when we have to report no such file error for
/dev/btrfs-control we could confirm if btrfs kernel
module is loaded and report it and skip registration
where appropriate

Further this patch pretty prints the dev scan results.

Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
 cmds-device.c | 56 +++++++++++++++++++++++++++++++++++++++++++-------------
 mkfs.c        | 13 +++++++++++--
 utils.c       | 22 ++++++++++++++++++++++
 utils.h       |  1 +
 4 files changed, 77 insertions(+), 15 deletions(-)

diff --git a/cmds-device.c b/cmds-device.c
index a90fb67..0e1e6de 100644
--- a/cmds-device.c
+++ b/cmds-device.c
@@ -185,9 +185,10 @@ static const char * const cmd_scan_dev_usage[] = {
 
 static int cmd_scan_dev(int argc, char **argv)
 {
-       int     i, fd, e;
+       int     i, fd = -1, e, ret = 0;
        int     checklist = 1;
        int     devstart = 1;
+       u64     flag_reg = 0ull;
 
        if( argc > 1 && !strcmp(argv[1],"--all-devices")){
                if (check_argc_max(argc, 2))
@@ -197,11 +198,16 @@ static int cmd_scan_dev(int argc, char **argv)
                devstart += 1;
        }
 
+       if (is_btrfs_kernel_loaded())
+               flag_reg = BTRFS_SCAN_REGISTER;
+       else
+               fprintf(stderr, "btrfs kernel module is not loaded\n");
+
        if(argc<=devstart){
 
                int ret;
 
-               printf("Scanning for Btrfs filesystems\n");
+               printf("Scanning for Btrfs filesystems ");
                if(checklist)
                        ret = btrfs_scan_block_devices(BTRFS_SCAN_REGISTER);
                else
@@ -210,20 +216,39 @@ static int cmd_scan_dev(int argc, char **argv)
                        fprintf(stderr, "ERROR: error %d while scanning\n", 
ret);
                        return 18;
                }
+               printf("..done\n");
                return 0;
        }
 
-       fd = open("/dev/btrfs-control", O_RDWR);
-       if (fd < 0) {
-               perror("failed to open /dev/btrfs-control");
-               return 10;
+       if (!flag_reg)
+               return -1;
+
+       if ((fd = open("/dev/btrfs-control", O_RDWR)) < 0) {
+               fprintf(stderr, "ERROR: failed to open "\
+                       "/dev/btrfs-control - %s\n", strerror(errno));
+               return -1;
        }
 
+       printf("Scanning for Btrfs in\n");
        for( i = devstart ; i < argc ; i++ ){
+               int fdt;
                struct btrfs_ioctl_vol_args args;
-               int ret;
+               printf("  %s ", argv[i]);
+               fflush(stdout);
 
-               printf("Scanning for Btrfs filesystems in '%s'\n", argv[i]);
+               /*
+                * If for a multipath (mp) disk user provides the
+                * non-mp path then open with flag O_EXCL will fail,
+                * (also ioctl opens with O_EXCL), So test it before
+                * calling ioctl.
+                */
+               fdt = open(argv[i], O_RDONLY|O_EXCL);
+               if (fdt < 0) {
+                       perror("ERROR");
+                       ret = -1;
+                       continue;
+               }
+               close(fdt);
 
                strncpy_null(args.name, argv[i]);
                /*
@@ -235,15 +260,16 @@ static int cmd_scan_dev(int argc, char **argv)
                e = errno;
 
                if( ret < 0 ){
-                       close(fd);
-                       fprintf(stderr, "ERROR: unable to scan the device '%s' 
- %s\n",
-                               argv[i], strerror(e));
-                       return 11;
+                       fprintf(stderr, "ERROR: unable to scan - %s\n",
+                               strerror(e));
+                       ret = -1;
+               } else {
+                       printf("found\n");
                }
        }
 
        close(fd);
-       return 0;
+       return ret;
 }
 
 static const char * const cmd_ready_dev_usage[] = {
@@ -261,6 +287,10 @@ static int cmd_ready_dev(int argc, char **argv)
        if (check_argc_min(argc, 2))
                usage(cmd_ready_dev_usage);
 
