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Re: [PATCH 4/5] Fix loop test
From: |
Jim Meyering |
Subject: |
Re: [PATCH 4/5] Fix loop test |
Date: |
Fri, 23 Dec 2011 22:05:26 +0100 |
Phillip Susi wrote:
> On 12/22/2011 04:54 PM, Jim Meyering wrote:
>> I'd really like to have a way to run two or more scsi_debug-using
>> tests in parallel but that is not possible: the kernel allows only one.
>>
>> Note that for many of our scsi-debug-using tests, you cannot duplicate
>> the functionality using a loop device. Besides, even where you can,
>
> I thought the only reason you needed scsi_debug was because loop
> devices couldn't be partitioned.
No.
> What other reason is there?
If you take a look, I'll bet you can guess:
(read about scsi_debug in the kernel docs for details,
or for a quick answer, read my prior reply that you quoted, below)
$ git grep -h scsi_debug_setup_ tests
scsi_debug_setup_ sector_size=$ss dev_size_mb=90 > dev-name ||
scsi_debug_setup_ dev_size_mb=80 > dev-name ||
scsi_debug_setup_ dev_size_mb=1 > dev-name ||
scsi_debug_setup_ dev_size_mb=550 > dev-name ||
scsi_debug_setup_ dev_size_mb=10 > dev-name ||
scsi_debug_setup_ dev_size_mb=8 sector_size=4096 > dev-name ||
scsi_debug_setup_ physblk_exp=3 lowest_aligned=7 num_parts=4 > dev-name ||
scsi_debug_setup_ physblk_exp=3 lowest_aligned=7 sector_size=$ss > dev-name ||
scsi_debug_setup_ sector_size=$ss dev_size_mb=$n_MiB > dev-name ||
scsi_debug_setup_ sector_size=$ss dev_size_mb=$n_MiB > dev-name ||
>> because we don't use e.g., special alignment or block size, you risk
>> being unable to create a loop device due to inherent limitations, or,
>> if you create a few because their tests are running in parallel, you
>> risk perturbing regular processes that (albeit rarely) need to create a
>> loop device. That is part of the reason for my using a private-homed
>> device tree: there I know I'm starting from a clean slate: i.e., far
>> less risk of interfering with some other loop-creating process.
>
> I don't follow. How does using loop devices interfere with other
> processes doing the same? And how does using your own /dev directory
> help at all? Just because you have your own /dev directory doesn't
> mean you have your own set of devices; any devices that actually exist
> when you start still exist ( and are in use ) so you can't re-create a
> private copy, and any devices you create still show up in the real
> /dev.
I guess the isolation was useful only for lvm-related things,
not for loop-related.
- Re: [PATCH 3/5] Avoid the HDIO_GETGEO when possible, (continued)
- [PATCH 5/5] Try harder to clean up scsi_debug, Phillip Susi, 2011/12/16
- [PATCH 4/5] Fix loop test, Phillip Susi, 2011/12/16
- Re: [PATCH 4/5] Fix loop test, Jim Meyering, 2011/12/21
- Re: [PATCH 4/5] Fix loop test, Phillip Susi, 2011/12/21
- Re: [PATCH 4/5] Fix loop test, Jim Meyering, 2011/12/21
- Re: [PATCH 4/5] Fix loop test, Phillip Susi, 2011/12/21
- Re: [PATCH 4/5] Fix loop test, Keshav P R, 2011/12/21
- Re: [PATCH 4/5] Fix loop test, Jim Meyering, 2011/12/22
- Re: [PATCH 4/5] Fix loop test, Phillip Susi, 2011/12/22
- Re: [PATCH 4/5] Fix loop test,
Jim Meyering <=
[PATCH 2/5] Remove has_partitions check to allow loopback partitions, Phillip Susi, 2011/12/16
Re: [PATCH 1/5] Remove loop_get_partition_range, Jim Meyering, 2011/12/21