linux_old1/include/linux/file.h

75 lines
1.7 KiB
C
Raw Normal View History

/*
* Wrapper functions for accessing the file_struct fd array.
*/
#ifndef __LINUX_FILE_H
#define __LINUX_FILE_H
#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/posix_types.h>
struct file;
extern void fput(struct file *);
r/o bind mounts: filesystem helpers for custom 'struct file's Why do we need r/o bind mounts? This feature allows a read-only view into a read-write filesystem. In the process of doing that, it also provides infrastructure for keeping track of the number of writers to any given mount. This has a number of uses. It allows chroots to have parts of filesystems writable. It will be useful for containers in the future because users may have root inside a container, but should not be allowed to write to somefilesystems. This also replaces patches that vserver has had out of the tree for several years. It allows security enhancement by making sure that parts of your filesystem read-only (such as when you don't trust your FTP server), when you don't want to have entire new filesystems mounted, or when you want atime selectively updated. I've been using the following script to test that the feature is working as desired. It takes a directory and makes a regular bind and a r/o bind mount of it. It then performs some normal filesystem operations on the three directories, including ones that are expected to fail, like creating a file on the r/o mount. This patch: Some filesystems forego the vfs and may_open() and create their own 'struct file's. This patch creates a couple of helper functions which can be used by these filesystems, and will provide a unified place which the r/o bind mount code may patch. Also, rename an existing, static-scope init_file() to a less generic name. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 14:31:13 +08:00
struct file_operations;
struct vfsmount;
struct dentry;
struct path;
extern struct file *alloc_file(struct path *, fmode_t mode,
const struct file_operations *fop);
r/o bind mounts: filesystem helpers for custom 'struct file's Why do we need r/o bind mounts? This feature allows a read-only view into a read-write filesystem. In the process of doing that, it also provides infrastructure for keeping track of the number of writers to any given mount. This has a number of uses. It allows chroots to have parts of filesystems writable. It will be useful for containers in the future because users may have root inside a container, but should not be allowed to write to somefilesystems. This also replaces patches that vserver has had out of the tree for several years. It allows security enhancement by making sure that parts of your filesystem read-only (such as when you don't trust your FTP server), when you don't want to have entire new filesystems mounted, or when you want atime selectively updated. I've been using the following script to test that the feature is working as desired. It takes a directory and makes a regular bind and a r/o bind mount of it. It then performs some normal filesystem operations on the three directories, including ones that are expected to fail, like creating a file on the r/o mount. This patch: Some filesystems forego the vfs and may_open() and create their own 'struct file's. This patch creates a couple of helper functions which can be used by these filesystems, and will provide a unified place which the r/o bind mount code may patch. Also, rename an existing, static-scope init_file() to a less generic name. Signed-off-by: Dave Hansen <haveblue@us.ibm.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-17 14:31:13 +08:00
static inline void fput_light(struct file *file, int fput_needed)
{
if (fput_needed)
fput(file);
}
struct fd {
struct file *file;
int need_put;
};
static inline void fdput(struct fd fd)
{
if (fd.need_put)
fput(fd.file);
}
extern struct file *fget(unsigned int fd);
extern struct file *fget_light(unsigned int fd, int *fput_needed);
static inline struct fd fdget(unsigned int fd)
{
int b;
struct file *f = fget_light(fd, &b);
return (struct fd){f,b};
}
extern struct file *fget_raw(unsigned int fd);
extern struct file *fget_raw_light(unsigned int fd, int *fput_needed);
static inline struct fd fdget_raw(unsigned int fd)
{
int b;
struct file *f = fget_raw_light(fd, &b);
return (struct fd){f,b};
}
extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
extern int replace_fd(unsigned fd, struct file *file, unsigned flags);
extern void set_close_on_exec(unsigned int fd, int flag);
extern bool get_close_on_exec(unsigned int fd);
extern void put_filp(struct file *);
extern int get_unused_fd_flags(unsigned flags);
#define get_unused_fd() get_unused_fd_flags(0)
extern void put_unused_fd(unsigned int fd);
extern void fd_install(unsigned int fd, struct file *file);
extern void flush_delayed_fput(void);
extern void __fput_sync(struct file *);
#endif /* __LINUX_FILE_H */