Date: Sun, 18 Nov 2018 01:27:17 +0000 (UTC) From: Alan Cox <alc@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r340546 - head/sys/vm Message-ID: <201811180127.wAI1RHUv019324@repo.freebsd.org>
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Author: alc Date: Sun Nov 18 01:27:17 2018 New Revision: 340546 URL: https://svnweb.freebsd.org/changeset/base/340546 Log: Tidy up vm_map_simplify_entry() and its recently introduced helper functions. Notably, reflow the text of some comments so that they occupy fewer lines, and introduce an assertion in one of the new helper functions so that it is not misused by a future caller. In collaboration with: Doug Moore <dougm@rice.edu> MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D17635 Modified: head/sys/vm/vm_map.c Modified: head/sys/vm/vm_map.c ============================================================================== --- head/sys/vm/vm_map.c Sun Nov 18 01:07:36 2018 (r340545) +++ head/sys/vm/vm_map.c Sun Nov 18 01:27:17 2018 (r340546) @@ -1644,16 +1644,25 @@ vm_map_find_min(vm_map_t map, vm_object_t object, vm_o } } +/* + * A map entry with any of the following flags set must not be merged with + * another entry. + */ +#define MAP_ENTRY_NOMERGE_MASK (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP | \ + MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP) + static bool vm_map_mergeable_neighbors(vm_map_entry_t prev, vm_map_entry_t entry) { - vm_size_t prevsize; - prevsize = prev->end - prev->start; + KASSERT((prev->eflags & MAP_ENTRY_NOMERGE_MASK) == 0 || + (entry->eflags & MAP_ENTRY_NOMERGE_MASK) == 0, + ("vm_map_mergeable_neighbors: neither %p nor %p are mergeable", + prev, entry)); return (prev->end == entry->start && prev->object.vm_object == entry->object.vm_object && (prev->object.vm_object == NULL || - prev->offset + prevsize == entry->offset) && + prev->offset + (prev->end - prev->start) == entry->offset) && prev->eflags == entry->eflags && prev->protection == entry->protection && prev->max_protection == entry->max_protection && @@ -1667,18 +1676,14 @@ vm_map_merged_neighbor_dispose(vm_map_t map, vm_map_en { /* - * If the backing object is a vnode object, - * vm_object_deallocate() calls vrele(). - * However, vrele() does not lock the vnode - * because the vnode has additional - * references. Thus, the map lock can be kept - * without causing a lock-order reversal with - * the vnode lock. + * If the backing object is a vnode object, vm_object_deallocate() + * calls vrele(). However, vrele() does not lock the vnode because + * the vnode has additional references. Thus, the map lock can be + * kept without causing a lock-order reversal with the vnode lock. * - * Since we count the number of virtual page - * mappings in object->un_pager.vnp.writemappings, - * the writemappings value should not be adjusted - * when the entry is disposed of. + * Since we count the number of virtual page mappings in + * object->un_pager.vnp.writemappings, the writemappings value + * should not be adjusted when the entry is disposed of. */ if (entry->object.vm_object != NULL) vm_object_deallocate(entry->object.vm_object); @@ -1704,10 +1709,8 @@ vm_map_simplify_entry(vm_map_t map, vm_map_entry_t ent { vm_map_entry_t next, prev; - if ((entry->eflags & (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP | - MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP)) != 0) + if ((entry->eflags & MAP_ENTRY_NOMERGE_MASK) != 0) return; - prev = entry->prev; if (vm_map_mergeable_neighbors(prev, entry)) { vm_map_entry_unlink(map, prev); @@ -1717,7 +1720,6 @@ vm_map_simplify_entry(vm_map_t map, vm_map_entry_t ent vm_map_entry_resize_free(map, entry->prev); vm_map_merged_neighbor_dispose(map, prev); } - next = entry->next; if (vm_map_mergeable_neighbors(entry, next)) { vm_map_entry_unlink(map, next); @@ -1726,6 +1728,7 @@ vm_map_simplify_entry(vm_map_t map, vm_map_entry_t ent vm_map_merged_neighbor_dispose(map, next); } } + /* * vm_map_clip_start: [ internal use only ] *
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