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Message-Id: <20071010163442.2228C7E9@kernel>
Date: Wed, 10 Oct 2007 09:34:42 -0700
From: Dave Hansen <haveblue@...ibm.com>
To: linux-kernel@...r.kernel.org
Cc: miklos@...redi.hu, hch@...radead.org,
Dave Hansen <haveblue@...ibm.com>
Subject: [RFC][PATCH 4/7] make open_namei() return a filp
If open_namei() succeeds, there is potentially a mnt_want_write()
that needs to get balanced. If the caller doesn't create a
'struct file' and eventually __fput() it, or manually drop the
write count on an error, we have a bug.
Forcing open_namei() to return a filp fixes this. Any caller
getting 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@...ibm.com>
---
lxc-dave/fs/namei.c | 16 ++++++++--------
lxc-dave/fs/open.c | 7 +------
lxc-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
--- lxc/fs/namei.c~make-open_namei-return-a-filp 2007-10-03 09:01:45.000000000 -0700
+++ lxc-dave/fs/namei.c 2007-10-03 09:01:45.000000000 -0700
@@ -1728,8 +1728,8 @@ 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;
@@ -1755,7 +1755,7 @@ 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;
}
@@ -1764,7 +1764,7 @@ 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
@@ -1798,7 +1798,7 @@ do_last:
error = __open_namei_create(nd, &path, flag, mode);
if (error)
goto exit;
- return 0;
+ return nameidata_to_filp(nd, sys_open_flag);
}
/*
@@ -1831,7 +1831,7 @@ ok:
error = may_open(nd, acc_mode, flag);
if (error)
goto exit;
- return 0;
+ return nameidata_to_filp(nd, sys_open_flag);
exit_mutex_unlock:
mutex_unlock(&dir->d_inode->i_mutex);
@@ -1841,7 +1841,7 @@ 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;
@@ -1868,7 +1868,7 @@ 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
--- lxc/fs/open.c~make-open_namei-return-a-filp 2007-10-03 09:01:45.000000000 -0700
+++ lxc-dave/fs/open.c 2007-10-03 09:01:45.000000000 -0700
@@ -846,14 +846,9 @@ 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
--- lxc/include/linux/fs.h~make-open_namei-return-a-filp 2007-10-03 09:01:45.000000000 -0700
+++ lxc-dave/include/linux/fs.h 2007-10-03 09:01:45.000000000 -0700
@@ -1721,7 +1721,7 @@ 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);
_
-
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