/* * Copyright (c) 2006 Apple Computer, Inc. All rights reserved. * * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. The rights granted to you under the License * may not be used to create, or enable the creation or redistribution of, * unlawful or unlicensed copies of an Apple operating system, or to * circumvent, violate, or enable the circumvention or violation of, any * terms of an Apple operating system software license agreement. * * Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ */ /* * Copyright (c) 1982, 1986, 1989, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Scooter Morris at Genentech Inc. * * 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. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 THE REGENTS OR CONTRIBUTORS 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. * * @(#)ufs_lockf.c 8.3 (Berkeley) 1/6/94 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * This variable controls the maximum number of processes that will * be checked in doing deadlock detection. */ static int maxlockdepth = MAXDEPTH; #ifdef LOCKF_DEBUGGING #include #include #include void lf_print(const char *tag, struct lockf *lock); void lf_printlist(const char *tag, struct lockf *lock); static int lockf_debug = 2; SYSCTL_INT(_debug, OID_AUTO, lockf_debug, CTLFLAG_RW, &lockf_debug, 0, ""); /* * If there is no mask bit selector, or there is on, and the selector is * set, then output the debugging diagnostic. */ #define LOCKF_DEBUG(mask, ...) \ do { \ if( !(mask) || ((mask) & lockf_debug)) { \ printf(__VA_ARGS__); \ } \ } while(0) #else /* !LOCKF_DEBUGGING */ #define LOCKF_DEBUG(mask, ...) /* mask */ #endif /* !LOCKF_DEBUGGING */ MALLOC_DEFINE(M_LOCKF, "lockf", "Byte-range locking structures"); #define NOLOCKF (struct lockf *)0 #define SELF 0x1 #define OTHERS 0x2 #define OFF_MAX 0x7fffffffffffffffULL /* max off_t */ /* * Overlapping lock states */ typedef enum { OVERLAP_NONE = 0, OVERLAP_EQUALS_LOCK, OVERLAP_CONTAINS_LOCK, OVERLAP_CONTAINED_BY_LOCK, OVERLAP_STARTS_BEFORE_LOCK, OVERLAP_ENDS_AFTER_LOCK } overlap_t; static int lf_clearlock(struct lockf *); static overlap_t lf_findoverlap(struct lockf *, struct lockf *, int, struct lockf ***, struct lockf **); static struct lockf *lf_getblock(struct lockf *); static int lf_getlock(struct lockf *, struct flock *); static int lf_setlock(struct lockf *); static int lf_split(struct lockf *, struct lockf *); static void lf_wakelock(struct lockf *, boolean_t); /* * in order to mitigate risk * don't switch to new wake-one method unless * we have at least this many waiters to wake up */ #define SAFE_WAITER_LIMIT 20 /* * lf_advlock * * Description: Advisory record locking support * * Parameters: ap Argument pointer to a vnop_advlock_args * argument descriptor structure for the * lock operation to be attempted. * * Returns: 0 Success * EOVERFLOW * EINVAL * ENOLCK Number of locked regions exceeds limit * lf_setlock:EAGAIN * lf_setlock:EDEADLK * lf_setlock:EINTR * lf_setlock:ENOLCK * lf_clearlock:ENOLCK * vnode_size:??? * * Notes: We return ENOLCK when we run out of memory to support locks; as * such, there is no specific expectation limit other than the * amount of available resources. */ int lf_advlock(struct vnop_advlock_args *ap) { struct vnode *vp = ap->a_vp; struct flock *fl = ap->a_fl; vfs_context_t context = ap->a_context; struct lockf *lock; off_t start, end, oadd; u_quad_t size; int error; struct lockf **head = &vp->v_lockf; /* XXX HFS may need a !vnode_isreg(vp) EISDIR error here */ /* * Avoid the common case of unlocking