/*
* Copyright (C) 2011 Karel Zak <kzak@redhat.com>
*
* This file may be redistributed under the terms of the
* GNU Lesser General Public License.
*/
/*
* DOCS: - "lo@" prefix for fstype is unsupported
*/
#include <blkid.h>
#include "mountP.h"
#include "loopdev.h"
#include "linux_version.h"
int mnt_context_is_loopdev(struct libmnt_context *cxt)
{
const char *type, *src;
assert(cxt);
/* The mount flags have to be merged, otherwise we have to use
* expensive mnt_context_get_user_mflags() instead of cxt->user_mountflags. */
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
if (!cxt->fs)
return 0;
src = mnt_fs_get_srcpath(cxt->fs);
if (!src)
return 0; /* backing file not set */
if (cxt->user_mountflags & (MNT_MS_LOOP |
MNT_MS_OFFSET |
MNT_MS_SIZELIMIT)) {
DBG(CXT, mnt_debug_h(cxt, "loopdev specific options detected"));
return 1;
}
if ((cxt->mountflags & (MS_BIND | MS_MOVE))
|| mnt_context_propagation_only(cxt))
return 0;
/* Automatically create a loop device from a regular file if a
* filesystem is not specified or the filesystem is known for libblkid
* (these filesystems work with block devices only). The file size
* should be at least 1KiB, otherwise we will create an empty loopdev with
* no mountable filesystem...
*
* Note that there is no restriction (on kernel side) that would prevent a regular
* file as a mount(2) source argument. A filesystem that is able to mount
* regular files could be implemented.
*/
type = mnt_fs_get_fstype(cxt->fs);
if (mnt_fs_is_regular(cxt->fs) &&
(!type || strcmp(type, "auto") == 0 || blkid_known_fstype(type))) {
struct stat st;
if (stat(src, &st) == 0 && S_ISREG(st.st_mode) &&
st.st_size > 1024) {
DBG(CXT, mnt_debug_h(cxt, "automatically enabling loop= option"));
cxt->user_mountflags |= MNT_MS_LOOP;
mnt_optstr_append_option(&cxt->fs->user_optstr, "loop", NULL);
return 1;
}
}
return 0;
}
/* Check if there already exists a mounted loop device on the mountpoint node
* with the same parameters.
*/
static int __attribute__((nonnull))
is_mounted_same_loopfile(struct libmnt_context *cxt,
const char *target,
const char *backing_file,
uint64_t offset)
{
struct libmnt_table *tb;
struct libmnt_iter itr;
struct libmnt_fs *fs;
struct libmnt_cache *cache;
assert(cxt);
assert(cxt->fs);
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
if (!target || !backing_file || mnt_context_get_mtab(cxt, &tb))
return 0;
DBG(CXT, mnt_debug_h(cxt, "checking if %s mounted on %s",
backing_file, target));
cache = mnt_context_get_cache(cxt);
mnt_reset_iter(&itr, MNT_ITER_BACKWARD);
/* Search for a mountpoint node in mtab, proceed if any of these have the
* loop option set or the device is a loop device
*/
while (mnt_table_next_fs(tb, &itr, &fs) == 0) {
const char *src = mnt_fs_get_source(fs);
const char *opts = mnt_fs_get_user_options(fs);
char *val;
size_t len;
int res = 0;
if (!src || !mnt_fs_match_target(fs, target, cache))
continue;
if (strncmp(src, "/dev/loop", 9) == 0) {
res = loopdev_is_used((char *) src, backing_file,
offset, LOOPDEV_FL_OFFSET);
} else if (opts && (cxt->user_mountflags & MNT_MS_LOOP) &&
mnt_optstr_get_option(opts, "loop", &val, &len) == 0 && val) {
val = strndup(val, len);
res = loopdev_is_used((char *) val, backing_file,
offset, LOOPDEV_FL_OFFSET);
free(val);
}
if (res) {
DBG(CXT, mnt_debug_h(cxt, "%s already mounted", backing_file));
return 1;
}
}
return 0;
}
int mnt_context_setup_loopdev(struct libmnt_context *cxt)
{
const char *backing_file, *optstr, *loopdev = NULL;
char *val = NULL;
size_t len;
struct loopdev_cxt lc;
int rc = 0, lo_flags = 0;
uint64_t offset = 0, sizelimit = 0;
assert(cxt->fs);
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
if (!cxt)
return -EINVAL;
backing_file = mnt_fs_get_srcpath(cxt->fs);
if (!backing_file)
return -EINVAL;
DBG(CXT, mnt_debug_h(cxt, "trying to setup loopdev for %s", backing_file));
if (cxt->mountflags & MS_RDONLY) {
DBG(CXT, mnt_debug_h(cxt, "enabling READ-ONLY flag"));
lo_flags |= LO_FLAGS_READ_ONLY;
}
rc = loopcxt_init(&lc, 0);
if (rc)
return rc;
ON_DBG(CXT, loopcxt_enable_debug(&lc, 1));
optstr = mnt_fs_get_user_options(cxt->fs);
/*
* loop=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_LOOP) &&
mnt_optstr_get_option(optstr, "loop", &val, &len) == 0 && val) {
val = strndup(val, len);
rc = val ? loopcxt_set_device(&lc, val) : -ENOMEM;
free(val);
if (rc == 0)
loopdev = loopcxt_get_device(&lc);
}
/*
* offset=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_OFFSET) &&
mnt_optstr_get_option(optstr, "offset", &val, &len) == 0) {
rc = mnt_parse_offset(val, len, &offset);
if (rc) {
DBG(CXT, mnt_debug_h(cxt, "failed to parse offset="));
rc = -MNT_ERR_MOUNTOPT;
}
}
/*
* sizelimit=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_SIZELIMIT) &&
mnt_optstr_get_option(optstr, "sizelimit", &val, &len) == 0) {
rc = mnt_parse_offset(val, len, &sizelimit);
if (rc) {
DBG(CXT, mnt_debug_h(cxt, "failed to parse sizelimit="));
rc = -MNT_ERR_MOUNTOPT;
}
}
/*
* encryption=
*/
if (rc == 0 && (cxt->user_mountflags & MNT_MS_ENCRYPTION) &&
mnt_optstr_get_option(optstr, "encryption", &val, &len) == 0) {
DBG(CXT, mnt_debug_h(cxt, "encryption no longer supported"));
rc = -MNT_ERR_MOUNTOPT;
}
if (rc == 0 && is_mounted_same_loopfile(cxt,
mnt_context_get_target(cxt),
backing_file, offset))
rc = -EBUSY;
if (rc)
goto done;
/* since 2.6.37 we don't have to store backing filename to mtab
* because kernel provides the name in /sys.
