In ext2fs_extent_set_bmap() and ext2fs_punch_extent(), fix the parents
when altering either end of an extent so that the parent nodes reflect
the added mapping.
There's a slight complication to using fix_parents: if there are two
mappings to an lblk in the tree, the value of handle->path->curr can
point to either extent afterwards), which is documented in a comment.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
lib/ext2fs/extent.c | 30 ++++++++++++++++++++++++------
lib/ext2fs/punch.c | 14 ++++++++++----
2 files changed, 34 insertions(+), 10 deletions(-)
diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
index f27344e..80ce88f 100644
--- a/lib/ext2fs/extent.c
+++ b/lib/ext2fs/extent.c
@@ -720,7 +720,14 @@ errcode_t ext2fs_extent_goto(ext2_extent_handle_t handle,
* and so on.
*
* Safe to call for any position in node; if not at the first entry,
- * will simply return.
+ * it will simply return.
+ *
+ * Note a subtlety of this function -- if there happen to be two extents
+ * mapping the same lblk and someone calls fix_parents on the second of the two
+ * extents, the position of the extent handle after the call will be the second
+ * extent if nothing happened, or the first extent if something did. A caller
+ * in this situation must use ext2fs_extent_goto() after calling this function.
+ * Or simply don't map the same lblk with two extents, ever.
*/
errcode_t ext2fs_extent_fix_parents(ext2_extent_handle_t handle)
{
@@ -1379,17 +1386,25 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle,
&next_extent);
if (retval)
goto done;
- retval = ext2fs_extent_fix_parents(handle);
- if (retval)
- goto done;
} else
retval = ext2fs_extent_insert(handle,
EXT2_EXTENT_INSERT_AFTER, &newextent);
if (retval)
goto done;
- /* Now pointing at inserted extent; move back to prev */
+ retval = ext2fs_extent_fix_parents(handle);
+ if (retval)
+ goto done;
+ /*
+ * Now pointing at inserted extent; move back to prev.
+ *
+ * We cannot use EXT2_EXTENT_PREV to go back; note the
+ * subtlety in the comment for fix_parents().
+ */
+ retval = ext2fs_extent_goto(handle, logical);
+ if (retval)
+ goto done;
retval = ext2fs_extent_get(handle,
- EXT2_EXTENT_PREV_LEAF,
+ EXT2_EXTENT_CURRENT,
&extent);
if (retval)
goto done;
@@ -1422,6 +1437,9 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle,
0, &newextent);
if (retval)
goto done;
+ retval = ext2fs_extent_fix_parents(handle);
+ if (retval)
+ goto done;
retval = ext2fs_extent_get(handle,
EXT2_EXTENT_NEXT_LEAF,
&extent);
diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
index a3d020e..2a2cf10 100644
--- a/lib/ext2fs/punch.c
+++ b/lib/ext2fs/punch.c
@@ -343,10 +343,16 @@ static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
EXT2_EXTENT_INSERT_AFTER, &newex);
if (retval)
goto errout;
- /* Now pointing at inserted extent; so go back */
- retval = ext2fs_extent_get(handle,
- EXT2_EXTENT_PREV_LEAF,
- &newex);
+ retval = ext2fs_extent_fix_parents(handle);
+ if (retval)
+ goto errout;
+ /*
+ * Now pointing at inserted extent; so go back.
+ *
+ * We cannot use EXT2_EXTENT_PREV to go back; note the
+ * subtlety in the comment for fix_parents().
+ */
+ retval = ext2fs_extent_goto(handle, extent.e_lblk);
if (retval)
goto errout;
}
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
