xfs: remove callback dequeue loop from xlog_state_do_iclog_callbacks

mainline-inclusion
from mainline-v5.13-rc4
commit b6903358
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4KIAO
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b6903358c230c517b29ecdb6123276d96cc0beab



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If we are processing callbacks on an iclog, nothing can be
concurrently adding callbacks to the loop. We only add callbacks to
the iclog when they are in ACTIVE or WANT_SYNC state, and we
explicitly do not add callbacks if the iclog is already in IOERROR
state.

The only way to have a dequeue racing with an enqueue is to be
processing a shutdown without a direct reference to an iclog in
ACTIVE or WANT_SYNC state. As the enqueue avoids this race
condition, we only ever need a single dequeue operation in
xlog_state_do_iclog_callbacks(). Hence we can remove the loop.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Guo Xuenan <guoxuenan@huawei.com>
Reviewed-by: Lihong Kou <koulihong@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>