*/
if (get_linux_version() >= KERNEL_VERSION(2, 6, 37) ||
!cxt->mtab_writable) {
DBG(CXT, mnt_debug_h(cxt, "enabling AUTOCLEAR flag"));
lo_flags |= LO_FLAGS_AUTOCLEAR;
}
do {
/* found free device */
if (!loopdev) {
rc = loopcxt_find_unused(&lc);
if (rc)
goto done;
DBG(CXT, mnt_debug_h(cxt, "trying to use %s",
loopcxt_get_device(&lc)));
}
/* set device attributes
* -- note that loopcxt_find_unused() resets "lc"
*/
rc = loopcxt_set_backing_file(&lc, backing_file);
if (!rc && offset)
rc = loopcxt_set_offset(&lc, offset);
if (!rc && sizelimit)
rc = loopcxt_set_sizelimit(&lc, sizelimit);
if (!rc)
loopcxt_set_flags(&lc, lo_flags);
if (rc) {
DBG(CXT, mnt_debug_h(cxt, "failed to set loopdev attributes"));
goto done;
}
/* setup the device */
rc = loopcxt_setup_device(&lc);
if (!rc)
break; /* success */
if (loopdev || rc != -EBUSY) {
DBG(CXT, mnt_debug_h(cxt, "failed to setup device"));
rc = -MNT_ERR_LOOPDEV;
goto done;
}
DBG(CXT, mnt_debug_h(cxt, "loopdev stolen...trying again"));
} while (1);
if (!rc)
rc = mnt_fs_set_source(cxt->fs, loopcxt_get_device(&lc));
if (!rc) {
/* success */
cxt->flags |= MNT_FL_LOOPDEV_READY;
if ((cxt->user_mountflags & MNT_MS_LOOP) &&
loopcxt_is_autoclear(&lc)) {
/*
* autoclear flag accepted by the kernel, don't store
* the "loop=" option to mtab.
*/
cxt->user_mountflags &= ~MNT_MS_LOOP;
mnt_optstr_remove_option(&cxt->fs->user_optstr, "loop");
}
if (!(cxt->mountflags & MS_RDONLY) &&
loopcxt_is_readonly(&lc))
/*
* mount planned read-write, but loopdev is read-only,
* let's fix mount options...
*/
mnt_context_set_mflags(cxt, cxt->mountflags | MS_RDONLY);
/* we have to keep the device open until mount(1),
* otherwise it will be auto-cleared by kernel
*/
cxt->loopdev_fd = loopcxt_get_fd(&lc);
loopcxt_set_fd(&lc, -1, 0);
}
done:
loopcxt_deinit(&lc);
return rc;
}
/*
* Deletes loop device
*/
int mnt_context_delete_loopdev(struct libmnt_context *cxt)
{
const char *src;
int rc;
assert(cxt);
assert(cxt->fs);
if (!cxt)
return -EINVAL;
src = mnt_fs_get_srcpath(cxt->fs);
if (!src)
return -EINVAL;
if (cxt->loopdev_fd > -1)
close(cxt->loopdev_fd);
rc = loopdev_delete(src);
cxt->flags &= ~MNT_FL_LOOPDEV_READY;
cxt->loopdev_fd = -1;
DBG(CXT, mnt_debug_h(cxt, "loopdev deleted [rc=%d]", rc));
return rc;
}
/*
* Clears loopdev stuff in context, should be called after
* failed or successful mount(2).
*/
int mnt_context_clear_loopdev(struct libmnt_context *cxt)
{
assert(cxt);
if (!cxt)
return -EINVAL;
if (mnt_context_get_status(cxt) == 0 &&
(cxt->flags & MNT_FL_LOOPDEV_READY)) {
/*
* mount(2) failed, delete loopdev
*/
mnt_context_delete_loopdev(cxt);
} else if (cxt->loopdev_fd > -1) {
/*
* mount(2) success, close the device
*/
DBG(CXT, mnt_debug_h(cxt, "closing loopdev FD"));
close(cxt->loopdev_fd);
}
cxt->loopdev_fd = -1;
return 0;
}
