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authorDave Hansen <haveblue@us.ibm.com>2008-02-15 14:37:55 -0800
committerAl Viro <viro@zeniv.linux.org.uk>2008-04-19 00:29:26 -0400
commit2f676cbc0d60ae806216c7a61c6971bd72dedde8 (patch)
tree57287366150093260f18bdbe81596492e3e40aa1 /fs/open.c
parent9ac9b8474c39c3ae2c2b37d8e1f08db8a9146124 (diff)
downloadlwn-2f676cbc0d60ae806216c7a61c6971bd72dedde8.tar.gz
lwn-2f676cbc0d60ae806216c7a61c6971bd72dedde8.zip
[PATCH] r/o bind mounts: make access() use new r/o helper
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: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/open.c')
-rw-r--r--fs/open.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/fs/open.c b/fs/open.c
index 4d690e33446f..e58382d57e72 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -459,8 +459,17 @@ asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
if(res || !(mode & S_IWOTH) ||
special_file(nd.path.dentry->d_inode->i_mode))
goto out_path_release;
-
- if(IS_RDONLY(nd.path.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.path.mnt))
res = -EROFS;
out_path_release: