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* block device read-only handling regression in 2.6.38-rc4 (bisected)
@ 2011-02-13  2:02 Milan Broz
  2011-02-13 10:58 ` [PATCH] loop: clear read-only flag in loop_clr_fd Tao Ma
  0 siblings, 1 reply; 8+ messages in thread
From: Milan Broz @ 2011-02-13  2:02 UTC (permalink / raw)
  To: Tejun Heo; +Cc: Jens Axboe, Linux Kernel Mailing List

Hi Tejun,

Seems this commit cause regressions:

commit 75f1dc0d076d1c1168f2115f1941ea627d38bd5a
Author: Tejun Heo <tj@kernel.org>
Date:   Sat Nov 13 11:55:17 2010 +0100

    block: check bdev_read_only() from blkdev_get()
    
    bdev read-only status can be queried using bdev_read_only() and may
    change while the device is being opened.  Enforce it by checking it
    from blkdev_get() after open succeeds.


1) loop device once set read-only is not able to be used read-write afterward

touch /x1.img
losetup -r /dev/loop0 /x1.img
losetup -d /dev/loop0
losetup /dev/loop0 /x1.img
/dev/loop0: Permission denied


2) it breaks read-only dm-snapshots
(Fedora LiveCD operations is broken by this as well.)

(x.img is backing device, xs.img is prepared COW, you can simply run it
once in read-write to create dm-snap header and then re-run this commands)

losetup -r /dev/loop0 /x.img
losetup -r /dev/loop1 /xs.img
dmsetup create x --readonly --table '0 131072 snapshot /dev/loop0 /dev/loop1 p 8'
device-mapper: reload ioctl failed: Permission denied

Milan

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2011-02-14 14:08 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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2011-02-13 20:41   ` [PATCH] loop: clear read-only flag in loop_clr_fd Bodo Eggert
2011-02-13  2:02 block device read-only handling regression in 2.6.38-rc4 (bisected) Milan Broz
2011-02-13 10:58 ` [PATCH] loop: clear read-only flag in loop_clr_fd Tao Ma
2011-02-13 14:11   ` Milan Broz
2011-02-13 15:05     ` Tao Ma
2011-02-13 16:44       ` Milan Broz
2011-02-14 10:30         ` Tejun Heo
2011-02-14 11:47           ` Milan Broz
2011-02-14 14:07             ` Tejun Heo

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