/* * Copyright 1998 Marshall Kirk McKusick. All Rights Reserved. * * The soft updates code is derived from the appendix of a University * of Michigan technical report (Gregory R. Ganger and Yale N. Patt, * "Soft Updates: A Solution to the Metadata Update Problem in File * Systems", CSE-TR-254-95, August 1995). * * The following are the copyrights and redistribution conditions that * apply to this copy of the soft update software. For a license * to use, redistribute or sell the soft update software under * conditions other than those described here, please contact the * author at one of the following addresses: * * Marshall Kirk McKusick mckusick@mckusick.com * 1614 Oxford Street +1-510-843-9542 * Berkeley, CA 94709-1608 * USA * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. None of the names of McKusick, Ganger, Patt, or the University of * Michigan may be used to endorse or promote products derived from * this software without specific prior written permission. * 4. Redistributions in any form must be accompanied by information on * how to obtain complete source code for any accompanying software * that uses this software. This source code must either be included * in the distribution or be available for no more than the cost of * distribution plus a nominal fee, and must be freely redistributable * under reasonable conditions. For an executable file, complete * source code means the source code for all modules it contains. * It does not mean source code for modules or files that typically * accompany the operating system on which the executable file runs, * e.g., standard library modules or system header files. * * THIS SOFTWARE IS PROVIDED BY MARSHALL KIRK MCKUSICK ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL MARSHALL KIRK MCKUSICK BE LIABLE FOR * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)softdep.h 9.6 (McKusick) 2/25/99 * $FreeBSD$ */ #include /* * Allocation dependencies are handled with undo/redo on the in-memory * copy of the data. A particular data dependency is eliminated when * it is ALLCOMPLETE: that is ATTACHED, DEPCOMPLETE, and COMPLETE. * * ATTACHED means that the data is not currently being written to * disk. UNDONE means that the data has been rolled back to a safe * state for writing to the disk. When the I/O completes, the data is * restored to its current form and the state reverts to ATTACHED. * The data must be locked throughout the rollback, I/O, and roll * forward so that the rolled back information is never visible to * user processes. The COMPLETE flag indicates that the item has been * written. For example, a dependency that requires that an inode be * written will be marked COMPLETE after the inode has been written * to disk. The DEPCOMPLETE flag indicates the completion of any other * dependencies such as the writing of a cylinder group map has been * completed. A dependency structure may be freed only when both it * and its dependencies have completed and any rollbacks that are in * progress have finished as indicated by the set of ALLCOMPLETE flags * all being set. The two MKDIR flags indicate additional dependencies * that must be done when creating a new directory. MKDIR_BODY is * cleared when the directory data block containing the "." and ".." * entries has been written. MKDIR_PARENT is cleared when the parent * inode with the increased link count for ".." has been written. When * both MKDIR flags have been cleared, the DEPCOMPLETE flag is set to * indicate that the directory dependencies have been completed. The * writing of the directory inode itself sets the COMPLETE flag which * then allows the directory entry for the new directory to be written * to disk. The RMDIR flag marks a dirrem structure as representing * the removal of a directory rather than a file. When the removal * dependencies are completed, additional work needs to be done * (truncation of the "." and ".." entries, an additional decrement * of the associated inode, and a decrement of the parent inode). The * DIRCHG flag marks a diradd structure as representing the changing * of an existing entry rather than the addition of a new one. When * the update is complete the dirrem associated with the inode for * the old name must be added to the worklist to do the necessary * reference count decrement. The GOINGAWAY flag indicates that the * data structure is frozen from further change until its dependencies * have been completed and its resources freed after which it will be * discarded. The IOSTARTED