On Linux do BLKROGET ioctl to make sure the device is not read-only: after "blockdev...

[android-x86/external-exfat.git] / libexfat / io.c

diff --git a/libexfat/io.c b/libexfat/io.c
index 7d416ed..e89349b 100644 (file)
--- a/libexfat/io.c
+++ b/libexfat/io.c
@@ -23,6 +23,7 @@
 #include <sys/types.h>
 #include <sys/uio.h>
 #include <sys/stat.h>
+#include <sys/mount.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <string.h>
@@ -38,13 +39,38 @@
 struct exfat_dev
 {
        int fd;
+       enum exfat_mode mode;
 #ifdef USE_UBLIO
        off_t pos;
        ublio_filehandle_t ufh;
 #endif
 };
 
-struct exfat_dev* exfat_open(const char* spec, int ro)
+static int open_ro(const char* spec)
+{
+       return open(spec, O_RDONLY);
+}
+
+static int open_rw(const char* spec)
+{
+       int fd = open(spec, O_RDWR);
+#ifdef __linux__
+       int ro = 0;
+
+       /*
+          This ioctl is needed because after "blockdev --setro" kernel still
+          allows to open the device in read-write mode but fails writes.
+       */
+       if (fd != -1 && ioctl(fd, BLKROGET, &ro) == 0 && ro)
+       {
+               close(fd);
+               return -1;
+       }
+#endif
+       return fd;
+}
+
+struct exfat_dev* exfat_open(const char* spec, enum exfat_mode mode)
 {
        struct exfat_dev* dev;
        struct stat stbuf;
@@ -59,14 +85,47 @@ struct exfat_dev* exfat_open(const char* spec, int ro)
                return NULL;
        }
 
-       dev->fd = open(spec, ro ? O_RDONLY : O_RDWR);
-       if (dev->fd < 0)
+       switch (mode)
        {
+       case EXFAT_MODE_RO:
+               dev->fd = open_ro(spec);
+               if (dev->fd == -1)
+               {
+                       free(dev);
+                       exfat_error("failed to open `%s' in read-only mode", spec);
+                       return NULL;
+               }
+               dev->mode = EXFAT_MODE_RO;
+               break;
+       case EXFAT_MODE_RW:
+               dev->fd = open_rw(spec);
+               if (dev->fd == -1)
+               {
+                       free(dev);
+                       exfat_error("failed to open `%s' in read-write mode", spec);
+                       return NULL;
+               }
+               dev->mode = EXFAT_MODE_RW;
+               break;
+       case EXFAT_MODE_ANY:
+               dev->fd = open_rw(spec);
+               if (dev->fd != -1)
+               {
+                       dev->mode = EXFAT_MODE_RW;
+                       break;
+               }
+               dev->fd = open_ro(spec);
+               if (dev->fd != -1)
+               {
+                       dev->mode = EXFAT_MODE_RO;
+                       exfat_warn("`%s' is write-protected, mounting read-only", spec);
+                       break;
+               }
                free(dev);
-               exfat_error("failed to open `%s' in read-%s mode", spec,
-                               ro ? "only" : "write");
+               exfat_error("failed to open `%s'", spec);
                return NULL;
        }
+
        if (fstat(dev->fd, &stbuf) != 0)
        {
                close(dev->fd);
@@ -135,6 +194,11 @@ int exfat_fsync(struct exfat_dev* dev)
        return 0;
 }
 
+enum exfat_mode exfat_mode(const struct exfat_dev* dev)
+{
+       return dev->mode;
+}
+
 off_t exfat_seek(struct exfat_dev* dev, off_t offset, int whence)
 {
 #ifdef USE_UBLIO