Author: dougm
Date: Sat Jul 25 18:29:10 2020
New Revision: 363532
URL: https://svnweb.freebsd.org/changeset/base/363532

Log:
  Fix an overflow bug in the blist allocator that needlessly capped max
  swap size by dividing a value, which was always a multiple of 64, by
  64.  Remove the code that reduced max swap size down to that cap.
  
  Eliminate the distinction between BLIST_BMAP_RADIX and
  BLIST_META_RADIX.  Call them both BLIST_RADIX.
  
  Make improvments to the blist self-test code to silence compiler
  warnings and to test larger blists.
  
  Reported by:  jmallett
  Reviewed by:  alc
  Discussed with:       kib
  Tested by:    pho
  Differential Revision:        https://reviews.freebsd.org/D25736

Modified:
  head/sys/kern/subr_blist.c
  head/sys/sys/blist.h
  head/sys/vm/swap_pager.c

Modified: head/sys/kern/subr_blist.c
==============================================================================
--- head/sys/kern/subr_blist.c  Sat Jul 25 18:09:04 2020        (r363531)
+++ head/sys/kern/subr_blist.c  Sat Jul 25 18:29:10 2020        (r363532)
@@ -36,15 +36,14 @@
  *
  *     A radix tree controls access to pieces of the bitmap, and includes
  *     auxiliary information at each interior node about the availabilty of
- *     contiguous free blocks in the subtree rooted at that node.  Two radix
- *     constants are involved: one for the size of the bitmaps contained in the
- *     leaf nodes (BLIST_BMAP_RADIX), and one for the number of descendents of
- *     each of the meta (interior) nodes (BLIST_META_RADIX).  Each subtree is
- *     associated with a range of blocks.  The root of any subtree stores a
- *     hint field that defines an upper bound on the size of the largest
- *     allocation that can begin in the associated block range.  A hint is an
- *     upper bound on a potential allocation, but not necessarily a tight upper
- *     bound.
+ *     contiguous free blocks in the subtree rooted at that node.  A radix
+ *     constant defines the size of the bitmaps contained in a leaf node
+ *     and the number of descendents of each of the meta (interior) nodes.
+ *     Each subtree is associated with a range of blocks.  The root of any
+ *     subtree stores a hint field that defines an upper bound on the size
+ *     of the largest allocation that can begin in the associated block
+ *     range.  A hint is an upper bound on a potential allocation, but not
+ *     necessarily a tight upper bound.
  *
  *     The bitmap field in each node directs the search for available blocks.
  *     For a leaf node, a bit is set if the corresponding block is free.  For a
@@ -64,17 +63,16 @@
  *
  *     LAYOUT: The radix tree is laid out recursively using a linear array.
  *     Each meta node is immediately followed (laid out sequentially in
- *     memory) by BLIST_META_RADIX lower level nodes.  This is a recursive
+ *     memory) by BLIST_RADIX lower-level nodes.  This is a recursive
  *     structure but one that can be easily scanned through a very simple
  *     'skip' calculation.  The memory allocation is only large enough to
  *     cover the number of blocks requested at creation time.  Nodes that
  *     represent blocks beyond that limit, nodes that would never be read
  *     or written, are not allocated, so that the last of the
- *     BLIST_META_RADIX lower level nodes of a some nodes may not be
- *     allocated.
+ *     BLIST_RADIX lower-level nodes of a some nodes may not be allocated.
  *
  *     NOTE: the allocator cannot currently allocate more than
- *     BLIST_BMAP_RADIX blocks per call.  It will panic with 'allocation too
+ *     BLIST_RADIX blocks per call.  It will panic with 'allocation too
  *     large' if you try.  This is an area that could use improvement.  The
  *     radix is large enough that this restriction does not effect the swap
  *     system, though.  Currently only the allocation code is affected by
@@ -152,24 +150,19 @@ static void       blst_radix_print(blmeta_t *scan, 
daddr_t b
 static MALLOC_DEFINE(M_SWAP, "SWAP", "Swap space");
 #endif
 
