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linux/include/uapi/asm-generic/fcntl.h
Jeff Layton 5d50ffd7c3 locks: add new fcntl cmd values for handling file private locks 
Due to some unfortunate history, POSIX locks have very strange and
unhelpful semantics. The thing that usually catches people by surprise
is that they are dropped whenever the process closes any file descriptor
associated with the inode.

This is extremely problematic for people developing file servers that
need to implement byte-range locks. Developers often need a "lock
management" facility to ensure that file descriptors are not closed
until all of the locks associated with the inode are finished.

Additionally, "classic" POSIX locks are owned by the process. Locks
taken between threads within the same process won't conflict with one
another, which renders them useless for synchronization between threads.

This patchset adds a new type of lock that attempts to address these
issues. These locks conflict with classic POSIX read/write locks, but
have semantics that are more like BSD locks with respect to inheritance
and behavior on close.

This is implemented primarily by changing how fl_owner field is set for
these locks. Instead of having them owned by the files_struct of the
process, they are instead owned by the filp on which they were acquired.
Thus, they are inherited across fork() and are only released when the
last reference to a filp is put.

These new semantics prevent them from being merged with classic POSIX
locks, even if they are acquired by the same process. These locks will
also conflict with classic POSIX locks even if they are acquired by
the same process or on the same file descriptor.

The new locks are managed using a new set of cmd values to the fcntl()
syscall. The initial implementation of this converts these values to
"classic" cmd values at a fairly high level, and the details are not
exposed to the underlying filesystem. We may eventually want to push
this handing out to the lower filesystem code but for now I don't
see any need for it.

Also, note that with this implementation the new cmd values are only
available via fcntl64() on 32-bit arches. There's little need to
add support for legacy apps on a new interface like this.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
2014-03-31 08:24:43 -04:00

