[PATCH 05/30] do namei_flags calculation inside open_namei()

Dave Hansen
2008-02-15T22:42:09Z

My end goal here is to make sure all users of may_open()
return filps. This will ensure that we properly release
mount write counts which were taken for the filp in
may_open().

This patch moves the sys_open flags to namei flags
calculation into fs/namei.c. We'll shortly be moving
the nameidata_to_filp() calls into namei.c, and this
gets the sys_open flags to a place where we can get
at them when we need them.

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

linux-2.6.git-dave/fs/namei.c | 43 +++++++++++++++++++++++++++++++++---------
linux-2.6.git-dave/fs/open.c | 22 +--------------------
2 files changed, 36 insertions(+), 29 deletions(-)

diff -puN fs/namei.c~do-namei_flags-calculation-inside-open_namei fs/namei.c
--- linux-2.6.git/fs/namei.c~do-namei_flags-calculation-inside-open_namei 2008-02-15 13:25:44.000000000 -0800
+++ linux-2.6.git-dave/fs/namei.c 2008-02-15 13:25:44.000000000 -0800
@@ -1676,7 +1676,12 @@ int may_open(struct nameidata *nd, int a
return 0;
}

-static int open_namei_create(struct nameidata *nd, struct path *path,
+/*
+ * Be careful about ever adding any more callers of this
+ * function. Its flags must be in the namei format, not
+ * what get passed to sys_open().
+ */
+static int __open_namei_create(struct nameidata *nd, struct path *path,
int flag, int mode)
{
int error;
@@ -1695,26 +1700,46 @@ static int open_namei_create(struct name
}

/*
+ * Note that while the flag value (low two bits) for sys_open means:
+ * 00 - read-only
+ * 01 - write-only
+ * 10 - read-write
+ * 11 - special
+ * it is changed into
+ * 00 - no permissions needed
+ * 01 - read-permission
+ * 10 - write-permission
+ * 11 - read-write
+ * for the internal routines (ie open_namei()/follow_link() etc)
+ * This is more logical, and also allows the 00 "no perm needed"
+ * to be used for symlinks (where the permissions are checked
+ * later).
+ *
+*/
+static inline int open_to_namei_flags(int flag)
+{
+ if ((flag+1) & O_ACCMODE)
+ flag++;
+ return flag;
+}
+
+/*
* open_namei()
*
* namei for open - this is in fact almost the whole open-routine.
*
* Note that the low bits of "flag" aren't the same as in the open
- * system call - they are 00 - no permissions needed
- * 01 - read permission needed
- * 10 - write permission needed
- * 11 - read/write permissions needed
- * which is a lot more logical, and also allows the "no perm" needed
- * for symlinks (where the permissions are checked later).
+ * system call. See open_to_namei_flags().
* SMP-safe
*/
-int open_namei(int dfd, const char *pathname, int flag,
+int open_namei(int dfd, const char *pathname, int open_flag,
int mode, struct nameidata *nd)
{
int acc_mode, error;
struct path path;
struct dentry *dir;
int count = 0;
+ int flag = open_to_namei_flags(open_flag);

acc_mode = ACC_MODE(flag);

@@ -1775,7 +1800,7 @@ do_last:

/* Negative dentry, just create the file */
if (!path.dentry->d_inode) {
- error = open_namei_create(nd, &path, flag, mode);
+ error = __open_namei_create(nd, &path, flag, mode);
if (error)
goto exit;
return 0;
diff -puN fs/open.c~do-namei_flags-calculation-inside-open_namei fs/open.c
--- linux-2.6.git/fs/open.c~do-namei_flags-calculation-inside-open_namei 2008-02-15 13:25:44.000000000 -0800
+++ linux-2.6.git-dave/fs/open.c 2008-02-15 13:25:44.000000000 -0800
@@ -796,31 +796,13 @@ cleanup_file:
return ERR_PTR(error);
}

-/*
- * Note that while the flag value (low two bits) for sys_open means:
- * 00 - read-only
- * 01 - write-only
- * 10 - read-write
- * 11 - special
- * it is changed into
- * 00 - no permissions needed
- * 01 - read-permission
- * 10 - write-permission
- * 11 - read-write
- * for the internal routines (ie open_namei()/follow_link() etc). 00 is
- * used by symlinks.
- */
static struct file *do_filp_open(int dfd, const char *filename, int flags,
int mode)
{
- int namei_flags, error;
+ int error;
struct nameidata nd;

- namei_flags = flags;
- if ((namei_flags+1) & O_ACCMODE)
- namei_flags++;
-
- error = open_namei(dfd, filename, namei_flags, mode, &nd);
+ error = open_namei(dfd, filename, flags, mode, &nd);
if (!error)
return nameidata_to_filp(&nd, flags);

_