X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/91447636331957f3d9b5ca5b508f07c526b0074d..36401178fd6817c043cc00b0c00c7f723e58efae:/bsd/kern/kern_lockf.c diff --git a/bsd/kern/kern_lockf.c b/bsd/kern/kern_lockf.c index 1ef3470ce..4e61180b6 100644 --- a/bsd/kern/kern_lockf.c +++ b/bsd/kern/kern_lockf.c @@ -1,3 +1,30 @@ +/* + * 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. @@ -39,7 +66,9 @@ #include #include #include +#include #include +#include #include #include #include @@ -47,24 +76,34 @@ #include #include -#if DEAD_CODE /* * This variable controls the maximum number of processes that will * be checked in doing deadlock detection. */ static int maxlockdepth = MAXDEPTH; -#endif /* DEAD_CODE */ -#ifdef LOCKF_DEBUG +#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, ""); -#endif + +/* + * 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"); @@ -72,29 +111,55 @@ MALLOC_DEFINE(M_LOCKF, "lockf", "Byte-range locking structures"); #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 int lf_findoverlap(struct lockf *, +static overlap_t lf_findoverlap(struct lockf *, struct lockf *, int, struct lockf ***, struct lockf **); -static struct lockf * - lf_getblock(struct lockf *); +static struct lockf *lf_getblock(struct lockf *); static int lf_getlock(struct lockf *, struct flock *); static int lf_setlock(struct lockf *); -static void lf_split(struct lockf *, struct lockf *); +static int lf_split(struct lockf *, struct lockf *); static void lf_wakelock(struct lockf *); + /* - * Advisory record locking support + * 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(ap) - struct vnop_advlock_args /* { - struct vnode *a_vp; - caddr_t a_id; - int a_op; - struct flock *a_fl; - int a_flags; - vfs_context_t a_context; - } */ *ap; +lf_advlock(struct vnop_advlock_args *ap) { struct vnode *vp = ap->a_vp; struct flock *fl = ap->a_fl; @@ -113,9 +178,7 @@ lf_advlock(ap) if (*head == (struct lockf *)0) { if (ap->a_op != F_SETLK) { fl->l_type = F_UNLCK; -#ifdef LOCKF_DEBUG - printf("lf_advlock: unlock without lock\n"); -#endif /* LOCKF_DEBUG */ + LOCKF_DEBUG(0, "lf_advlock: '%s' unlock without lock\n", vfs_context_proc(context)->p_comm); return (0); } } @@ -136,67 +199,59 @@ lf_advlock(ap) case SEEK_END: - if ((error = vnode_size(vp, &size, context))) -{ -#ifdef LOCKF_DEBUG - printf("lf_advlock: vnode_getattr failed: %d\n", error); -#endif /* LOCKF_DEBUG */ + /* + * 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 > OFF_MAX - fl->l_start)) + (fl->l_start > 0 && + size > (u_quad_t)(OFF_MAX - fl->l_start))) return (EOVERFLOW); start = size + fl->l_start; break; default: -#ifdef LOCKF_DEBUG - printf("lf_advlock: unknown whence %d\n", fl->l_whence); -#endif /* LOCKF_DEBUG */ + LOCKF_DEBUG(0, "lf_advlock: unknown whence %d\n", fl->l_whence); return (EINVAL); } - if (start < 0) -{ -#ifdef LOCKF_DEBUG - printf("lf_advlock: start < 0 (%qd)\n", start); -#endif /* LOCKF_DEBUG */ + if (start < 0) { + LOCKF_DEBUG(0, "lf_advlock: start < 0 (%qd)\n", start); return (EINVAL); -} + } if (fl->l_len < 0) { - if (start == 0) -{ -#ifdef LOCKF_DEBUG - printf("lf_advlock: len < 0 & start == 0\n"); -#endif /* LOCKF_DEBUG */ + 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) -{ -#ifdef LOCKF_DEBUG - printf("lf_advlock: start < 0 (%qd)\n", start); -#endif /* LOCKF_DEBUG */ + 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)) -{ -#ifdef LOCKF_DEBUG - printf("lf_advlock: overflow\n"); -#endif /* LOCKF_DEBUG */ + 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; @@ -233,30 +288,108 @@ lf_advlock(ap) } lck_mtx_unlock(&vp->v_lock); /* done maniplulating the list */ -#ifdef LOCKF_DEBUG - printf("lf_advlock: normal exit: %d\n", error); -#endif /* LOCKF_DEBUG */ + LOCKF_DEBUG(0, "lf_advlock: normal exit: %d\n\n", error); return (error); } + /* - * Set a byte-range lock. + * 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(lock) - struct lockf *lock; +lf_setlock(struct lockf *lock) { struct lockf *block; struct lockf **head = lock->lf_head; struct lockf **prev, *overlap, *ltmp; static char lockstr[] = "lockf"; - int