 if (fsp->conn->vfs_ops.fstat(fsp,fsp->fd,&st) == 0) {
178                         int dosmode = dos_mode(fsp->conn,fsp->fsp_name,&st);
179                         fsp->size = st.st_size;
180                         if (MAP_ARCHIVE(fsp->conn) && !IS_DOS_ARCHIVE(dosmode))
181                                 file_chmod(fsp->conn,fsp->fsp_name,dosmode | aARCH,&st);
182
183                         /*
184                          * If this is the first write and we have an exclusive oplock then setup
185                          * the write cache.
186                          */
187
188                         if (EXCLUSIVE_OPLOCK_TYPE(fsp->oplock_type) && !wcp) {
189                                 setup_write_cache(fsp, st.st_size);
190                                 wcp = fsp->wcp;
191                         } 
192                 }  
193         }
194
195 #ifdef WITH_PROFILE
196         DO_PROFILE_INC(writecache_total_writes);
197         if (!fsp->oplock_type) {
198                 DO_PROFILE_INC(writecache_non_oplock_writes);
199         }
200 #endif
201
202         /*
203          * If this file is level II oplocked then we need
204          * to grab the shared memory lock and inform all
205          * other files with a level II lock that they need
206          * to flush their read caches. We keep the lock over
207          * the shared memory area whilst doing this.
208          */
209
210         release_level_2_oplocks_on_change(fsp);
211
212 #ifdef WITH_PROFILE
213         if (profile_p && profile_p->writecache_total_writes % 500 == 0) {
214                 DEBUG(3,("WRITECACHE: initwrites=%u abutted=%u total=%u \
215 nonop=%u allocated=%u active=%u direct=%u perfect=%u readhits=%u\n",
216                         profile_p->writecache_init_writes,
217                         profile_p->writecache_abutted_writes,
218                         profile_p->writecache_total_writes,
219                         profile_p->writecache_non_oplock_writes,
220                         profile_p->writecache_allocated_write_caches,
221                         profile_p->writecache_num_write_caches,
222                         profile_p->writecache_direct_writes,
223                         profile_p->writecache_num_perfect_writes,
224                         profile_p->writecache_read_hits ));
225
226                 DEBUG(3,("WRITECACHE: Flushes SEEK=%d, READ=%d, WRITE=%d, READRAW=%d, OPLOCK=%d, CLOSE=%d, SYNC=%d\n",
227                         profile_p->writecache_flushed_writes[SEEK_FLUSH],
228                         profile_p->writecache_flushed_writes[READ_FLUSH],
229                         profile_p->writecache_flushed_writes[WRITE_FLUSH],
230                         profile_p->writecache_flushed_writes[READRAW_FLUSH],
231                         profile_p->writecache_flushed_writes[OPLOCK_RELEASE_FLUSH],
232                         profile_p->writecache_flushed_writes[CLOSE_FLUSH],
233                         profile_p->writecache_flushed_writes[SYNC_FLUSH] ));
234         }
235 #endif
236
237         if(!wcp) {
238                 DO_PROFILE_INC(writecache_direct_writes);
239                 total_written = real_write_file(fsp, data, pos, n);
240                 if ((total_written != -1) && (pos + total_written > fsp->size))
241                         fsp->size = pos + total_written;
242                 return total_written;
243         }
244
245         DEBUG(9,("write_file (%s)(fd=%d pos=%.0f size=%u) wcp->offset=%.0f wcp->data_size=%u\n",
246                 fsp->fsp_name, fsp->fd, (double)pos, (unsigned int)n, (double)wcp->offset, (unsigned int)wcp->data_size));
247
248         /* 
249          * If we have active cache and it isn't contiguous then we flush.
250          * NOTE: There is a small problem with running out of disk ....
251          */
252
253         if (wcp->data_size) {
254
255                 BOOL cache_flush_needed = False;
256
257                 if ((pos >= wcp->offset) && (pos <= wcp->offset + wcp->data_size)) {
258       
259                         /* ASCII art.... JRA.
