diff options
Diffstat (limited to 'libbb/loop.c')
| -rw-r--r-- | libbb/loop.c | 42 |
1 files changed, 36 insertions, 6 deletions
diff --git a/libbb/loop.c b/libbb/loop.c index c78535a20..ada0c7638 100644 --- a/libbb/loop.c +++ b/libbb/loop.c @@ -78,6 +78,24 @@ int FAST_FUNC del_loop(const char *device) return rc; } +/* Obtain an unused loop device number */ +int FAST_FUNC get_free_loop(void) +{ + int fd; + int loopdevno; + + fd = open("/dev/loop-control", O_RDWR | O_CLOEXEC); + if (fd == -1) + return fd - 1; /* -2: "no /dev/loop-control" */ + +#ifndef LOOP_CTL_GET_FREE +# define LOOP_CTL_GET_FREE 0x4C82 +#endif + loopdevno = ioctl(fd, LOOP_CTL_GET_FREE); + close(fd); + return loopdevno; /* can be -1 if error */ +} + /* Returns opened fd to the loop device, <0 on error. * *device is loop device to use, or if *device==NULL finds a loop device to * mount it on and sets *device to a strdup of that loop device name. This @@ -106,12 +124,24 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse return -errno; } -//TODO: use LOOP_CTL_GET_FREE instead of trying every loopN in sequence? a-la: -// fd = open("/dev/loop-control", O_RDWR); -// loopN = ioctl(fd, LOOP_CTL_GET_FREE); -// + try = *device; + if (!try) { + i = get_free_loop(); + if (i == -2) { /* no /dev/loop-control */ + i = 0; + try = dev; + goto old_style; + } + if (i == -1) { + close(ffd); + return -1; /* no free loop devices */ + } + try = *device = xasprintf(LOOP_FORMAT, i); + goto try_to_open; + } + + old_style: /* Find a loop device. */ - try = *device ? *device : dev; /* 1048575 (0xfffff) is a max possible minor number in Linux circa 2010 */ for (i = 0; rc && i < 1048576; i++) { sprintf(dev, LOOP_FORMAT, i); @@ -170,7 +200,7 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse rc = ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo); } if (rc != 0) { - ioctl(dfd, LOOP_CLR_FD, 0); + ioctl(dfd, LOOP_CLR_FD, 0); // actually, 0 param is unnecessary } } } else { |