[dm-devel] [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings

[Alasdair G Kergon]

On Tue, Feb 15, 2011 at 01:17:56PM +0100, Milan Broz wrote:
>         fd = open(device, O_RDWR | flags);
>         if (fd == -1 && errno == EROFS) {
>                 *readonly = 1;
>                 fd = open(device, O_RDONLY | flags);
>         }

Would it be reasonable for your patch to return EROFS rather than
EACCES?

man 2 open:
       int open(const char *pathname, int flags, mode_t mode);

       EROFS  pathname  refers  to a file on a read-only file system and write
              access was requested.

       EACCES The requested access to the file is not allowed, or search  per‐
              mission  is denied for one of the directories in the path prefix
              of pathname, or the file did not exist yet and write  access  to
              the  parent  directory  is  not allowed.  (See also path_resolu‐
              tion(7).)

Alasdair