From a68d2ebc1581a3aec57bd032651e013fa609f530 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 3 Aug 2005 10:07:09 -0700 Subject: [PATCH] Fix up recent get_user_pages() handling The VM_FAULT_WRITE thing is an extra bit, not a valid return value, and has to be treated as such by get_user_pages(). Signed-off-by: Linus Torvalds --- mm/memory.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 81d7117aa58b..e046b7e4b530 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -949,6 +949,8 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, cond_resched_lock(&mm->page_table_lock); while (!(page = follow_page(mm, start, write_access))) { + int ret; + /* * Shortcut for anonymous pages. We don't want * to force the creation of pages tables for @@ -961,16 +963,18 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, break; } spin_unlock(&mm->page_table_lock); - switch (__handle_mm_fault(mm, vma, start, - write_access)) { - case VM_FAULT_WRITE: - /* - * do_wp_page has broken COW when - * necessary, even if maybe_mkwrite - * decided not to set pte_write - */ + ret = __handle_mm_fault(mm, vma, start, write_access); + + /* + * The VM_FAULT_WRITE bit tells us that do_wp_page has + * broken COW when necessary, even if maybe_mkwrite + * decided not to set pte_write. We can thus safely do + * subsequent page lookups as if they were reads. + */ + if (ret & VM_FAULT_WRITE) write_access = 0; - /* FALLTHRU */ + + switch (ret & ~VM_FAULT_WRITE) { case VM_FAULT_MINOR: tsk->min_flt++; break; -- 2.20.1