1 /* 2 * Copyright 1998 Marshall Kirk McKusick. All Rights Reserved. 3 * 4 * The soft updates code is derived from the appendix of a University 5 * of Michigan technical report (Gregory R. Ganger and Yale N. Patt, 6 * "Soft Updates: A Solution to the Metadata Update Problem in File 7 * Systems", CSE-TR-254-95, August 1995). 8 * 9 * The following are the copyrights and redistribution conditions that 10 * apply to this copy of the soft update software. For a license 11 * to use, redistribute or sell the soft update software under 12 * conditions other than those described here, please contact the 13 * author at one of the following addresses: 14 * 15 * Marshall Kirk McKusick mckusick@mckusick.com 16 * 1614 Oxford Street +1-510-843-9542 17 * Berkeley, CA 94709-1608 18 * USA 19 * 20 * Redistribution and use in source and binary forms, with or without 21 * modification, are permitted provided that the following conditions 22 * are met: 23 * 24 * 1. Redistributions of source code must retain the above copyright 25 * notice, this list of conditions and the following disclaimer. 26 * 2. Redistributions in binary form must reproduce the above copyright 27 * notice, this list of conditions and the following disclaimer in the 28 * documentation and/or other materials provided with the distribution. 29 * 3. None of the names of McKusick, Ganger, Patt, or the University of 30 * Michigan may be used to endorse or promote products derived from 31 * this software without specific prior written permission. 32 * 4. Redistributions in any form must be accompanied by information on 33 * how to obtain complete source code for any accompanying software 34 * that uses this software. This source code must either be included 35 * in the distribution or be available for no more than the cost of 36 * distribution plus a nominal fee, and must be freely redistributable 37 * under reasonable conditions. For an executable file, complete 38 * source code means the source code for all modules it contains. 39 * It does not mean source code for modules or files that typically 40 * accompany the operating system on which the executable file runs, 41 * e.g., standard library modules or system header files. 42 * 43 * THIS SOFTWARE IS PROVIDED BY MARSHALL KIRK MCKUSICK ``AS IS'' AND ANY 44 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 45 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 46 * DISCLAIMED. IN NO EVENT SHALL MARSHALL KIRK MCKUSICK BE LIABLE FOR 47 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 48 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 49 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 50 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 51 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 52 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 53 * SUCH DAMAGE. 54 * 55 * @(#)softdep.h 9.5 (McKusick) 2/11/98 56 * $Id:$ 57 */ 58 59 #include <sys/queue.h> 60 61 /* 62 * Allocation dependencies are handled with undo/redo on the in-memory 63 * copy of the data. A particular data dependency is eliminated when 64 * it is ALLCOMPLETE: that is ATTACHED, DEPCOMPLETE, and COMPLETE. 65 * 66 * ATTACHED means that the data is not currently being written to 67 * disk. UNDONE means that the data has been rolled back to a safe 68 * state for writing to the disk. When the I/O completes, the data is 69 * restored to its current form and the state reverts to ATTACHED. 70 * The data must be locked throughout the rollback, I/O, and roll 71 * forward so that the rolled back information is never visible to 72 * user processes. The COMPLETE flag indicates that the item has been 73 * written. For example, a dependency that requires that an inode be 74 * written will be marked COMPLETE after the inode has been written 75 * to disk. The DEPCOMPLETE flag indicates the completion of any other 76 * dependencies such as the writing of a cylinder group map has been 77 * completed. A dependency structure may be freed only when both it 78 * and its dependencies have completed and any rollbacks that are in 79 * progress have finished as indicated by the set of ALLCOMPLETE flags 80 * all being set. The two MKDIR flags indicate additional dependencies 81 * that must be done when creating a new directory. MKDIR_BODY is 82 * cleared when the directory data block containing the "." and ".." 