From 5988dd09c4983bed7c2671446de5715a63036bb3 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 11 Sep 2013 14:20:20 -0700 Subject: [PATCH] mm: mmap_region: kill correct_wcount/inode, use allow_write_access() correct_wcount and inode in mmap_region() just complicate the code. This boolean was needed previously, when deny_write_access() was called before vma_merge(), now we can simply check VM_DENYWRITE and do allow_write_access() if it is set. allow_write_access() checks file != NULL, so this is safe even if it was possible to use VM_DENYWRITE && !file. Just we need to ensure we use the same file which was deny_write_access()'ed, so the patch also moves "file = vma->vm_file" down after allow_write_access(). Signed-off-by: Oleg Nesterov Cc: Hugh Dickins Cc: Al Viro Cc: Colin Cross Cc: David Rientjes Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Change-Id: I05df8842b7c4b7e3e29b35d914f297ce37af1685 Origin: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e86867720e617774b560dfbc169b7f3d0d490950 Backported-by: Maciej Wereski Signed-off-by: Maciej Wereski --- mm/mmap.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 8f87b14..f97c319 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1474,11 +1474,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr, { struct mm_struct *mm = current->mm; struct vm_area_struct *vma, *prev; - int correct_wcount = 0; int error; struct rb_node **rb_link, *rb_parent; unsigned long charged = 0; - struct inode *inode = file ? file_inode(file) : NULL; /* Check against address space limit. */ if (!may_expand_vm(mm, len >> PAGE_SHIFT)) { @@ -1551,7 +1549,6 @@ munmap_back: error = deny_write_access(file); if (error) goto free_vma; - correct_wcount = 1; } vma->vm_file = get_file(file); error = file->f_op->mmap(file, vma); @@ -1594,11 +1591,10 @@ munmap_back: } vma_link(mm, vma, prev, rb_link, rb_parent); - file = vma->vm_file; - /* Once vma denies write, undo our temporary denial count */ - if (correct_wcount) - atomic_inc(&inode->i_writecount); + if (vm_flags & VM_DENYWRITE) + allow_write_access(file); + file = vma->vm_file; out: perf_event_mmap(vma); @@ -1617,8 +1613,8 @@ out: return addr; unmap_and_free_vma: - if (correct_wcount) - atomic_inc(&inode->i_writecount); + if (vm_flags & VM_DENYWRITE) + allow_write_access(file); vma->vm_file = NULL; fput(file); -- 2.7.4