when inode has no locks. */ if (*head == (struct lockf *)0) { if (ap->a_op != F_SETLK) { fl->l_type = F_UNLCK; LOCKF_DEBUG(0, "lf_advlock: '%s' unlock without lock\n", vfs_context_proc(context)->p_comm); return (0); } } /* * Convert the flock structure into a start and end. */ switch (fl->l_whence) { case SEEK_SET: case SEEK_CUR: /* * Caller is responsible for adding any necessary offset * when SEEK_CUR is used. */ start = fl->l_start; break; case SEEK_END: /* * It's OK to cast the u_quad_t to and off_t here, since they * are the same storage size, and the value of the returned * contents will never overflow into the sign bit. We need to * do this because we will use size to force range checks. */ if ((error = vnode_size(vp, (off_t *)&size, context))) { LOCKF_DEBUG(0, "lf_advlock: vnode_getattr failed: %d\n", error); return (error); } if (size > OFF_MAX || (fl->l_start > 0 && size > (u_quad_t)(OFF_MAX - fl->l_start))) return (EOVERFLOW); start = size + fl->l_start; break; default: LOCKF_DEBUG(0, "lf_advlock: unknown whence %d\n", fl->l_whence); return (EINVAL); } if (start < 0) { LOCKF_DEBUG(0, "lf_advlock: start < 0 (%qd)\n", start); return (EINVAL); } if (fl->l_len < 0) { if (start == 0) { LOCKF_DEBUG(0, "lf_advlock: len < 0 & start == 0\n"); return (EINVAL); } end = start - 1; start += fl->l_len; if (start < 0) { LOCKF_DEBUG(0, "lf_advlock: start < 0 (%qd)\n", start); return (EINVAL); } } else if (fl->l_len == 0) end = -1; else { oadd = fl->l_len - 1; if (oadd > (off_t)(OFF_MAX - start)) { LOCKF_DEBUG(0, "lf_advlock: overflow\n"); return (EOVERFLOW); } end = start + oadd; } /* * Create the lockf structure */ MALLOC(lock, struct lockf *, sizeof *lock, M_LOCKF, M_WAITOK); if (lock == NULL) return (ENOLCK); lock->lf_start = start; lock->lf_end = end; lock->lf_id = ap->a_id; lock->lf_vnode = vp; lock->lf_type = fl->l_type; lock->lf_head = head; lock->lf_next = (struct lockf *)0; lock->lf_waiters = 0; TAILQ_INIT(&lock->lf_blkhd); lock->lf_flags = ap->a_flags; if (ap->a_flags & F_FLOCK) lock->lf_flags |= F_WAKE1_SAFE; lck_mtx_lock(&vp->v_lock); /* protect the lockf list */ /* * Do the requested operation. */ switch(ap->a_op) { case F_SETLK: error = lf_setlock(lock); break; case F_UNLCK: error = lf_clearlock(lock); FREE(lock, M_LOCKF); break; case F_GETLK: error = lf_getlock(lock, fl); FREE(lock, M_LOCKF); break; default: FREE(lock, M_LOCKF); error = EINVAL; break; } lck_mtx_unlock(&vp->v_lock); /* done maniplulating the list */ LOCKF_DEBUG(0, "lf_advlock: normal exit: %d\n\n", error); return (error); } /* * lf_coelesce_adjacent * * Description: Helper function: when setting a lock, coelesce adjacent * locks. Needed because adjacent locks are not overlapping, * but POSIX requires that they be coelesced. * * Parameters: lock The new lock which may be adjacent * to already locked reagions, and which * should therefore be coelesced with them * * Returns: */ static void lf_coelesce_adjacent(struct lockf *lock) { struct lockf **lf = lock->lf_head; while (*lf != NOLOCKF) { /* reject locks that obviously could not be coelesced */ if ((*lf == lock) || ((*lf)->lf_id != lock->lf_id) || ((*lf)->lf_type != lock->lf_type)) { lf = &(*lf)->lf_next; continue; } /* If the lock ends adjacent to us, we can coelesce it */ if ((*lf)->lf_end != -1 && ((*lf)->lf_end + 1) == lock->lf_start) { struct lockf *adjacent = *lf; LOCKF_DEBUG(0, "lf_coelesce_adjacent: coelesce adjacent previous\n"); lock->lf_start = (*lf)->lf_start; *lf = lock; lf = &(*lf)->lf_next; FREE(adjacent, M_LOCKF); continue; } /* If the lock