From: Dave Hansen <haveblue@us.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
hch@infradead.org, Dave Hansen <haveblue@us.ibm.com>
Subject: [PATCH 08/23] make access() use mnt check
Date: Wed, 11 Jul 2007 17:17:20 -0700 [thread overview]
Message-ID: <20070712001720.CC0E212B@kernel> (raw)
In-Reply-To: <20070712001710.654CD9ED@kernel>
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@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 2007-07-10 12:46:07.000000000 -0700
+++ lxc-dave/fs/open.c 2007-07-10 12:46:07.000000000 -0700
@@ -396,8 +396,17 @@ 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:
_
next prev parent reply other threads:[~2007-07-12 0:17 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-12 0:17 [PATCH 00/23] Mount writer count API (read-only bind mounts prep) Dave Hansen
2007-07-12 0:17 ` [PATCH 01/23] rearrange may_open() to be r/o friendly Dave Hansen
2007-07-12 0:17 ` [PATCH 02/23] create cleanup helper svc_msnfs() Dave Hansen
2007-07-12 0:17 ` [PATCH 03/23] filesystem helpers for custom 'struct file's Dave Hansen
2007-07-12 0:17 ` [PATCH 04/23] r/o bind mounts: stub functions Dave Hansen
2007-07-12 0:17 ` [PATCH 05/23] elevate write count open()'d files Dave Hansen
2007-07-12 0:17 ` [PATCH 06/23] r/o bind mounts: elevate write count for some ioctls Dave Hansen
2007-07-12 0:17 ` [PATCH 07/23] elevate writer count for chown and friends Dave Hansen
2007-07-12 0:17 ` Dave Hansen [this message]
2007-07-12 0:17 ` [PATCH 09/23] elevate mnt writers for callers of vfs_mkdir() Dave Hansen
2007-07-12 0:17 ` [PATCH 10/23] elevate write count during entire ncp_ioctl() Dave Hansen
2007-07-12 0:17 ` [PATCH 11/23] elevate write count for link and symlink calls Dave Hansen
2007-07-12 0:17 ` [PATCH 12/23] elevate mount count for extended attributes Dave Hansen
2007-07-12 0:17 ` [PATCH 13/23] elevate write count for file_update_time() Dave Hansen
2007-07-12 0:17 ` [PATCH 14/23] mount_is_safe(): add comment Dave Hansen
2007-07-12 0:17 ` [PATCH 15/23] unix_find_other() elevate write count for touch_atime() Dave Hansen
2007-07-12 0:17 ` [PATCH 16/23] elevate write count over calls to vfs_rename() Dave Hansen
2007-07-12 0:17 ` [PATCH 17/23] nfs: check mnt instead of superblock directly Dave Hansen
2007-07-12 0:17 ` [PATCH 18/23] elevate writer count for do_sys_truncate() Dave Hansen
2007-07-12 0:17 ` [PATCH 19/23] elevate write count for do_utimes() Dave Hansen
2007-07-12 0:17 ` [PATCH 20/23] elevate write count for do_sys_utime() and touch_atime() Dave Hansen
2007-07-12 0:17 ` [PATCH 21/23] sys_mknodat(): elevate write count for vfs_mknod/create() Dave Hansen
2007-07-12 0:17 ` [PATCH 22/23] elevate mnt writers for vfs_unlink() callers Dave Hansen
2007-07-12 0:17 ` [PATCH 23/23] do_rmdir(): elevate write count Dave Hansen
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