-_Static_assert(BLIST_BMAP_RADIX % BLIST_META_RADIX == 0,
-    "radix divisibility error");
-#define        BLIST_BMAP_MASK (BLIST_BMAP_RADIX - 1)
-#define        BLIST_META_MASK (BLIST_META_RADIX - 1)
+#define        BLIST_MASK      (BLIST_RADIX - 1)
 
 /*
  * For a subtree that can represent the state of up to 'radix' blocks, the
- * number of leaf nodes of the subtree is L=radix/BLIST_BMAP_RADIX.  If 'm'
- * is short for BLIST_META_RADIX, then for a tree of height h with L=m**h
+ * number of leaf nodes of the subtree is L=radix/BLIST_RADIX.  If 'm'
+ * is short for BLIST_RADIX, then for a tree of height h with L=m**h
  * leaf nodes, the total number of tree nodes is 1 + m + m**2 + ... + m**h,
  * or, equivalently, (m**(h+1)-1)/(m-1).  This quantity is called 'skip'
  * in the 'meta' functions that process subtrees.  Since integer division
  * discards remainders, we can express this computation as
  * skip = (m * m**h) / (m - 1)
- * skip = (m * (radix / BLIST_BMAP_RADIX)) / (m - 1)
- * and since m divides BLIST_BMAP_RADIX, we can simplify further to
- * skip = (radix / (BLIST_BMAP_RADIX / m)) / (m - 1)
- * skip = radix / ((BLIST_BMAP_RADIX / m) * (m - 1))
+ * skip = (m * (radix / m)) / (m - 1)
+ * skip = radix / (m - 1)
  * so that simple integer division by a constant can safely be used for the
  * calculation.
  */
@@ -177,8 +170,7 @@ static inline daddr_t
 radix_to_skip(daddr_t radix)
 {
 
-       return (radix /
-           ((BLIST_BMAP_RADIX / BLIST_META_RADIX) * BLIST_META_MASK));
+       return (radix / BLIST_MASK);
 }
 
 /*
@@ -189,7 +181,7 @@ bitrange(int n, int count)
 {
 
        return (((u_daddr_t)-1 << n) &
-           ((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - (n + count))));
+           ((u_daddr_t)-1 >> (BLIST_RADIX - (n + count))));
 }
 
 /*
@@ -201,7 +193,7 @@ generic_bitpos(u_daddr_t mask)
        int hi, lo, mid;
 
        lo = 0;
-       hi = BLIST_BMAP_RADIX;
+       hi = BLIST_RADIX;
        while (lo + 1 < hi) {
                mid = (lo + hi) >> 1;
                if (mask & bitrange(0, mid))
@@ -238,7 +230,7 @@ bitpos(u_daddr_t mask)
  *     flags  - malloc flags
  *
  *     The smallest blist consists of a single leaf node capable of
- *     managing BLIST_BMAP_RADIX blocks.
+ *     managing BLIST_RADIX blocks.
  */
 blist_t
 blist_create(daddr_t blocks, int flags)
@@ -252,11 +244,8 @@ blist_create(daddr_t blocks, int flags)
         * Calculate the radix and node count used for scanning.
         */
        nodes = 1;
-       radix = BLIST_BMAP_RADIX;
-       while (radix <= blocks) {
-               nodes += 1 + (blocks - 1) / radix;
-               radix *= BLIST_META_RADIX;
-       }
+       for (radix = 1; radix <= blocks / BLIST_RADIX; radix *= BLIST_RADIX)
+               nodes += 1 + (blocks - 1) / radix / BLIST_RADIX;
 
        bl = malloc(offsetof(struct blist, bl_root[nodes]), M_SWAP, flags |
            M_ZERO);
@@ -549,19 +538,12 @@ blist_stats(blist_t bl, struct sbuf *s)
 
