On 2022/6/18 18:34, Matthew Wilcox wrote: > On Sat, Jun 18, 2022 at 04:38:20PM +0800, Miaohe Lin wrote: >> The invalidate_locks of two mappings should be unlocked in reverse order >> relative to the locking order in filemap_invalidate_lock_two(). Modifying > > Why? It's perfectly valid to lock(A) lock(B) unlock(A) unlock(B). > If it weren't we'd have lockdep check it and complain. For spin_lock, they are lock(A) lock(B) unlock(B) unlock(A) e.g. in copy_huge_pud, copy_huge_pmd, move_huge_pmd and so on: dst_ptl = pmd_lock(dst_mm, dst_pmd); src_ptl = pmd_lockptr(src_mm, src_pmd); spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); ... spin_unlock(src_ptl); spin_unlock(dst_ptl); For rw_semaphore, they are also lock(A) lock(B) unlock(B) unlock(A) e.g. in dup_mmap(): mmap_write_lock_killable(oldmm) mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING); ... mmap_write_unlock(mm); mmap_write_unlock(oldmm); and ntfs_extend_mft(): down_write(&ni->file.run_lock); down_write_nested(&sbi->used.bitmap.rw_lock, BITMAP_MUTEX_CLUSTERS); ... up_write(&sbi->used.bitmap.rw_lock); up_write(&ni->file.run_lock); But I see some lock(A) lock(B) unlock(A) unlock(B) examples in some fs codes. Could you please tell me the right lock/unlock order? I'm somewhat confused now... BTW: If lock(A) lock(B) unlock(A) unlock(B) is requested, filemap_invalidate_lock_two might still need to be changed to respect that order? Thanks! > > . >
