From 8b81f4411eef2334b46cd1004775ca1b8a8b2dc7 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Sun, 18 Jul 2010 17:03:33 +0200
Subject: [PATCH] write_begin and sync_page fixes.

1/ write_begin needs to drop the page lock and failure,
  and generally clean up properly.
2/ sync_page does not need to 'get_block' as a pointer is
  readily available - so just use that with appropriate locking.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 file.c | 53 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 34 insertions(+), 19 deletions(-)

diff --git a/file.c b/file.c
index 2442b43..6275d96 100644
--- a/file.c
+++ b/file.c
@@ -160,8 +160,10 @@ lafs_write_begin(struct file *file, struct address_space *mapping,
 
 	fb = lafs_get_block(ino, first, page, GFP_KERNEL, MKREF(write));
 	dprintk("PREPARE %p\n", fb);
-	if (!fb)
-		return -ENOMEM;
+	if (!fb) {
+		err = -ENOMEM;
+		goto fail;
+	}
 	/* Further lafs_get_block calls cannot fail as both the page
 	 * and the block structures exist
 	 */
@@ -208,14 +210,18 @@ retry:
 		goto retry;
 	}
 	if (err < 0)
-		goto fail;
+		goto fail_unlock;
 	*fsdata = fb;
 	return 0;
 
-fail:
+fail_unlock:
 	lafs_checkpoint_unlock(fs);
-	while (--i >= first)
-		putdref(&fb[i-first], MKREF(write));
+fail:
+	if (fb)
+		for (i = first; i <= last ; i++)
+			putdref(&fb[i-first], MKREF(write));
+	unlock_page(page);
+	page_cache_release(page);
 	return err;
 }
 
@@ -372,6 +378,13 @@ static void lafs_sync_page(struct page *page)
 	struct fs *fs;
 	int bits;
 	int i;
+	int want_flush = 0;
+
+	if (!PageWriteback(page))
+		/* Presumably page is locked - nothing
+		 * we can do
+		 */
+		return;
 
 	mapping = page->mapping;
 	if (!mapping)
@@ -380,21 +393,23 @@ static void lafs_sync_page(struct page *page)
 	fs = fs_from_inode(ino);
 	bits = PAGE_SHIFT - ino->i_blkbits;
 
-	for (i = 0; i < (1<<bits); i++) {
-		struct datablock *b = lafs_get_block(ino, i, page,
-						     GFP_KERNEL, MKREF(sync_page));
-		if (!b)
-			continue;
-		/* If this block is still dirty though the page is in
-		 * writeback, the block must be in the current cluster
-		 */
-		if (test_bit(B_Dirty, &b->b.flags)) {
-			putdref(b, MKREF(sync_page));
-			lafs_cluster_flush(fs, 0);
-			break;
+	spin_lock(&mapping->private_lock);
+	if (PagePrivate(page)) {
+		struct datablock *bl = (struct datablock *)page->private;
+
+		for (i = 0; i < (1<<bits); i++) {
+			/* If this block is still dirty though the page is in
+			 * writeback, the block must be in the current cluster
+			 */
+			if (test_bit(B_Dirty, &bl[i].b.flags)) {
+				want_flush = 1;
+				break;
+			}
 		}
-		putdref(b, MKREF(sync_page));
 	}
+	spin_unlock(&mapping->private_lock);
+	if (want_flush)
+		lafs_cluster_flush(fs, 0);
 }
 
 static int
-- 
2.39.5