hi, i tried to understand the man page and had some problems (maybe because i am not an FS expert) So far i understand the use case is to make a virtual copy of a file (or range). but it works only on the same fs. reading this: https://lwn.net/Articles/331576/ I got the impression there is already a syscall ? Since when is this function available ? Perhaps you can add a simple use case so readers get a better idea how/why to use this ? just my 2 cents, re, wh Am 15.03.2016 17:48, schrieb Darrick J. Wong: > Document the FICLONE and FICLONERANGE ioctls, formerly known as the > BTRFS_IOC_CLONE and BTRFS_IOC_CLONE_RANGE ioctls. > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > --- > man2/ioctl_ficlone.2 | 1 > man2/ioctl_ficlonerange.2 | 124 +++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 125 insertions(+) > create mode 100644 man2/ioctl_ficlone.2 > create mode 100644 man2/ioctl_ficlonerange.2 > > > diff --git a/man2/ioctl_ficlone.2 b/man2/ioctl_ficlone.2 > new file mode 100644 > index 0000000..19bb348 > --- /dev/null > +++ b/man2/ioctl_ficlone.2 > @@ -0,0 +1 @@ > +.so man2/ioctl_ficlonerange.2 > diff --git a/man2/ioctl_ficlonerange.2 b/man2/ioctl_ficlonerange.2 > new file mode 100644 > index 0000000..c5c72aa > --- /dev/null > +++ b/man2/ioctl_ficlonerange.2 > @@ -0,0 +1,124 @@ > +.\" Copyright (C) 2016 Oracle. All rights reserved. > +.\" > +.\" %%%LICENSE_START(VERBATIM) > +.\" This program is free software; you can redistribute it and/or > +.\" modify it under the terms of the GNU General Public License as > +.\" published by the Free Software Foundation. > +.\" > +.\" This program is distributed in the hope that it would be useful, > +.\" but WITHOUT ANY WARRANTY; without even the implied warranty of > +.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +.\" GNU General Public License for more details. > +.\" > +.\" You should have received a copy of the GNU General Public License > +.\" along with this program; if not, write the Free Software Foundation, > +.\" Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA > +.\" %%%LICENSE_END > +.TH IOCTL-FICLONERANGE 2 2016-02-10 "Linux" "Linux Programmer's Manual" > +.SH NAME > +ioctl_ficlonerange, ioctl_ficlone \- share some the data of one file with another file > +.SH SYNOPSIS > +.br > +.B #include <sys/ioctl.h> > +.br > +.B #include <linux/fs.h> > +.sp > +.BI "int ioctl(int " dest_fd ", FICLONERANGE, struct file_clone_range * " arg ); > +.br > +.BI "int ioctl(int " dest_fd ", FICLONE, int " src_fd ); > +.SH DESCRIPTION > +If a filesystem supports files sharing physical storage between multiple > +files ("reflink"), this > +.BR ioctl (2) > +system call can be used to make some of the data in the > +.B src_fd > +file appear in the > +.B dest_fd > +file by sharing the underlying storage, which is faster than making a separate > +physical copy of the data. If a file write should occur to a shared region, > +the filesystem must ensure that the changes remain private to the file being > +written. This behavior is commonly referred to as "copy on write". > + > +This ioctl reflinks up to > +.IR src_length > +bytes from file descriptor > +.IR src_fd > +at offset > +.IR src_offset > +into the file > +.IR dest_fd > +at offset > +.IR dest_offset ", > +provided that both are files. This information is conveyed in a structure of > +the following form: > +.in +4n > +.nf > + > +struct file_clone_range { > + __s64 src_fd; > + __u64 src_offset; > + __u64 src_length; > + __u64 dest_offset; > +}; > + > +.fi > +.in > +Clones are atomic with regards to concurrent writes, so no locks need to be > +taken to obtain a consistent cloned copy. > + > +The FICLONE ioctl clones entire files. > +.SH RETURN VALUE > +On error, \-1 is returned, and > +.I errno > +is set to indicate the error. > +.PP > +.SH ERRORS > +Error codes can be one of, but are not limited to, the following: > +.TP > +.B EXDEV > +.IR dest_fd " and " src_fd > +are not on the same mounted filesystem. > +.TP > +.B EISDIR > +One of the files is a directory and the filesystem does not support shared > +regions in directories. > +.TP > +.B EINVAL > +The filesystem does not support reflinking the ranges of the given files. This > +error can also appear if either file descriptor represents a device, fifo, or > +socket. Disk filesystems generally require the offset and length arguments > +to be aligned to the fundamental block size. XFS and btrfs do not support > +overlapping reflink ranges in the same file. > +.TP > +.B EBADF > +.IR src_fd > +is not open for reading; > +.IR dest_fd > +is not open for writing or is open for append-only writes; or the filesystem > +which > +.IR src_fd > +resides on does not support reflink. > +.TP > +.B EPERM > +.IR dest_fd > +is immutable. > +.TP > +.B ETXTBSY > +One of the files is a swap file. Swap files cannot share storage. > +.TP > +.B EOPNOTSUPP > +This can appear if the filesystem does not support reflinking either file > +descriptor. > +.SH NOTES > +Because a copy on write operation requires the allocation of new storage, the > +.B fallocate (2) > +operation may un-share shared blocks to guarantee that subsequent writes will > +not fail because of lack of disk space. > +.SH CONFORMING TO > +This API is Linux-specific. This ioctl was previously known as > +.B BTRFS_IOC_CLONE_RANGE > +and was private to btrfs. > +.fi > +.in > +.SH SEE ALSO > +.BR ioctl (2) > > -- > To unsubscribe from this list: send the line "unsubscribe linux-man" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