starts adjacent to us, we can coelesce it */ if (lock->lf_end != -1 && (lock->lf_end + 1) == (*lf)->lf_start) { struct lockf *adjacent = *lf; LOCKF_DEBUG(0, "lf_coelesce_adjacent: coelesce adjacent following\n"); lock->lf_end = (*lf)->lf_end; lock->lf_next = (*lf)->lf_next; lf = &lock->lf_next; FREE(adjacent, M_LOCKF); continue; } /* no matching conditions; go on to next lock */ lf = &(*lf)->lf_next; } } /* * lf_setlock * * Description: Set a byte-range lock. * * Parameters: lock The lock structure describing the lock * to be set; allocated by the caller, it * will be linked into the lock list if * the set is successful, and freed if the * set is unsuccessful. * * Returns: 0 Success * EAGAIN * EDEADLK * lf_split:ENOLCK * lf_clearlock:ENOLCK * msleep:EINTR * * Notes: We add the lock to the provisional lock list. We do not * coelesce at this time; this has implications for other lock * requestors in the blocker search mechanism. */ static int lf_setlock(struct lockf *lock) { struct lockf *block; struct lockf **head = lock->lf_head; struct lockf **prev, *overlap, *ltmp; static char lockstr[] = "lockf"; int priority, needtolink, error; struct vnode *vp = lock->lf_vnode; overlap_t ovcase; #ifdef LOCKF_DEBUGGING if (lockf_debug & 1) { lf_print("lf_setlock", lock); lf_printlist("lf_setlock(in)", lock); } #endif /* LOCKF_DEBUGGING */ /* * Set the priority */ priority = PLOCK; if (lock->lf_type == F_WRLCK) priority += 4; priority |= PCATCH; /* * Scan lock list for this file looking for locks that would block us. */ while ((block = lf_getblock(lock))) { /* * Free the structure and return if nonblocking. */ if ((lock->lf_flags & F_WAIT) == 0) { FREE(lock, M_LOCKF); return (EAGAIN); } /* * We are blocked. Since flock style locks cover * the whole file, there is no chance for deadlock. * For byte-range locks we must check for deadlock. * * Deadlock detection is done by looking through the * wait channels to see if there are any cycles that * involve us. MAXDEPTH is set just to make sure we * do not go off into neverland. */ if ((lock->lf_flags & F_POSIX) && (block->lf_flags & F_POSIX)) { struct proc *wproc, *bproc; struct uthread *ut; struct lockf *waitblock; int i = 0; /* The block is waiting on something */ wproc = (struct proc *)block->lf_id; proc_lock(wproc); TAILQ_FOREACH(ut, &wproc->p_uthlist, uu_list) { /* * While the thread is asleep (uu_wchan != 0) * in this code (uu_wmesg == lockstr) * and we have not exceeded the maximum cycle * depth (i < maxlockdepth), then check for a * cycle to see if the lock is blocked behind * someone blocked behind us. */ while (((waitblock = (struct lockf *)ut->uu_wchan) != NULL) && ut->uu_wmesg == lockstr && (i++ < maxlockdepth)) { waitblock = (struct lockf *)ut->uu_wchan; /* * Get the lock blocking the lock * which would block us, and make * certain it hasn't come unblocked * (been granted, e.g. between the time * we called lf_getblock, and the time * we successfully acquired the * proc_lock). */ waitblock = waitblock->lf_next; if (waitblock == NULL) break; /* * Make sure it's an advisory range * lock and not an overall file lock; * if we mix lock types, it's our own * fault. */ if ((waitblock->lf_flags & F_POSIX) == 0) break; /* * If the owner of the lock that's * blocking a lock that's blocking us * getting the requested lock, then we * would deadlock, so error out. */ bproc = (struct proc *)waitblock->lf_id; if (bproc == (struct proc *)lock->lf_id) { proc_unlock(wproc); FREE(lock, M_LOCKF); return (EDEADLK); } } } proc_unlock(wproc); } /* * For flock type locks, we must first remove * any shared locks that we hold before we sleep * waiting for an exclusive lock. */ if ((lock->lf_flags & F_FLOCK) && lock->lf_type == F_WRLCK) { lock->lf_type = F_UNLCK; if ((error = lf_clearlock(lock)) != 0) { FREE(lock, M_LOCKF); return (error); } lock->lf_type = F_WRLCK; } /* * Add our lock to the blocked list and sleep until we're free. * Remember who blocked us (for deadlock detection). */ lock->lf_next = block; TAILQ_INSERT_TAIL(&block->lf_blkhd, lock, lf_block); block->lf_waiters++; if ( !