flag prevents multiple calls to the I/O * start routine from doing multiple rollbacks. The ONWORKLIST flag * shows whether the structure is currently linked onto a worklist. */ #define ATTACHED 0x0001 #define UNDONE 0x0002 #define COMPLETE 0x0004 #define DEPCOMPLETE 0x0008 #define MKDIR_PARENT 0x0010 #define MKDIR_BODY 0x0020 #define RMDIR 0x0040 #define DIRCHG 0x0080 #define GOINGAWAY 0x0100 #define IOSTARTED 0x0200 #define ONWORKLIST 0x8000 #define ALLCOMPLETE (ATTACHED | COMPLETE | DEPCOMPLETE) /* * The workitem queue. * * It is sometimes useful and/or necessary to clean up certain dependencies * in the background rather than during execution of an application process * or interrupt service routine. To realize this, we append dependency * structures corresponding to such tasks to a "workitem" queue. In a soft * updates implementation, most pending workitems should not wait for more * than a couple of seconds, so the filesystem syncer process awakens once * per second to process the items on the queue. */ /* LIST_HEAD(workhead, worklist); -- declared in buf.h */ /* * Each request can be linked onto a work queue through its worklist structure. * To avoid the need for a pointer to the structure itself, this structure * MUST be declared FIRST in each type in which it appears! If more than one * worklist is needed in the structure, then a wk_data field must be added * and the macros below changed to use it. */ struct worklist { LIST_ENTRY(worklist) wk_list; /* list of work requests */ unsigned short wk_type; /* type of request */ unsigned short wk_state; /* state flags */ }; #define WK_DATA(wk) ((void *)(wk)) #define WK_PAGEDEP(wk) ((struct pagedep *)(wk)) #define WK_INODEDEP(wk) ((struct inodedep *)(wk)) #define WK_NEWBLK(wk) ((struct newblk *)(wk)) #define WK_BMSAFEMAP(wk) ((struct bmsafemap *)(wk)) #define WK_ALLOCDIRECT(wk) ((struct allocdirect *)(wk)) #define WK_INDIRDEP(wk) ((struct indirdep *)(wk)) #define WK_ALLOCINDIR(wk) ((struct allocindir *)(wk)) #define WK_FREEFRAG(wk) ((struct freefrag *)(wk)) #define WK_FREEBLKS(wk) ((struct freeblks *)(wk)) #define WK_FREEFILE(wk) ((struct freefile *)(wk)) #define WK_DIRADD(wk) ((struct diradd *)(wk)) #define WK_MKDIR(wk) ((struct mkdir *)(wk)) #define WK_DIRREM(wk) ((struct dirrem *)(wk)) /* * Various types of lists */ LIST_HEAD(dirremhd, dirrem); LIST_HEAD(diraddhd, diradd); LIST_HEAD(newblkhd, newblk); LIST_HEAD(inodedephd, inodedep); LIST_HEAD(allocindirhd, allocindir); LIST_HEAD(allocdirecthd, allocdirect); TAILQ_HEAD(allocdirectlst, allocdirect); /* * The "pagedep" structure tracks the various dependencies related to * a particular directory page. If a directory page has any dependencies, * it will have a pagedep linked to its associated buffer. The * pd_dirremhd list holds the list of dirrem requests which decrement * inode reference counts. These requests are processed after the * directory page with the corresponding zero'ed entries has been * written. The pd_diraddhd list maintains the list of diradd requests * which cannot be committed until their corresponding inode has been * written to disk. Because a directory may have many new entries * being created, several lists are maintained hashed on bits of the * offset of the entry into the directory page to keep the lists from * getting too long. Once a new directory entry has been cleared to * be written, it is moved to the pd_pendinghd list. After the new * entry has been written to disk it is removed from the pd_pendinghd * list, any removed operations are done, and the dependency structure * is freed. */ #define DAHASHSZ 6 #define DIRADDHASH(offset) (((offset) >> 2) % DAHASHSZ) struct pagedep { struct worklist pd_list; /* page buffer */ # define pd_state pd_list.wk_state /* check for multiple I/O starts */ LIST_ENTRY(pagedep) pd_hash; /* hashed lookup */ struct mount *pd_mnt; /* associated mount point */ ino_t pd_ino; /* associated file */ ufs_lbn_t pd_lbn; /* block within file */ struct dirremhd pd_dirremhd; /* dirrem's waiting for page */ struct diraddhd pd_diraddhd[DAHASHSZ]; /* diradd dir entry updates */ struct diraddhd pd_pendinghd; /* directory entries awaiting write */ }; /* * The "inodedep" structure tracks the set of dependencies associated * with an inode. One task that it must manage is delayed operations * (i.e., work requests that must be held until the inodedep's associated * inode has been written to disk). Getting an inode from its incore * state to the disk requires two steps to be taken by the filesystem * in this order: first the inode must be copied to its disk buffer by * the VOP_UPDATE operation; second the inode's buffer must be written * to disk. To ensure that both operations have happened in the required * order, the inodedep maintains two lists. Delayed operations are * placed on the id_inowait list. When the VOP_UPDATE is done, all * operations on the id_inowait list are moved to the id_bufwait list. * When the buffer is written, the items on the id_bufwait list can be * safely moved to the work queue to be processed. A second task of the * inodedep structure is to track the status of block allocation within * the inode. Each block that is allocated is represented by an * "allocdirect" structure (see below). It is linked onto the id_newinoupdt * list until both its contents and its allocation in the cylinder * group map have been written to disk. Once these dependencies have been * satisfied, it is removed from the id_newinoupdt list and any followup * actions such as releasing the previous block or fragment are placed * on the id_inowait list. When an inode is updated (a VOP_UPDATE is * done), the "inodedep" structure is linked onto the buffer through * its worklist. Thus, it will be notified when the buffer is about * to be written and when it is done. At the update time, all the * elements on the id_newinoupdt list are moved to the id_inoupdt list * since those changes are now relevant to the copy of the inode in the * buffer. Also at update time, the tasks on the id_inowait list are * moved to the id_bufwait list so that they will be executed when * the updated inode has been written to disk. When the buffer containing * the inode is written to disk, any updates listed on the id_inoupdt * list are rolled back as they are not yet safe. Following the write, * the changes are once again rolled forward and any actions on the * id_bufwait list are processed (since those actions are now safe). * The entries on the id_inoupdt and id_newinoupdt lists must be kept * sorted by logical block number to speed the calculation of the size * of the rolled back inode (see explanation in initiate_write_inodeblock). * When a directory entry is created, it is represented by a diradd. * The diradd is added to the id_inowait list as it cannot be safely * written to disk until the inode that it represents is on disk. After * the inode is written, the id_bufwait list is processed and the diradd * entries are moved to the id_pendinghd list where they remain until * the directory block containing the name has been written to disk. * The purpose of keeping the entries on the id_pendinghd list is so that * the softdep_fsync function can find and push the inode's directory * name(s) as part of the fsync operation for that file. */ struct inodedep { struct worklist id_list; /* buffer holding inode block */ # define id_state id_list.wk_state /* inode dependency state */ LIST_ENTRY(inodedep) id_hash; /* hashed lookup */ struct fs *id_fs; /* associated filesystem */ ino_t id_ino; /* dependent inode */ nlink_t id_nlinkdelta; /* saved effective link count */ struct dinode *id_savedino; /* saved dinode contents */ LIST_ENTRY(inodedep) id_deps; /* bmsafemap's list of inodedep's */ struct buf *id_buf; /* related bmsafemap (if pending) */ off_t id_savedsize; /* file size saved during rollback */ struct workhead id_pendinghd; /* entries awaiting directory write */ struct workhead id_bufwait; /* operations after inode written */ struct workhead id_inowait; /* operations waiting inode update */ struct allocdirectlst id_inoupdt; /* updates before inode written */ struct allocdirectlst id_newinoupdt; /* updates when inode written */ }; /* * A "newblk" structure is attached to a bmsafemap structure when a block * or fragment is allocated from a cylinder group. Its state is set to * DEPCOMPLETE when its cylinder group map is written. It is consumed by * an associated allocdirect or allocindir allocation which will attach * themselves to the bmsafemap structure if the newblk's DEPCOMPLETE flag * is not set (i.e., its cylinder group map has not been written). */ struct newblk { LIST_ENTRY(newblk) nb_hash; /* hashed lookup */ struct fs *nb_fs; /* associated filesystem */ ufs_daddr_t nb_newblkno; /* allocated block number */ int nb_state; /* state of bitmap dependency */ LIST_ENTRY(newblk) nb_deps; /* bmsafemap's list of newblk's */ struct bmsafemap *nb_bmsafemap; /* associated bmsafemap */ }; /* * A "bmsafemap" structure maintains a list of dependency structures * that depend on the update of a particular cylinder group map. * It has lists for newblks, allocdirects, allocindirs, and inodedeps. * It is attached to the buffer of a cylinder group block when any of * these things are allocated from the cylinder group. It is freed * after the cylinder group map is written and the state of its * dependencies are updated with DEPCOMPLETE to indicate that it has * been processed. */ struct bmsafemap { struct worklist sm_list; /* cylgrp buffer */ struct buf *sm_buf; /* associated buffer */ struct allocdirecthd sm_allocdirecthd; /* allocdirect deps */ struct allocindirhd sm_allocindirhd; /* allocindir deps */ struct inodedephd sm_inodedephd; /* inodedep deps */ struct newblkhd sm_newblkhd; /* newblk deps */ }; /* * An "allocdirect" structure is attached to an "inodedep" when a new block * or fragment is allocated and pointed to by the inode described by * "inodedep". The worklist is linked to the buffer that holds the block. * When the block is first allocated, it is linked to the bmsafemap * structure associated with the buffer holding the cylinder group map * from which it was allocated. When the cylinder group map is written * to disk, ad_state has the DEPCOMPLETE flag set. When the block itself * is written, the COMPLETE flag is set. Once both the cylinder group map * and the data itself have been written, it is safe to write the inode * that claims the block. If there was a previous fragment that had been * allocated before the file was increased in size, the old fragment may * be freed once the inode claiming the new block is written to disk. * This ad_fragfree request is attached to the id_inowait list of the * associated inodedep (pointed to by ad_inodedep) for processing after * the inode is written. */ struct allocdirect { struct worklist ad_list; /* buffer holding block */ # define ad_state ad_list.wk_state /* block pointer state */ TAILQ_ENTRY(allocdirect) ad_next; /* inodedep's list of allocdirect's */ ufs_lbn_t ad_lbn; /* block within file */ ufs_daddr_t ad_newblkno; /* new value of block pointer */ ufs_daddr_t ad_oldblkno; /* old value of block pointer */ long ad_newsize; /* size of new block */ long ad_oldsize; /* size of old block */ LIST_ENTRY(allocdirect) ad_deps; /* bmsafemap's list of allocdirect's */ struct buf *ad_buf; /* cylgrp buffer (if pending) */ struct inodedep *ad_inodedep; /* associated inodedep */ struct freefrag *ad_freefrag; /* fragment to be freed (if any) */ }; /* * A single "indirdep" structure manages all allocation dependencies for * pointers in an indirect block. The up-to-date state of the indirect * block is stored in ir_savedata. The set of pointers that may be safely * written to the disk is stored in ir_safecopy. The state field is used * only to track whether the buffer is currently being written (in which * case it is not safe to update ir_safecopy). Ir_deplisthd contains the * list of allocindir structures, one for each block that needs to be * written to disk. Once the block and its bitmap allocation have been * written the safecopy can be updated to reflect the allocation and the * allocindir structure freed. If ir_state indicates that an I/O on the * indirect block is in progress when ir_safecopy is to be updated, the * update is deferred by placing the allocindir on the ir_donehd list. * When the I/O on the indirect block completes, the entries on the * ir_donehd list are processed by updating their corresponding ir_safecopy * pointers and then freeing the allocindir structure. */ struct indirdep { struct worklist ir_list; /* buffer holding indirect block */ # define ir_state ir_list.wk_state /* indirect block pointer state */ caddr_t ir_saveddata; /* buffer cache contents */ struct buf *ir_savebp; /* buffer holding safe copy */ struct allocindirhd ir_donehd; /* done waiting to update safecopy */ struct allocindirhd ir_deplisthd; /* allocindir deps for this block */ }; /* * An "allocindir" structure is attached to an "indirdep" when a new block * is allocated and pointed to by the indirect block described by the * "indirdep". The worklist is linked to the buffer that holds the new block. * When the block is first allocated, it is linked to the bmsafemap * structure associated with the buffer holding the cylinder group map * from which it was allocated. When the cylinder group map is written * to disk, ai_state has the DEPCOMPLETE flag set. When the block itself * is written, the COMPLETE flag is set. Once both the cylinder group map * and the