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