Merge tag 'xfs-4.12-merge-7' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull xfs updates from Darrick Wong:
 "Here are the XFS changes for 4.12. The big new feature for this
  release is the new space mapping ioctl that we've been discussing
  since LSF2016, but other than that most of the patches are larger bug
  fixes, memory corruption prevention, and other cleanups.

  Summary:
   - various code cleanups
   - introduce GETFSMAP ioctl
   - various refactoring
   - avoid dio reads past eof
   - fix memory corruption and other errors with fragmented directory blocks
   - fix accidental userspace memory corruptions
   - publish fs uuid in superblock
   - make fstrim terminatable
   - fix race between quotaoff and in-core inode creation
   - avoid use-after-free when finishing up w/ buffer heads
   - reserve enough space to handle bmap tree resizing during cow remap"

* tag 'xfs-4.12-merge-7' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (53 commits)
  xfs: fix use-after-free in xfs_finish_page_writeback
  xfs: reserve enough blocks to handle btree splits when remapping
  xfs: wait on new inodes during quotaoff dquot release
  xfs: update ag iterator to support wait on new inodes
  xfs: support ability to wait on new inodes
  xfs: publish UUID in struct super_block
  xfs: Allow user to kill fstrim process
  xfs: better log intent item refcount checking
  xfs: fix up quotacheck buffer list error handling
  xfs: remove xfs_trans_ail_delete_bulk
  xfs: don't use bool values in trace buffers
  xfs: fix getfsmap userspace memory corruption while setting OF_LAST
  xfs: fix __user annotations for xfs_ioc_getfsmap
  xfs: corruption needs to respect endianess too!
  xfs: use NULL instead of 0 to initialize a pointer in xfs_ioc_getfsmap
  xfs: use NULL instead of 0 to initialize a pointer in xfs_getfsmap
  xfs: simplify validation of the unwritten extent bit
  xfs: remove unused values from xfs_exntst_t
  xfs: remove the unused XFS_MAXLINK_1 define
  xfs: more do_div cleanups
  ...

1 files changed, 24 insertions, 15 deletions

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index f5969c8274fc..2011620008de 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -263,6 +263,28 @@ xfs_trans_alloc(
 }
 
 /*
+ * Create an empty transaction with no reservation.  This is a defensive
+ * mechanism for routines that query metadata without actually modifying
+ * them -- if the metadata being queried is somehow cross-linked (think a
+ * btree block pointer that points higher in the tree), we risk deadlock.
+ * However, blocks grabbed as part of a transaction can be re-grabbed.
+ * The verifiers will notice the corrupt block and the operation will fail
+ * back to userspace without deadlocking.
+ *
+ * Note the zero-length reservation; this transaction MUST be cancelled
+ * without any dirty data.
+ */
+int
+xfs_trans_alloc_empty(
+	struct xfs_mount		*mp,
+	struct xfs_trans		**tpp)
+{
+	struct xfs_trans_res		resv = {0};
+
+	return xfs_trans_alloc(mp, &resv, 0, 0, XFS_TRANS_NO_WRITECOUNT, tpp);
+}
+
+/*
  * Record the indicated change to the given field for application
  * to the file system's superblock when the transaction commits.
  * For now, just store the change in the transaction structure.
@@ -1012,17 +1034,14 @@ xfs_trans_cancel(
  * chunk we've been working on and get a new transaction to continue.
  */
 int
-__xfs_trans_roll(
+xfs_trans_roll(
 	struct xfs_trans	**tpp,
-	struct xfs_inode	*dp,
-	int			*committed)
+	struct xfs_inode	*dp)
 {
 	struct xfs_trans	*trans;
 	struct xfs_trans_res	tres;
 	int			error;
 
-	*committed = 0;
-
 	/*
 	 * Ensure that the inode is always logged.
 	 */
@@ -1048,7 +1067,6 @@ __xfs_trans_roll(
 	if (error)
 		return error;
 
-	*committed = 1;
 	trans = *tpp;
 
 	/*
@@ -1071,12 +1089,3 @@ __xfs_trans_roll(
 		xfs_trans_ijoin(trans, dp, 0);
 	return 0;
 }
-
-int
-xfs_trans_roll(
-	struct xfs_trans	**tpp,
-	struct xfs_inode	*dp)
-{
-	int			committed;
-	return __xfs_trans_roll(tpp, dp, &committed);
-}