260
261       +--------------+-----
262       | Cached data  | Rest of allocated cache buffer....
263       +--------------+-----
264
265             +-------------------+
266             | Data to write     |
267             +-------------------+
268
269                         */
270
271                         /*
272                          * Start of write overlaps or abutts the existing data.
273                          */
274
275                         size_t data_used = MIN((wcp->alloc_size - (pos - wcp->offset)), n);
276
277                         memcpy(wcp->data + (pos - wcp->offset), data, data_used);
278
279                         /*
280                          * Update the current buffer size with the new data.
281                          */
282
283                         if(pos + data_used > wcp->offset + wcp->data_size)
284                                 wcp->data_size = pos + data_used - wcp->offset;
285
286                         /*
287                          * Update the file size if changed.
288                          */
289
290                         if (wcp->offset + wcp->data_size > wcp->file_size)
291                                 fsp->size = wcp->file_size = wcp->offset + wcp->data_size;
292
293                         /*
294                          * If we used all the data then
295                          * return here.
296                          */
297
298                         if(n == data_used)
299                                 return n;
300                         else
301                                 cache_flush_needed = True;
302
303                         /*
304                          * Move the start of data forward by the amount used,
305                          * cut down the amount left by the same amount.
306                          */
307
308                         data += data_used;
309                         pos += data_used;
310                         n -= data_used;
311
312                         DO_PROFILE_INC(writecache_abutted_writes);
313                         total_written = data_used;
314
315                         write_path = 1;
316
317                 } else if ((pos < wcp->offset) && (pos + n > wcp->offset) && 
318                                         (pos + n <= wcp->offset + wcp->alloc_size)) {
319
320                         /* ASCII art.... JRA.
321
322                         +---------------+
323                         | Cache buffer  |
324                         +---------------+
325
326             +-------------------+
327             | Data to write     |
328             +-------------------+
329
330                         */
331
332                         /*
333                          * End of write overlaps the existing data.
334                          */
335
336                         size_t data_used = pos + n - wcp->offset;
337
338                         memcpy(wcp->data, data + n - data_used, data_used);
339
340                         /*
341                          * Update the current buffer size with the new data.
342                          */
343
344                         if(pos + n > wcp->offset + wcp->data_size)
345                                 wcp->data_size = pos + n - wcp->offset;
346
347                         /*
348                          * Update the file size if changed.
349                          */
350
351                         if (wcp->offset + wcp->data_size > wcp->file_size)
352                                 fsp->size = wcp->file_size = wcp->offset + wcp->data_size;
353
354                         /*
355                          * We don't need to move the start of data, but we
356                          * cut down the amount left by the amount used.
357                          */
358
359                         n -= data_used;
360
361                         /*
362                          * We cannot have used all the data here.
363                          */
364
365                         cache_flush_needed = True;
366
367                         DO_PROFILE_INC(writecache_abutted_writes);
368                         total_written = data_used;
369
370                         write_path = 2;
371
372                 } else if ( (pos >= wcp->file_size) && 
373                                         (wcp->offset + wcp->data_size == wcp->file_size) &&
374                                         (pos > wcp->offset + wcp->data_size) && 
375                                         (pos < wcp->offset + wcp->alloc_size) ) {
376
377                         /* ASCII art.... JRA.
378
379                        End of file ---->|
380
381                         +---------------+---------------+
382                         | Cached data   | Cache buffer  |
383                         +---------------+---------------+
384
385                                               +-------------------+
386                                               | Data to write     |
387                                               +-------------------+
388
389                         */
390
391                         /*
392                          * Non-contiguous write part of which fits within
393                          * the cache buffer and is extending the file
394                          * and the cache contents reflect the current
395                          * data up to the current end of the file.