83 * entries has been written. MKDIR_PARENT is cleared when the parent 84 * inode with the increased link count for ".." has been written. When 85 * both MKDIR flags have been cleared, the DEPCOMPLETE flag is set to 86 * indicate that the directory dependencies have been completed. The 87 * writing of the directory inode itself sets the COMPLETE flag which 88 * then allows the directory entry for the new directory to be written 89 * to disk. The RMDIR flag marks a dirrem structure as representing 90 * the removal of a directory rather than a file. When the removal 91 * dependencies are completed, additional work needs to be done 92 * (truncation of the "." and ".." entries, an additional decrement 93 * of the associated inode, and a decrement of the parent inode). The 94 * DIRCHG flag marks a diradd structure as representing the changing 95 * of an existing entry rather than the addition of a new one. When 96 * the update is complete the dirrem associated with the inode for 97 * the old name must be added to the worklist to do the necessary 98 * reference count decrement. The GOINGAWAY flag indicates that the 99 * data structure is frozen from further change until its dependencies 100 * have been completed and its resources freed after which it will be 101 * discarded. The IOSTARTED flag prevents multiple calls to the I/O 102 * start routine from doing multiple rollbacks. The ONWORKLIST flag 103 * shows whether the structure is currently linked onto a worklist. 104 */ 105 #define ATTACHED 0x0001 106 #define UNDONE 0x0002 107 #define COMPLETE 0x0004 108 #define DEPCOMPLETE 0x0008 109 #define MKDIR_PARENT 0x0010 110 #define MKDIR_BODY 0x0020 111 #define RMDIR 0x0040 112 #define DIRCHG 0x0080 113 #define GOINGAWAY 0x0100 114 #define IOSTARTED 0x0200 115 #define ONWORKLIST 0x8000 116 117 #define ALLCOMPLETE (ATTACHED | COMPLETE | DEPCOMPLETE) 118 119 /* 120 * The workitem queue. 121 * 122 * It is sometimes useful and/or necessary to clean up certain dependencies 123 * in the background rather than during execution of an application process 124 * or interrupt service routine. To realize this, we append dependency 125 * structures corresponding to such tasks to a "workitem" queue. In a soft 126 * updates implementation, most pending workitems should not wait for more 127 * than a couple of seconds, so the filesystem syncer process awakens once 128 * per second to process the items on the queue. 129 */ 130 131 /* LIST_HEAD(workhead, worklist); -- declared in buf.h */ 132 133 /* 134 * Each request can be linked onto a work queue through its worklist structure. 135 * To avoid the need for a pointer to the structure itself, this structure 136 * MUST be declared FIRST in each type in which it appears! If more than one 137 * worklist is needed in the structure, then a wk_data field must be added 138 * and the macros below changed to use it. 139 */ 140 struct worklist { 141 LIST_ENTRY(worklist) wk_list; /* list of work requests */ 142 unsigned short wk_type; /* type of request */ 143 unsigned short wk_state; /* state flags */ 144 }; 145 #define WK_DATA(wk) ((void *)(wk)) 146 #define WK_PAGEDEP(wk) ((struct pagedep *)(wk)) 147 #define WK_INODEDEP(wk) ((struct inodedep *)(wk)) 148 #define WK_NEWBLK(wk) ((struct newblk *)(wk)) 149 #define WK_BMSAFEMAP(wk) ((struct bmsafemap *)(wk)) 150 #define WK_ALLOCDIRECT(wk) ((struct allocdirect *)(wk)) 151 #define WK_INDIRDEP(wk) ((struct indirdep *)(wk)) 152 #define WK_ALLOCINDIR(wk) ((struct allocindir *)(wk)) 153 #define WK_FREEFRAG(wk) ((struct freefrag *)(wk)) 154 #define WK_FREEBLKS(wk) ((struct freeblks *)(wk)) 155 #define WK_FREEFILE(wk) ((struct freefile *)(wk)) 156 #define WK_DIRADD(wk) ((struct diradd *)(wk)) 157 #define WK_MKDIR(wk) ((struct mkdir *)(wk)) 158 #define WK_DIRREM(wk) ((struct dirrem *)(wk)) 159 160 /* 161 * Various types of lists 162 */ 163 LIST_HEAD(dirremhd, dirrem); 164 LIST_HEAD(diraddhd, diradd); 165 LIST_HEAD(newblkhd, newblk); 166 LIST_HEAD(inodedephd, inodedep); 167 LIST_HEAD(allocindirhd, allocindir); 168 LIST_HEAD(allocdirecthd, allocdirect); 169 TAILQ_HEAD(allocdirectlst, allocdirect); 170 171 /* 172 * The "pagedep" structure tracks the various dependencies related to 