Btrfs: Fix a number of inline extent problems that Yan Zheng reported.

The fixes do a number of things:

1) Most btrfs_drop_extent callers will try to leave the inline extents in
place.  It can truncate bytes off the beginning of the inline extent if
required.

2) writepage can now update the inline extent, allowing mmap writes to
go directly into the inline extent.

3) btrfs_truncate_in_transaction truncates inline extents

4) extent_map.c fixed to not merge inline extent mappings and hole
mappings together

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5d10b64..0c65141 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -89,6 +89,9 @@
 	ret = btrfs_drop_extents(trans, root, inode,
 				 start, start + num_bytes, start, &alloc_hint);
 
+	if (alloc_hint == EXTENT_MAP_INLINE)
+		goto out;
+
 	ret = btrfs_alloc_extent(trans, root, inode->i_ino, num_bytes, 0,
 				 alloc_hint, (u64)-1, &ins, 1);
 	if (ret) {
@@ -558,6 +561,7 @@
 	u64 item_end = 0;
 	int found_extent;
 	int del_item;
+	int extent_type = -1;
 
 	btrfs_drop_extent_cache(inode, inode->i_size, (u64)-1);
 	path = btrfs_alloc_path();
@@ -597,10 +601,15 @@
 		if (found_type == BTRFS_EXTENT_DATA_KEY) {
 			fi = btrfs_item_ptr(leaf, path->slots[0],
 					    struct btrfs_file_extent_item);
-			if (btrfs_file_extent_type(leaf, fi) !=
-			    BTRFS_FILE_EXTENT_INLINE) {
+			extent_type = btrfs_file_extent_type(leaf, fi);
+			if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
 				item_end +=
 				    btrfs_file_extent_num_bytes(leaf, fi);
+			} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+				struct btrfs_item *item = btrfs_item_nr(leaf,
+							        path->slots[0]);
+				item_end += btrfs_file_extent_inline_len(leaf,
+									 item);
 			}
 		}
 		if (found_type == BTRFS_CSUM_ITEM_KEY) {
@@ -608,7 +617,7 @@
 						  inode->i_size);
 			BUG_ON(ret);
 		}
-		if (item_end < inode->i_size) {
+		if (item_end <= inode->i_size) {
 			if (found_type == BTRFS_DIR_ITEM_KEY) {
 				found_type = BTRFS_INODE_ITEM_KEY;
 			} else if (found_type == BTRFS_EXTENT_ITEM_KEY) {
@@ -629,9 +638,10 @@
 		found_extent = 0;
 
 		/* FIXME, shrink the extent if the ref count is only 1 */
-		if (found_type == BTRFS_EXTENT_DATA_KEY &&
-			   btrfs_file_extent_type(leaf, fi) !=
-			   BTRFS_FILE_EXTENT_INLINE) {
+		if (found_type != BTRFS_EXTENT_DATA_KEY)
+			goto delete;
+
+		if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
 			u64 num_dec;
 			extent_start = btrfs_file_extent_disk_bytenr(leaf, fi);
 			if (!del_item) {
@@ -659,7 +669,15 @@
 					inode->i_blocks -= num_dec;
 				}
 			}
+		} else if (extent_type == BTRFS_FILE_EXTENT_INLINE &&
+			   !del_item) {
+			u32 newsize = inode->i_size - found_key.offset;
+			newsize = btrfs_file_extent_calc_inline_size(newsize);
+			ret = btrfs_truncate_item(trans, root, path,
+						  newsize, 1);
+			BUG_ON(ret);
 		}
+delete:
 		if (del_item) {
 			ret = btrfs_del_item(trans, root, path);
 			if (ret)
@@ -769,7 +787,7 @@
 		u64 pos = (inode->i_size + mask) & ~mask;
 		u64 block_end = attr->ia_size | mask;
 		u64 hole_size;
-		u64 alloc_hint;
+		u64 alloc_hint = 0;
 
 		if (attr->ia_size <= pos)
 			goto out;
@@ -786,8 +804,11 @@
 					 pos, pos + hole_size, pos,
 					 &alloc_hint);
 
-		err = btrfs_insert_file_extent(trans, root, inode->i_ino,
-					       pos, 0, 0, hole_size);
+		if (alloc_hint != EXTENT_MAP_INLINE) {
+			err = btrfs_insert_file_extent(trans, root,
+						       inode->i_ino,
+						       pos, 0, 0, hole_size);
+		}
 		btrfs_end_transaction(trans, root);
 		mutex_unlock(&root->fs_info->fs_mutex);
 		unlock_extent(em_tree, pos, block_end, GFP_NOFS);
@@ -1531,8 +1552,8 @@
 		em->end = EXTENT_MAP_HOLE;
 	}
 	em->bdev = inode->i_sb->s_bdev;
-	ret = btrfs_lookup_file_extent(NULL, root, path,
-				       objectid, start, 0);
+	ret = btrfs_lookup_file_extent(trans, root, path,
+				       objectid, start, trans != NULL);
 	if (ret < 0) {
 		err = ret;
 		goto out;
@@ -1627,15 +1648,23 @@
 			((u64)root->sectorsize -1);
 		map = kmap(page);
 		ptr = btrfs_file_extent_inline_start(item) + extent_offset;
-		read_extent_buffer(leaf, map + page_offset, ptr, copy_size);
-		
-		if (em->start + copy_size <= em->end) {
-			size = min_t(u64, em->end + 1 - em->start,
-				PAGE_CACHE_SIZE - page_offset) - copy_size;
-			memset(map + page_offset + copy_size, 0, size);
+		if (create == 0 && !PageUptodate(page)) {
+			read_extent_buffer(leaf, map + page_offset, ptr,
+					   copy_size);
+			flush_dcache_page(page);
+		} else if (create && PageUptodate(page)) {
+			if (!trans) {
+				kunmap(page);
+				free_extent_map(em);
+				em = NULL;
+				btrfs_release_path(root, path);
+				trans = btrfs_start_transaction(root, 1);
+				goto again;
+			}
+			write_extent_buffer(leaf, map + page_offset, ptr,
+					    copy_size);
+			btrfs_mark_buffer_dirty(leaf);
 		}
-
-		flush_dcache_page(page);
 		kunmap(page);
 		set_extent_uptodate(em_tree, em->start, em->end, GFP_NOFS);
 		goto insert;