396                          */
397
398                         size_t data_used;
399
400                         if(pos + n <= wcp->offset + wcp->alloc_size)
401                                 data_used = n;
402                         else
403                                 data_used = wcp->offset + wcp->alloc_size - pos;
404
405                         /*
406                          * Fill in the non-continuous area with zeros.
407                          */
408
409                         memset(wcp->data + wcp->data_size, '\0',
410                                 pos - (wcp->offset + wcp->data_size) );
411
412                         memcpy(wcp->data + (pos - wcp->offset), data, data_used);
413
414                         /*
415                          * Update the current buffer size with the new data.
416                          */
417
418                         if(pos + data_used > wcp->offset + wcp->data_size)
419                                 wcp->data_size = pos + data_used - wcp->offset;
420
421                         /*
422                          * Update the file size if changed.
423                          */
424
425                         if (wcp->offset + wcp->data_size > wcp->file_size)
426                                 fsp->size = wcp->file_size = wcp->offset + wcp->data_size;
427
428                         /*
429                          * If we used all the data then
430                          * return here.
431                          */
432
433                         if(n == data_used)
434                                 return n;
435                         else
436                                 cache_flush_needed = True;
437
438                         /*
439                          * Move the start of data forward by the amount used,
440                          * cut down the amount left by the same amount.
441                          */
442
443                         data += data_used;
444                         pos += data_used;
445                         n -= data_used;
446
447                         DO_PROFILE_INC(writecache_abutted_writes);
448                         total_written = data_used;
449
450                         write_path = 3;
451
452                 } else {
453
454                         /* ASCII art..... JRA.
455
456    Case 1).
457
458                         +---------------+---------------+
459                         | Cached data   | Cache buffer  |
460                         +---------------+---------------+
461
462                                                               +-------------------+
463                                                               | Data to write     |
464                                                               +-------------------+
465
466    Case 2).
467
468                            +---------------+---------------+
469                            | Cached data   | Cache buffer  |
470                            +---------------+---------------+
471
472    +-------------------+
473    | Data to write     |
474    +-------------------+
475
476     Case 3).
477
478                            +---------------+---------------+
479                            | Cached data   | Cache buffer  |
480                            +---------------+---------------+
481
482                   +-----------------------------------------------------+
483                   | Data to write                                       |
484                   +-----------------------------------------------------+
485
486                   */
487
488                         /*
489                          * Write is bigger than buffer, or there is no overlap on the
490                          * low or high ends.
491                          */
492
493                         DEBUG(9,("write_file: non cacheable write : fd = %d, pos = %.0f, len = %u, current cache pos = %.0f \
494 len = %u\n",fsp->fd, (double)pos, (unsigned int)n, (double)wcp->offset, (unsigned int)wcp->data_size ));
495
496                         /*
497                          * Update the file size if needed.
498                          */
499
500                         if(pos + n > wcp->file_size)
501                                 fsp->size = wcp->file_size = pos + n;
502
503                         /*
504                          * If write would fit in the cache, and is larger than
505                          * the data already in the cache, flush the cache and
506                          * preferentially copy the data new data into it. Otherwise
507                          * just write the data directly.
508                          */
509
510                         if ( n <= wcp->alloc_size && n > wcp->data_size) {
511                                 cache_flush_needed = True;
512                         } else {
513                                 ssize_t ret = real_write_file(fsp, data, pos, n);
514
515                                 /*
516                                  * If the write overlaps the entire cache, then
517                                  * discard the current contents of the cache.
518                                  * Fix from Rasmus Borup Hansen rbh@math.ku.dk.
