Date: Mon, 13 Oct 2014 15:58:04 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r273044 - stable/10/sys/vm Message-ID: <201410131558.s9DFw4u4017497@svn.freebsd.org>
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Author: kib Date: Mon Oct 13 15:58:03 2014 New Revision: 273044 URL: https://svnweb.freebsd.org/changeset/base/273044 Log: MFC r272907: Make MAP_NOSYNC handling in the vm_fault() read-locked object path compatible with write-locked path. Modified: stable/10/sys/vm/vm_fault.c Directory Properties: stable/10/ (props changed) Modified: stable/10/sys/vm/vm_fault.c ============================================================================== --- stable/10/sys/vm/vm_fault.c Mon Oct 13 15:56:47 2014 (r273043) +++ stable/10/sys/vm/vm_fault.c Mon Oct 13 15:58:03 2014 (r273044) @@ -174,6 +174,70 @@ unlock_and_deallocate(struct faultstate } } +static void +vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, + vm_prot_t fault_type, int fault_flags, boolean_t set_wd) +{ + boolean_t need_dirty; + + if (((prot & VM_PROT_WRITE) == 0 && + (fault_flags & VM_FAULT_DIRTY) == 0) || + (m->oflags & VPO_UNMANAGED) != 0) + return; + + VM_OBJECT_ASSERT_LOCKED(m->object); + + need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && + (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) || + (fault_flags & VM_FAULT_DIRTY) != 0; + + if (set_wd) + vm_object_set_writeable_dirty(m->object); + else + /* + * If two callers of vm_fault_dirty() with set_wd == + * FALSE, one for the map entry with MAP_ENTRY_NOSYNC + * flag set, other with flag clear, race, it is + * possible for the no-NOSYNC thread to see m->dirty + * != 0 and not clear VPO_NOSYNC. Take vm_page lock + * around manipulation of VPO_NOSYNC and + * vm_page_dirty() call, to avoid the race and keep + * m->oflags consistent. + */ + vm_page_lock(m); + + /* + * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC + * if the page is already dirty to prevent data written with + * the expectation of being synced from not being synced. + * Likewise if this entry does not request NOSYNC then make + * sure the page isn't marked NOSYNC. Applications sharing + * data should use the same flags to avoid ping ponging. + */ + if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { + if (m->dirty == 0) { + m->oflags |= VPO_NOSYNC; + } + } else { + m->oflags &= ~VPO_NOSYNC; + } + + /* + * If the fault is a write, we know that this page is being + * written NOW so dirty it explicitly to save on + * pmap_is_modified() calls later. + * + * Also tell the backing pager, if any, that it should remove + * any swap backing since the page is now dirty. + */ + if (need_dirty) + vm_page_dirty(m); + if (!set_wd) + vm_page_unlock(m); + if (need_dirty) + vm_pager_page_unswapped(m); +} + /* * TRYPAGER - used by vm_fault to calculate whether the pager for the * current object *might* contain the page. @@ -321,11 +385,8 @@ RetryFault:; vm_page_hold(m); vm_page_unlock(m); } - if ((fault_type & VM_PROT_WRITE) != 0 && - (m->oflags & VPO_UNMANAGED) == 0) { - vm_page_dirty(m); - vm_pager_page_unswapped(m); - } + vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, + FALSE); VM_OBJECT_RUNLOCK(fs.first_object); if (!wired) vm_fault_prefault(&fs, vaddr, 0, 0); @@ -898,42 +959,7 @@ vnode_locked: if (hardfault) fs.entry->next_read = fs.pindex + faultcount - reqpage; - if (((prot & VM_PROT_WRITE) != 0 || - (fault_flags & VM_FAULT_DIRTY) != 0) && - (fs.m->oflags & VPO_UNMANAGED) == 0) { - vm_object_set_writeable_dirty(fs.object); - - /* - * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC - * if the page is already dirty to prevent data written with - * the expectation of being synced from not being synced. - * Likewise if this entry does not request NOSYNC then make - * sure the page isn't marked NOSYNC. Applications sharing - * data should use the same flags to avoid ping ponging. - */ - if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { - if (fs.m->dirty == 0) - fs.m->oflags |= VPO_NOSYNC; - } else { - fs.m->oflags &= ~VPO_NOSYNC; - } - - /* - * If the fault is a write, we know that this page is being - * written NOW so dirty it explicitly to save on - * pmap_is_modified() calls later. - * - * Also tell the backing pager, if any, that it should remove - * any swap backing since the page is now dirty. - */ - if (((fault_type & VM_PROT_WRITE) != 0 && - (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) || - (fault_flags & VM_FAULT_DIRTY) != 0) { - vm_page_dirty(fs.m); - vm_pager_page_unswapped(fs.m); - } - } - + vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); vm_page_assert_xbusied(fs.m); /*
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