From: Josef Bacik <jbacik@redhat.com>
Date: Tue, 10 Feb 2009 13:49:16 -0500
Subject: [mm] kill the zero-length iovec segments handling
Message-id: 1234291777-15344-4-git-send-email-jbacik@redhat.com
O-Subject: [PATCH 03/24] [RHEL 5.4] kill the zero-length iovec segments handling
Bugzilla: 445433
RH-Acked-by: Jeff Layton <jlayton@redhat.com>

This patch is a backport of

4b49643fbb3fa8bf4910f82be02d45e94e8972a4

and is in reference to bz 445433.

This is a revert of 81b0c8713385ce1b1b9058e916edcf9561ad76d6.  This is
needed in order to properly apply some of the following patches.

Signed-off-by: Josef Bacik <jbacik@redhat.com>

diff --git a/mm/filemap.c b/mm/filemap.c
index d413c95..5b88813 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2188,12 +2188,6 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
 			break;
 		}
 
-		if (unlikely(bytes == 0)) {
-			status = 0;
-			copied = 0;
-			goto zero_length_segment;
-		}
-
 		status = a_ops->prepare_write(file, page, offset, offset+bytes);
 		if (unlikely(status)) {
 			loff_t isize = i_size_read(inode);
@@ -2223,8 +2217,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
 			page_cache_release(page);
 			continue;
 		}
-zero_length_segment:
-		if (likely(copied >= 0)) {
+		if (likely(copied > 0)) {
 			if (!status)
 				status = copied;
 
diff --git a/mm/filemap.h b/mm/filemap.h
index c2bff04..a1e10a2 100644
--- a/mm/filemap.h
+++ b/mm/filemap.h
@@ -87,7 +87,7 @@ filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
 	const struct iovec *iov = *iovp;
 	size_t base = *basep;
 
-	do {
+	while (bytes) {
 		int copy = min(bytes, iov->iov_len - base);
 
 		bytes -= copy;
@@ -96,7 +96,7 @@ filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
 			iov++;
 			base = 0;
 		}
-	} while (bytes);
+	}
 	*iovp = iov;
 	*basep = base;
 }