We use inline_dentry which requires to allocate dentry page when adding a link.
If we allow to reclaim memory from filesystem, we do down_read(&sbi->cp_rwsem)
twice by f2fs_lock_op(). I think this should be okay, but how about stopping
the lockdep complaint [1]?

f2fs_create()
 - f2fs_lock_op()
 - f2fs_do_add_link()
  - __f2fs_find_entry
   - f2fs_get_read_data_page()
   -> kswapd
    - shrink_node
     - f2fs_evict_inode
      - f2fs_lock_op()

[1]

fs_reclaim
){+.+.}-{0:0}
:
kswapd0:        lock_acquire+0x114/0x394
kswapd0:        __fs_reclaim_acquire+0x40/0x50
kswapd0:        prepare_alloc_pages+0x94/0x1ec
kswapd0:        __alloc_pages_nodemask+0x78/0x1b0
kswapd0:        pagecache_get_page+0x2e0/0x57c
kswapd0:        f2fs_get_read_data_page+0xc0/0x394
kswapd0:        f2fs_find_data_page+0xa4/0x23c
kswapd0:        find_in_level+0x1a8/0x36c
kswapd0:        __f2fs_find_entry+0x70/0x100
kswapd0:        f2fs_do_add_link+0x84/0x1ec
kswapd0:        f2fs_mkdir+0xe4/0x1e4
kswapd0:        vfs_mkdir+0x110/0x1c0
kswapd0:        do_mkdirat+0xa4/0x160
kswapd0:        __arm64_sys_mkdirat+0x24/0x34
kswapd0:        el0_svc_common.llvm.17258447499513131576+0xc4/0x1e8
kswapd0:        do_el0_svc+0x28/0xa0
kswapd0:        el0_svc+0x24/0x38
kswapd0:        el0_sync_handler+0x88/0xec
kswapd0:        el0_sync+0x1c0/0x200
kswapd0:
-> #1
(
&sbi->cp_rwsem
){++++}-{3:3}
:
kswapd0:        lock_acquire+0x114/0x394
kswapd0:        down_read+0x7c/0x98
kswapd0:        f2fs_do_truncate_blocks+0x78/0x3dc
kswapd0:        f2fs_truncate+0xc8/0x128
kswapd0:        f2fs_evict_inode+0x2b8/0x8b8
kswapd0:        evict+0xd4/0x2f8
kswapd0:        iput+0x1c0/0x258
kswapd0:        do_unlinkat+0x170/0x2a0
kswapd0:        __arm64_sys_unlinkat+0x4c/0x68
kswapd0:        el0_svc_common.llvm.17258447499513131576+0xc4/0x1e8
kswapd0:        do_el0_svc+0x28/0xa0
kswapd0:        el0_svc+0x24/0x38
kswapd0:        el0_sync_handler+0x88/0xec
kswapd0:        el0_sync+0x1c0/0x200

Cc: stable@vger.kernel.org
Fixes: bdbc90fa ("f2fs: don't put dentry page in pagecache into highmem")
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Light Hsieh <light.hsieh@mediatek.com>
Tested-by: Light Hsieh <light.hsieh@mediatek.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>