519                                  */
520
521                                 if ((pos <= wcp->offset) &&
522                                                 (pos + n >= wcp->offset + wcp->data_size) ) {
523                                         DEBUG(9,("write_file: discarding overwritten write \
524 cache: fd = %d, off=%.0f, size=%u\n", fsp->fd, (double)wcp->offset, (unsigned int)wcp->data_size ));
525                                         wcp->data_size = 0;
526                                 }
527
528                                 DO_PROFILE_INC(writecache_direct_writes);
529                                 if (ret == -1)
530                                         return ret;
531
532                                 if (pos + ret > wcp->file_size)
533                                         fsp->size = wcp->file_size = pos + ret;
534
535                                 return ret;
536                         }
537
538                         write_path = 4;
539
540                 }
541
542                 if(wcp->data_size > wcp->file_size)
543                         fsp->size = wcp->file_size = wcp->data_size;
544
545                 if (cache_flush_needed) {
546                         DEBUG(3,("WRITE_FLUSH:%d: due to noncontinuous write: fd = %d, size = %.0f, pos = %.0f, \
547 n = %u, wcp->offset=%.0f, wcp->data_size=%u\n",
548                                 write_path, fsp->fd, (double)wcp->file_size, (double)pos, (unsigned int)n,
549                                 (double)wcp->offset, (unsigned int)wcp->data_size ));
550
551                         flush_write_cache(fsp, WRITE_FLUSH);
552                 }
553         }
554
555         /*
556          * If the write request is bigger than the cache
557          * size, write it all out.
558          */
559
560         if (n > wcp->alloc_size ) {
561                 ssize_t ret = real_write_file(fsp, data, pos, n);
562                 if (ret == -1)
563                         return -1;
564
565                 if (pos + ret > wcp->file_size)
566                         fsp->size = wcp->file_size = pos + n;
567
568                 DO_PROFILE_INC(writecache_direct_writes);
569                 return total_written + n;
570         }
571
572         /*
573          * If there's any data left, cache it.
574          */
575
576         if (n) {
577 #ifdef WITH_PROFILE
578                 if (wcp->data_size) {
579                         DO_PROFILE_INC(writecache_abutted_writes);
580                 } else {
581                         DO_PROFILE_INC(writecache_init_writes);
582                 }
583 #endif
584                 memcpy(wcp->data+wcp->data_size, data, n);
585                 if (wcp->data_size == 0) {
586                         wcp->offset = pos;
587                         DO_PROFILE_INC(writecache_num_write_caches);
588                 }
589                 wcp->data_size += n;
590
591                 /*
592                  * Update the file size if changed.
593                  */
594
595                 if (wcp->offset + wcp->data_size > wcp->file_size)
596                         fsp->size = wcp->file_size = wcp->offset + wcp->data_size;
597                 DEBUG(9,("wcp->offset = %.0f wcp->data_size = %u cache return %u\n",
598                         (double)wcp->offset, (unsigned int)wcp->data_size, (unsigned int)n));
599
600                 total_written += n;
601                 return total_written; /* .... that's a write :) */
602         }
603   
604         return total_written;
605 }
606
607 /****************************************************************************
608  Delete the write cache structure.
609 ****************************************************************************/
610
611 void delete_write_cache(files_struct *fsp)
612 {
613         write_cache *wcp;
614
615         if(!fsp)
616                 return;
617
618         if(!(wcp = fsp->wcp))
619                 return;
620
621         DO_PROFILE_DEC(writecache_allocated_write_caches);
622         allocated_write_caches--;
623
624         SMB_ASSERT(wcp->data_size == 0);
625
626         SAFE_FREE(wcp->data);
627         SAFE_FREE(fsp->wcp);
628
629         DEBUG(10,("delete_write_cache: File %s deleted write cache\n", fsp->fsp_name ));
630 }
631
632 /****************************************************************************
