1 files changed, 30 insertions, 21 deletions

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 70f42ea86dfb..2011620008de 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -134,7 +134,7 @@ xfs_trans_reserve(
 	bool		rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;
 
 	/* Mark this thread as being in a transaction */
-	current_set_flags_nested(&tp->t_pflags, PF_FSTRANS);
+	current_set_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
 
 	/*
 	 * Attempt to reserve the needed disk blocks by decrementing
@@ -144,7 +144,7 @@ xfs_trans_reserve(
 	if (blocks > 0) {
 		error = xfs_mod_fdblocks(tp->t_mountp, -((int64_t)blocks), rsvd);
 		if (error != 0) {
-			current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
+			current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
 			return -ENOSPC;
 		}
 		tp->t_blk_res += blocks;
@@ -221,7 +221,7 @@ undo_blocks:
 		tp->t_blk_res = 0;
 	}
 
-	current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
+	current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
 
 	return error;
 }
@@ -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.
@@ -914,7 +936,7 @@ __xfs_trans_commit(
 
 	xfs_log_commit_cil(mp, tp, &commit_lsn, regrant);
 
-	current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
+	current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
 	xfs_trans_free(tp);
 
 	/*
@@ -944,7 +966,7 @@ out_unreserve:
 		if (commit_lsn == -1 && !error)
 			error = -EIO;
 	}
-	current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
+	current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
 	xfs_trans_free_items(tp, NULLCOMMITLSN, !!error);
 	xfs_trans_free(tp);
 
@@ -998,7 +1020,7 @@ xfs_trans_cancel(
 		xfs_log_done(mp, tp->t_ticket, NULL, false);
 
 	/* mark this thread as no longer being in a transaction */
-	current_restore_flags_nested(&tp->t_pflags, PF_FSTRANS);
+	current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
 
 	xfs_trans_free_items(tp, NULLCOMMITLSN, dirty);
 	xfs_trans_free(tp);
@@ -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);
-}