Extend the kernel unit number allocator for allocating specific unit
numbers. This change adds a new function alloc_unr_specific() which returns the requested unit number if it is free. If the number is already allocated or out of the range, -1 is returned. Update alloc_unr(9) manual page accordingly and add a MLINK for alloc_unr_specific(9). Discussed on: freebsd-hackers
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=209710
@ -374,6 +374,7 @@ MAN= accept_filter.9 \
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zone.9
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MLINKS= alloc_unr.9 alloc_unrl.9 \
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alloc_unr.9 alloc_unr_specific.9 \
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alloc_unr.9 delete_unrhdr.9 \
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alloc_unr.9 free_unr.9 \
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alloc_unr.9 new_unrhdr.9
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@ -24,13 +24,14 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 7, 2010
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.Dd July 5, 2010
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.Dt ALLOC_UNR 9
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.Os
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.Sh NAME
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.Nm new_unrhdr ,
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.Nm delete_unrhdr ,
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.Nm alloc_unr ,
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.Nm alloc_unr_specific ,
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.Nm free_unr
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.Nd "kernel unit number allocator"
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.Sh SYNOPSIS
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@ -43,6 +44,8 @@
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.Fn alloc_unr "struct unrhdr *uh"
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.Ft int
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.Fn alloc_unrl "struct unrhdr *uh"
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.Ft int
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.Fn alloc_unr_specific "struct unrhdr *uh" "u_int item"
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.Ft void
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.Fn free_unr "struct unrhdr *uh" "u_int item"
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.Sh DESCRIPTION
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@ -81,6 +84,13 @@ is returned.
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Same as
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.Fn alloc_unr
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except that mutex is assumed to be already locked and thus is not used.
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.It Fn alloc_unr_specific uh item
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Allocate a specific unit number.
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This function allocates memory and thus may sleep.
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The allocated unit number is returned on success.
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If the specified number is already allocated or out of the range,
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.Li \-1
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is returned.
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.It Fn free_unr uh item
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Free a previously allocated unit number.
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This function may require allocating memory, and thus it can sleep.
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@ -628,6 +628,132 @@ alloc_unr(struct unrhdr *uh)
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return (i);
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}
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static int
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alloc_unr_specificl(struct unrhdr *uh, u_int item, void **p1, void **p2)
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{
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struct unr *up, *upn;
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struct unrb *ub;
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u_int i, last, tl;
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mtx_assert(uh->mtx, MA_OWNED);
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if (item < uh->low + uh->first || item > uh->high)
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return (-1);
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up = TAILQ_FIRST(&uh->head);
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/* Ideal split. */
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if (up == NULL && item - uh->low == uh->first) {
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uh->first++;
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uh->last--;
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uh->busy++;
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check_unrhdr(uh, __LINE__);
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return (item);
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}
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i = item - uh->low - uh->first;
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if (up == NULL) {
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up = new_unr(uh, p1, p2);
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up->ptr = NULL;
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up->len = i;
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TAILQ_INSERT_TAIL(&uh->head, up, list);
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up = new_unr(uh, p1, p2);
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up->ptr = uh;
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up->len = 1;
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TAILQ_INSERT_TAIL(&uh->head, up, list);
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uh->last = uh->high - uh->low - i;
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uh->busy++;
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check_unrhdr(uh, __LINE__);
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return (item);
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} else {
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/* Find the item which contains the unit we want to allocate. */
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TAILQ_FOREACH(up, &uh->head, list) {
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if (up->len > i)
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break;
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i -= up->len;
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}
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}
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if (up == NULL) {
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if (i > 0) {
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up = new_unr(uh, p1, p2);
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up->ptr = NULL;
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up->len = i;
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TAILQ_INSERT_TAIL(&uh->head, up, list);
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}
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up = new_unr(uh, p1, p2);
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up->ptr = uh;
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up->len = 1;
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TAILQ_INSERT_TAIL(&uh->head, up, list);
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goto done;
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}
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if (is_bitmap(uh, up)) {
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ub = up->ptr;
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if (bit_test(ub->map, i) == 0) {
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bit_set(ub->map, i);
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ub->busy++;
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goto done;
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} else
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return (-1);
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} else if (up->ptr == uh)
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return (-1);
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KASSERT(up->ptr == NULL,
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("alloc_unr_specificl: up->ptr != NULL (up=%p)", up));
