On Thu, 3 Jul 2014 18:29:19 +0200 Philippe De Muyter <[email protected]> wrote:
> On Wed, Jul 02, 2014 at 12:46:51PM -0700, Andrew Morton wrote: > > On Fri, 27 Jun 2014 10:20:58 +0200 Philippe De Muyter <[email protected]> > > wrote: > > > > > Currently, the initial mount of the root file system by the linux > > > kernel fails with a cryptic message instead of being retried with > > > the MS_RDONLY flag set, when the device is read-only and the > > > combination of block driver and filesystem driver yields EROFS. > > > > > > I do not know if POSIX mandates that mount(2) must fail with EACCES, nor > > > if linux aims to strict compliance with POSIX on that point. Consensus > > > amongst the messages that I have read so far seems to show that linux > > > kernel hackers feel that EROFS is a more appropriate error code than > > > EACCES in that case. > > > > Isn't the core problem that "the combination of block driver and > > filesystem driver yields EROFS"? That the fs should instead be > > returning EACCESS in this case? > > Does POSIX or Linux mandate that it should ? > > > > > What fs and block driver are we talking about here, anyway? > > The problem happened to me with a f2fs filesystem on a sd-card that was > accidentally write-protected and that was put in a SD-card slot (mmc block > driver). > > I retested using mount(8) with a similar now intentionnaly write-protected > sd card in a usb reader (usb_storage driver ?) with vfat, f2fs and ext4 > filesystems with the following results : > > mywdesk:~ # strace -e mount mount /dev/sdb1 /mnt > mount("/dev/sdb1", "/mnt", "vfat", MS_MGC_VAL, NULL) = -1 EROFS (Read-only > file system) > mount: /dev/sdb1 is write-protected, mounting read-only > mount("/dev/sdb1", "/mnt", "vfat", MS_MGC_VAL|MS_RDONLY, NULL) = 0 > +++ exited with 0 +++ > mywdesk:~ # umount /mnt > mywdesk:~ # strace -e mount mount -t f2fs /dev/sdb2 /mnt > mount("/dev/sdb2", "/mnt", "f2fs", MS_MGC_VAL, NULL) = -1 EROFS (Read-only > file system) > mount: /dev/sdb2 is write-protected, mounting read-only > mount("/dev/sdb2", "/mnt", "f2fs", MS_MGC_VAL|MS_RDONLY, NULL) = 0 > +++ exited with 0 +++ > mywdesk:~ # umount /mnt > mywdesk:~ # strace -e mount mount /dev/sdb3 /mnt > mount("/dev/sdb3", "/mnt", "ext4", MS_MGC_VAL, NULL) = -1 EROFS (Read-only > file system) > mount: /dev/sdb3 is write-protected, mounting read-only > mount("/dev/sdb3", "/mnt", "ext4", MS_MGC_VAL|MS_RDONLY, NULL) = 0 > +++ exited with 0 +++ > mywdesk:~ # > > All three file-systems (vfat, f2fs & ext4) yield EROFS. > > I also quickly grepped for occurences of EROFS under fs/, and found no check > to replace EROFS by EACCES, > while the same grep under drivers/{block,cdrom,ide,md,memstick, mtd, > s390/block,scsi,usb} gives plenty of "return -EROFS;" > > So, if no filesystem driver replaces EROFS by EACCES and many block drivers > return EROFS, it seems to me that many combinations will yield EROFS. hm. I'm thinking that in an ideal world, those block drivers will return -EACCES rather than -EROFS. You open() a read-only device for rw, you get "permission denied". Al, speak to us. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