        init_gap_stats(stats);
        nodes = 0;
-       i = bl->bl_radix;
-       while (i < bl->bl_radix + bl->bl_blocks) {
+       radix = bl->bl_radix;
+       for (i = 0; i < bl->bl_blocks; ) {
                /*
-                * Find max size subtree starting at i.
-                */
-               radix = BLIST_BMAP_RADIX;
-               while (((i / radix) & BLIST_META_MASK) == 0)
-                       radix *= BLIST_META_RADIX;
-
-               /*
                 * Check for skippable subtrees starting at i.
                 */
-               while (radix > BLIST_BMAP_RADIX) {
+               while (radix != 1) {
                        if (bl->bl_root[nodes].bm_bitmap == 0) {
                                if (gap_stats_counting(stats))
                                        update_gap_stats(stats, i);
@@ -572,9 +554,9 @@ blist_stats(blist_t bl, struct sbuf *s)
                         * Skip subtree root.
                         */
                        nodes++;
-                       radix /= BLIST_META_RADIX;
+                       radix /= BLIST_RADIX;
                }
-               if (radix == BLIST_BMAP_RADIX) {
+               if (radix == 1) {
                        /*
                         * Scan leaf.
                         */
@@ -588,8 +570,16 @@ blist_stats(blist_t bl, struct sbuf *s)
                                diff ^= bitrange(digit, 1);
                        }
                }
-               nodes += radix_to_skip(radix);
-               i += radix;
+               nodes += radix_to_skip(radix * BLIST_RADIX);
+               i += radix * BLIST_RADIX;
+
+               /*
+                * Find max size subtree starting at i.
+                */
+               for (radix = 1; 
+                   ((i / BLIST_RADIX / radix) & BLIST_MASK) == 0;
+                   radix *= BLIST_RADIX)
+                       ;
        }
        update_gap_stats(stats, i);
        dump_gap_stats(stats, s);
@@ -623,13 +613,13 @@ blst_next_leaf_alloc(blmeta_t *scan, daddr_t start, in
        daddr_t blk;
        int avail, digit;
 
-       start += BLIST_BMAP_RADIX;
-       for (blk = start; blk - start < maxcount; blk += BLIST_BMAP_RADIX) {
+       start += BLIST_RADIX;
+       for (blk = start; blk - start < maxcount; blk += BLIST_RADIX) {
                /* Skip meta-nodes, as long as they promise more free blocks. */
-               radix = BLIST_BMAP_RADIX;
+               radix = BLIST_RADIX;
                while (((++scan)->bm_bitmap & 1) == 1 &&
-                   ((blk / radix) & BLIST_META_MASK) == 0)
-                       radix *= BLIST_META_RADIX;
+                   ((blk / radix) & BLIST_MASK) == 0)
+                       radix *= BLIST_RADIX;
                if (~scan->bm_bitmap != 0) {
                        /*
                         * Either there is no next leaf with any free blocks,
@@ -647,39 +637,37 @@ blst_next_leaf_alloc(blmeta_t *scan, daddr_t start, in
                                return (avail);
                        }
                        maxcount = imin(avail, maxcount);
-                       if (maxcount % BLIST_BMAP_RADIX == 0) {
+                       if (maxcount % BLIST_RADIX == 0) {
                                /*
                                 * There was no next leaf.  Back scan up to
                                 * last leaf.
                                 */
-                               --scan;
-                               while (radix != BLIST_BMAP_RADIX) {
-                                       radix /= BLIST_META_RADIX;
+                               do {
+                                       radix /= BLIST_RADIX;
                                        --scan;
-                               }
-                               blk -= BLIST_BMAP_RADIX;
+                               } while (radix != 1);
+                               blk -= BLIST_RADIX;
                        }
                }
        }
        