173 * a particular directory page. If a directory page has any dependencies, 174 * it will have a pagedep linked to its associated buffer. The 175 * pd_dirremhd list holds the list of dirrem requests which decrement 176 * inode reference counts. These requests are processed after the 177 * directory page with the corresponding zero'ed entries has been 178 * written. The pd_diraddhd list maintains the list of diradd requests 179 * which cannot be committed until their corresponding inode has been 180 * written to disk. Because a directory may have many new entries 181 * being created, several lists are maintained hashed on bits of the 182 * offset of the entry into the directory page to keep the lists from 183 * getting too long. Once a new directory entry has been cleared to 184 * be written, it is moved to the pd_pendinghd list. After the new 185 * entry has been written to disk it is removed from the pd_pendinghd 186 * list, any removed operations are done, and the dependency structure 187 * is freed. 188 */ 189 #define DAHASHSZ 6 190 #define DIRADDHASH(offset) (((offset) >> 2) % DAHASHSZ) 191 struct pagedep { 192 struct worklist pd_list; /* page buffer */ 193 # define pd_state pd_list.wk_state /* check for multiple I/O starts */ 194 LIST_ENTRY(pagedep) pd_hash; /* hashed lookup */ 195 struct mount *pd_mnt; /* associated mount point */ 196 ino_t pd_ino; /* associated file */ 197 ufs_lbn_t pd_lbn; /* block within file */ 198 struct dirremhd pd_dirremhd; /* dirrem's waiting for page */ 199 struct diraddhd pd_diraddhd[DAHASHSZ]; /* diradd dir entry updates */ 200 struct diraddhd pd_pendinghd; /* directory entries awaiting write */ 201 }; 202 203 /* 204 * The "inodedep" structure tracks the set of dependencies associated 205 * with an inode. One task that it must manage is delayed operations 206 * (i.e., work requests that must be held until the inodedep's associated 207 * inode has been written to disk). Getting an inode from its incore 208 * state to the disk requires two steps to be taken by the filesystem 209 * in this order: first the inode must be copied to its disk buffer by 210 * the VOP_UPDATE operation; second the inode's buffer must be written 211 * to disk. To ensure that both operations have happened in the required 212 * order, the inodedep maintains two lists. Delayed operations are 213 * placed on the id_inowait list. When the VOP_UPDATE is done, all 214 * operations on the id_inowait list are moved to the id_bufwait list. 215 * When the buffer is written, the items on the id_bufwait list can be 216 * safely moved to the work queue to be processed. A second task of the 217 * inodedep structure is to track the status of block allocation within 218 * the inode. Each block that is allocated is represented by an 219 * "allocdirect" structure (see below). It is linked onto the id_newinoupdt 220 * list until both its contents and its allocation in the cylinder 221 * group map have been written to disk. Once these dependencies have been 222 * satisfied, it is removed from the id_newinoupdt list and any followup 223 * actions such as releasing the previous block or fragment are placed 224 * on the id_inowait list. When an inode is updated (a VOP_UPDATE is 225 * done), the "inodedep" structure is linked onto the buffer through 226 * its worklist. Thus, it will be notified when the buffer is about 227 * to be written and when it is done. At the update time, all the 228 * elements on the id_newinoupdt list are moved to the id_inoupdt list 229 * since those changes are now relevant to the copy of the inode in the 230 * buffer. Also at update time, the tasks on the id_inowait list are 231 * moved to the id_bufwait list so that they will be executed when 232 * the updated inode has been written to disk. When the buffer containing 233 * the inode is written to disk, any updates listed on the id_inoupdt 234 * list are rolled back as they are not yet safe. Following the write, 235 * the changes are once again rolled forward and any actions on the 236 * id_bufwait list are processed (since those actions are now safe). 237 * The entries on the id_inoupdt and id_newinoupdt lists must be kept 238 * sorted by logical block number to speed the calculation of the size 239 * of the rolled back inode (see explanation in initiate_write_inodeblock). 