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Diffstat (limited to 'sys/ufs/ffs/softdep.h')
| -rw-r--r-- | sys/ufs/ffs/softdep.h | 546 |
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diff --git a/sys/ufs/ffs/softdep.h b/sys/ufs/ffs/softdep.h new file mode 100644 index 00000000000..3435f630417 --- /dev/null +++ b/sys/ufs/ffs/softdep.h @@ -0,0 +1,546 @@ +/* + * 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 9.5 (McKusick) 2/11/98 + */ + +#include <sys/queue.h> + +/* + * 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 */ + ufs_daddr_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 */ + 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 |