ubifs: Fix space leak when powercut happens in linking tmpfile

There is a potential space leak problem when powercut happens in linking
tmpfile, in which case, inode node (with nlink=0) and its' data nodes can
be found from tnc (on flash), but there are no dentries related to the
inode, so the file is invisible but takes free space. Detailed process is
shown as:
 ubifs_tmpfile
  ubifs_jnl_update // Add bud A into log area
   ubifs_add_orphan // Add inode into orphan list

     P1             P2
 ubifs_link
  ubifs_delete_orphan // Delete inode from orphan list, then inode won't
		      // be written into orphan area, there is no chance
		      // to delete inode by replaying orphan.
                commit // bud A won't be replayed in next mounting
   >> powercut <<
  ubifs_jnl_update // Link inode to dentry

The root cause is that orphan entry deletion and journal writing(for link)
are interrupted by commit, which makes the two operations are not atomic.
Fix it by doing ubifs_delete_orphan under the protection of c->commit_sem
within ubifs_jnl_update. This is also a preparation to support all creating
new files by orphan inode.

v1 is https://lore.kernel.org/linux-mtd/20200701093227.674945-1-chengzhihao1@huawei.com/

Fixes: 32fe905c17f0 ("ubifs: Fix O_TMPFILE corner case in ubifs_link()")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=208405
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
index 74aee92433d7..2b4b05c2d9b2 100644
--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -643,6 +643,7 @@ static void set_dent_cookie(struct ubifs_info *c, struct ubifs_dent_node *dent)
  * @inode: inode to update
  * @deletion: indicates a directory entry deletion i.e unlink or rmdir
  * @xent: non-zero if the directory entry is an extended attribute entry
+ * @delete_orphan: indicates an orphan entry deletion for @inode
  *
  * This function updates an inode by writing a directory entry (or extended
  * attribute entry), the inode itself, and the parent directory inode (or the
@@ -664,7 +665,7 @@ static void set_dent_cookie(struct ubifs_info *c, struct ubifs_dent_node *dent)
  */
 int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
 		     const struct fscrypt_name *nm, const struct inode *inode,
-		     int deletion, int xent)
+		     int deletion, int xent, int delete_orphan)
 {
 	int err, dlen, ilen, len, lnum, ino_offs, dent_offs, orphan_added = 0;
 	int aligned_dlen, aligned_ilen, sync = IS_DIRSYNC(dir);
@@ -806,6 +807,9 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
 	if (err)
 		goto out_ro;
 
+	if (delete_orphan)
+		ubifs_delete_orphan(c, inode->i_ino);
+
 	finish_reservation(c);
 	spin_lock(&ui->ui_lock);
 	ui->synced_i_size = ui->ui_size;