From bccdea450b37005ada49d974baff95be1d8821c7 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Fri, 27 May 2016 06:05:12 +0000 Subject: [PATCH] Use vm_page_replace_checked() instead of vm_page_rename() for implementing optimized copy-on-write faults. This has two advantages: (1) one less radix tree operation is performed and (2) vm_page_replace_checked() cannot fail, making the code simpler. Submitted by: Ryan Libby Reviewed by: kib Sponsored by: EMC / Isilon Storage Division Differential Revision: https://reviews.freebsd.org/D4478 --- sys/vm/vm_fault.c | 27 ++++++++++----------------- 1 file changed, 10 insertions(+), 17 deletions(-) diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c index 66506f3cdb6..50bf725fa7b 100644 --- a/sys/vm/vm_fault.c +++ b/sys/vm/vm_fault.c @@ -799,26 +799,15 @@ RetryFault:; * We don't chase down the shadow chain */ fs.object == fs.first_object->backing_object) { - /* - * get rid of the unnecessary page - */ - vm_page_lock(fs.first_m); - vm_page_remove(fs.first_m); - vm_page_unlock(fs.first_m); - /* - * grab the page and put it into the - * process'es object. The page is - * automatically made dirty. - */ - if (vm_page_rename(fs.m, fs.first_object, - fs.first_pindex)) { - VM_OBJECT_WUNLOCK(fs.first_object); - unlock_and_deallocate(&fs); - goto RetryFault; - } + vm_page_lock(fs.m); + vm_page_remove(fs.m); + vm_page_unlock(fs.m); vm_page_lock(fs.first_m); + vm_page_replace_checked(fs.m, fs.first_object, + fs.first_pindex, fs.first_m); vm_page_free(fs.first_m); vm_page_unlock(fs.first_m); + vm_page_dirty(fs.m); #if VM_NRESERVLEVEL > 0 /* * Rename the reservation. @@ -827,6 +816,10 @@ RetryFault:; fs.object, OFF_TO_IDX( fs.first_object->backing_object_offset)); #endif + /* + * Removing the page from the backing object + * unbusied it. + */ vm_page_xbusy(fs.m); fs.first_m = fs.m; fs.m = NULL; -- 2.45.2