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#ifndef _ASM_GENERIC_FCNTL_H
#define _ASM_GENERIC_FCNTL_H
#include <linux/types.h>
/*
* FMODE_EXEC is 0x20
* FMODE_NONOTIFY is 0x1000000
* These cannot be used by userspace O_* until internal and external open
* flags are split.
* -Eric Paris
*/
/*
* When introducing new O_* bits, please check its uniqueness in fcntl_init().
*/
#define O_ACCMODE 00000003
#define O_RDONLY 00000000
#define O_WRONLY 00000001
#define O_RDWR 00000002
#ifndef O_CREAT
#define O_CREAT 00000100 /* not fcntl */
#endif
#ifndef O_EXCL
#define O_EXCL 00000200 /* not fcntl */
#endif
#ifndef O_NOCTTY
#define O_NOCTTY 00000400 /* not fcntl */
#endif
#ifndef O_TRUNC
#define O_TRUNC 00001000 /* not fcntl */
#endif
#ifndef O_APPEND
#define O_APPEND 00002000
#endif
#ifndef O_NONBLOCK
#define O_NONBLOCK 00004000
#endif
#ifndef O_DSYNC
#define O_DSYNC 00010000 /* used to be O_SYNC, see below */
#endif
#ifndef FASYNC
#define FASYNC 00020000 /* fcntl, for BSD compatibility */
#endif
#ifndef O_DIRECT
#define O_DIRECT 00040000 /* direct disk access hint */
#endif
#ifndef O_LARGEFILE
#define O_LARGEFILE 00100000
#endif
#ifndef O_DIRECTORY
#define O_DIRECTORY 00200000 /* must be a directory */
#endif
#ifndef O_NOFOLLOW
#define O_NOFOLLOW 00400000 /* don't follow links */
#endif
#ifndef O_NOATIME
#define O_NOATIME 01000000
#endif
#ifndef O_CLOEXEC
#define O_CLOEXEC 02000000 /* set close_on_exec */
#endif
/*
* Before Linux 2.6.33 only O_DSYNC semantics were implemented, but using
* the O_SYNC flag. We continue to use the existing numerical value
* for O_DSYNC semantics now, but using the correct symbolic name for it.
* This new value is used to request true Posix O_SYNC semantics. It is
* defined in this strange way to make sure applications compiled against
* new headers get at least O_DSYNC semantics on older kernels.
*
* This has the nice side-effect that we can simply test for O_DSYNC
* wherever we do not care if O_DSYNC or O_SYNC is used.
*
* Note: __O_SYNC must never be used directly.
*/
#ifndef O_SYNC
#define __O_SYNC 04000000
#define O_SYNC (__O_SYNC|O_DSYNC)
#endif
#ifndef O_PATH
#define O_PATH 010000000
#endif
#ifndef __O_TMPFILE
#define __O_TMPFILE 020000000
#endif
/* a horrid kludge trying to make sure that this will fail on old kernels */
#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
#define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT)
#ifndef O_NDELAY
#define O_NDELAY O_NONBLOCK
#endif
#define F_DUPFD 0 /* dup */
#define F_GETFD 1 /* get close_on_exec */
#define F_SETFD 2 /* set/clear close_on_exec */
#define F_GETFL 3 /* get file->f_flags */
#define F_SETFL 4 /* set file->f_flags */
#ifndef F_GETLK
#define F_GETLK 5
#define F_SETLK 6
#define F_SETLKW 7
#endif
#ifndef F_SETOWN
#define F_SETOWN 8 /* for sockets. */
#define F_GETOWN 9 /* for sockets. */
#endif
#ifndef F_SETSIG
#define F_SETSIG 10 /* for sockets. */
#define F_GETSIG 11 /* for sockets. */
#endif
#ifndef CONFIG_64BIT
#ifndef F_GETLK64
#define F_GETLK64 12 /* using 'struct flock64' */
#define F_SETLK64 13
#define F_SETLKW64 14
#endif
#endif
#ifndef F_SETOWN_EX
#define F_SETOWN_EX 15
#define F_GETOWN_EX 16
#endif
#ifndef F_GETOWNER_UIDS
#define F_GETOWNER_UIDS 17
#endif
/*
* fd "private" POSIX locks.
*
* Usually POSIX locks held by a process are released on *any* close and are
* not inherited across a fork().
*
* These cmd values will set locks that conflict with normal POSIX locks, but
* are "owned" by the opened file, not the process. This means that they are
* inherited across fork() like BSD (flock) locks, and they are only released
* automatically when the last reference to the the open file against which
* they were acquired is put.
*/
#define F_GETLKP 36
#define F_SETLKP 37
#define F_SETLKPW 38
#define F_OWNER_TID 0
#define F_OWNER_PID 1
#define F_OWNER_PGRP 2
struct f_owner_ex {
int type;
__kernel_pid_t pid;
};
/* for F_[GET|SET]FL */
#define FD_CLOEXEC 1 /* actually anything with low bit set goes */
/* for posix fcntl() and lockf() */
#ifndef F_RDLCK
#define F_RDLCK 0
#define F_WRLCK 1
#define F_UNLCK 2
#endif
/* for old implementation of bsd flock () */
#ifndef F_EXLCK
#define F_EXLCK 4 /* or 3 */
#define F_SHLCK 8 /* or 4 */
#endif
/* operations for bsd flock(), also used by the kernel implementation */
#define LOCK_SH 1 /* shared lock */
#define LOCK_EX 2 /* exclusive lock */
#define LOCK_NB 4 /* or'd with one of the above to prevent
blocking */
#define LOCK_UN 8 /* remove lock */
#define LOCK_MAND 32 /* This is a mandatory flock ... */
#define LOCK_READ 64 /* which allows concurrent read operations */
#define LOCK_WRITE 128 /* which allows concurrent write operations */
#define LOCK_RW 192 /* which allows concurrent read & write ops */
#define F_LINUX_SPECIFIC_BASE 1024
#ifndef HAVE_ARCH_STRUCT_FLOCK
#ifndef __ARCH_FLOCK_PAD
#define __ARCH_FLOCK_PAD
#endif
struct flock {
short l_type;
short l_whence;
__kernel_off_t l_start;
__kernel_off_t l_len;
__kernel_pid_t l_pid;
__ARCH_FLOCK_PAD
};
#endif
#ifndef HAVE_ARCH_STRUCT_FLOCK64
#ifndef __ARCH_FLOCK64_PAD
#define __ARCH_FLOCK64_PAD
#endif
struct flock64 {
short l_type;
short l_whence;
__kernel_loff_t l_start;
__kernel_loff_t l_len;
__kernel_pid_t l_pid;
__ARCH_FLOCK64_PAD
};
#endif
#endif /* _ASM_GENERIC_FCNTL_H */
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