633  Setup the write cache structure.
634 ****************************************************************************/
635
636 static BOOL setup_write_cache(files_struct *fsp, SMB_OFF_T file_size)
637 {
638         ssize_t alloc_size = lp_write_cache_size(SNUM(fsp->conn));
639         write_cache *wcp;
640
641         if (allocated_write_caches >= MAX_WRITE_CACHES) 
642                 return False;
643
644         if(alloc_size == 0 || fsp->wcp)
645                 return False;
646
647         if((wcp = (write_cache *)malloc(sizeof(write_cache))) == NULL) {
648                 DEBUG(0,("setup_write_cache: malloc fail.\n"));
649                 return False;
650         }
651
652         wcp->file_size = file_size;
653         wcp->offset = 0;
654         wcp->alloc_size = alloc_size;
655         wcp->data_size = 0;
656         if((wcp->data = malloc(wcp->alloc_size)) == NULL) {
657                 DEBUG(0,("setup_write_cache: malloc fail for buffer size %u.\n",
658                         (unsigned int)wcp->alloc_size ));
659                 SAFE_FREE(wcp);
660                 return False;
661         }
662
663         memset(wcp->data, '\0', wcp->alloc_size );
664
665         fsp->wcp = wcp;
666         DO_PROFILE_INC(writecache_allocated_write_caches);
667         allocated_write_caches++;
668
669         DEBUG(10,("setup_write_cache: File %s allocated write cache size %u\n",
670                 fsp->fsp_name, wcp->alloc_size ));
671
672         return True;
673 }
674
675 /****************************************************************************
676  Cope with a size change.
677 ****************************************************************************/
678
679 void set_filelen_write_cache(files_struct *fsp, SMB_OFF_T file_size)
680 {
681         fsp->size = file_size;
682         if(fsp->wcp) {
683                 /* The cache *must* have been flushed before we do this. */
684                 if (fsp->wcp->data_size != 0) {
685                         pstring msg;
686                         slprintf(msg, sizeof(msg)-1, "set_filelen_write_cache: size change \
687 on file %s with write cache size = %u\n", fsp->fsp_name, fsp->wcp->data_size );
688                         smb_panic(msg);
689                 }
690                 fsp->wcp->file_size = file_size;
691         }
692 }
693
694 /*******************************************************************
695  Flush a write cache struct to disk.
696 ********************************************************************/
697
698 ssize_t flush_write_cache(files_struct *fsp, enum flush_reason_enum reason)
699 {
700         write_cache *wcp = fsp->wcp;
701         size_t data_size;
702         ssize_t ret;
703
704         if(!wcp || !wcp->data_size)
705                 return 0;
706
707         data_size = wcp->data_size;
708         wcp->data_size = 0;
709
710         DO_PROFILE_DEC_INC(writecache_num_write_caches,writecache_flushed_writes[reason]);
711
712         DEBUG(9,("flushing write cache: fd = %d, off=%.0f, size=%u\n",
713                 fsp->fd, (double)wcp->offset, (unsigned int)data_size));
714
715 #ifdef WITH_PROFILE
716         if(data_size == wcp->alloc_size)
717                 DO_PROFILE_INC(writecache_num_perfect_writes);
718 #endif
719
720         ret = real_write_file(fsp, wcp->data, wcp->offset, data_size);
721
722         /*
723          * Ensure file size if kept up to date if write extends file.
724          */
725
726         if ((ret != -1) && (wcp->offset + ret > wcp->file_size))
727                 wcp->file_size = wcp->offset + ret;
728
729         return ret;
730 }
731
732 /*******************************************************************
733 sync a file
734 ********************************************************************/
735
736 void sync_file(connection_struct *conn, files_struct *fsp)
737 {
738         if(lp_strict_sync(SNUM(conn)) && fsp->fd != -1) {
739                 flush_write_cache(fsp, SYNC_FLUSH);
740                 conn->vfs_ops.fsync(fsp,fsp->fd);
741         }
742 }
743
744
745 /************************************************************
746  Perform a stat whether a valid fd or not.
747 ************************************************************/
748
749 int fsp_stat(files_struct *fsp, SMB_STRUCT_STAT *pst)
750 {
751         if (fsp->fd == -1)
752                 return vfs_stat(fsp->conn, fsp->fsp_name, pst);
753         else
754                 return vfs_fstat(fsp,fsp->fd, pst);
755 }