hello,
On 06/30/2016 09:52 PM, Eryu Guan wrote:
On Thu, Jun 30, 2016 at 04:25:49PM +0800, Wang Xiaoguang wrote:
In btrfs, when truncate operation fails for enospc reason, file may still
have some disk blocks, but it will fail to update filesize accordingly.
Kernel commit c0d2f61 has fixed this bug for btrfs:
btrfs: fix disk_i_size update bug when ftruncate() fails
Signed-off-by: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>
---
v2: move this test to generic test and add comments why testcase
use reflink.
Thanks for the updated version. Did it fail for you when testing on
unpatched kernel? I ran the test more than 10 times on 4.6 kernel (which
doesn't have the fix) and all passed, as well as RHEL7 kernel.
Can you please confirm?
I tested this case in v4.6-rc7-162-g415b35a and it failed as expected,
but I used the newest version btrfs-progs.
In RHEL7.2ga, its btrfs-progs version is btrfs-progs-3.19.1-1.el7.x86_64,
which is somewhat old. For small fs, it'll enable mixed mode for data and
metadata default, so the reflink operation in this test case does not
consume
enough metadata, truncate operation can still succeed, then test will always
pass. I can create a big fs to have test, but then this fs will have more
metadata, which then need more reflink operations to consume metadata and
increase the test time greatly.
In mkfs.btrfs manpage, there is such description：
versions up to 4.2.x forced the mixed mode for devices smaller
than 1GiB. This has been removed in 4.3+ as it caused some
usability issues.
Regards,
Xiaoguang Wang
Thanks,
Eryu
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