[PATCH] async write errors: fix spurious fs truncate errors

From: Oliver Xymoron <oxymoron@waste.org>

Currently, a writepage() which detects that it is writing outside i_size (due
to concurrent truncate) will abandon the write, returning -EIO.

The return value will bogusly cause an error to be recorded in the
address_space.  So convert all those writepage() instances to return zero in
this case.

fs/buffer.c

@@ -2610,7 +2610,7 @@ int block_write_full_page(struct page *page, get_block_t *get_block,
 		 */
 		block_invalidatepage(page, 0);
 		unlock_page(page);
-		return -EIO;
+		return 0; /* don't care */
 	}
 
 	/*

fs/cifs/file.c

@@ -500,12 +500,19 @@ cifs_partialpagewrite(struct page *page,unsigned from, unsigned to)
 	write_data = kmap(page);
 	write_data += from;
 
-	if((to > PAGE_CACHE_SIZE) || (from > to) || (offset > mapping->host->i_size)) {
+	if((to > PAGE_CACHE_SIZE) || (from > to)) {
 		kunmap(page);
 		FreeXid(xid);
 		return -EIO;
 	}
 
+	/* racing with truncate? */
+	if(offset > mapping->host->i_size) {
+		kunmap(page);
+		FreeXid(xid);
+		return 0; /* don't care */
+	}
+
 	/* check to make sure that we are not extending the file */
 	if(mapping->host->i_size - offset < (loff_t)to)
 		to = (unsigned)(mapping->host->i_size - offset); 

fs/nfs/write.c

@@ -242,7 +242,7 @@ nfs_writepage(struct page *page, struct writeback_control *wbc)
 	offset = i_size & (PAGE_CACHE_SIZE-1);
 
 	/* OK, are we completely out? */
-	err = -EIO;
+	err = 0; /* potential race with truncate - ignore */
 	if (page->index >= end_index+1 || !offset)
 		goto out;
 do_it:

fs/ntfs/aops.c

@@ -811,8 +811,8 @@ static int ntfs_writepage(struct page *page, struct writeback_control *wbc)
 	if (unlikely(page->index >= (vi->i_size + PAGE_CACHE_SIZE - 1) >>
 			PAGE_CACHE_SHIFT)) {
 		unlock_page(page);
-		ntfs_debug("Write outside i_size. Returning i/o error.");
-		return -EIO;
+		ntfs_debug("Write outside i_size - truncated?");
+		return 0;
 	}
 
 	ni = NTFS_I(vi);

fs/reiserfs/inode.c

@@ -2048,8 +2048,8 @@ static int reiserfs_write_full_page(struct page *page, struct writeback_control
         last_offset = inode->i_size & (PAGE_CACHE_SIZE - 1) ;
 	/* no file contents in this page */
 	if (page->index >= end_index + 1 || !last_offset) {
-	    error =  -EIO ;
-	    goto fail ;
+	    error = 0 ;
+	    goto done ;
 	}
 	kaddr = kmap_atomic(page, KM_USER0);
 	memset(kaddr + last_offset, 0, PAGE_CACHE_SIZE-last_offset) ;

fs/smbfs/file.c

@@ -193,7 +193,7 @@ smb_writepage(struct page *page, struct writeback_control *wbc)
 	offset = inode->i_size & (PAGE_CACHE_SIZE-1);
 	/* OK, are we completely out? */
 	if (page->index >= end_index+1 || !offset)
-		return -EIO;
+		return 0; /* truncated - don't care */
 do_it:
 	page_cache_get(page);
 	err = smb_writepage_sync(inode, page, 0, offset);