data itself have been written, it is safe to write the entry in * the indirect block that claims the block; the "allocindir" dependency * can then be freed as it is no longer applicable. */ struct allocindir { struct worklist ai_list; /* buffer holding indirect block */ # define ai_state ai_list.wk_state /* indirect block pointer state */ LIST_ENTRY(allocindir) ai_next; /* indirdep's list of allocindir's */ int ai_offset; /* pointer offset in indirect block */ ufs_daddr_t ai_newblkno; /* new block pointer value */ ufs_daddr_t ai_oldblkno; /* old block pointer value */ struct freefrag *ai_freefrag; /* block to be freed when complete */ struct indirdep *ai_indirdep; /* address of associated indirdep */ LIST_ENTRY(allocindir) ai_deps; /* bmsafemap's list of allocindir's */ struct buf *ai_buf; /* cylgrp buffer (if pending) */ }; /* * A "freefrag" structure is attached to an "inodedep" when a previously * allocated fragment is replaced with a larger fragment, rather than extended. * The "freefrag" structure is constructed and attached when the replacement * block is first allocated. It is processed after the inode claiming the * bigger block that replaces it has been written to disk. Note that the * ff_state field is is used to store the uid, so may lose data. However, * the uid is used only in printing an error message, so is not critical. * Keeping it in a short keeps the data structure down to 32 bytes. */ struct freefrag { struct worklist ff_list; /* id_inowait or delayed worklist */ # define ff_state ff_list.wk_state /* owning user; should be uid_t */ struct vnode *ff_devvp; /* filesystem device vnode */ struct fs *ff_fs; /* addr of superblock */ ufs_daddr_t ff_blkno; /* fragment physical block number */ long ff_fragsize; /* size of fragment being deleted */ ino_t ff_inum; /* owning inode number */ }; /* * A "freeblks" structure is attached to an "inodedep" when the * corresponding file's length is reduced to zero. It records all * the information needed to free the blocks of a file after its * zero'ed inode has been written to disk. */ struct freeblks { struct worklist fb_list; /* id_inowait or delayed worklist */ ino_t fb_previousinum; /* inode of previous owner of blocks */ struct vnode *fb_devvp; /* filesystem device vnode */ struct fs *fb_fs; /* addr of superblock */ off_t fb_oldsize; /* previous file size */ off_t fb_newsize; /* new file size */ int fb_chkcnt; /* used to check cnt of blks released */ uid_t fb_uid; /* uid of previous owner of blocks */ ufs_daddr_t fb_dblks[NDADDR]; /* direct blk ptrs to deallocate */ ufs_daddr_t fb_iblks[NIADDR]; /* indirect blk ptrs to deallocate */ }; /* * A "freefile" structure is attached to an inode when its * link count is reduced to zero. It marks the inode as free in * the cylinder group map after the zero'ed inode has been written * to disk and any associated blocks and fragments have been freed. */ struct freefile { struct worklist fx_list; /* id_inowait or delayed worklist */ mode_t fx_mode; /* mode of inode */ ino_t fx_oldinum; /* inum of the unlinked file */ struct vnode *fx_devvp; /* filesystem device vnode */ struct fs *fx_fs; /* addr of superblock */ }; /* * A "diradd" structure is linked to an "inodedep" id_inowait list when a * new directory entry is allocated that references the inode described * by "inodedep". When the inode itself is written (either the initial * allocation for new inodes or with the increased link count for * existing inodes), the COMPLETE flag is set in da_state. If the entry * is for a newly allocated inode, the "inodedep" structure is associated * with a bmsafemap which prevents the inode from being written to disk * until the cylinder group has been updated. Thus the da_state COMPLETE * flag cannot be set until the inode bitmap dependency has been removed. * When creating a new file, it is safe to write the directory entry that * claims the inode once the referenced inode has been written. Since * writing the inode clears the bitmap dependencies, the DEPCOMPLETE flag * in the diradd can be set unconditionally when creating a file. When * creating a directory, there are two additional dependencies described by * mkdir structures (see their description below). When these dependencies * are resolved the DEPCOMPLETE flag is set in the diradd structure. * If there are multiple links created to the same inode, there will be * a separate diradd structure created for each link. The diradd is * linked onto the pg_diraddhd list of the pagedep for the directory * page that contains the entry. When a directory page is written, * the pg_diraddhd list is traversed to rollback any entries that are * not yet ready to be written to disk. If a directory entry is being * changed (by rename) rather than added, the DIRCHG flag is set and * the da_previous entry points to the entry that will be "removed" * once the new entry has been committed. During rollback, entries * with da_previous are replaced with the previous inode number rather * than zero. * * The overlaying of da_pagedep and da_previous is done to keep the * structure down to 32 bytes in size on a 32-bit machine. If a * da_previous entry is present, the pointer to its pagedep is available * in the associated dirrem entry. If the DIRCHG flag is set, the * da_previous entry is valid; if not set the da_pagedep entry is valid. * The DIRCHG flag never changes; it is set when the structure is created * if appropriate and is never cleared. */ struct diradd { struct worklist da_list; /* id_inowait or id_pendinghd list */ # define da_state da_list.wk_state /* state of the new directory entry */ LIST_ENTRY(diradd) da_pdlist; /* pagedep holding directory block */ doff_t da_offset; /* offset of new dir entry in dir blk */ ino_t da_newinum; /* inode number for the new dir entry */ union { struct dirrem *dau_previous; /* entry being replaced in dir change */ struct pagedep *dau_pagedep; /* pagedep dependency for addition */ } da_un; }; #define da_previous da_un.dau_previous #define da_pagedep da_un.dau_pagedep /* * Two "mkdir" structures are needed to track the additional dependencies * associated with creating a new directory entry. Normally a directory * addition can be committed as soon as the newly referenced inode has been * written to disk with its increased link count. When a directory is * created there are two additional dependencies: writing the directory * data block containing the "." and ".." entries (MKDIR_BODY) and writing * the parent inode with the increased link count for ".." (MKDIR_PARENT). * These additional dependencies are tracked by two mkdir structures that * reference the associated "diradd" structure. When they have completed, * they set the DEPCOMPLETE flag on the diradd so that it knows that its * extra dependencies have been completed. The md_state field is used only * to identify which type of dependency the mkdir structure is tracking. * It is not used in the mainline code for any purpose other than consistency * checking. All the mkdir structures in the system are linked together on * a list. This list is needed so that a diradd can find its associated * mkdir structures and deallocate them if it is prematurely freed (as for * example if a mkdir is immediately followed by a rmdir of the same directory). * Here, the free of the diradd must traverse the list to find the associated * mkdir structures that reference it. The deletion would be faster if the * diradd structure were simply augmented to have two pointers that referenced * the associated mkdir's. However, this would increase the size of the diradd * structure from 32 to 64-bits to speed a very infrequent operation. */ struct mkdir { struct worklist md_list; /* id_inowait or buffer holding dir */ # define md_state md_list.wk_state /* type: MKDIR_PARENT or MKDIR_BODY */ struct diradd *md_diradd; /* associated diradd */ struct buf *md_buf; /* MKDIR_BODY: buffer holding dir */ LIST_ENTRY(mkdir) md_mkdirs; /* list of all mkdirs */ }; LIST_HEAD(mkdirlist, mkdir) mkdirlisthd; /* * A "dirrem" structure describes an operation to decrement the link * count on an inode. The dirrem structure is attached to the pg_dirremhd * list of the pagedep for the directory page that contains the entry. * It is processed after the directory page with the deleted entry has * been written to disk. * * The overlaying of dm_pagedep and dm_dirinum is done to keep the * structure down to 32 bytes in size on a 32-bit machine. It works * because they are never used concurrently. */ struct dirrem { struct worklist dm_list; /* delayed worklist */ # define dm_state dm_list.wk_state /* state of the old directory entry */ LIST_ENTRY(dirrem) dm_next; /* pagedep's list of dirrem's */ struct mount *dm_mnt; /* associated mount point */ ino_t dm_oldinum; /* inum of the removed dir entry */ union { struct pagedep *dmu_pagedep; /* pagedep dependency for remove */ ino_t dmu_dirinum; /* parent inode number (for rmdir) */ } dm_un; }; #define dm_pagedep dm_un.dmu_pagedep #define dm_dirinum dm_un.dmu_dirinum