multidevice support for check_mounted

Check_mount() should also work with multi device filesystems.
This patch adds checks that allow to detect if a file is a device
file used by a mounted single or multi device btrfs or if it is a
regular file used by a loopback device that is part of a mounted
single or multi device btrfs.

The single device checks also work for non-btrfs filesystems.
This might be helpful to prevent users from running btrfs programs
(e.g. mkfs.btrfs) accidentally on a filesystem used somewhere else.

Signed-off-by: Andi Drebes <lists-receive@programmierforen.de>

diff --git a/kerncompat.h b/kerncompat.h
index e4c8ce0..46236cd 100644 (file)
--- a/kerncompat.h
+++ b/kerncompat.h
@@ -42,7 +42,11 @@
 #define GFP_NOFS 0
 #define __read_mostly
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+#ifndef ULONG_MAX
 #define ULONG_MAX       (~0UL)
+#endif
+
 #define BUG() abort()
 #ifdef __CHECKER__
 #define __force    __attribute__((force))

diff --git a/utils.c b/utils.c
index 2f4c6e1..fd894f3 100644 (file)
--- a/utils.c
+++ b/utils.c
@@ -31,6 +31,10 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <mntent.h>
+#include <linux/loop.h>
+#include <linux/major.h>
+#include <linux/kdev_t.h>
+#include <limits.h>
 #include "kerncompat.h"
 #include "radix-tree.h"
 #include "ctree.h"
@@ -586,55 +590,224 @@ error:
        return ret;
 }
 
+/* checks if a device is a loop device */
+int is_loop_device (const char* device) {
+       struct stat statbuf;
+
+       if(stat(device, &statbuf) < 0)
+               return -errno;
+
+       return (S_ISBLK(statbuf.st_mode) &&
+               MAJOR(statbuf.st_rdev) == LOOP_MAJOR);
+}
+
+
+/* Takes a loop device path (e.g. /dev/loop0) and returns
+ * the associated file (e.g. /images/my_btrfs.img) */
+int resolve_loop_device(const char* loop_dev, char* loop_file, int max_len)
+{
+       int loop_fd;
+       int ret_ioctl;
+       struct loop_info loopinfo;
+
+       if ((loop_fd = open(loop_dev, O_RDONLY)) < 0)
+               return -errno;
+
+       ret_ioctl = ioctl(loop_fd, LOOP_GET_STATUS, &loopinfo);
+       close(loop_fd);
+
+       if (ret_ioctl == 0)
+               strncpy(loop_file, loopinfo.lo_name, max_len);
+       else
+               return -errno;
+
+       return 0;
+}
+
+/* Checks whether a and b are identical or device
+ * files associated with the same block device
+ */
+int is_same_blk_file(const char* a, const char* b)
+{
+       struct stat st_buf_a, st_buf_b;
+       char real_a[PATH_MAX];
+       char real_b[PATH_MAX];
+
+       if(!realpath(a, real_a) ||
+          !realpath(b, real_b))
+       {
+               return -errno;
+       }
+
+       /* Identical path? */
+       if(strcmp(real_a, real_b) == 0)
+               return 1;
+
+       if(stat(a, &st_buf_a) < 0 ||
+          stat(b, &st_buf_b) < 0)
+       {
+               return -errno;
+       }
+
+       /* Same blockdevice? */
+       if(S_ISBLK(st_buf_a.st_mode) &&
+          S_ISBLK(st_buf_b.st_mode) &&
+          st_buf_a.st_rdev == st_buf_b.st_rdev)
+       {
+               return 1;
+       }
+
+       /* Hardlink? */
+       if (st_buf_a.st_dev == st_buf_b.st_dev &&
+           st_buf_a.st_ino == st_buf_b.st_ino)
+       {
+               return 1;
+       }
+
+       return 0;
+}
+
+/* checks if a and b are identical or device
+ * files associated with the same block device or
+ * if one file is a loop device that uses the other
+ * file.
+ */
+int is_same_loop_file(const char* a, const char* b)
+{
+       char res_a[PATH_MAX];
+       char res_b[PATH_MAX];
+       const char* final_a;
+       const char* final_b;
+       int ret;
+
+       /* Resolve a if it is a loop device */
+       if((ret = is_loop_device(a)) < 0) {
+          return ret;
+       } else if(ret) {
+               if((ret = resolve_loop_device(a, res_a, sizeof(res_a))) < 0)
+                       return ret;
+
+               final_a = res_a;
+       } else {
+               final_a = a;
+       }
+
+       /* Resolve b if it is a loop device */
+       if((ret = is_loop_device(b)) < 0) {
+          return ret;
+       } else if(ret) {
+               if((ret = resolve_loop_device(b, res_b, sizeof(res_b))) < 0)
+                       return ret;
+
+               final_b = res_b;
+       } else {
+               final_b = b;
+       }
+
+       return is_same_blk_file(final_a, final_b);
+}
+
+/* Checks if a file exists and is a block or regular file*/
+int is_existing_blk_or_reg_file(const char* filename)
+{
+       struct stat st_buf;
+
+       if(stat(filename, &st_buf) < 0) {
+               if(errno == ENOENT)
+                       return 0;
+               else
+                       return -errno;
+       }
+
+       return (S_ISBLK(st_buf.st_mode) || S_ISREG(st_buf.st_mode));
+}
+
+/* Checks if a file is used (directly or indirectly via a loop device)
+ * by a device in fs_devices
+ */
+int blk_file_in_dev_list(struct btrfs_fs_devices* fs_devices, const char* file)
+{
+       int ret;
+       struct list_head *head;
+       struct list_head *cur;
+       struct btrfs_device *device;
+
+       head = &fs_devices->devices;
+       list_for_each(cur, head) {
+               device = list_entry(cur, struct btrfs_device, dev_list);
+
+               if((ret = is_same_loop_file(device->name, file)))
+                       return ret;
+       }
+
+       return 0;
+}
+
 /*
  * returns 1 if the device was mounted, < 0 on error or 0 if everything
- * is safe to continue.  TODO, this should also scan multi-device filesystems
+ * is safe to continue.
  */
-int check_mounted(char *file)
+int check_mounted(const char* file)
 {
-       struct mntent *mnt;
-       struct stat st_buf;
-       dev_t file_dev = 0;
-       dev_t file_rdev = 0;
-       ino_t file_ino = 0;
+       int ret;
+       int fd;
+       u64 total_devs = 1;
+       int is_btrfs;
+       struct btrfs_fs_devices* fs_devices_mnt = NULL;
        FILE *f;
-       int ret = 0;
+       struct mntent *mnt;
 
