From: Josef Bacik <jbacik@redhat.com>
Date: Tue, 10 Feb 2009 13:49:19 -0500
Subject: [mm] cleanup error handling
Message-id: 1234291777-15344-7-git-send-email-jbacik@redhat.com
O-Subject: [PATCH 06/24] [RHEL 5.4] mm: cleanup error handling
Bugzilla: 445433
RH-Acked-by: Jeff Layton <jlayton@redhat.com>

This is a backport of

64649a58919e66ec21792dbb6c48cb3da22cbd7f

and is in reference to bz 445433.

It consolidates all of the error handling for prepare_write and commit_write
into one area.

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

diff --git a/mm/filemap.c b/mm/filemap.c
index 52bdb97..88113ca 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2186,22 +2186,9 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
 		}
 
 		status = a_ops->prepare_write(file, page, offset, offset+bytes);
-		if (unlikely(status)) {
-			loff_t isize = i_size_read(inode);
+		if (unlikely(status))
+			goto fs_write_aop_error;
 
-			if (status != AOP_TRUNCATED_PAGE)
-				unlock_page(page);
-			page_cache_release(page);
-			if (status == AOP_TRUNCATED_PAGE)
-				continue;
-			/*
-			 * prepare_write() may have instantiated a few blocks
-			 * outside i_size.  Trim these off again.
-			 */
-			if (pos + bytes > isize)
-				vmtruncate(inode, isize);
-			break;
-		}
 		if (likely(nr_segs == 1))
 			copied = filemap_copy_from_user(page, offset,
 							buf, bytes);
@@ -2210,40 +2197,53 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
 						cur_iov, iov_offset, bytes);
 		flush_dcache_page(page);
 		status = a_ops->commit_write(file, page, offset, offset+bytes);
-		if (status == AOP_TRUNCATED_PAGE) {
-			page_cache_release(page);
-			continue;
+		if (unlikely(status < 0 || status == AOP_TRUNCATED_PAGE))
+			goto fs_write_aop_error;
+		if (unlikely(copied != bytes)) {
+			status = -EFAULT;
+			goto fs_write_aop_error;
 		}
+		if (unlikely(status > 0)) /* filesystem did partial write */
+			copied = status;
+
 		if (likely(copied > 0)) {
-			if (!status)
-				status = copied;
-
-			if (status >= 0) {
-				written += status;
-				count -= status;
-				pos += status;
-				buf += status;
-				if (unlikely(nr_segs > 1)) {
-					filemap_set_next_iovec(&cur_iov,
-							&iov_offset, status);
-					if (count)
-						buf = cur_iov->iov_base +
-							iov_offset;
-				} else {
-					iov_offset += status;
-				}
+			written += copied;
+			count -= copied;
+			pos += copied;
+			buf += copied;
+			if (unlikely(nr_segs > 1)) {
+				filemap_set_next_iovec(&cur_iov,
+						&iov_offset, copied);
+				if (count)
+					buf = cur_iov->iov_base + iov_offset;
+			} else {
+				iov_offset += copied;
 			}
 		}
-		if (unlikely(copied != bytes))
-			if (status >= 0)
-				status = -EFAULT;
 		unlock_page(page);
 		mark_page_accessed(page);
 		page_cache_release(page);
-		if (status < 0)
-			break;
 		balance_dirty_pages_ratelimited(mapping);
 		cond_resched();
+		continue;
+
+fs_write_aop_error:
+		if (status != AOP_TRUNCATED_PAGE)
+			unlock_page(page);
+		page_cache_release(page);
+
+		/*
+		 * prepare_write() may have instantiated a few blocks
+		 * outside i_size.  Trim these off again. Don't need
+		 * i_size_read because we hold i_mutex.
+		 */
+		if (pos + bytes > inode->i_size)
+			vmtruncate(inode, inode->i_size);
+		if (status == AOP_TRUNCATED_PAGE)
+			continue;
+		else
+			break;
+
 	} while (count);
 	*ppos = pos;