losetup: implement -r option. Closes 4033.

function                                             old     new   delta
packed_usage                                       28595   28633     +38
losetup_main                                         285     290      +5
singlemount                                          906     908      +2
set_loop                                             674     672      -2

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/libbb/loop.c b/libbb/loop.c
index b798932fa..b3a520848 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -84,7 +84,7 @@ int FAST_FUNC del_loop(const char *device)
    search will re-use an existing loop device already bound to that
    file/offset if it finds one.
  */
-int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset)
+int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset, int ro)
 {
         char dev[LOOP_NAMESIZE];
         char *try;
@@ -93,11 +93,13 @@ int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offse
         int i, dfd, ffd, mode, rc = -1;
 
         /* Open the file.  Barf if this doesn't work.  */
-        mode = O_RDWR;
+        mode = ro ? O_RDONLY : O_RDWR;
         ffd = open(file, mode);
         if (ffd < 0) {
-                mode = O_RDONLY;
-                ffd = open(file, mode);
+                if (mode != O_RDONLY) {
+                        mode = O_RDONLY;
+                        ffd = open(file, mode);
+                }
                 if (ffd < 0)
                         return -errno;
         }