-       if ((f = setmntent ("/proc/mounts", "r")) == NULL)
+       fd = open(file, O_RDONLY);
+       if (fd < 0) {
+               fprintf (stderr, "check_mounted(): Could not open %s\n", file);
                return -errno;
+       }
 
-       if (stat(file, &st_buf) < 0) {
-               return -errno;
-       } else {
-               if (S_ISBLK(st_buf.st_mode)) {
-                       file_rdev = st_buf.st_rdev;
-               } else {
-                       file_dev = st_buf.st_dev;
-                       file_ino = st_buf.st_ino;
-               }
+       /* scan the initial device */
+       ret = btrfs_scan_one_device(fd, file, &fs_devices_mnt,
+                                   &total_devs, BTRFS_SUPER_INFO_OFFSET);
+       is_btrfs = (ret >= 0);
+       close(fd);
+
+       /* scan other devices */
+       if (is_btrfs && total_devs > 1) {
+               if((ret = btrfs_scan_for_fsid(fs_devices_mnt, total_devs, 1)))
+                       return ret;
        }
 
+       /* iterate over the list of currently mountes filesystems */
+       if ((f = setmntent ("/proc/mounts", "r")) == NULL)
+               return -errno;
+
        while ((mnt = getmntent (f)) != NULL) {
-               if (strcmp(file, mnt->mnt_fsname) == 0)
-                       break;
+               if(is_btrfs) {
+                       if(strcmp(mnt->mnt_type, "btrfs") != 0)
+                               continue;
 
-               if (stat(mnt->mnt_fsname, &st_buf) == 0) {
-                       if (S_ISBLK(st_buf.st_mode)) {
-                               if (file_rdev && (file_rdev == st_buf.st_rdev))
-                                       break;
-                       } else if (file_dev && ((file_dev == st_buf.st_dev) &&
-                                               (file_ino == st_buf.st_ino))) {
-                                       break;
-                       }
+                       ret = blk_file_in_dev_list(fs_devices_mnt, mnt->mnt_fsname);
+               } else {
+                       /* ignore entries in the mount table that are not
+                          associated with a file*/
+                       if((ret = is_existing_blk_or_reg_file(mnt->mnt_fsname)) < 0)
+                               goto out_mntloop_err;
+                       else if(!ret)
+                               continue;
+
+                       ret = is_same_loop_file(file, mnt->mnt_fsname);
                }
-       }
 
-       if (mnt) {
-               /* found an entry in mnt table */
-               ret = 1;
+               if(ret < 0)
+                       goto out_mntloop_err;
+               else if(ret)
+                       break;
        }
 
+       /* Did we find an entry in mnt table? */
+       ret = (mnt != NULL);
+
+out_mntloop_err:
        endmntent (f);
+
        return ret;
 }
 

diff --git a/utils.h b/utils.h
index 7ff542b..9dce5b0 100644 (file)
--- a/utils.h
+++ b/utils.h
@@ -36,7 +36,7 @@ int btrfs_scan_for_fsid(struct btrfs_fs_devices *fs_devices, u64 total_devs,
                        int run_ioctls);
 void btrfs_register_one_device(char *fname);
 int btrfs_scan_one_dir(char *dirname, int run_ioctl);
-int check_mounted(char *devicename);
+int check_mounted(const char *devicename);
 int btrfs_device_already_in_root(struct btrfs_root *root, int fd,
                                 int super_offset);
 char *pretty_sizes(u64 size);