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Bug or Feature? Multiply mounted device

DISCUSSION Ron House 2 participants 2 messages Jul 16, 2004

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Ron House

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Hi all, apologies for posting here, but I need to ask the guys who know for sure. In my fstab, I have two entries for my DOS HD so I can mount it with or without CRLF mangling, as follows (sorry for the line splitting):

/dev/hda5   /d      vfat rw,suid,dev,async,users,umask=033,uid=1500,gid=1001,conv=b 0 0
/dev/hda5   /dc     vfat rw,suid,dev,async,users,umask=033,uid=1500,gid=1001,noauto,conv=a 0 0

I just noticed with my new Linux setup (kernel 2.4.20-8smp - don't know what all that means) that it will let me mount both at once, so I can see the partition as either /d or /dc at the same time. I may be going mad, but I seem to recall with my previous kernel that I couldn't do this.

My question: Bug or feature? If I write all sorts of stuff to both logical devices, will it correctly sort it all out on the same physical device, or will I wreck the partition? All help much appreciated!

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Ron House     [email protected]
              http://www.sci.usq.edu.au/staff/house
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Quoted 9 lines · Ron House

Hi all, apologies for posting here, but I need to ask the guys who know for sure. In my fstab, I have two entries for my DOS HD so I can mount it with or without CRLF mangling, as follows (sorry for the line splitting):

/dev/hda5 /d vfat
rw,suid,dev,async,users,umask=033,uid=1500,gid=1001,conv=b 0 0
/dev/hda5 /dc vfat
rw,suid,dev,async,users,umask=033,uid=1500,gid=1001,noauto,conv=a 0 0

Quoted 8 lines

I just noticed with my new Linux setup (kernel 2.4.20-8smp - don't know what all that means) that it will let me mount both at once, so I can see the partition as either /d or /dc at the same time. I may be going mad, but I seem to recall with my previous kernel that I couldn't do this.

My question: Bug or feature? If I write all sorts of stuff to both logical devices, will it correctly sort it all out on the same physical device, or will I wreck the partition? All help much appreciated!

You will get both mountpoints as aliases to the tree. Note that all fs-specific flags will be ignored on subsequent mounts right now. Eventually different flags will give you -EBUSY.

BTW, conv= is silently ignored by vfat, so your conv=a is a no-op - that stuff simply doesn't belong in kernel and CRLF mangling had been removed quite a while ago (try to make it play nice with mmap(2) and see how soon you'll run away screaming).