Ross Zwisler <ross.zwisler(a)linux.intel.com&gt; writes:

> +static int dax_radix_entry(struct address_space *mapping, pgoff_t index, IMHO it would be sane to call that function as dax_radix_entry_insert()

> +/* > + * Flush the mapping to the persistent domain within the byte range of [start, > + * end]. This is required by data integrity operations to ensure file data is > + * on persistent storage prior to completion of the operation. > + */ > +int dax_writeback_mapping_range(struct address_space *mapping, loff_t start, > + loff_t end) > +{ > + struct inode *inode = mapping->host; > + struct block_device *bdev = inode->i_sb->s_bdev; > + pgoff_t indices[PAGEVEC_SIZE]; > + pgoff_t start_page, end_page; > + struct pagevec pvec; > + void *entry; > + int i, ret = 0; > + > + if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) > + return -EIO; > + > + rcu_read_lock(); > + entry = radix_tree_lookup(&mapping->page_tree, start & PMD_MASK); > + rcu_read_unlock(); > + > + /* see if the start of our range is covered by a PMD entry */ > + if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) > + start &= PMD_MASK; > + > + start_page = start >> PAGE_CACHE_SHIFT; > + end_page = end >> PAGE_CACHE_SHIFT; > + > + tag_pages_for_writeback(mapping, start_page, end_page); > + > + pagevec_init(&pvec, 0); > + while (1) { > + pvec.nr = find_get_entries_tag(mapping, start_page, > + PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE, > + pvec.pages, indices); > + > + if (pvec.nr == 0) > + break; > + > + for (i = 0; i < pvec.nr; i++) { > + ret = dax_writeback_one(bdev, mapping, indices[i], > + pvec.pages[i]); > + if (ret < 0) > + return ret; > + } I think it would be more efficient to use batched locking like follows: spin_lock_irq(&mapping->tree_lock); for (i = 0; i < pvec.nr; i++) { struct blk_dax_ctl dax[PAGEVEC_SIZE]; radix_tree_tag_clear(page_tree, indices[i], PAGECACHE_TAG_TOWRITE); /* It is also reasonable to merge adjacent dax * regions in to one */ dax[i].sector = RADIX_DAX_SECTOR(entry); dax[i].size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE); } spin_unlock_irq(&mapping->tree_lock); if (blk_queue_enter(q, true) != 0) goto error; for (i = 0; i < pvec.nr; i++) { rc = bdev_direct_access(bdev, dax[i]); wb_cache_pmem(dax[i].addr, dax[i].size); } ret = blk_queue_exit(q, true)