libext2fs: reset handle after inserting new extent

Commit 53422e8a5644e22ea3f6e0efba82a765b72e4308 moved the new extent insertion in ext2fs_extent_set_bmap prior to the modification of the original extent, but the insert function left the handle pointing a the new extent; this left us modifying the -new- extent not the original one, and winding up with a corrupt extent tree something like:

BLOCKS:
(0-1):588791-588792, (0):588791

We need to move back to the previous extent prior to modification, if we inserted a new one.

---

(aside: should there be functions to simply move the handle around, w/o necessarily populating an extent structure?)

(aside2: maybe ext2fs_extent_insert should take a flag saying whether the handle should be moved after the insertion; moving it around to back where we want to be seems a bit tedious)

index 35b080e..9ea5c30 100644
@@ -1257,6 +1257,11 @@ again:
 					EXT2_EXTENT_INSERT_AFTER, &newextent);
 			if (retval)
 				goto done;
+			/* Now pointing at new extent; move back to prev */
+			retval = ext2fs_extent_get(handle, EXT2_EXTENT_PREV,
+						   &extent);
+			if (retval)
+				goto done;
 		}
 		extent.e_len--;
 		retval = ext2fs_extent_replace(handle, 0, &extent);

Hmm, I just thought of something awful; what if the insert resulted in a node split? Instead of using ext2fs_extent_get(EXT2_EXTENT_PREV), we may need to use ext2fs_extent_goto() to seek to the correct logical block instead.

- Ted

Hm....

so PREV doesn't go to the node for the previous logical block, but to what, the node to the left at this level? Guess I need to read more carefully...

-Eric

Commit 53422e8a5644e22ea3f6e0efba82a765b72e4308 moved the new extent insertion in ext2fs_extent_set_bmap prior to the modification of the original extent, but the insert function left the handle pointing a the new extent; this left us modifying the -new- extent not the original one, and winding up with a corrupt extent tree something like:

BLOCKS:
(0-1):588791-588792, (0):588791

We need to move back to the previous extent prior to modification, if we inserted a new one.

V2: Use extent_goto vs. extent_get.

---

index 35b080e..4a4fd2c 100644
@@ -1257,6 +1257,10 @@ again:
 					EXT2_EXTENT_INSERT_AFTER, &newextent);
 			if (retval)
 				goto done;
+			/* Now pointing at inserted extent; move back to prev */
+			retval = ext2fs_extent_goto(handle, logical - 1);
+			if (retval)
+				goto done;
 		}
 		extent.e_len--;
 		retval = ext2fs_extent_replace(handle, 0, &extent);