+       if (!is_btrfs_kernel_loaded()) {
+               fprintf(stderr, "btrfs kernel module is not loaded\n");
+               return 10;
+       }
        fd = open("/dev/btrfs-control", O_RDWR);
        if (fd < 0) {
                perror("failed to open /dev/btrfs-control");
diff --git a/mkfs.c b/mkfs.c
index 7d23520..dc4120a 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -1420,6 +1420,7 @@ int main(int ac, char **av)
        u64 flags;
        int dev_cnt=0;
        int saved_optind;
+       int flag_reg=1;
 
        while(1) {
                int c;
@@ -1508,6 +1509,12 @@ int main(int ac, char **av)
        printf("\nWARNING! - %s IS EXPERIMENTAL\n", BTRFS_BUILD_VERSION);
        printf("WARNING! - see http://btrfs.wiki.kernel.org before using\n\n");
 
+       if (!is_btrfs_kernel_loaded()) {
+               printf("btrfs kernel module is not loaded, "
+                       "would skip device registration\n");
+               flag_reg = 0;
+       }
+
        file = av[optind++];
        dev_cnt--;
 
@@ -1594,7 +1601,8 @@ int main(int ac, char **av)
        if (dev_cnt == 0)
                goto raid_groups;
 
-       btrfs_register_one_device(file);
+       if (flag_reg)
+               btrfs_register_one_device(file);
 
        zero_end = 1;
        while(dev_cnt-- > 0) {
@@ -1629,7 +1637,8 @@ int main(int ac, char **av)
                ret = btrfs_add_to_fsid(trans, root, fd, file, dev_block_count,
                                        sectorsize, sectorsize, sectorsize);
                BUG_ON(ret);
-               btrfs_register_one_device(file);
+               if (flag_reg)
+                       btrfs_register_one_device(file);
        }
 
 raid_groups:
diff --git a/utils.c b/utils.c
index 27574a0..21483b8 100644
--- a/utils.c
+++ b/utils.c
@@ -1016,6 +1016,23 @@ struct pending_dir {
        char name[PATH_MAX];
 };
 
+/*
+ * return 1 for btrfs kernel module loaded
+ * return 0 for not
+ */
+int is_btrfs_kernel_loaded()
+{
+       FILE *mfd = popen("lsmod | grep btrfs", "r");
+       char buf[16];
+
+       if (fread (buf, 1, sizeof (buf), mfd) > 0) {
+               pclose(mfd);
+               return 1;
+       }
+       pclose(mfd);
+       return 0;
+}
+
 void btrfs_register_one_device(char *fname)
 {
        struct btrfs_ioctl_vol_args args;
@@ -1023,6 +1040,11 @@ void btrfs_register_one_device(char *fname)
        int ret;
        int e;
 
+       if (!is_btrfs_kernel_loaded()) {
+               fprintf(stderr, "btrfs kernel module is not loaded, "
+                       "skipping device registration\n");
+               return;
+       }
        fd = open("/dev/btrfs-control", O_RDONLY);
        if (fd < 0) {
                fprintf(stderr, "failed to open /dev/btrfs-control "
diff --git a/utils.h b/utils.h
index ab22b02..50957b7 100644
--- a/utils.h
+++ b/utils.h
@@ -64,6 +64,7 @@ int get_btrfs_mount(const char *path, char *mp, size_t 
mp_size);
 int open_path_or_dev_mnt(const char *path);
 int is_swap_device(const char *file);
 u64 btrfs_device_size(int fd, struct stat *st);
+int is_btrfs_kernel_loaded();
 /* Helper to always get proper size of the destination string */
 #define strncpy_null(dest, src) __strncpy__null(dest, src, sizeof(dest))
 
-- 
1.8.1.227.g44fe835

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