240 * When a directory entry is created, it is represented by a diradd. 241 * The diradd is added to the id_inowait list as it cannot be safely 242 * written to disk until the inode that it represents is on disk. After 243 * the inode is written, the id_bufwait list is processed and the diradd 244 * entries are moved to the id_pendinghd list where they remain until 245 * the directory block containing the name has been written to disk. 246 * The purpose of keeping the entries on the id_pendinghd list is so that 247 * the softdep_fsync function can find and push the inode's directory 248 * name(s) as part of the fsync operation for that file. 249 */ 250 struct inodedep { 251 struct worklist id_list; /* buffer holding inode block */ 252 # define id_state id_list.wk_state /* inode dependency state */ 253 LIST_ENTRY(inodedep) id_hash; /* hashed lookup */ 254 struct fs *id_fs; /* associated filesystem */ 255 ino_t id_ino; /* dependent inode */ 256 nlink_t id_nlinkdelta; /* saved effective link count */ 257 struct dinode *id_savedino; /* saved dinode contents */ 258 LIST_ENTRY(inodedep) id_deps; /* bmsafemap's list of inodedep's */ 259 struct buf *id_buf; /* related bmsafemap (if pending) */ 260 off_t id_savedsize; /* file size saved during rollback */ 261 struct workhead id_pendinghd; /* entries awaiting directory write */ 262 struct workhead id_bufwait; /* operations after inode written */ 263 struct workhead id_inowait; /* operations waiting inode update */ 264 struct allocdirectlst id_inoupdt; /* updates before inode written */ 265 struct allocdirectlst id_newinoupdt; /* updates when inode written */ 266 }; 267 268 /* 269 * A "newblk" structure is attached to a bmsafemap structure when a block 270 * or fragment is allocated from a cylinder group. Its state is set to 271 * DEPCOMPLETE when its cylinder group map is written. It is consumed by 272 * an associated allocdirect or allocindir allocation which will attach 273 * themselves to the bmsafemap structure if the newblk's DEPCOMPLETE flag 274 * is not set (i.e., its cylinder group map has not been written). 275 */ 276 struct newblk { 277 LIST_ENTRY(newblk) nb_hash; /* hashed lookup */ 278 struct fs *nb_fs; /* associated filesystem */ 279 ufs_daddr_t nb_newblkno; /* allocated block number */ 280 int nb_state; /* state of bitmap dependency */ 281 LIST_ENTRY(newblk) nb_deps; /* bmsafemap's list of newblk's */ 282 struct bmsafemap *nb_bmsafemap; /* associated bmsafemap */ 283 }; 284 285 /* 286 * A "bmsafemap" structure maintains a list of dependency structures 287 * that depend on the update of a particular cylinder group map. 288 * It has lists for newblks, allocdirects, allocindirs, and inodedeps. 289 * It is attached to the buffer of a cylinder group block when any of 290 * these things are allocated from the cylinder group. It is freed 291 * after the cylinder group map is written and the state of its 292 * dependencies are updated with DEPCOMPLETE to indicate that it has 293 * been processed. 294 */ 295 struct bmsafemap { 296 struct worklist sm_list; /* cylgrp buffer */ 297 struct buf *sm_buf; /* associated buffer */ 298 struct allocdirecthd sm_allocdirecthd; /* allocdirect deps */ 299 struct allocindirhd sm_allocindirhd; /* allocindir deps */ 300 struct inodedephd sm_inodedephd; /* inodedep deps */ 301 struct newblkhd sm_newblkhd; /* newblk deps */ 302 }; 303 304 /* 305 * An "allocdirect" structure is attached to an "inodedep" when a new block 306 * or fragment is allocated and pointed to by the inode described by 307 * "inodedep". The worklist is linked to the buffer that holds the block. 308 * When the block is first allocated, it is linked to the bmsafemap 309 * structure associated with the buffer holding the cylinder group map 310 * from which it was allocated. When the cylinder group map is written 311 * to disk, ad_state has the DEPCOMPLETE flag set. When the block itself 312 * is written, the COMPLETE flag is set. Once both the cylinder group map 313 * and the data itself have been written, it is safe to write the inode 314 * that claims the block. If there was a previous fragment that had been 315 * allocated before the file was increased in size, the old fragment may 316 * be freed once the inode claiming the new block is written to disk. 317 * This ad_fragfree request is attached to the id_inowait list of the 318 * associated inodedep (pointed to by ad_inodedep) for processing after 319 * the inode is written. 