ovcase, priority, needtolink, error; + int priority, needtolink, error; struct vnode *vp = lock->lf_vnode; + overlap_t ovcase; -#ifdef LOCKF_DEBUG - if (lockf_debug & 1) +#ifdef LOCKF_DEBUGGING + if (lockf_debug & 1) { lf_print("lf_setlock", lock); -#endif /* LOCKF_DEBUG */ + lf_printlist("lf_setlock(in)", lock); + } +#endif /* LOCKF_DEBUGGING */ /* * Set the priority @@ -276,10 +409,7 @@ lf_setlock(lock) FREE(lock, M_LOCKF); return (EAGAIN); } -#if DEAD_CODE -/* - * XXX This is dead code on MacOS X; it shouldn't be. - */ + /* * We are blocked. Since flock style locks cover * the whole file, there is no chance for deadlock. @@ -292,35 +422,66 @@ lf_setlock(lock) */ if ((lock->lf_flags & F_POSIX) && (block->lf_flags & F_POSIX)) { - struct proc *wproc; - struct thread *td; + struct proc *wproc, *bproc; + struct uthread *ut; struct lockf *waitblock; int i = 0; /* The block is waiting on something */ - /* XXXKSE this is not complete under threads */ wproc = (struct proc *)block->lf_id; - mtx_lock_spin(&sched_lock); - FOREACH_THREAD_IN_PROC(wproc, td) { - while (td->td_wchan && - (td->td_wmesg == lockstr) && + 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 *)td->td_wchan; - /* Get the owner of the blocking lock */ + 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; - wproc = (struct proc *)waitblock->lf_id; - if (wproc == (struct proc *)lock->lf_id) { - mtx_unlock_spin(&sched_lock); + + /* + * 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); } } } - mtx_unlock_spin(&sched_lock); + proc_unlock(wproc); } -#endif /* DEAD_CODE */ + /* * For flock type locks, we must first remove * any shared locks that we hold before we sleep @@ -329,7 +490,10 @@ lf_setlock(lock) if ((lock->lf_flags & F_FLOCK) && lock->lf_type == F_WRLCK) { lock->lf_type = F_UNLCK; - (void) lf_clearlock(lock); + if ((error = lf_clearlock(lock)) != 0) { + FREE(lock, M_LOCKF); + return (error); + } lock->lf_type = F_WRLCK; } /* @@ -338,12 +502,12 @@ lf_setlock(lock) */ lock->lf_next = block; TAILQ_INSERT_TAIL(&block->lf_blkhd, lock, lf_block); -#ifdef LOCKF_DEBUG +#ifdef LOCKF_DEBUGGING if (lockf_debug & 1) { lf_print("lf_setlock: blocking on", block); - lf_printlist("lf_setlock", block); + lf_printlist("lf_setlock(block)", block); } -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */ error = msleep(lock, &vp->v_lock, priority, lockstr, 0); if (error) { /* XXX */ /* @@ -387,14 +551,14 @@ lf_setlock(lock) * 5) overlap ends after lock */ switch (ovcase) { - case 0: /* no overlap */ + case OVERLAP_NONE: if (needtolink) { *prev = lock; lock->lf_next = overlap; } break; - case 1: /* overlap == lock */ + case OVERLAP_EQUALS_LOCK: /* * If downgrading lock, others may be * able to acquire it. @@ -404,28 +568,37 @@ lf_setlock(lock) lf_wakelock(overlap); overlap->lf_type = lock->lf_type; FREE(lock, M_LOCKF); - lock = overlap; /* for debug output below */ + lock = overlap; /* for lf_coelesce_adjacent() */ break; - case 2: /* overlap contains lock */ + 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 debug output below */ + 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 - lf_split(overlap, lock); + } 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); break; - case 3: /* lock contains overlap */ + case OVERLAP_CONTAINED_BY_LOCK: /* * If downgrading lock, others may be able to * acquire it, otherwise take the list. @@ -456,7 +629,7 @@ lf_setlock(lock) FREE(overlap, M_LOCKF); continue; - case 4: /* overlap starts before lock */ + case OVERLAP_STARTS_BEFORE_LOCK: /* * Add lock after overlap on the list. */ @@ -468,7 +641,7 @@ lf_setlock(lock) needtolink = 0; continue; - case 5: /* overlap ends after lock */ + case OVERLAP_ENDS_AFTER_LOCK: /* * Add the new lock before overlap. */ @@ -482,101 +655,136 @@ lf_setlock(lock) } break; } -#ifdef LOCKF_DEBUG + /* 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", lock); + lf_printlist("lf_setlock(out)", lock); } -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */ return (0); } + /* - * Remove a byte-range lock on an inode. + * 