(lock->lf_flags & F_FLOCK)) block->lf_flags &= ~F_WAKE1_SAFE; #ifdef LOCKF_DEBUGGING if (lockf_debug & 1) { lf_print("lf_setlock: blocking on", block); lf_printlist("lf_setlock(block)", block); } #endif /* LOCKF_DEBUGGING */ error = msleep(lock, &vp->v_lock, priority, lockstr, 0); if (!TAILQ_EMPTY(&lock->lf_blkhd)) { struct lockf *tlock; if ((block = lf_getblock(lock))) { TAILQ_FOREACH(tlock, &lock->lf_blkhd, lf_block) { tlock->lf_next = block; } TAILQ_CONCAT(&block->lf_blkhd, &lock->lf_blkhd, lf_block); block->lf_waiters += lock->lf_waiters; lock->lf_waiters = 0; } } if (error) { /* XXX */ /* * We may have been awakened by a signal and/or by a * debugger continuing us (in which cases we must remove * ourselves from the blocked list) and/or by another * process releasing a lock (in which case we have * already been removed from the blocked list and our * lf_next field set to NOLOCKF). */ if (lock->lf_next) { TAILQ_REMOVE(&lock->lf_next->lf_blkhd, lock, lf_block); lock->lf_next->lf_waiters--; lock->lf_next = NOLOCKF; } if (!TAILQ_EMPTY(&lock->lf_blkhd)) lf_wakelock(lock, TRUE); FREE(lock, M_LOCKF); return (error); } /* XXX */ } /* * No blocks!! Add the lock. Note that we will * downgrade or upgrade any overlapping locks this * process already owns. * * Skip over locks owned by other processes. * Handle any locks that overlap and are owned by ourselves. */ prev = head; block = *head; needtolink = 1; for (;;) { ovcase = lf_findoverlap(block, lock, SELF, &prev, &overlap); if (ovcase) block = overlap->lf_next; /* * Six cases: * 0) no overlap * 1) overlap == lock * 2) overlap contains lock * 3) lock contains overlap * 4) overlap starts before lock * 5) overlap ends after lock */ switch (ovcase) { case OVERLAP_NONE: if (needtolink) { *prev = lock; lock->lf_next = overlap; } break; case OVERLAP_EQUALS_LOCK: /* * If downgrading lock, others may be * able to acquire it. */ if (lock->lf_type == F_RDLCK && overlap->lf_type == F_WRLCK) lf_wakelock(overlap, TRUE); overlap->lf_type = lock->lf_type; FREE(lock, M_LOCKF); lock = overlap; /* for lf_coelesce_adjacent() */ break; case OVERLAP_CONTAINS_LOCK: /* * Check for common starting point and different types. */ if (overlap->lf_type == lock->lf_type) { FREE(lock, M_LOCKF); lock = overlap; /* for lf_coelesce_adjacent() */ break; } if (overlap->lf_start == lock->lf_start) { *prev = lock; lock->lf_next = overlap; overlap->lf_start = lock->lf_end + 1; } else { /* * If we can't split the lock, we can't * grant it. Claim a system limit for the * resource shortage. */ if (lf_split(overlap, lock)) { FREE(lock, M_LOCKF); return (ENOLCK); } } lf_wakelock(overlap, TRUE); break; case OVERLAP_CONTAINED_BY_LOCK: /* * If downgrading lock, others may be able to * acquire it, otherwise take the list. */ if (lock->lf_type == F_RDLCK && overlap->lf_type == F_WRLCK) { lf_wakelock(overlap, TRUE); } else { while (!TAILQ_EMPTY(&overlap->lf_blkhd)) { ltmp = TAILQ_FIRST(&overlap->lf_blkhd); TAILQ_REMOVE(&overlap->lf_blkhd, ltmp, lf_block); overlap->lf_waiters--; TAILQ_INSERT_TAIL(&lock->lf_blkhd, ltmp, lf_block); lock->lf_waiters++; ltmp->lf_next = lock; } } /* * Add the new lock if necessary and delete the overlap. */ if (needtolink) { *prev = lock; lock->lf_next = overlap->lf_next; prev = &lock->lf_next; needtolink = 0; } else *prev = overlap->lf_next; FREE(overlap, M_LOCKF); continue; case OVERLAP_STARTS_BEFORE_LOCK: /* * Add lock after overlap on the list. */ lock->lf_next = overlap->lf_next; overlap->lf_next = lock; overlap->lf_end = lock->lf_start - 1; prev = &lock->lf_next; lf_wakelock(overlap, TRUE); needtolink = 0; continue; case OVERLAP_ENDS_AFTER_LOCK: /* * Add the new lock before overlap. */ if (needtolink) { *prev = lock; lock->lf_next = overlap; } overlap->lf_start = lock->lf_end + 1; lf_wakelock(overlap, TRUE); break; } break; } /* Coelesce adjacent locks with identical attributes */ lf_coelesce_adjacent(lock); #ifdef LOCKF_DEBUGGING if (lockf_debug & 1) { lf_print("lf_setlock: got the lock", lock); lf_printlist("lf_setlock(out)", lock); } #endif /* LOCKF_DEBUGGING */ return (0); } /* * lf_clearlock * * Description: Remove a byte-range lock on an vnode. Generally, find the * lock (or an overlap to that lock) and remove it (or shrink * it), then wakeup anyone we can. * * Parameters: unlock The lock to clear * * Returns: 0 Success * lf_split:ENOLCK * * Notes: A caller may unlock all the locks owned by the caller by * specifying the entire file range; locks owned by other * callers are not effected by this operation. */ static int lf_clearlock(struct lockf *unlock) { struct lockf **head = unlock->lf_head; struct lockf *lf = *head; struct lockf *overlap, **prev; overlap_t ovcase; if (lf == NOLOCKF) return (0); #ifdef LOCKF_DEBUGGING if (unlock->lf_type != F_UNLCK) panic("lf_clearlock: bad type"); if (lockf_debug & 1) lf_print("lf_clearlock", unlock); #endif /* LOCKF_DEBUGGING */ prev = head; while ((ovcase = lf_findoverlap(lf, unlock, SELF, &prev, &overlap)) != OVERLAP_NONE) { /* * Wakeup the list of locks to be retried. */ lf_wakelock(overlap, FALSE); switch (ovcase) { case OVERLAP_NONE: /* satisfy compiler enum/switch */ break; case OVERLAP_EQUALS_LOCK: *prev = overlap->lf_next; FREE(overlap, M_LOCKF); break; case OVERLAP_CONTAINS_LOCK: /* split it */ if (overlap->lf_start == unlock->lf_start) { overlap->lf_start = unlock->lf_end + 1; break; } /* * If we can't split the lock, we can't grant it. * Claim a system limit for the resource shortage. */ if (lf_split(overlap, unlock)) return (ENOLCK); overlap->lf_next = unlock->lf_next; break; case OVERLAP_CONTAINED_BY_LOCK: *prev = overlap->lf_next; lf = overlap->lf_next; FREE(overlap, M_LOCKF); continue; case OVERLAP_STARTS_BEFORE_LOCK: overlap->lf_end = unlock->lf_start - 1; prev = &overlap->lf_next; lf = overlap->lf_next; continue; case OVERLAP_ENDS_AFTER_LOCK: overlap->lf_start = unlock->lf_end + 1; break; } break; } #ifdef LOCKF_DEBUGGING if (lockf_debug & 1) lf_printlist("lf_clearlock", unlock); #endif /* LOCKF_DEBUGGING */ return (0); } /* * lf_getlock * * Description: Check whether there is a blocking lock, and if so return * its process identifier into the lock being requested. * * Parameters: lock Pointer to lock to test for blocks * fl Pointer to flock structure to receive * the blocking lock information, if a * blocking lock is found. * * Returns: 0 Success * * Implicit Returns: * *fl Contents modified to reflect the * blocking lock, if one is found; not * modified otherwise * * Notes: fl->l_pid will be (-1) for file locks and will only be set to * the blocking