        /*
         * 'scan' is the last leaf that provides blocks.  Clear from 1 to
-        * BLIST_BMAP_RADIX bits to represent the allocation of those last
-        * blocks.
+        * BLIST_RADIX bits to represent the allocation of those last blocks.
         */
-       if (maxcount % BLIST_BMAP_RADIX != 0)
-               scan->bm_bitmap &= ~bitrange(0, maxcount % BLIST_BMAP_RADIX);
+       if (maxcount % BLIST_RADIX != 0)
+               scan->bm_bitmap &= ~bitrange(0, maxcount % BLIST_RADIX);
        else
                scan->bm_bitmap = 0;
 
        for (;;) {
                /* Back up over meta-nodes, clearing bits if necessary. */
-               blk -= BLIST_BMAP_RADIX;
-               radix = BLIST_BMAP_RADIX;
-               while ((digit = ((blk / radix) & BLIST_META_MASK)) == 0) {
+               blk -= BLIST_RADIX;
+               for (radix = BLIST_RADIX;
+                   (digit = ((blk / radix) & BLIST_MASK)) == 0;
+                   radix *= BLIST_RADIX) {
                        if ((scan--)->bm_bitmap == 0)
                                scan->bm_bitmap ^= 1;
-                       radix *= BLIST_META_RADIX;
                }
                if ((scan--)->bm_bitmap == 0)
                        scan[-digit * radix_to_skip(radix)].bm_bitmap ^=
@@ -734,17 +722,17 @@ blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int *coun
        }
 
        /* Discard any candidates that appear before blk. */
-       if ((blk & BLIST_BMAP_MASK) != 0) {
-               if ((~mask & bitrange(0, blk & BLIST_BMAP_MASK)) != 0) {
+       if ((blk & BLIST_MASK) != 0) {
+               if ((~mask & bitrange(0, blk & BLIST_MASK)) != 0) {
                        /* Grow bighint in case all discarded bits are set. */
-                       bighint += blk & BLIST_BMAP_MASK;
-                       mask |= bitrange(0, blk & BLIST_BMAP_MASK);
+                       bighint += blk & BLIST_MASK;
+                       mask |= bitrange(0, blk & BLIST_MASK);
                        if (~mask == 0) {
                                scan->bm_bighint = bighint;
                                return (SWAPBLK_NONE);
                        }
                }
-               blk -= blk & BLIST_BMAP_MASK;
+               blk -= blk & BLIST_MASK;
        }
 
        /*
@@ -763,17 +751,17 @@ blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int *coun
                        hi = lo + maxcount;
                *count = hi - lo;
                mask = ~bitrange(lo, *count);
-       } else if (maxcount <= BLIST_BMAP_RADIX - lo) {
+       } else if (maxcount <= BLIST_RADIX - lo) {
                /* All the blocks we can use are available here. */
                hi = lo + maxcount;
                *count = maxcount;
                mask = ~bitrange(lo, *count);
-               if (hi == BLIST_BMAP_RADIX)
+               if (hi == BLIST_RADIX)
                        scan->bm_bighint = bighint;
        } else {
                /* Check next leaf for some of the blocks we want or need. */
-               count1 = *count - (BLIST_BMAP_RADIX - lo);
-               maxcount -= BLIST_BMAP_RADIX - lo;
+               count1 = *count - (BLIST_RADIX - lo);
+               maxcount -= BLIST_RADIX - lo;
                hi = blst_next_leaf_alloc(scan, blk, count1, maxcount);
                if (hi < count1)
                        /*
@@ -785,7 +773,7 @@ blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int *coun
                         * this leaf.
                         */
                        return (SWAPBLK_NONE);
-               *count = BLIST_BMAP_RADIX - lo + hi;
+               *count = BLIST_RADIX - lo + hi;
                scan->bm_bighint = bighint;
        }
 
@@ -811,16 +799,15 @@ blst_meta_alloc(blmeta_t *scan, daddr_t cursor, int *c
        bool scan_from_start;
        int digit;
 
-       if (radix == BLIST_BMAP_RADIX)
+       if (radix == 1)
                return (blst_leaf_alloc(scan, cursor, count, maxcount));
-       blk = cursor & -radix;
+       blk = cursor & -(radix * BLIST_RADIX);
        scan_from_start = (cursor == blk);
-       radix /= BLIST_META_RADIX;
        skip = radix_to_skip(radix);
        mask = scan->bm_bitmap;
 
