45c9b11a1d
When the linkat() syscall was added the flag parameter was added in the
last minute but it wasn't used so far. The following patch should change
that. My tests show that this is all that's needed.
If OLDNAME is a symlink setting the flag causes linkat to follow the
symlink and create a hardlink with the target. This is actually the
behavior POSIX demands for link() as well but Linux wisely does not do
this. With this flag (which will most likely be in the next POSIX
revision) the programmer can choose the behavior, defaulting to the safe
variant. As a side effect it is now possible to implement a
POSIX-compliant link(2) function for those who are interested.
touch file
ln -s file symlink
linkat(fd, "symlink", fd, "newlink", 0)
-> newlink is hardlink of symlink
linkat(fd, "symlink", fd, "newlink", AT_SYMLINK_FOLLOW)
-> newlink is hardlink of file
The value of AT_SYMLINK_FOLLOW is determined by the definition we already
use in glibc.
Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
63 lines
2.0 KiB
C
63 lines
2.0 KiB
C
#ifndef _LINUX_FCNTL_H
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#define _LINUX_FCNTL_H
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#include <asm/fcntl.h>
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#define F_SETLEASE (F_LINUX_SPECIFIC_BASE+0)
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#define F_GETLEASE (F_LINUX_SPECIFIC_BASE+1)
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/*
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* Request nofications on a directory.
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* See below for events that may be notified.
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*/
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#define F_NOTIFY (F_LINUX_SPECIFIC_BASE+2)
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/*
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* Types of directory notifications that may be requested.
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*/
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#define DN_ACCESS 0x00000001 /* File accessed */
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#define DN_MODIFY 0x00000002 /* File modified */
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#define DN_CREATE 0x00000004 /* File created */
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#define DN_DELETE 0x00000008 /* File removed */
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#define DN_RENAME 0x00000010 /* File renamed */
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#define DN_ATTRIB 0x00000020 /* File changed attibutes */
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#define DN_MULTISHOT 0x80000000 /* Don't remove notifier */
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#define AT_FDCWD -100 /* Special value used to indicate
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openat should use the current
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working directory. */
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#define AT_SYMLINK_NOFOLLOW 0x100 /* Do not follow symbolic links. */
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#define AT_REMOVEDIR 0x200 /* Remove directory instead of
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unlinking file. */
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#define AT_SYMLINK_FOLLOW 0x400 /* Follow symbolic links. */
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#ifdef __KERNEL__
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#ifndef force_o_largefile
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#define force_o_largefile() (BITS_PER_LONG != 32)
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#endif
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#if BITS_PER_LONG == 32
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#define IS_GETLK32(cmd) ((cmd) == F_GETLK)
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#define IS_SETLK32(cmd) ((cmd) == F_SETLK)
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#define IS_SETLKW32(cmd) ((cmd) == F_SETLKW)
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#define IS_GETLK64(cmd) ((cmd) == F_GETLK64)
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#define IS_SETLK64(cmd) ((cmd) == F_SETLK64)
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#define IS_SETLKW64(cmd) ((cmd) == F_SETLKW64)
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#else
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#define IS_GETLK32(cmd) (0)
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#define IS_SETLK32(cmd) (0)
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#define IS_SETLKW32(cmd) (0)
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#define IS_GETLK64(cmd) ((cmd) == F_GETLK)
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#define IS_SETLK64(cmd) ((cmd) == F_SETLK)
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#define IS_SETLKW64(cmd) ((cmd) == F_SETLKW)
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#endif /* BITS_PER_LONG == 32 */
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#define IS_GETLK(cmd) (IS_GETLK32(cmd) || IS_GETLK64(cmd))
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#define IS_SETLK(cmd) (IS_SETLK32(cmd) || IS_SETLK64(cmd))
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#define IS_SETLKW(cmd) (IS_SETLKW32(cmd) || IS_SETLKW64(cmd))
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#endif /* __KERNEL__ */
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#endif
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