Author: dougm Date: Fri May 10 19:55:29 2019 New Revision: 347464 URL: https://svnweb.freebsd.org/changeset/base/347464
Log: Replace the expression "-mask & ~mask" with a function call that does the same thing, but is commented so that it might be better understood. Approved by: kib (mentor) Differential Revision: https://reviews.freebsd.org/D20231 Modified: head/sys/kern/subr_blist.c Modified: head/sys/kern/subr_blist.c ============================================================================== --- head/sys/kern/subr_blist.c Fri May 10 19:36:14 2019 (r347463) +++ head/sys/kern/subr_blist.c Fri May 10 19:55:29 2019 (r347464) @@ -643,6 +643,19 @@ blst_next_leaf_alloc(blmeta_t *scan, daddr_t blk, int } /* + * Given a bitmask, flip all the bits from the least-significant 1-bit to the + * most significant bit. If the result is non-zero, then the least-significant + * 1-bit of the result is in the same position as the least-signification 0-bit + * in mask that is followed by a 1-bit. + */ +static inline u_daddr_t +flip_hibits(u_daddr_t mask) +{ + + return (-mask & ~mask); +} + +/* * BLST_LEAF_ALLOC() - allocate at a leaf in the radix tree (a bitmap). * * This function is the core of the allocator. Its execution time is @@ -659,7 +672,7 @@ blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count count1 = count - 1; num_shifts = fls(count1); mask = scan->bm_bitmap; - while ((-mask & ~mask) != 0 && num_shifts > 0) { + while (flip_hibits(mask) != 0 && num_shifts > 0) { /* * If bit i is set in mask, then bits in [i, i+range1] are set * in scan->bm_bitmap. The value of range1 is equal to count1 _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