        /* Discard any candidates that appear before cursor. */
-       digit = (cursor / radix) & BLIST_META_MASK;
+       digit = (cursor / radix) & BLIST_MASK;
        mask &= (u_daddr_t)-1 << digit;
        if (mask == 0)
                return (SWAPBLK_NONE);
@@ -846,7 +833,7 @@ blst_meta_alloc(blmeta_t *scan, daddr_t cursor, int *c
                         * The allocation might fit beginning in the i'th 
subtree.
                         */
                        r = blst_meta_alloc(&scan[i], cursor + digit * radix,
-                           count, maxcount, radix);
+                           count, maxcount, radix / BLIST_RADIX);
                        if (r != SWAPBLK_NONE) {
                                if (scan[i].bm_bitmap == 0)
                                        scan->bm_bitmap ^= bitrange(digit, 1);
@@ -860,7 +847,7 @@ blst_meta_alloc(blmeta_t *scan, daddr_t cursor, int *c
         * We couldn't allocate count in this subtree.  If the whole tree was
         * scanned, and the last tree node is allocated, update bighint.
         */
-       if (scan_from_start && !(digit == BLIST_META_RADIX - 1 &&
+       if (scan_from_start && !(digit == BLIST_RADIX - 1 &&
            scan[i].bm_bighint == BLIST_MAX_ALLOC))
                scan->bm_bighint = *count - 1;
 
@@ -882,7 +869,7 @@ blst_leaf_free(blmeta_t *scan, daddr_t blk, int count)
         *          \_________/\__/
         *              count   n
         */
-       mask = bitrange(blk & BLIST_BMAP_MASK, count);
+       mask = bitrange(blk & BLIST_MASK, count);
        KASSERT((scan->bm_bitmap & mask) == 0,
            ("freeing free block: %jx, size %d, mask %jx",
            (uintmax_t)blk, count, (uintmax_t)scan->bm_bitmap & mask));
@@ -913,20 +900,26 @@ blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_
         */
        scan->bm_bighint = BLIST_MAX_ALLOC;
 
-       if (radix == BLIST_BMAP_RADIX)
+       if (radix == 1)
                return (blst_leaf_free(scan, freeBlk, count));
 
-       endBlk = ummin(freeBlk + count, (freeBlk + radix) & -radix);
-       radix /= BLIST_META_RADIX;
+       endBlk = freeBlk + count;
+       blk = (freeBlk + radix * BLIST_RADIX) & -(radix * BLIST_RADIX);
+       /*
+        * blk is first block past the end of the range of this meta node,
+        * or 0 in case of overflow.
+        */
+       if (blk != 0)
+               endBlk = ummin(endBlk, blk);
        skip = radix_to_skip(radix);
        blk = freeBlk & -radix;
-       digit = (blk / radix) & BLIST_META_MASK;
-       endDigit = 1 + (((endBlk - 1) / radix) & BLIST_META_MASK);
+       digit = (blk / radix) & BLIST_MASK;
+       endDigit = 1 + (((endBlk - 1) / radix) & BLIST_MASK);
        scan->bm_bitmap |= bitrange(digit, endDigit - digit);
        for (i = 1 + digit * skip; blk < endBlk; i += skip) {
                blk += radix;
                count = ummin(blk, endBlk) - freeBlk;
-               blst_meta_free(&scan[i], freeBlk, count, radix);
+               blst_meta_free(&scan[i], freeBlk, count, radix / BLIST_RADIX);
                freeBlk = blk;
        }
 }
@@ -947,7 +940,7 @@ blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, 
         * Leaf node
         */
 
-       if (radix == BLIST_BMAP_RADIX) {
+       if (radix == 1) {
                u_daddr_t v = scan->bm_bitmap;
 
                if (v == (u_daddr_t)-1) {
@@ -975,14 +968,14 @@ blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, 
        }
 
        endBlk = blk + count;
-       radix /= BLIST_META_RADIX;
        skip = radix_to_skip(radix);
        for (i = 1; blk < endBlk; i += skip) {
                blk += radix;
                count = radix;
                if (blk >= endBlk)
                        count -= blk - endBlk;
-               blst_copy(&scan[i], blk - radix, radix, dest, count);
+               blst_copy(&scan[i], blk - radix,
+                   radix / BLIST_RADIX, dest, count);
        }
 }
 
