remove SWRITE* I/O types

These flags aren't real I/O types, but tell ll_rw_block to always
lock the buffer instead of giving up on a failed trylock.

Instead add a new write_dirty_buffer helper that implements this semantic
and use it from the existing SWRITE* callers.  Note that the ll_rw_block
code had a bug where it didn't promote WRITE_SYNC_PLUG properly, which
this patch fixes.

In the ufs code clean up the helper that used to call ll_rw_block
to mirror sync_dirty_buffer, which is the function it implements for
compound buffers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 29 insertions, 23 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 6c8ad977f3d4..3e7dca279d1c 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -770,11 +770,12 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
                                 spin_unlock(lock);
                                 /*
                                  * Ensure any pending I/O completes so that
-                                 * ll_rw_block() actually writes the current
-                                 * contents - it is a noop if I/O is still in
-                                 * flight on potentially older contents.
+                                 * write_dirty_buffer() actually writes the
+                                 * current contents - it is a noop if I/O is
+                                 * still in flight on potentially older
+                                 * contents.
                                  */
-                                ll_rw_block(SWRITE_SYNC_PLUG, 1, &bh);
+                                write_dirty_buffer(bh, WRITE_SYNC_PLUG);
 
                                 /*
                                  * Kick off IO for the previous mapping. Note
@@ -2949,22 +2950,21 @@ EXPORT_SYMBOL(submit_bh);
 
 /**
  * ll_rw_block: low-level access to block devices (DEPRECATED)
- * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
+ * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
  * @nr: number of &struct buffer_heads in the array
  * @bhs: array of pointers to &struct buffer_head
  *
  * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
  * requests an I/O operation on them, either a %READ or a %WRITE.  The third
- * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
- * are sent to disk. The fourth %READA option is described in the documentation
- * for generic_make_request() which ll_rw_block() calls.
+ * %READA option is described in the documentation for generic_make_request()
+ * which ll_rw_block() calls.
  *
  * This function drops any buffer that it cannot get a lock on (with the
- * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
- * clean when doing a write request, and any buffer that appears to be
- * up-to-date when doing read request.  Further it marks as clean buffers that
- * are processed for writing (the buffer cache won't assume that they are
- * actually clean until the buffer gets unlocked).
+ * BH_Lock state bit), any buffer that appears to be clean when doing a write
+ * request, and any buffer that appears to be up-to-date when doing read
+ * request.  Further it marks as clean buffers that are processed for
+ * writing (the buffer cache won't assume that they are actually clean
+ * until the buffer gets unlocked).
  *
  * ll_rw_block sets b_end_io to simple completion handler that marks
  * the buffer up-to-date (if approriate), unlocks the buffer and wakes
@@ -2980,20 +2980,13 @@ void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
         for (i = 0; i < nr; i++) {
                 struct buffer_head *bh = bhs[i];
 
-                if (rw == SWRITE || rw == SWRITE_SYNC || rw == SWRITE_SYNC_PLUG)
-                        lock_buffer(bh);
-                else if (!trylock_buffer(bh))
+                if (!trylock_buffer(bh))
                         continue;
-
-                if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC ||
-                    rw == SWRITE_SYNC_PLUG) {
+                if (rw == WRITE) {
                         if (test_clear_buffer_dirty(bh)) {
                                 bh->b_end_io = end_buffer_write_sync;
                                 get_bh(bh);
-                                if (rw == SWRITE_SYNC)
-                                        submit_bh(WRITE_SYNC, bh);
-                                else
-                                        submit_bh(WRITE, bh);
+                                submit_bh(WRITE, bh);
                                 continue;
                         }
                 } else {
@@ -3009,6 +3002,19 @@ void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
 }
 EXPORT_SYMBOL(ll_rw_block);
 
+void write_dirty_buffer(struct buffer_head *bh, int rw)
+{
+        lock_buffer(bh);
+        if (!test_clear_buffer_dirty(bh)) {
+                unlock_buffer(bh);
+                return;
+        }
+        bh->b_end_io = end_buffer_write_sync;
+        get_bh(bh);
+        submit_bh(rw, bh);
+}
+EXPORT_SYMBOL(write_dirty_buffer);
+
 /*
  * For a data-integrity writeout, we need to wait upon any in-progress I/O
  * and then start new I/O and then wait upon it.  The caller must have a ref on