320 */ 321 struct allocdirect { 322 struct worklist ad_list; /* buffer holding block */ 323 # define ad_state ad_list.wk_state /* block pointer state */ 324 TAILQ_ENTRY(allocdirect) ad_next; /* inodedep's list of allocdirect's */ 325 ufs_lbn_t ad_lbn; /* block within file */ 326 ufs_daddr_t ad_newblkno; /* new value of block pointer */ 327 ufs_daddr_t ad_oldblkno; /* old value of block pointer */ 328 long ad_newsize; /* size of new block */ 329 long ad_oldsize; /* size of old block */ 330 LIST_ENTRY(allocdirect) ad_deps; /* bmsafemap's list of allocdirect's */ 331 struct buf *ad_buf; /* cylgrp buffer (if pending) */ 332 struct inodedep *ad_inodedep; /* associated inodedep */ 333 struct freefrag *ad_freefrag; /* fragment to be freed (if any) */ 334 }; 335 336 /* 337 * A single "indirdep" structure manages all allocation dependencies for 338 * pointers in an indirect block. The up-to-date state of the indirect 339 * block is stored in ir_savedata. The set of pointers that may be safely 340 * written to the disk is stored in ir_safecopy. The state field is used 341 * only to track whether the buffer is currently being written (in which 342 * case it is not safe to update ir_safecopy). Ir_deplisthd contains the 343 * list of allocindir structures, one for each block that needs to be 344 * written to disk. Once the block and its bitmap allocation have been 345 * written the safecopy can be updated to reflect the allocation and the 346 * allocindir structure freed. If ir_state indicates that an I/O on the 347 * indirect block is in progress when ir_safecopy is to be updated, the 348 * update is deferred by placing the allocindir on the ir_donehd list. 349 * When the I/O on the indirect block completes, the entries on the 350 * ir_donehd list are processed by updating their corresponding ir_safecopy 351 * pointers and then freeing the allocindir structure. 352 */ 353 struct indirdep { 354 struct worklist ir_list; /* buffer holding indirect block */ 355 # define ir_state ir_list.wk_state /* indirect block pointer state */ 356 caddr_t ir_saveddata; /* buffer cache contents */ 357 struct buf *ir_savebp; /* buffer holding safe copy */ 358 struct allocindirhd ir_donehd; /* done waiting to update safecopy */ 359 struct allocindirhd ir_deplisthd; /* allocindir deps for this block */ 360 }; 361 362 /* 363 * An "allocindir" structure is attached to an "indirdep" when a new block 364 * is allocated and pointed to by the indirect block described by the 365 * "indirdep". The worklist is linked to the buffer that holds the new block. 366 * When the block is first allocated, it is linked to the bmsafemap 367 * structure associated with the buffer holding the cylinder group map 368 * from which it was allocated. When the cylinder group map is written 369 * to disk, ai_state has the DEPCOMPLETE flag set. When the block itself 370 * is written, the COMPLETE flag is set. Once both the cylinder group map 371 * and the data itself have been written, it is safe to write the entry in 372 * the indirect block that claims the block; the "allocindir" dependency 373 * can then be freed as it is no longer applicable. 374 */ 375 struct allocindir { 376 struct worklist ai_list; /* buffer holding indirect block */ 377 # define ai_state ai_list.wk_state /* indirect block pointer state */ 378 LIST_ENTRY(allocindir) ai_next; /* indirdep's list of allocindir's */ 379 int ai_offset; /* pointer offset in indirect block */ 380 ufs_daddr_t ai_newblkno; /* new block pointer value */ 381 ufs_daddr_t ai_oldblkno; /* old block pointer value */ 382 struct freefrag *ai_freefrag; /* block to be freed when complete */ 383 struct indirdep *ai_indirdep; /* address of associated indirdep */ 384 LIST_ENTRY(allocindir) ai_deps; /* bmsafemap's list of allocindir's */ 385 struct buf *ai_buf; /* cylgrp buffer (if pending) */ 386 }; 387 388 /* 389 * A "freefrag" structure is attached to an "inodedep" when a previously 390 * allocated fragment is replaced with a larger fragment, rather than extended. 