[PATCH 02/27] make open_namei() return a filp

Dave Hansen
2007-11-01T23:08:49Z

open_namei() will, in the future, need to take mount write counts
over its creation and truncation (via may_open()) operations. It
needs to keep these write counts until any potential filp that is
created gets __fput()'d.

This gets complicated in the error handling and becomes very murky
as to how far open_namei() actually got, and whether or not that
mount write count was taken.

Creating the filps inside of open_namei() lets us shift the write
count to be taken and released along with the filp. We can hold
a temporary write count during those creation and truncation
operations, then release them once the write for the filp has
been established.

Any caller who gets a 'struct file' back must consider that filp
instantiated and fput() it normally. The callers no longer
have to worry about ever manually releasing a mnt write count.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

linux-2.6.git-dave/fs/namei.c | 16 ++++++++--------
linux-2.6.git-dave/fs/open.c | 7 +------
linux-2.6.git-dave/include/linux/fs.h | 2 +-
3 files changed, 10 insertions(+), 15 deletions(-)

diff -puN fs/namei.c~make-open_namei-return-a-filp fs/namei.c
--- linux-2.6.git/fs/namei.c~make-open_namei-return-a-filp 2007-11-01 14:46:05.000000000 -0700
+++ linux-2.6.git-dave/fs/namei.c 2007-11-01 14:46:05.000000000 -0700
@@ -1730,8 +1730,8 @@ static inline int sys_open_flags_to_name
* system call. See sys_open_flags_to_namei_flags().
* SMP-safe
*/
-int open_namei(int dfd, const char *pathname, int sys_open_flag,
- int mode, struct nameidata *nd)
+struct file *open_namei(int dfd, const char *pathname, int sys_open_flag,
+ int mode, struct nameidata *nd)
{
int acc_mode, error;
struct path path;
@@ -1757,7 +1757,7 @@ int open_namei(int dfd, const char *path
error = path_lookup_open(dfd, pathname, lookup_flags(flag),
nd, flag);
if (error)
- return error;
+ return ERR_PTR(error);
goto ok;
}

@@ -1766,7 +1766,7 @@ int open_namei(int dfd, const char *path
*/
error = path_lookup_create(dfd,pathname,LOOKUP_PARENT,nd,flag,mode);
if (error)
- return error;
+ return ERR_PTR(error);

/*
* We have the parent and last component. First of all, check
@@ -1801,7 +1801,7 @@ do_last:
error = __open_namei_create(nd, &path, flag, mode);
if (error)
goto exit;
- return 0;
+ return nameidata_to_filp(nd, sys_open_flag);
}

/*
@@ -1834,7 +1834,7 @@ ok:
error = may_open(nd, acc_mode, flag);
if (error)
goto exit;
- return 0;
+ return nameidata_to_filp(nd, sys_open_flag);

exit_dput:
dput_path(&path, nd);
@@ -1842,7 +1842,7 @@ exit:
if (!IS_ERR(nd->intent.open.file))
release_open_intent(nd);
path_release(nd);
- return error;
+ return ERR_PTR(error);

do_link:
error = -ELOOP;
@@ -1869,7 +1869,7 @@ do_link:
* with "intent.open".
*/
release_open_intent(nd);
- return error;
+ return ERR_PTR(error);
}
nd->flags &= ~LOOKUP_PARENT;
if (nd->last_type == LAST_BIND)
diff -puN fs/open.c~make-open_namei-return-a-filp fs/open.c
--- linux-2.6.git/fs/open.c~make-open_namei-return-a-filp 2007-11-01 14:46:05.000000000 -0700
+++ linux-2.6.git-dave/fs/open.c 2007-11-01 14:46:05.000000000 -0700
@@ -803,14 +803,9 @@ cleanup_file:
static struct file *do_filp_open(int dfd, const char *filename, int flags,
int mode)
{
- int error;
struct nameidata nd;

- error = open_namei(dfd, filename, flags, mode, &nd);
- if (!error)
- return nameidata_to_filp(&nd, flags);
-
- return ERR_PTR(error);
+ return open_namei(dfd, filename, flags, mode, &nd);
}

struct file *filp_open(const char *filename, int flags, int mode)
diff -puN include/linux/fs.h~make-open_namei-return-a-filp include/linux/fs.h
--- linux-2.6.git/include/linux/fs.h~make-open_namei-return-a-filp 2007-11-01 14:46:05.000000000 -0700
+++ linux-2.6.git-dave/include/linux/fs.h 2007-11-01 14:46:05.000000000 -0700
@@ -1714,7 +1714,7 @@ extern struct file *create_read_pipe(str
extern struct file *create_write_pipe(void);
extern void free_write_pipe(struct file *);

-extern int open_namei(int dfd, const char *, int, int, struct nameidata *);
+extern struct file *open_namei(int dfd, const char *, int, int, struct nameidata *);
extern int may_open(struct nameidata *, int, int);

extern int kernel_read(struct file *, unsigned long, char *, unsigned long);
_