process ID for advisory record locks. */ static int lf_getlock(struct lockf *lock, struct flock *fl) { struct lockf *block; #ifdef LOCKF_DEBUGGING if (lockf_debug & 1) lf_print("lf_getlock", lock); #endif /* LOCKF_DEBUGGING */ if ((block = lf_getblock(lock))) { fl->l_type = block->lf_type; fl->l_whence = SEEK_SET; fl->l_start = block->lf_start; if (block->lf_end == -1) fl->l_len = 0; else fl->l_len = block->lf_end - block->lf_start + 1; if (block->lf_flags & F_POSIX) fl->l_pid = proc_pid((struct proc *)(block->lf_id)); else fl->l_pid = -1; } else { fl->l_type = F_UNLCK; } return (0); } /* * lf_getblock * * Description: Walk the list of locks for an inode and return the first * blocking lock. A lock is considered blocking if we are not * the lock owner; otherwise, we are permitted to upgrade or * downgrade it, and it's not considered blocking. * * Parameters: lock The lock for which we are interested * in obtaining the blocking lock, if any * * Returns: NOLOCKF No blocking lock exists * !NOLOCKF The address of the blocking lock's * struct lockf. */ static struct lockf * lf_getblock(struct lockf *lock) { struct lockf **prev, *overlap, *lf = *(lock->lf_head); int ovcase; prev = lock->lf_head; while ((ovcase = lf_findoverlap(lf, lock, OTHERS, &prev, &overlap)) != OVERLAP_NONE) { /* * We've found an overlap, see if it blocks us */ if ((lock->lf_type == F_WRLCK || overlap->lf_type == F_WRLCK)) return (overlap); /* * Nope, point to the next one on the list and * see if it blocks us */ lf = overlap->lf_next; } return (NOLOCKF); } /* * lf_findoverlap * * Description: Walk the list of locks to find an overlapping lock (if any). * * Parameters: lf First lock on lock list * lock The lock we are checking for an overlap * check Check type * prev pointer to pointer pointer to contain * address of pointer to previous lock * pointer to overlapping lock, if overlap * overlap pointer to pointer to contain address * of overlapping lock * * Returns: OVERLAP_NONE * OVERLAP_EQUALS_LOCK * OVERLAP_CONTAINS_LOCK * OVERLAP_CONTAINED_BY_LOCK * OVERLAP_STARTS_BEFORE_LOCK * OVERLAP_ENDS_AFTER_LOCK * * Implicit Returns: * *prev The address of the next pointer in the * lock previous to the overlapping lock; * this is generally used to relink the * lock list, avoiding a second iteration. * *overlap The pointer to the overlapping lock * itself; this is ussed to return data in * the check == OTHERS case, and for the * caller to modify the overlapping lock, * in the check == SELF case * * Note: This returns only the FIRST overlapping lock. There may be * more than one. lf_getlock will return the first blocking lock, * while lf_setlock will iterate over all overlapping locks to * * The check parameter can be SELF, meaning we are looking for * overelapping locks owned by us, or it can be OTHERS, meaning * we are looking for overlapping locks owned by someone else so * we can report a blocking lock on an F_GETLK request. * * The value of *overlap and *prev are modified, even if there is * no overlapping lock found; always check the return code. */ static overlap_t lf_findoverlap(struct lockf *lf, struct lockf *lock, int type, struct lockf ***prev, struct lockf **overlap) { off_t start, end; *overlap = lf; if (lf == NOLOCKF) return (0); #ifdef LOCKF_DEBUGGING if (lockf_debug & 2) lf_print("lf_findoverlap: looking for overlap in", lock); #endif /* LOCKF_DEBUGGING */ start = lock->lf_start; end = lock->lf_end; while (lf != NOLOCKF) { if (((type & SELF) && lf->lf_id != lock->lf_id) || ((type & OTHERS) && lf->lf_id == lock->lf_id)) { *prev = &lf->lf_next; *overlap = lf = lf->lf_next; continue; } #ifdef LOCKF_DEBUGGING if (lockf_debug & 2) lf_print("\tchecking", lf); #endif /* LOCKF_DEBUGGING */ /* * OK, check for overlap */ if ((lf->lf_end != -1 && start > lf->lf_end) || (end != -1 && lf->lf_start > end)) { /* Case 0 */ LOCKF_DEBUG(2, "no overlap\n"); if ((type & SELF) && end != -1 && lf->lf_start > end) return (OVERLAP_NONE); *prev = &lf->lf_next; *overlap = lf = lf->lf_next; continue; } if ((lf->lf_start == start) && (lf->lf_end == end)) { LOCKF_DEBUG(2, "overlap == lock\n"); return (OVERLAP_EQUALS_LOCK); } if ((lf->lf_start <= start) && (end != -1) && ((lf->lf_end >= end) || (lf->lf_end == -1))) { LOCKF_DEBUG(2, "overlap contains lock\n"); return (OVERLAP_CONTAINS_LOCK); } if (start <= lf->lf_start && (end == -1 || (lf->lf_end != -1 && end >= lf->lf_end))) { LOCKF_DEBUG(2, "lock contains overlap\n"); return (OVERLAP_CONTAINED_BY_LOCK); } if ((lf->lf_start < start) && ((lf->lf_end >= start) || (lf->lf_end == -1))) { LOCKF_DEBUG(2, "overlap starts before lock\n"); return (OVERLAP_STARTS_BEFORE_LOCK); } if ((lf->lf_start > start) && (end != -1) && ((lf->lf_end > end) || (lf->lf_end == -1))) { LOCKF_DEBUG(2, "overlap ends after lock\n"); return (OVERLAP_ENDS_AFTER_LOCK); } panic("lf_findoverlap: default"); } return (OVERLAP_NONE); } /* * lf_split * * Description: Split a lock and a contained region into two or three locks * as necessary. * * Parameters: lock1 Lock to split * lock2 Overlapping lock region requiring the * split (upgrade/downgrade/unlock) * * Returns: 0 Success * ENOLCK No memory for new lock * * Implicit Returns: * *lock1 Modified original lock * *lock2 Overlapping lock (inserted into list) * (new lock) Potential new lock inserted into list * if split results in 3 locks * * Notes: This operation can only fail if the split would result in three * locks, and there is insufficient memory to allocate the third * lock; in that case, neither of the locks will be modified. */ static int lf_split(struct lockf *lock1, struct lockf *lock2) { struct lockf *splitlock; #ifdef LOCKF_DEBUGGING if (lockf_debug & 2) { lf_print("lf_split", lock1); lf_print("splitting from", lock2); } #endif /* LOCKF_DEBUGGING */ /* * Check to see if spliting into only two pieces. */ if (lock1->lf_start == lock2->lf_start) { lock1->lf_start = lock2->lf_end + 1; lock2->lf_next = lock1; return (0); } if (lock1->lf_end == lock2->lf_end) { lock1->lf_end = lock2->lf_start - 1; lock2->lf_next = lock1->lf_next; lock1->lf_next = lock2; return (0); } /* * Make a new lock consisting of the last part of * the encompassing lock */ MALLOC(splitlock, struct lockf *, sizeof *splitlock, M_LOCKF, M_WAITOK); if (splitlock == NULL) return (ENOLCK); bcopy(lock1, splitlock, sizeof *splitlock); splitlock->lf_start = lock2->lf_end + 1; TAILQ_INIT(&splitlock->lf_blkhd); lock1->lf_end = lock2->lf_start - 1; /* * OK, now link it in */ splitlock->lf_next = lock1->lf_next; lock2->lf_next = splitlock; lock1->lf_next = lock2; return (0); } /* * lf_wakelock * * Wakeup a blocklist in the case of a downgrade or unlock, since others * waiting on the lock may now be able to acquire it. * * Parameters: listhead Lock list head on which waiters may * have pending locks * * Returns: * * Notes: This function iterates a list of locks and wakes all waiters, * rather than only waiters for the contended regions. Because * of this, for heavily contended files, this can result in a * "thundering herd" situation. Refactoring the code could make * this operation more efficient, if