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 * - * Generally, find the lock (or an overlap to that lock) - * and remove it (or shrink it), then wakeup anyone we can. + * 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(unlock) - struct lockf *unlock; +lf_clearlock(struct lockf *unlock) { struct lockf **head = unlock->lf_head; struct lockf *lf = *head; struct lockf *overlap, **prev; - int ovcase; + overlap_t ovcase; if (lf == NOLOCKF) return (0); -#ifdef LOCKF_DEBUG +#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_DEBUG */ +#endif /* LOCKF_DEBUGGING */ prev = head; - while ((ovcase = lf_findoverlap(lf, unlock, SELF, &prev, &overlap))) { + while ((ovcase = lf_findoverlap(lf, unlock, SELF, &prev, &overlap)) != OVERLAP_NONE) { /* * Wakeup the list of locks to be retried. */ lf_wakelock(overlap); switch (ovcase) { + case OVERLAP_NONE: /* satisfy compiler enum/switch */ + break; - case 1: /* overlap == lock */ + case OVERLAP_EQUALS_LOCK: *prev = overlap->lf_next; FREE(overlap, M_LOCKF); break; - case 2: /* overlap contains lock: split it */ + case OVERLAP_CONTAINS_LOCK: /* split it */ if (overlap->lf_start == unlock->lf_start) { overlap->lf_start = unlock->lf_end + 1; break; } - lf_split(overlap, unlock); + /* + * 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 3: /* lock contains overlap */ + case OVERLAP_CONTAINED_BY_LOCK: *prev = overlap->lf_next; lf = overlap->lf_next; FREE(overlap, M_LOCKF); continue; - case 4: /* overlap starts before lock */ + case OVERLAP_STARTS_BEFORE_LOCK: overlap->lf_end = unlock->lf_start - 1; prev = &overlap->lf_next; lf = overlap->lf_next; continue; - case 5: /* overlap ends after lock */ + case OVERLAP_ENDS_AFTER_LOCK: overlap->lf_start = unlock->lf_end + 1; break; } break; } -#ifdef LOCKF_DEBUG +#ifdef LOCKF_DEBUGGING if (lockf_debug & 1) lf_printlist("lf_clearlock", unlock); -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */ return (0); } + /* - * Check whether there is a blocking lock, - * and if so return its process identifier. + * 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(lock, fl) - struct lockf *lock; - struct flock *fl; +lf_getlock(struct lockf *lock, struct flock *fl) { struct lockf *block; -#ifdef LOCKF_DEBUG +#ifdef LOCKF_DEBUGGING if (lockf_debug & 1) lf_print("lf_getlock", lock); -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */ if ((block = lf_getblock(lock))) { fl->l_type = block->lf_type; @@ -596,19 +804,30 @@ lf_getlock(lock, fl) return (0); } + /* - * Walk the list of locks for an inode and - * return the first blocking lock. + * 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(lock) - struct lockf *lock; +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))) { + while ((ovcase = lf_findoverlap(lf, lock, OTHERS, &prev, &overlap)) != OVERLAP_NONE) { /* * We've found an overlap, see if it blocks us */ @@ -623,30 +842,64 @@ lf_getblock(lock) return (NOLOCKF); } + /* - * Walk the list of locks to - * find an overlapping lock (if any). + * 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 * - * NOTE: this returns only the FIRST overlapping lock. There - * may be more than one. + * 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 int -lf_findoverlap(lf, lock, type, prev, overlap) - struct lockf *lf; - struct lockf *lock; - int type; - struct lockf ***prev; - struct lockf **overlap; +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_DEBUG +#ifdef LOCKF_DEBUGGING if (lockf_debug & 2) lf_print("lf_findoverlap: looking for overlap in", lock); -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */ start = lock->lf_start; end = lock->lf_end; while (lf != NOLOCKF) { @@ -656,122 +909,111 @@ lf_findoverlap(lf, lock, type, prev, overlap) *overlap = lf = lf->lf_next; continue; } -#ifdef LOCKF_DEBUG +#ifdef LOCKF_DEBUGGING if (lockf_debug & 2) lf_print("\tchecking", lf); -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */ /* * OK, check for overlap - * - * 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 */ if ((lf->lf_end != -1 && start > lf->lf_end) || (end != -1 && lf->lf_start > end)) { /* Case 0 */ -#ifdef