Messages in this thread | | | Subject | bug with multiple mounts of filesystems in 2.6 | From | John S J Anderson <> | Date | Mon, 26 Jul 2004 12:29:15 -0400 |
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Hi --
We're working on migrating to the 2.6 kernel series, and one big problem has popped up: we have a number of NFS mounts that are mounted read-only in one location and read-write in a distinct location (on the same machine). With 2.4 series kernels, this worked without issue, but with 2.6, it doesn't: it's not possible to mount the same filesystem twice with different options for each mount; the two mount points have to share the same mount options.
Furthermore, if you do mount one filesystem at two different places, changing the mount options on one mount point ('mount -o remount,rw $MOUNT1', for example) also results in the mount options on the other mount point being changed. Finally, the information returned by 'mount' about the mount points is wrong -- 'mount' will show (for example) one mount point being 'rw' and the other being 'ro', when in fact attempting to use the 'rw' mount point will show it to be read-only. /proc/mounts correctly indicates that both mounts are read-only.
Further experimentation has shown:
* the NFS layer is not involved; it is possible to reproduce this problem using just locally-attached filesystems. * this affects at least 2.6.3, 2.6.5, and 2.6.7. * it happens with mount version 2.11r and 2.12.
Because the options of the first mount point "wins" (i.e., mounting a filesystem once read-write, and then a second time as read-only, leaves both mounts in a read-write state), it seems like there's some sort of caching optimization going on -- but I haven't looked into the code to find out if that guess is correct.
Any pointers towards restoring the 2.4 behavior welcomed.
thanks, john. -- Perhaps you have forgotten that this is an engineering discipline, not some sort of black magic. Mark Jason Dominus's Good Advice #11946 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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