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/* Split off the tail end, if any. */
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tl = up->len - (1 + i);
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if (tl > 0) {
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upn = new_unr(uh, p1, p2);
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upn->ptr = NULL;
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upn->len = tl;
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TAILQ_INSERT_AFTER(&uh->head, up, upn, list);
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}
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/* Split off head end, if any */
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if (i > 0) {
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upn = new_unr(uh, p1, p2);
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upn->len = i;
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upn->ptr = NULL;
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TAILQ_INSERT_BEFORE(up, upn, list);
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}
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up->len = 1;
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up->ptr = uh;
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done:
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last = uh->high - uh->low - (item - uh->low);
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if (uh->last > last)
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uh->last = last;
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uh->busy++;
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collapse_unr(uh, up);
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check_unrhdr(uh, __LINE__);
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return (item);
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}
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int
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alloc_unr_specific(struct unrhdr *uh, u_int item)
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{
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void *p1, *p2;
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int i;
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "alloc_unr_specific");
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p1 = Malloc(sizeof(struct unr));
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p2 = Malloc(sizeof(struct unr));
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mtx_lock(uh->mtx);
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i = alloc_unr_specificl(uh, item, &p1, &p2);
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mtx_unlock(uh->mtx);
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if (p1 != NULL)
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Free(p1);
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if (p2 != NULL)
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Free(p2);
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return (i);
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}
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/*
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* Free a unr.
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*
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@ -810,6 +936,42 @@ print_unrhdr(struct unrhdr *uh)
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}
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}
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static void
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test_alloc_unr(struct unrhdr *uh, u_int i, char a[])
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{
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int j;
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if (a[i]) {
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printf("F %u\n", i);
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free_unr(uh, i);
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a[i] = 0;
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} else {
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no_alloc = 1;
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j = alloc_unr(uh);
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if (j != -1) {
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a[j] = 1;
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printf("A %d\n", j);
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}
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no_alloc = 0;
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}
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}
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static void
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test_alloc_unr_specific(struct unrhdr *uh, u_int i, char a[])
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{
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int j;
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j = alloc_unr_specific(uh, i);
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if (j == -1) {
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printf("F %u\n", i);
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a[i] = 0;
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free_unr(uh, i);
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} else {
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a[i] = 1;
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printf("A %d\n", j);
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}
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}
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/* Number of unrs to test */
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#define NN 10000
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@ -825,6 +987,7 @@ main(int argc __unused, const char **argv __unused)
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print_unrhdr(uh);
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memset(a, 0, sizeof a);
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srandomdev();
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fprintf(stderr, "sizeof(struct unr) %zu\n", sizeof(struct unr));
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fprintf(stderr, "sizeof(struct unrb) %zu\n", sizeof(struct unrb));
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@ -838,19 +1001,11 @@ main(int argc __unused, const char **argv __unused)
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if (a[i] && (j & 1))
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continue;
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#endif
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if (a[i]) {
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printf("F %u\n", i);
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free_unr(uh, i);
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a[i] = 0;
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} else {
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no_alloc = 1;
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i = alloc_unr(uh);
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if (i != -1) {
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a[i] = 1;
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printf("A %u\n", i);
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}
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no_alloc = 0;
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}
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if ((random() & 1) != 0)
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test_alloc_unr(uh, i, a);
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else
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test_alloc_unr_specific(uh, i, a);
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if (1) /* XXX: change this for detailed debug printout */
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print_unrhdr(uh);
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check_unrhdr(uh, __LINE__);
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void clean_unrhdr(struct unrhdr *uh);
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void clean_unrhdrl(struct unrhdr *uh);
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int alloc_unr(struct unrhdr *uh);
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int alloc_unr_specific(struct unrhdr *uh, u_int item);
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int alloc_unrl(struct unrhdr *uh);
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void free_unr(struct unrhdr *uh, u_int item);
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