Re: Bug Report: Btrfs prompts "can't allocate space for delete" when block size arounds 512M

[Hongzhi, Song]

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Thanks,

--Hongzhi


On 7/17/19 4:34 PM, Hongzhi, Song wrote:
> Hi friends,
>
> *Description:*
>
>
> ÂÂÂ One LTP testcase, fs_fill.c, fails on btrfs with kernel error when 
> unlink files on Btrfs device:
>
> ÂÂÂ "BTRFS warning (device loop0): could not allocate space for a 
> delete; will truncate on mount".
>
>
> ÂÂÂ I found the loop block device formatted with btrfs roughly rangs 
> from 460M to 560M will cause the error.
>
> ÂÂÂ 256M and 1G all pass.
>
>
> ÂÂÂ The fs_fill.c source code:
>
> [https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/fs/fs_fill/fs_fill.c] 
>
>
> ÂÂÂ The fs_fill.c calls unlink which triggers the error.
>
> [https://github.com/linux-test-project/ltp/blob/e3457e42c1b93f54bb81da746eba314fd34ad40e/testcases/kernel/fs/fs_fill/fs_fill.c#L55] 
>
>
> [https://github.com/linux-test-project/ltp/blob/e3457e42c1b93f54bb81da746eba314fd34ad40e/lib/safe_macros.c#L358] 
>
>
>
> *Error info:*
>
> ÂÂÂ The issue maybe not reproduced everytime but four fifths chance.
>
> ÂÂÂ fs_fill.c:53: INFO: Unlinking mntpoint/thread5/file0
> ÂÂÂ safe_macros.c:360: BROK: fs_fill.c:55: 
> unlink(mntpoint/thread10/file0) failed: ENOSPC
> ÂÂÂ safe_macros.c:360: BROK: fs_fill.c:55: 
> unlink(mntpoint/thread11/file0) failed: ENOSPC
> ÂÂÂ [62477.378848] BTRFS warning (device loop0): could not allocate 
> space for a delete; will truncate on mount
> ÂÂÂ [62477.378905] BTRFS warning (device loop0): could not allocate 
> space for a delete; will truncate on mount
>
>
>
> *Kernel:*
>
> ÂÂÂ After v5.2-rc1, qemux86-64
>
> ÂÂÂ # make -j40 ARCH=x86_64 CROSS_COMPILE=x86-64-gcc
> ÂÂÂ use qemu to bootup kernel
>
>
> *LTP:*
>
> ÂÂÂ master branch: I tested on 20190625
> ÂÂÂ Reproduce:
>
> ÂÂÂ // build Ltp
> ÂÂÂ # cd Ltp-source
> ÂÂÂ # ./build.sh
>
> ÂÂÂ // copy files to qemu
> ÂÂÂ # cp runltp testcases/kernel/fs/fs_fill/fs_fill to qemu
>
> ÂÂÂ // login to qemu:
> ÂÂÂ // adjust block device size to 512M
> ÂÂÂ # vi runltp
> ÂÂÂ in function: create_block()
> ÂÂÂ ÂÂÂ dd if=/dev/zero of=${TMP}/test.img bs=1024 count=262144
> ÂÂÂ ÂÂÂ --->
> ÂÂÂ ÂÂÂ dd if=/dev/zero of=${TMP}/test.img bs=1024 count=524288
>
> ÂÂÂ // execute testcase
> ÂÂÂ # runltp -f fs -s fs_fill
>
>
> *Analysis:*
>
> ÂÂÂ One new kernel commit contained in v5.2-rc1 introduces the issue.
>
> ÂÂÂ commit c8eaeac7b734347c3afba7008b7af62f37b9c140
> ÂÂÂ Author: Josef Bacik <josef@xxxxxxxxxxxxxx>
> ÂÂÂ Date:ÂÂ Wed Apr 10 15:56:10 2019 -0400
>
> ÂÂÂ ÂÂÂ btrfs: reserve delalloc metadata differently
> ÂÂ ÂÂ Â ...
>
>
> Anyone's reply will be appreciated.
>
> --Hongzhi