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Subject[PATCH 09/25] make access() use mnt check
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Date

It is OK to let access() go without using a mnt_want/drop_write()
pair because it doesn't actually do writes to the filesystem,
and it is inherently racy anyway. This is a rare case when it is
OK to use __mnt_is_readonly() directly.

Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---
lxc-dave/fs/open.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff -puN fs/open.c~make-access-use-helper fs/open.c
--- lxc/fs/open.c~make-access-use-helper 2007-09-20 12:16:13.000000000 -0700
+++ lxc-dave/fs/open.c 2007-09-20 12:16:13.000000000 -0700
@@ -457,8 +457,17 @@ asmlinkage long sys_faccessat(int dfd, c
if(res || !(mode & S_IWOTH) ||
special_file(nd.dentry->d_inode->i_mode))
goto out_path_release;
-
- if(IS_RDONLY(nd.dentry->d_inode))
+ /*
+ * This is a rare case where using __mnt_is_readonly()
+ * is OK without a mnt_want/drop_write() pair. Since
+ * no actual write to the fs is performed here, we do
+ * not need to telegraph to that to anyone.
+ *
+ * By doing this, we accept that this access is
+ * inherently racy and know that the fs may change
+ * state before we even see this result.
+ */
+ if (__mnt_is_readonly(nd.mnt))
res = -EROFS;

out_path_release:
_
-
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