gfs2: Fix filesystem block deallocation for short writes

stable inclusion
from stable-v5.10.117
commit 88091c0275b2eed5ad24a444b58e1545abaca859
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L66B

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=88091c0275b2eed5ad24a444b58e1545abaca859



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[ Upstream commit d031a886 ]

When a write cannot be carried out in full, gfs2_iomap_end() releases
blocks that have been allocated for this write but haven't been used.

To compute the end of the allocation, gfs2_iomap_end() incorrectly
rounded the end of the attempted write down to the next block boundary
to arrive at the end of the allocation.  It would have to round up, but
the end of the allocation is also available as iomap->offset +
iomap->length, so just use that instead.

In addition, use round_up() for computing the start of the unused range.

Fixes: 64bc06bb ("gfs2: iomap buffered write support")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>