heavy contention ever results * in a real-world performance problem. */ static void lf_wakelock(struct lockf *listhead, boolean_t force_all) { struct lockf *wakelock; boolean_t wake_all = TRUE; if (force_all == FALSE && (listhead->lf_flags & F_WAKE1_SAFE) && listhead->lf_waiters > SAFE_WAITER_LIMIT) wake_all = FALSE; while (!TAILQ_EMPTY(&listhead->lf_blkhd)) { wakelock = TAILQ_FIRST(&listhead->lf_blkhd); TAILQ_REMOVE(&listhead->lf_blkhd, wakelock, lf_block); listhead->lf_waiters--; wakelock->lf_next = NOLOCKF; #ifdef LOCKF_DEBUGGING if (lockf_debug & 2) lf_print("lf_wakelock: awakening", wakelock); #endif /* LOCKF_DEBUGGING */ if (wake_all == FALSE) { TAILQ_CONCAT(&wakelock->lf_blkhd, &listhead->lf_blkhd, lf_block); wakelock->lf_waiters = listhead->lf_waiters; listhead->lf_waiters = 0; if (!TAILQ_EMPTY(&wakelock->lf_blkhd)) { struct lockf *tlock; TAILQ_FOREACH(tlock, &wakelock->lf_blkhd, lf_block) { tlock->lf_next = wakelock; } } } wakeup(wakelock); if (wake_all == FALSE) break; } } #ifdef LOCKF_DEBUGGING /* * lf_print DEBUG * * Print out a lock; lock information is prefixed by the string in 'tag' * * Parameters: tag A string tag for debugging * lock The lock whose information should be * displayed * * Returns: */ void lf_print(const char *tag, struct lockf *lock) { printf("%s: lock %p for ", tag, (void *)lock); if (lock->lf_flags & F_POSIX) printf("proc %ld", (long)((struct proc *)lock->lf_id)->p_pid); else printf("id %p", (void *)lock->lf_id); if (lock->lf_vnode != 0) printf(" in vno %p, %s, start 0x%016llx, end 0x%016llx", lock->lf_vnode, lock->lf_type == F_RDLCK ? "shared" : lock->lf_type == F_WRLCK ? "exclusive" : lock->lf_type == F_UNLCK ? "unlock" : "unknown", (intmax_t)lock->lf_start, (intmax_t)lock->lf_end); else printf(" %s, start 0x%016llx, end 0x%016llx", lock->lf_type == F_RDLCK ? "shared" : lock->lf_type == F_WRLCK ? "exclusive" : lock->lf_type == F_UNLCK ? "unlock" : "unknown", (intmax_t)lock->lf_start, (intmax_t)lock->lf_end); if (!TAILQ_EMPTY(&lock->lf_blkhd)) printf(" block %p\n", (void *)TAILQ_FIRST(&lock->lf_blkhd)); else printf("\n"); } /* * lf_printlist DEBUG * * Print out a lock list for the vnode associated with 'lock'; lock information * is prefixed by the string in 'tag' * * Parameters: tag A string tag for debugging * lock The lock whose vnode's lock list should * be displayed * * Returns: */ void lf_printlist(const char *tag, struct lockf *lock) { struct lockf *lf, *blk; if (lock->lf_vnode == 0) return; printf("%s: Lock list for vno %p:\n", tag, lock->lf_vnode); for (lf = lock->lf_vnode->v_lockf; lf; lf = lf->lf_next) { printf("\tlock %p for ",(void *)lf); if (lf->lf_flags & F_POSIX) printf("proc %ld", (long)((struct proc *)lf->lf_id)->p_pid); else printf("id %p", (void *)lf->lf_id); printf(", %s, start 0x%016llx, end 0x%016llx", lf->lf_type == F_RDLCK ? "shared" : lf->lf_type == F_WRLCK ? "exclusive" : lf->lf_type == F_UNLCK ? "unlock" : "unknown", (intmax_t)lf->lf_start, (intmax_t)lf->lf_end); TAILQ_FOREACH(blk, &lf->lf_blkhd, lf_block) { printf("\n\t\tlock request %p for ", (void *)blk); if (blk->lf_flags & F_POSIX) printf("proc %ld", (long)((struct proc *)blk->lf_id)->p_pid); else printf("id %p", (void *)blk->lf_id); printf(", %s, start 0x%016llx, end 0x%016llx", blk->lf_type == F_RDLCK ? "shared" : blk->lf_type == F_WRLCK ? "exclusive" : blk->lf_type == F_UNLCK ? "unlock" : "unknown", (intmax_t)blk->lf_start, (intmax_t)blk->lf_end); if (!TAILQ_EMPTY(&blk->lf_blkhd)) panic("lf_printlist: bad list"); } printf("\n"); } } #endif /* LOCKF_DEBUGGING */