@@ -999,7 +992,7 @@ blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count)
        daddr_t nblks;
        u_daddr_t mask;
 
-       mask = bitrange(blk & BLIST_BMAP_MASK, count);
+       mask = bitrange(blk & BLIST_MASK, count);
 
        /* Count the number of blocks that we are allocating. */
        nblks = bitcount64(scan->bm_bitmap & mask);
@@ -1022,20 +1015,27 @@ blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr
        daddr_t blk, endBlk, i, nblks, skip;
        int digit;
 
-       if (radix == BLIST_BMAP_RADIX)
+       if (radix == 1)
                return (blst_leaf_fill(scan, allocBlk, count));
 
-       endBlk = ummin(allocBlk + count, (allocBlk + radix) & -radix);
-       radix /= BLIST_META_RADIX;
+       endBlk = allocBlk + count;
+       blk = (allocBlk + radix * BLIST_RADIX) & -(radix * BLIST_RADIX);
+       /*
+        * blk is first block past the end of the range of this meta node,
+        * or 0 in case of overflow.
+        */
+       if (blk != 0)
+               endBlk = ummin(endBlk, blk);
        skip = radix_to_skip(radix);
        blk = allocBlk & -radix;
        nblks = 0;
        while (blk < endBlk) {
-               digit = (blk / radix) & BLIST_META_MASK;
+               digit = (blk / radix) & BLIST_MASK;
                i = 1 + digit * skip;
                blk += radix;
                count = ummin(blk, endBlk) - allocBlk;
-               nblks += blst_meta_fill(&scan[i], allocBlk, count, radix);
+               nblks += blst_meta_fill(&scan[i], allocBlk, count,
+                   radix / BLIST_RADIX);
                if (scan[i].bm_bitmap == 0)
                        scan->bm_bitmap &= ~((u_daddr_t)1 << digit);
                allocBlk = blk;
@@ -1052,12 +1052,12 @@ blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t 
        u_daddr_t mask;
        int digit;
 
-       if (radix == BLIST_BMAP_RADIX) {
+       if (radix == 1) {
                printf(
                    "%*.*s(%08llx,%lld): bitmap %0*llx big=%lld\n",
                    tab, tab, "",
-                   (long long)blk, (long long)radix,
-                   1 + (BLIST_BMAP_RADIX - 1) / 4,
+                   (long long)blk, (long long)BLIST_RADIX,
+                   (int)(1 + (BLIST_RADIX - 1) / 4),
                    (long long)scan->bm_bitmap,
                    (long long)scan->bm_bighint
                );
@@ -1067,14 +1067,13 @@ blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t 
        printf(
            "%*.*s(%08llx): subtree (%lld/%lld) bitmap %0*llx big=%lld {\n",
            tab, tab, "",
-           (long long)blk, (long long)radix,
-           (long long)radix,
-           1 + (BLIST_META_RADIX - 1) / 4,
+           (long long)blk, (long long)radix * BLIST_RADIX,
+           (long long)radix * BLIST_RADIX,
+           (int)(1 + (BLIST_RADIX - 1) / 4),
            (long long)scan->bm_bitmap,
            (long long)scan->bm_bighint
        );
 
-       radix /= BLIST_META_RADIX;
        skip = radix_to_skip(radix);
        tab += 4;
 
@@ -1083,7 +1082,7 @@ blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t 
        do {
                digit = bitpos(mask);
                blst_radix_print(&scan[1 + digit * skip], blk + digit * radix,
-                   radix, tab);
+                   radix / BLIST_RADIX, tab);
        } while ((mask ^= bitrange(digit, 1)) != 0);
        tab -= 4;
 
