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