tree 0ffd9252f53e9e964e962d6d428377851f12b015
parent ce8d2cdf3d2b73e346c82e6f0a46da331df6364c
author Dave Hansen <haveblue@us.ibm.com> 1192602674 -0700
committer Linus Torvalds <torvalds@woody.linux-foundation.org> 1192635785 -0700

r/o bind mounts: rearrange may_open() to be r/o friendly

may_open() calls vfs_permission() before it does checks for IS_RDONLY(inode).
It checks _again_ inside of vfs_permission().

The check inside of vfs_permission() is going away eventually.  With the
mnt_want/drop_write() functions, all of the r/o checks (except for this one)
are consistently done before calling permission().  Because of this, I'd like
to use permission() to hold a debugging check to make sure that the
mnt_want/drop_write() calls are actually being made.

So, to do this:
1. remove the IS_RDONLY() check from permission()
2. enforce that you must mnt_want_write() before
   even calling permission()
3. actually add the debugging check to permission()

We need to rearrange may_open() to do r/o checks before calling permission().
Here's the patch.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>