391 * The "freefrag" structure is constructed and attached when the replacement 392 * block is first allocated. It is processed after the inode claiming the 393 * bigger block that replaces it has been written to disk. Note that the 394 * ff_state field is is used to store the uid, so may lose data. However, 395 * the uid is used only in printing an error message, so is not critical. 396 * Keeping it in a short keeps the data structure down to 32 bytes. 397 */ 398 struct freefrag { 399 struct worklist ff_list; /* id_inowait or delayed worklist */ 400 # define ff_state ff_list.wk_state /* owning user; should be uid_t */ 401 struct vnode *ff_devvp; /* filesystem device vnode */ 402 struct fs *ff_fs; /* addr of superblock */ 403 ufs_daddr_t ff_blkno; /* fragment physical block number */ 404 long ff_fragsize; /* size of fragment being deleted */ 405 ino_t ff_inum; /* owning inode number */ 406 }; 407 408 /* 409 * A "freeblks" structure is attached to an "inodedep" when the 410 * corresponding file's length is reduced to zero. It records all 411 * the information needed to free the blocks of a file after its 412 * zero'ed inode has been written to disk. 413 */ 414 struct freeblks { 415 struct worklist fb_list; /* id_inowait or delayed worklist */ 416 ino_t fb_previousinum; /* inode of previous owner of blocks */ 417 struct vnode *fb_devvp; /* filesystem device vnode */ 418 struct fs *fb_fs; /* addr of superblock */ 419 off_t fb_oldsize; /* previous file size */ 420 off_t fb_newsize; /* new file size */ 421 int fb_chkcnt; /* used to check cnt of blks released */ 422 uid_t fb_uid; /* uid of previous owner of blocks */ 423 ufs_daddr_t fb_dblks[NDADDR]; /* direct blk ptrs to deallocate */ 424 ufs_daddr_t fb_iblks[NIADDR]; /* indirect blk ptrs to deallocate */ 425 }; 426 427 /* 428 * A "freefile" structure is attached to an inode when its 429 * link count is reduced to zero. It marks the inode as free in 430 * the cylinder group map after the zero'ed inode has been written 431 * to disk and any associated blocks and fragments have been freed. 432 */ 433 struct freefile { 434 struct worklist fx_list; /* id_inowait or delayed worklist */ 435 mode_t fx_mode; /* mode of inode */ 436 ino_t fx_oldinum; /* inum of the unlinked file */ 437 struct vnode *fx_devvp; /* filesystem device vnode */ 438 struct fs *fx_fs; /* addr of superblock */ 439 }; 440 441 /* 442 * A "diradd" structure is linked to an "inodedep" id_inowait list when a 443 * new directory entry is allocated that references the inode described 444 * by "inodedep". When the inode itself is written (either the initial 445 * allocation for new inodes or with the increased link count for 446 * existing inodes), the COMPLETE flag is set in da_state. If the entry 447 * is for a newly allocated inode, the "inodedep" structure is associated 448 * with a bmsafemap which prevents the inode from being written to disk 449 * until the cylinder group has been updated. Thus the da_state COMPLETE 450 * flag cannot be set until the inode bitmap dependency has been removed. 451 * When creating a new file, it is safe to write the directory entry that 452 * claims the inode once the referenced inode has been written. Since 453 * writing the inode clears the bitmap dependencies, the DEPCOMPLETE flag 454 * in the diradd can be set unconditionally when creating a file. When 455 * creating a directory, there are two additional dependencies described by 456 * mkdir structures (see their description below). When these dependencies 457 * are resolved the DEPCOMPLETE flag is set in the diradd structure. 458 * If there are multiple links created to the same inode, there will be 459 * a separate diradd structure created for each link. The diradd is 460 * linked onto the pg_diraddhd list of the pagedep for the directory 461 * page that contains the entry. When a directory page is written, 462 * the pg_diraddhd list is traversed to rollback any entries that are 463 * not yet ready to be written to disk. If a directory entry is being 464 * changed (by rename) rather than added, the DIRCHG flag is set and 465 * the da_previous entry points to the entry that will be "removed" 466 * once the new entry has been committed. During rollback, entries 467 * with da_previous are replaced with the previous inode number rather 468 * than zero. 469 * 470 * The overlaying of da_pagedep and da_previous is done to keep the 471 * structure down to 32 bytes in size on a 32-bit machine. If a 472 * da_previous entry is present, the pointer to its pagedep is available 473 * in the associated dirrem entry. If the DIRCHG flag is set, the 474 * da_previous entry is valid; if not set the da_pagedep entry is valid. 