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git.ipfire.org Git - thirdparty/systemd.git/blob - src/shared/loop-util.c
1 /* SPDX-License-Identifier: LGPL-2.1+ */
3 This file is part of systemd.
5 Copyright 2016 Lennart Poettering
7 systemd is free software; you can redistribute it and/or modify it
8 under the terms of the GNU Lesser General Public License as published by
9 the Free Software Foundation; either version 2.1 of the License, or
10 (at your option) any later version.
12 systemd is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public License
18 along with systemd; If not, see <http://www.gnu.org/licenses/>.
23 #include <linux/loop.h>
24 #include <sys/ioctl.h>
27 #include "alloc-util.h"
29 #include "loop-util.h"
31 int loop_device_make(int fd
, int open_flags
, LoopDevice
**ret
) {
32 const struct loop_info64 info
= {
33 .lo_flags
= LO_FLAGS_AUTOCLEAR
|LO_FLAGS_PARTSCAN
|(open_flags
== O_RDONLY
? LO_FLAGS_READ_ONLY
: 0),
36 _cleanup_close_
int control
= -1, loop
= -1;
37 _cleanup_free_
char *loopdev
= NULL
;
44 assert(IN_SET(open_flags
, O_RDWR
, O_RDONLY
));
46 if (fstat(fd
, &st
) < 0)
49 if (S_ISBLK(st
.st_mode
)) {
52 /* If this is already a block device, store a copy of the fd as it is */
54 copy
= fcntl(fd
, F_DUPFD_CLOEXEC
, 3);
58 d
= new0(LoopDevice
, 1);
72 if (!S_ISREG(st
.st_mode
))
75 control
= open("/dev/loop-control", O_RDWR
|O_CLOEXEC
|O_NOCTTY
|O_NONBLOCK
);
79 nr
= ioctl(control
, LOOP_CTL_GET_FREE
);
83 if (asprintf(&loopdev
, "/dev/loop%i", nr
) < 0)
86 loop
= open(loopdev
, O_CLOEXEC
|O_NONBLOCK
|O_NOCTTY
|open_flags
);
90 if (ioctl(loop
, LOOP_SET_FD
, fd
) < 0)
93 if (ioctl(loop
, LOOP_SET_STATUS64
, &info
) < 0)
96 d
= new(LoopDevice
, 1);
114 int loop_device_make_by_path(const char *path
, int open_flags
, LoopDevice
**ret
) {
115 _cleanup_close_
int fd
= -1;
119 assert(IN_SET(open_flags
, O_RDWR
, O_RDONLY
));
121 fd
= open(path
, O_CLOEXEC
|O_NONBLOCK
|O_NOCTTY
|open_flags
);
125 return loop_device_make(fd
, open_flags
, ret
);
128 LoopDevice
* loop_device_unref(LoopDevice
*d
) {
134 if (d
->nr
>= 0 && !d
->relinquished
) {
135 if (ioctl(d
->fd
, LOOP_CLR_FD
) < 0)
136 log_debug_errno(errno
, "Failed to clear loop device: %m");
143 if (d
->nr
>= 0 && !d
->relinquished
) {
144 _cleanup_close_
int control
= -1;
146 control
= open("/dev/loop-control", O_RDWR
|O_CLOEXEC
|O_NOCTTY
|O_NONBLOCK
);
148 log_debug_errno(errno
, "Failed to open loop control device: %m");
150 if (ioctl(control
, LOOP_CTL_REMOVE
, d
->nr
) < 0)
151 log_debug_errno(errno
, "Failed to remove loop device: %m");
159 void loop_device_relinquish(LoopDevice
*d
) {
162 /* Don't attempt to clean up the loop device anymore from this point on. Leave the clean-ing up to the kernel
163 * itself, using the loop device "auto-clear" logic we already turned on when creating the device. */
165 d
->relinquished
= true;