LOCKF_DEBUG - if (lockf_debug & 2) - printf("no overlap\n"); -#endif /* LOCKF_DEBUG */ + LOCKF_DEBUG(2, "no overlap\n"); if ((type & SELF) && end != -1 && lf->lf_start > end) - return (0); + return (OVERLAP_NONE); *prev = &lf->lf_next; *overlap = lf = lf->lf_next; continue; } if ((lf->lf_start == start) && (lf->lf_end == end)) { - /* Case 1 */ -#ifdef LOCKF_DEBUG - if (lockf_debug & 2) - printf("overlap == lock\n"); -#endif /* LOCKF_DEBUG */ - return (1); + 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))) { - /* Case 2 */ -#ifdef LOCKF_DEBUG - if (lockf_debug & 2) - printf("overlap contains lock\n"); -#endif /* LOCKF_DEBUG */ - return (2); + 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))) { - /* Case 3 */ -#ifdef LOCKF_DEBUG - if (lockf_debug & 2) - printf("lock contains overlap\n"); -#endif /* LOCKF_DEBUG */ - return (3); + 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))) { - /* Case 4 */ -#ifdef LOCKF_DEBUG - if (lockf_debug & 2) - printf("overlap starts before lock\n"); -#endif /* LOCKF_DEBUG */ - return (4); + 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))) { - /* Case 5 */ -#ifdef LOCKF_DEBUG - if (lockf_debug & 2) - printf("overlap ends after lock\n"); -#endif /* LOCKF_DEBUG */ - return (5); + LOCKF_DEBUG(2, "overlap ends after lock\n"); + return (OVERLAP_ENDS_AFTER_LOCK); } panic("lf_findoverlap: default"); } - return (0); + return (OVERLAP_NONE); } + /* - * Split a lock and a contained region into - * two or three locks as necessary. + * 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 void -lf_split(lock1, lock2) - struct lockf *lock1; - struct lockf *lock2; +static int +lf_split(struct lockf *lock1, struct lockf *lock2) { struct lockf *splitlock; -#ifdef LOCKF_DEBUG +#ifdef LOCKF_DEBUGGING if (lockf_debug & 2) { lf_print("lf_split", lock1); lf_print("splitting from", lock2); } -#endif /* LOCKF_DEBUG */ +#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; + 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; + 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); @@ -782,14 +1024,31 @@ lf_split(lock1, lock2) splitlock->lf_next = lock1->lf_next; lock2->lf_next = splitlock; lock1->lf_next = lock2; + + return (0); } + /* - * Wakeup a blocklist + * 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(listhead) - struct lockf *listhead; +lf_wakelock(struct lockf *listhead) { struct lockf *wakelock; @@ -797,38 +1056,44 @@ lf_wakelock(listhead) wakelock = TAILQ_FIRST(&listhead->lf_blkhd); TAILQ_REMOVE(&listhead->lf_blkhd, wakelock, lf_block); wakelock->lf_next = NOLOCKF; -#ifdef LOCKF_DEBUG +#ifdef LOCKF_DEBUGGING if (lockf_debug & 2) lf_print("lf_wakelock: awakening", wakelock); -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */ wakeup(wakelock); } } -#ifdef LOCKF_DEBUG + +#ifdef LOCKF_DEBUGGING /* - * Print out a lock. + * 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(tag, lock) - char *tag; - struct lockf *lock; +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 0x%08x, %s, start %jd, end %jd", + 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 %jd, end %jd", + 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", @@ -839,17 +1104,28 @@ lf_print(tag, lock) 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(tag, lock) - char *tag; - struct lockf *lock; +lf_printlist(const char *tag, struct lockf *lock) { struct lockf *lf, *blk; if (lock->lf_vnode == 0) return; - printf("%s: Lock list for vno 0x%08x:\n", + 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); @@ -858,7 +1134,7 @@ lf_printlist(tag, lock) (long)((struct proc *)lf->lf_id)->p_pid); else printf("id %p", (void *)lf->lf_id); - printf(", %s, start %jd, end %jd", + 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" : @@ -870,7 +1146,7 @@ lf_printlist(tag, lock) (long)((struct proc *)blk->lf_id)->p_pid); else printf("id %p", (void *)blk->lf_id); - printf(", %s, start %jd, end %jd", + 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" : @@ -882,4 +1158,4 @@ lf_printlist(tag, lock) printf("\n"); } } -#endif /* LOCKF_DEBUG */ +#endif /* LOCKF_DEBUGGING */