Re: [PATCH 11/11] ext4: add cross rename support

From: Miklos Szeredi
Date: Fri Jan 17 2014 - 09:40:45 EST

Hi Michael,

Thanks for the review. I updated the code and man page based on your and
Bruce's comments.

The code changes are pushed to the git tree and the updated man page is below.


RENAMEAT(2) Linux Programmer's Manual RENAMEAT(2)

renameat, renameat2 - rename a file relative to directory file descrip-

#include <fcntl.h> /* Definition of AT_* constants */
#include <stdio.h>

int renameat(int olddirfd, const char *oldpath,
int newdirfd, const char *newpath);

int renameat2(int olddirfd, const char *oldpath,
int newdirfd, const char *newpath, unsigned int flags);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

Since glibc 2.10:
_XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
Before glibc 2.10:

The renameat() and renameat2() system calls operate in exactly the same
way as rename(2), except for the differences described in this manual

If the pathname given in oldpath is relative, then it is interpreted
relative to the directory referred to by the file descriptor olddirfd
(rather than relative to the current working directory of the calling
process, as is done by rename(2) for a relative pathname).

If oldpath is relative and olddirfd is the special value AT_FDCWD, then
oldpath is interpreted relative to the current working directory of the
calling process (like rename(2)).

If oldpath is absolute, then olddirfd is ignored.

The interpretation of newpath is as for oldpath, except that a relative
pathname is interpreted relative to the directory referred to by the
file descriptor newdirfd.

renameat2() has an additional flags argument. renameat2() call with a
zero flags argument is equivalent to renameat().

The flags argument is a bitfield consisting of zero or more of the fol-
lowing constants defined in <linux/fs.h>:

Don't overwrite the target of the rename. Fail if the target
would be overwritten.

Atomically exchange the source and destination. Both must exist
but may be of a different type (e.g. one a non-empty directory
and the other a symbolic link). Specifying this flag together
with RENAME_NOREPLACE is invalid.

On success, renameat() and renameat2() return 0. On error, -1 is
returned and errno is set to indicate the error.

The same errors that occur for rename(2) can also occur for renameat()
and renameat2(). The following additional errors can occur for
renameat() and renameat2():

EBADF olddirfd or newdirfd is not a valid file descriptor.

oldpath is relative and olddirfd is a file descriptor referring
to a file other than a directory; or similar for newpath and

The following additional errors are defined for renameat2():

EINVAL The filesystem does not support a flag in flags

EINVAL Invalid combination of flags

EEXIST flags contain RENAME_NOREPLACE and the target of the rename

ENOENT flags contain RENAME_EXCHANGE and either of the two files does
not exist

renameat() was added to Linux in kernel 2.6.16; library support was
added to glibc in version 2.4.

renameat() is specified in POSIX.1-2008.

See openat(2) for an explanation of the need for renameat().

openat(2), rename(2), path_resolution(7)

Linux 2012-05-04 RENAMEAT(2)
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