diff options
Diffstat (limited to 'libmount/src/context_loopdev.c')
| -rw-r--r-- | libmount/src/context_loopdev.c | 368 |
1 files changed, 368 insertions, 0 deletions
diff --git a/libmount/src/context_loopdev.c b/libmount/src/context_loopdev.c new file mode 100644 index 0000000..da246e3 --- /dev/null +++ b/libmount/src/context_loopdev.c @@ -0,0 +1,368 @@ +/* + * 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 + * - encyption= mount option for loop device is unssuported + */ + +#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 | + MNT_MS_ENCRYPTION)) { + + DBG(CXT, mnt_debug_h(cxt, "loopdev specific options detected")); + return 1; + } + + if (cxt->mountflags & (MS_BIND | MS_MOVE | MS_PROPAGATION)) + 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 empty loopdev where + * is no mountable filesystem... + * + * Note that there is not a restriction (on kernel side) that prevents 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) + return 1; + } + + return 0; +} + + +/* Check, if there already exists a mounted loop device on the mountpoint node + * with the same parameters. + */ +static int 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 mountpoint node in mtab, procceed if any of these has 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, *enc = NULL, *pwd = NULL; + size_t len; + struct loopdev_cxt lc; + int rc = 0, lo_flags = 0; + uint64_t offset = 0, sizelimit = 0; + + assert(cxt); + assert(cxt->fs); + assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED)); + + 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) { + enc = strndup(val, len); + if (val && !enc) + rc = -ENOMEM; + if (enc && cxt->pwd_get_cb) { + DBG(CXT, mnt_debug_h(cxt, "asking for pass")); + pwd = cxt->pwd_get_cb(cxt); + } + } + + 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 && enc && pwd) + loopcxt_set_encryption(&lc, enc, pwd); + 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 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 auto-cleared by kernel + */ + cxt->loopdev_fd = loopcxt_get_fd(&lc); + loopcxt_set_fd(&lc, -1, 0); + } +done: + free(enc); + if (pwd && cxt->pwd_release_cb) { + DBG(CXT, mnt_debug_h(cxt, "release pass")); + cxt->pwd_release_cb(cxt, pwd); + } + 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); + + 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 (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; +} + |