nilfs2: prevent kernel bug at submit_bh_wbc()

stable inclusion
from stable-v4.19.312
commit 91e4c4595fae5e87069e44687ae879091783c183
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9L5DI
CVE: CVE-2024-26955

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=91e4c4595fae5e87069e44687ae879091783c183

--------------------------------

[ Upstream commit 269cdf353b5bdd15f1a079671b0f889113865f20 ]

Fix a bug where nilfs_get_block() returns a successful status when
searching and inserting the specified block both fail inconsistently.  If
this inconsistent behavior is not due to a previously fixed bug, then an
unexpected race is occurring, so return a temporary error -EAGAIN instead.

This prevents callers such as __block_write_begin_int() from requesting a
read into a buffer that is not mapped, which would cause the BUG_ON check
for the BH_Mapped flag in submit_bh_wbc() to fail.

Link: https://lkml.kernel.org/r/20240313105827.5296-3-konishi.ryusuke@gmail.com


Fixes: 1f5abe7e ("nilfs2: replace BUG_ON and BUG calls triggerable from ioctl")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Conflicts:
	fs/nilfs2/inode.c
[In upstream branch linux-4.19.y, a dependent commit 5c8f85e9ff21
("nilfs2: use a more common logging style"), but since bacporting
it will introduce more dependent commits and this fix is simple,
we can directly adapt this patch.]
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>