475 * The DIRCHG flag never changes; it is set when the structure is created 476 * if appropriate and is never cleared. 477 */ 478 struct diradd { 479 struct worklist da_list; /* id_inowait or id_pendinghd list */ 480 # define da_state da_list.wk_state /* state of the new directory entry */ 481 LIST_ENTRY(diradd) da_pdlist; /* pagedep holding directory block */ 482 doff_t da_offset; /* offset of new dir entry in dir blk */ 483 ino_t da_newinum; /* inode number for the new dir entry */ 484 union { 485 struct dirrem *dau_previous; /* entry being replaced in dir change */ 486 struct pagedep *dau_pagedep; /* pagedep dependency for addition */ 487 } da_un; 488 }; 489 #define da_previous da_un.dau_previous 490 #define da_pagedep da_un.dau_pagedep 491 492 /* 493 * Two "mkdir" structures are needed to track the additional dependencies 494 * associated with creating a new directory entry. Normally a directory 495 * addition can be committed as soon as the newly referenced inode has been 496 * written to disk with its increased link count. When a directory is 497 * created there are two additional dependencies: writing the directory 498 * data block containing the "." and ".." entries (MKDIR_BODY) and writing 499 * the parent inode with the increased link count for ".." (MKDIR_PARENT). 500 * These additional dependencies are tracked by two mkdir structures that 501 * reference the associated "diradd" structure. When they have completed, 502 * they set the DEPCOMPLETE flag on the diradd so that it knows that its 503 * extra dependencies have been completed. The md_state field is used only 504 * to identify which type of dependency the mkdir structure is tracking. 505 * It is not used in the mainline code for any purpose other than consistency 506 * checking. All the mkdir structures in the system are linked together on 507 * a list. This list is needed so that a diradd can find its associated 508 * mkdir structures and deallocate them if it is prematurely freed (as for 509 * example if a mkdir is immediately followed by a rmdir of the same directory). 510 * Here, the free of the diradd must traverse the list to find the associated 511 * mkdir structures that reference it. The deletion would be faster if the 512 * diradd structure were simply augmented to have two pointers that referenced 513 * the associated mkdir's. However, this would increase the size of the diradd 514 * structure from 32 to 64-bits to speed a very infrequent operation. 515 */ 516 struct mkdir { 517 struct worklist md_list; /* id_inowait or buffer holding dir */ 518 # define md_state md_list.wk_state /* type: MKDIR_PARENT or MKDIR_BODY */ 519 struct diradd *md_diradd; /* associated diradd */ 520 LIST_ENTRY(mkdir) md_mkdirs; /* list of all mkdirs */ 521 }; 522 LIST_HEAD(mkdirlist, mkdir) mkdirlisthd; 523 524 /* 525 * A "dirrem" structure describes an operation to decrement the link 526 * count on an inode. The dirrem structure is attached to the pg_dirremhd 527 * list of the pagedep for the directory page that contains the entry. 528 * It is processed after the directory page with the deleted entry has 529 * been written to disk. 530 * 531 * The overlaying of dm_pagedep and dm_dirinum is done to keep the 532 * structure down to 32 bytes in size on a 32-bit machine. It works 533 * because they are never used concurrently. 534 */ 535 struct dirrem { 536 struct worklist dm_list; /* delayed worklist */ 537 # define dm_state dm_list.wk_state /* state of the old directory entry */ 538 LIST_ENTRY(dirrem) dm_next; /* pagedep's list of dirrem's */ 539 struct mount *dm_mnt; /* associated mount point */ 540 ino_t dm_oldinum; /* inum of the removed dir entry */ 541 union { 542 struct pagedep *dmu_pagedep; /* pagedep dependency for remove */ 543 ino_t dmu_dirinum; /* parent inode number (for rmdir) */ 544 } dm_un; 545 }; 546 #define dm_pagedep dm_un.dmu_pagedep 547 #define dm_dirinum dm_un.dmu_dirinum 548