As described in commit 02117b8a ("f2fs: Set GF_NOFS in
read_cache_page_gfp while doing f2fs_quota_read"), we must not enter
filesystem reclaim while holding the dq_lock.  Prevent this more generally
by using memalloc_nofs_save() while holding the lock.

Link: https://lore.kernel.org/r/20220605143815.2330891-2-willy@infradead.orgSigned-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NJan Kara <jack@suse.cz>