From: Miklos Szeredi <mszeredi@xxxxxxx>
Add a new file operation f_op->open_other(). This acts just like
f_op->open() except the return value can be another open struct file
pointer. In that case the original file is discarded and the
replacement file is used instead.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/open.c | 23 +++++++++++++++++------
include/linux/fs.h | 1 +
2 files changed, 18 insertions(+), 6 deletions(-)
Index: linux-2.6/fs/open.c
===================================================================
--- linux-2.6.orig/fs/open.c 2010-08-19 09:45:50.000000000 +0200
+++ linux-2.6/fs/open.c 2010-08-19 09:46:27.000000000 +0200
@@ -657,6 +657,7 @@ static struct file *__dentry_open(struct
const struct cred *cred)
{
struct inode *inode;
+ struct file *ret;
int error;
f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
@@ -664,6 +665,7 @@ static struct file *__dentry_open(struct
inode = dentry->d_inode;
if (f->f_mode & FMODE_WRITE) {
error = __get_file_write_access(inode, mnt);
+ ret = ERR_PTR(error);
if (error)
goto cleanup_file;
if (!special_file(inode->i_mode))
@@ -678,15 +680,24 @@ static struct file *__dentry_open(struct
file_sb_list_add(f, inode->i_sb);
error = security_dentry_open(f, cred);
+ ret = ERR_PTR(error);
if (error)
goto cleanup_all;
- if (!open && f->f_op)
- open = f->f_op->open;
- if (open) {
- error = open(inode, f);
- if (error)
+ if (!open && f->f_op && f->f_op->open_other) {
+ /* NULL means keep f, non-error non-null means replace */
+ ret = f->f_op->open_other(f);
+ if (IS_ERR(ret) || ret != NULL)
goto cleanup_all;
+ } else {
+ if (!open && f->f_op)
+ open = f->f_op->open;
+ if (open) {
+ error = open(inode, f);
+ ret = ERR_PTR(error);
+ if (error)
+ goto cleanup_all;
+ }
}
ima_counts_get(f);
@@ -728,7 +739,7 @@ cleanup_file:
put_filp(f);
dput(dentry);
mntput(mnt);
- return ERR_PTR(error);
+ return ret;
}
/**
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h 2010-08-19 09:46:15.000000000 +0200
+++ linux-2.6/include/linux/fs.h 2010-08-19 09:46:27.000000000 +0200
@@ -1494,6 +1494,7 @@ struct file_operations {
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
int (*open) (struct inode *, struct file *);
+ struct file *(*open_other) (struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, int datasync);
--
--
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