NTFS: Change ntfs_rl_truncate_nolock() to throw away the runlist if the new

      length is zero.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

2 files changed, 15 insertions, 1 deletions

diff --git a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
index 45f806fc45f9..79d9899b3b01 100644
--- a/fs/ntfs/ChangeLog
+++ b/fs/ntfs/ChangeLog
@@ -51,6 +51,8 @@ ToDo/Notes:
         - Report unrepresentable inodes during ntfs_readdir() as KERN_WARNING
           messages and include the inode number.  Thanks to Yura Pakhuchiy for
           pointing this out.
+        - Change ntfs_rl_truncate_nolock() to throw away the runlist if the new
+          length is zero.
 
 2.1.23 - Implement extension of resident files and make writing safe as well as
          many bug fixes, cleanups, and enhancements...
diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c
index e4c4716939de..539fa2b7f361 100644
--- a/fs/ntfs/runlist.c
+++ b/fs/ntfs/runlist.c
@@ -1455,6 +1455,7 @@ err_out:
 
 /**
  * ntfs_rl_truncate_nolock - truncate a runlist starting at a specified vcn
+ * @vol:        ntfs volume (needed for error output)
  * @runlist:    runlist to truncate
  * @new_length: the new length of the runlist in VCNs
  *
@@ -1462,12 +1463,16 @@ err_out:
  * holding the runlist elements to a length of @new_length VCNs.
  *
  * If @new_length lies within the runlist, the runlist elements with VCNs of
- * @new_length and above are discarded.
+ * @new_length and above are discarded.  As a special case if @new_length is
+ * zero, the runlist is discarded and set to NULL.
  *
  * If @new_length lies beyond the runlist, a sparse runlist element is added to
  * the end of the runlist @runlist or if the last runlist element is a sparse
  * one already, this is extended.
  *
+ * Note, no checking is done for unmapped runlist elements.  It is assumed that
+ * the caller has mapped any elements that need to be mapped already.
+ *
  * Return 0 on success and -errno on error.
  *
  * Locking: The caller must hold @runlist->lock for writing.
@@ -1482,6 +1487,13 @@ int ntfs_rl_truncate_nolock(const ntfs_volume *vol, runlist *const runlist,
         BUG_ON(!runlist);
         BUG_ON(new_length < 0);
         rl = runlist->rl;
+        if (!new_length) {
+                ntfs_debug("Freeing runlist.");
+                runlist->rl = NULL;
+                if (rl)
+                        ntfs_free(rl);
+                return 0;
+        }
         if (unlikely(!rl)) {
                 /*
                  * Create a runlist consisting of a sparse runlist element of