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author | Karel Zak | 2007-09-11 14:35:34 +0200 |
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committer | Karel Zak | 2007-10-26 01:02:44 +0200 |
commit | 2368077223fa5800cf88659c9c57a7f6517f3fad (patch) | |
tree | f50e7a4fc58685921cd737f59b46f44183574083 /mount/lomount.c | |
parent | losetup: canonicalize loopfile name (diff) | |
download | kernel-qcow2-util-linux-2368077223fa5800cf88659c9c57a7f6517f3fad.tar.gz kernel-qcow2-util-linux-2368077223fa5800cf88659c9c57a7f6517f3fad.tar.xz kernel-qcow2-util-linux-2368077223fa5800cf88659c9c57a7f6517f3fad.zip |
mount: prevent loop mounting the same file twice
The mount syscall prevents mounting the same device twice
to the same mountpoint. When loop mounting a file, for each
file a new loop device gets allocated, which prevents the detection
of loop mounting the same file to the same mountpoint twice.
The patch adds a check to prevent double mounts, if the same loopfile
is going to be mounted with the same offset to the same mountpoint.
Co-Author: Matthias Koenig <mkoenig@suse.de>
Signed-off-by: Matthias Koenig <mkoenig@suse.de>
Signed-off-by: Karel Zak <kzak@redhat.com>
Diffstat (limited to 'mount/lomount.c')
-rw-r--r-- | mount/lomount.c | 108 |
1 files changed, 107 insertions, 1 deletions
diff --git a/mount/lomount.c b/mount/lomount.c index b3c16fb6b..5bd895407 100644 --- a/mount/lomount.c +++ b/mount/lomount.c @@ -139,7 +139,7 @@ show_used_loop_devices (void) { for (j = 0; j < SIZE(loop_formats); j++) { for(i = 0; i < 256; i++) { - sprintf(dev, loop_formats[j], i); + snprintf(dev, sizeof(dev), loop_formats[j], i); if (stat (dev, &statbuf) == 0 && S_ISBLK(statbuf.st_mode)) { fd = open (dev, O_RDONLY); if (fd >= 0) { @@ -165,6 +165,102 @@ show_used_loop_devices (void) { #endif +/* check if the loopfile is already associated with the same given + * parameters. + * + * returns: -1 error + * 0 unused + * 1 loop device already used + */ +static int +is_associated(int dev, struct stat *file, unsigned long long offset) +{ + struct loop_info64 linfo64; + struct loop_info64 linfo; + int ret = 0; + + if (ioctl(dev, LOOP_GET_STATUS64, &linfo64) == 0) { + if (file->st_dev == linfo64.lo_device && + file->st_ino == linfo64.lo_inode && + offset == linfo64.lo_offset) + ret = 1; + return ret; + } + if (ioctl(dev, LOOP_GET_STATUS, &linfo) == 0) { + if (file->st_dev == linfo.lo_device && + file->st_ino == linfo.lo_inode && + offset == linfo.lo_offset) + ret = 1; + return ret; + } + + return errno == ENXIO ? 0 : -1; +} + +/* check if the loop file is already used with the same given + * parameters. We check for device no, inode and offset. + * returns: associated devname or NULL + */ +char * +loopfile_used (const char *filename, unsigned long long offset) { + char dev[20]; + char *loop_formats[] = { "/dev/loop%d", "/dev/loop/%d" }; + int i, j, fd; + struct stat devstat, filestat; + struct loop_info loopinfo; + + if (stat(filename, &filestat) == -1) { + perror(filename); + return NULL; + } + + for (j = 0; j < SIZE(loop_formats); j++) { + for(i = 0; i < 256; i++) { + snprintf(dev, sizeof(dev), loop_formats[j], i); + if (stat (dev, &devstat) == 0 && S_ISBLK(devstat.st_mode)) { + fd = open (dev, O_RDONLY); + if (fd >= 0) { + int res = 0; + + if(ioctl (fd, LOOP_GET_STATUS, &loopinfo) == 0) + res = is_associated(fd, &filestat, offset); + close (fd); + if (res == 1) + return xstrdup(dev); + } + continue; /* continue trying as long as devices exist */ + } + break; + } + } + return NULL; +} + +int +loopfile_used_with(char *devname, const char *filename, unsigned long long offset) +{ + struct stat statbuf; + int fd, ret; + + if (!is_loop_device(devname)) + return 0; + + if (stat(filename, &statbuf) == -1) { + perror(filename); + return -1; + } + + fd = open(devname, O_RDONLY); + if (fd == -1) { + perror(devname); + return -1; + } + ret = is_associated(fd, &statbuf, offset); + + close(fd); + return ret; +} + int is_loop_device (const char *device) { struct stat statbuf; @@ -279,6 +375,16 @@ set_loop(const char *device, const char *file, unsigned long long offset, char *pass; char *filename; + if (verbose) { + char *xdev = loopfile_used(file, offset); + + if (xdev) { + printf(_("warning: %s is already associated with %s\n"), + file, xdev); + free(xdev); + } + } + mode = (*loopro ? O_RDONLY : O_RDWR); if ((ffd = open(file, mode)) < 0) { if (!*loopro && errno == EROFS) |