@@ -1100,7 +1099,7 @@ blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t 
 int
 main(int ac, char **av)
 {
-       int size = BLIST_META_RADIX * BLIST_BMAP_RADIX;
+       daddr_t size = BLIST_RADIX * BLIST_RADIX;
        int i;
        blist_t bl;
        struct sbuf *s;
@@ -1108,7 +1107,7 @@ main(int ac, char **av)
        for (i = 1; i < ac; ++i) {
                const char *ptr = av[i];
                if (*ptr != '-') {
-                       size = strtol(ptr, NULL, 0);
+                       size = strtoll(ptr, NULL, 0);
                        continue;
                }
                ptr += 2;
@@ -1116,6 +1115,10 @@ main(int ac, char **av)
                exit(1);
        }
        bl = blist_create(size, M_WAITOK);
+       if (bl == NULL) {
+               fprintf(stderr, "blist_create failed\n");
+               exit(1);
+       }
        blist_free(bl, 0, size);
 
        for (;;) {
@@ -1124,7 +1127,7 @@ main(int ac, char **av)
                int count = 0, maxcount = 0;
 
                printf("%lld/%lld/%lld> ", (long long)blist_avail(bl),
-                   (long long)size, (long long)bl->bl_radix);
+                   (long long)size, (long long)bl->bl_radix * BLIST_RADIX);
                fflush(stdout);
                if (fgets(buf, sizeof(buf), stdin) == NULL)
                        break;

Modified: head/sys/sys/blist.h
==============================================================================
--- head/sys/sys/blist.h        Sat Jul 25 18:09:04 2020        (r363531)
+++ head/sys/sys/blist.h        Sat Jul 25 18:29:10 2020        (r363532)
@@ -85,10 +85,9 @@ typedef struct blist {
        blmeta_t        bl_root[1];     /* root of radix tree           */
 } *blist_t;
 
-#define BLIST_BMAP_RADIX       (sizeof(u_daddr_t)*8)
-#define BLIST_META_RADIX       BLIST_BMAP_RADIX
+#define BLIST_RADIX            (sizeof(u_daddr_t) * 8)
 
-#define BLIST_MAX_ALLOC                BLIST_BMAP_RADIX
+#define BLIST_MAX_ALLOC                BLIST_RADIX
 
 struct sbuf;
 

Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c    Sat Jul 25 18:09:04 2020        (r363531)
+++ head/sys/vm/swap_pager.c    Sat Jul 25 18:29:10 2020        (r363532)
@@ -2369,7 +2369,6 @@ swaponsomething(struct vnode *vp, void *id, u_long nbl
 {
        struct swdevt *sp, *tsp;
        daddr_t dvbase;
-       u_long mblocks;
 
        /*
         * nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks.
@@ -2380,19 +2379,8 @@ swaponsomething(struct vnode *vp, void *id, u_long nbl
        nblks &= ~(ctodb(1) - 1);
        nblks = dbtoc(nblks);
 
-       /*
-        * If we go beyond this, we get overflows in the radix
-        * tree bitmap code.
-        */
-       mblocks = 0x40000000 / BLIST_META_RADIX;
-       if (nblks > mblocks) {
-               printf(
-    "WARNING: reducing swap size to maximum of %luMB per unit\n",
-                   mblocks / 1024 / 1024 * PAGE_SIZE);
-               nblks = mblocks;
-       }
-
        sp = malloc(sizeof *sp, M_VMPGDATA, M_WAITOK | M_ZERO);
+       sp->sw_blist = blist_create(nblks, M_WAITOK);
        sp->sw_vp = vp;
        sp->sw_id = id;
        sp->sw_dev = dev;
@@ -2402,7 +2390,6 @@ swaponsomething(struct vnode *vp, void *id, u_long nbl
        sp->sw_close = close;
        sp->sw_flags = flags;
 
-       sp->sw_blist = blist_create(nblks, M_WAITOK);
        /*
         * Do not free the first blocks in order to avoid overwriting
         * any bsd label at the front of the partition
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