[PATCH] Fix and add EXPORT_SYMBOL(filemap_write_and_wait)

This patch add EXPORT_SYMBOL(filemap_write_and_wait) and use it.

See mm/filemap.c:

And changes the filemap_write_and_wait() and filemap_write_and_wait_range().

Current filemap_write_and_wait() doesn't wait if filemap_fdatawrite()
returns error.  However, even if filemap_fdatawrite() returned an
error, it may have submitted the partially data pages to the device.
(e.g. in the case of -ENOSPC)

<quotation>
Andrew Morton writes,

If filemap_fdatawrite() returns an error, this might be due to some
I/O problem: dead disk, unplugged cable, etc.  Given the generally
crappy quality of the kernel's handling of such exceptions, there's a
good chance that the filemap_fdatawait() will get stuck in D state
forever.
</quotation>

So, this patch doesn't wait if filemap_fdatawrite() returns the -EIO.

Trond, could you please review the nfs part?  Especially I'm not sure,
nfs must use the "filemap_fdatawrite(inode->i_mapping) == 0", or not.

Acked-by: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 411c1f7..9558f51 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1148,8 +1148,7 @@
 	/* BB check if we need to refresh inode from server now ? BB */
 
 	/* need to flush data before changing file size on server */
-	filemap_fdatawrite(direntry->d_inode->i_mapping);
-	filemap_fdatawait(direntry->d_inode->i_mapping);
+	filemap_write_and_wait(direntry->d_inode->i_mapping);
 
 	if (attrs->ia_valid & ATTR_SIZE) {
 		/* To avoid spurious oplock breaks from server, in the case of