Author: dougm Date: Fri Jun 28 02:14:54 2019 New Revision: 349498 URL: https://svnweb.freebsd.org/changeset/base/349498
Log: If vm_map_protect fails with KERN_RESOURCE_SHORTAGE, be sure to simplify modified entries before returning. Reviewed by: alc, markj (earlier version), kib (earlier version) Approved by: kib, markj (mentors, implicit) Differential Revision: https://reviews.freebsd.org/D20753 Modified: head/sys/vm/vm_map.c Modified: head/sys/vm/vm_map.c ============================================================================== --- head/sys/vm/vm_map.c Fri Jun 28 01:57:59 2019 (r349497) +++ head/sys/vm/vm_map.c Fri Jun 28 02:14:54 2019 (r349498) @@ -2454,6 +2454,7 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_off vm_object_t obj; struct ucred *cred; vm_prot_t old_prot; + int rv; if (start == end) return (KERN_SUCCESS); @@ -2508,10 +2509,13 @@ again: } /* - * Do an accounting pass for private read-only mappings that - * now will do cow due to allowed write (e.g. debugger sets - * breakpoint on text segment) + * Before changing the protections, try to reserve swap space for any + * private (i.e., copy-on-write) mappings that are transitioning from + * read-only to read/write access. If a reservation fails, break out + * of this loop early and let the next loop simplify the entries, since + * some may now be mergeable. */ + rv = KERN_SUCCESS; vm_map_clip_start(map, entry, start); for (current = entry; current->start < end; current = current->next) { @@ -2529,8 +2533,9 @@ again: if (obj == NULL || (current->eflags & MAP_ENTRY_NEEDS_COPY)) { if (!swap_reserve(current->end - current->start)) { - vm_map_unlock(map); - return (KERN_RESOURCE_SHORTAGE); + rv = KERN_RESOURCE_SHORTAGE; + end = current->end; + break; } crhold(cred); current->cred = cred; @@ -2553,8 +2558,9 @@ again: obj, current)); if (!swap_reserve(ptoa(obj->size))) { VM_OBJECT_WUNLOCK(obj); - vm_map_unlock(map); - return (KERN_RESOURCE_SHORTAGE); + rv = KERN_RESOURCE_SHORTAGE; + end = current->end; + break; } crhold(cred); @@ -2564,11 +2570,14 @@ again: } /* - * Go back and fix up protections. [Note that clipping is not - * necessary the second time.] + * If enough swap space was available, go back and fix up protections. + * Otherwise, just simplify entries, since some may have been modified. + * [Note that clipping is not necessary the second time.] */ - for (current = entry; current->start < end; current = current->next) { - if ((current->eflags & MAP_ENTRY_GUARD) != 0) + for (current = entry; current->start < end; + vm_map_simplify_entry(map, current), current = current->next) { + if (rv != KERN_SUCCESS || + (current->eflags & MAP_ENTRY_GUARD) != 0) continue; old_prot = current->protection; @@ -2603,10 +2612,9 @@ again: current->protection & MASK(current)); #undef MASK } - vm_map_simplify_entry(map, current); } vm_map_unlock(map); - return (KERN_SUCCESS); + return (rv); } /* _______________________________________________ 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"
