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    SubjectRe: bug in 2.6.22-rc2: loop mount limited to one single iso image
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    On Monday 21 May 2007, Kay Sievers wrote:
    > On Mon, 2007-05-21 at 18:50 +0200, Uwe Bugla wrote:
    > > Am Montag, 21. Mai 2007 18:37 schrieben Sie:
    > > > On 5/21/07, Ken Chen <kenchen@google.com> wrote:
    > > > > yes and no. in that commit, I automatically create n+1 device when
    > > > > loop device n is created, allergically was tested to be fine with
    > > > > casual usage of "losetup" and "mount -o loop". However, there is a
    > > > > bug in that commit when loop.c was compiled as a module. And when Al
    > > > > fixed it, he also removed that magic "n+1" trick.
    > > > >
    > > > > Nevertheless, yes, I'm guilty of introducing the new behavior.
    > > >
    > > > The easiest way is to reinstate max_loop and create "max_loop" device
    > > > up front at module load time. However, that will lose all the "fancy
    > > > on-demand device instantiation feature".
    > > >
    > > > So I propose we do the following:
    > > >
    > > > 1. have the module honor "max_loop" parameter and create that many
    > > > device upfront on module load (max_loop will also be a hard max) iff
    > > > user specify the parameter.
    > > > 2. if max_loop is not specified, default create 8 loop device. User
    > > > can extent more loop device by create device node themselves and have
    > > > kernel automatically instantiate loop device on-demand.
    > >
    > > Sorry, Ken:
    > > My question on point 2 would be: Does "User can extent more loop device
    > > by create device node themselves and......." correspond or conflict to
    > > working with udev?
    >
    > Udev shouldn't care if the kernel tells udev about the new device, and
    > the node with the correct dev_t is already there, it will leave it as it
    > is, and only apply the configured user,group,mode values.
    >
    > The loop tools should probably extended to be able to request new
    > devices from the kernel in a different way than open().
    >

    Except as already mentioned it will introduce races between tool requesting
    new device and udev creating new node. We already had this with raw devices.
    My comparison with /dev/pts was incorrect because it is using internal
    filesystem that creates devices synchronously.

    May be all such cases has to be converted to use common file system.

    mount -t nodefs -o device=pts none /dev/pts
    mount -t nodefs -o device=loop none /dev/loop
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