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>

fs/ufs/util.h

diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 0466036..9f8775c 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -269,8 +269,7 @@
 extern void ubh_brelse_uspi (struct ufs_sb_private_info *);
 extern void ubh_mark_buffer_dirty (struct ufs_buffer_head *);
 extern void ubh_mark_buffer_uptodate (struct ufs_buffer_head *, int);
-extern void ubh_ll_rw_block(int, struct ufs_buffer_head *);
-extern void ubh_wait_on_buffer (struct ufs_buffer_head *);
+extern void ubh_sync_block(struct ufs_buffer_head *);
 extern void ubh_bforget (struct ufs_buffer_head *);
 extern int  ubh_buffer_dirty (struct ufs_buffer_head *);
 #define ubh_ubhcpymem(mem,ubh,size) _ubh_ubhcpymem_(uspi,mem,ubh,size)