MM: e86867720e617774b560dfbc169b7f3d0d490950
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 <o...@redhat.com>
Cc: Hugh Dickins <hu...@google.com>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: Colin Cross <ccr...@android.com>
Cc: David Rientjes <rient...@google.com>
Cc: KOSAKI Motohiro <kosaki.motoh...@jp.fujitsu.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Andrew Vagin <ava...@openvz.org>
---
mm/mmap.c | 14 +++++---------
1 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 826cf37..f87a78b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1494,11 +1494,9 @@ 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;
unsigned long ub_charged = 0;
/* Check against address space limit. */
@@ -1576,7 +1574,6 @@ 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);
@@ -1631,11 +1628,10 @@ 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);
@@ -1663,8 +1659,8 @@ 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);
--
1.7.1
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