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Message-Id: <20070917182728.116CADE8@kernel>
Date: Mon, 17 Sep 2007 11:27:28 -0700
From: Dave Hansen <haveblue@...ibm.com>
To: akpm@...l.org
Cc: linux-kernel@...r.kernel.org, hch@...radead.org,
Dave Hansen <haveblue@...ibm.com>
Subject: [PATCH 08/24] make access() use mnt check
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.
Signed-off-by: Dave Hansen <haveblue@...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 2007-09-17 09:44:00.000000000 -0700
+++ lxc-dave/fs/open.c 2007-09-17 09:44:00.000000000 -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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