thinkpad-acpi: silence hotkey enable warning for module parameter

[firefly-linux-kernel-4.4.55.git] / fs / buffer.c

diff --git a/fs/buffer.c b/fs/buffer.c
index 43afaa5d69014da26307910cc8cde01262a5aef6..13edf7ad3ff1524032d043ec10aa3b13465103ef 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1596,6 +1596,16 @@ EXPORT_SYMBOL(unmap_underlying_metadata);
  * locked buffer.   This only can happen if someone has written the buffer
  * directly, with submit_bh().  At the address_space level PageWriteback
  * prevents this contention from occurring.
+ *
+ * If block_write_full_page() is called with wbc->sync_mode ==
+ * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this
+ * causes the writes to be flagged as synchronous writes, but the
+ * block device queue will NOT be unplugged, since usually many pages
+ * will be pushed to the out before the higher-level caller actually
+ * waits for the writes to be completed.  The various wait functions,
+ * such as wait_on_writeback_range() will ultimately call sync_page()
+ * which will ultimately call blk_run_backing_dev(), which will end up
+ * unplugging the device queue.
  */
 static int __block_write_full_page(struct inode *inode, struct page *page,
                        get_block_t *get_block, struct writeback_control *wbc)
@@ -1606,7 +1616,8 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
        struct buffer_head *bh, *head;
        const unsigned blocksize = 1 << inode->i_blkbits;
        int nr_underway = 0;
-       int write_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
+       int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
+                       WRITE_SYNC_PLUG : WRITE);
 
        BUG_ON(!PageLocked(page));
 
@@ -3010,7 +3021,7 @@ int sync_dirty_buffer(struct buffer_head *bh)
        if (test_clear_buffer_dirty(bh)) {
                get_bh(bh);
                bh->b_end_io = end_buffer_write_sync;
-               ret = submit_bh(WRITE, bh);
+               ret = submit_bh(WRITE_SYNC, bh);
                wait_on_buffer(bh);
                if (buffer_eopnotsupp(bh)) {
                        clear_buffer_eopnotsupp(bh);