3 files changed, 42 insertions, 5 deletions

diff --git a/module/zfs/txg.c b/module/zfs/txg.c
index c234567d7..aefda6f69 100644
--- a/module/zfs/txg.c
+++ b/module/zfs/txg.c
@@ -382,6 +382,15 @@ txg_sync_thread(dsl_pool_t *dp)
 	callb_cpr_t cpr;
 	uint64_t start, delta;
 
+#ifdef _KERNEL
+	/*
+	 * Annotate this process with a flag that indicates that it is
+	 * unsafe to use KM_SLEEP during memory allocations due to the
+	 * potential for a deadlock.  KM_PUSHPAGE should be used instead.
+	 */
+	current->flags |= PF_NOFS;
+#endif /* _KERNEL */
+
 	txg_thread_enter(tx, &cpr);
 
 	start = delta = 0;
diff --git a/module/zfs/zpl_file.c b/module/zfs/zpl_file.c
index 2e9f72ad1..9c27b7f1d 100644
--- a/module/zfs/zpl_file.c
+++ b/module/zfs/zpl_file.c
@@ -357,8 +357,16 @@ zpl_putpage(struct page *pp, struct writeback_control *wbc, void *data)
 
 	ASSERT(PageLocked(pp));
 	ASSERT(!PageWriteback(pp));
-
+	ASSERT(!(current->flags & PF_NOFS));
+
+	/*
+	 * Annotate this call path with a flag that indicates that it is
+	 * unsafe to use KM_SLEEP during memory allocations due to the
+	 * potential for a deadlock.  KM_PUSHPAGE should be used instead.
+	 */
+	current->flags |= PF_NOFS;
 	(void) zfs_putpage(mapping->host, pp, wbc);
+	current->flags &= ~PF_NOFS;
 
 	return (0);
 }
diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 07bda6dba..60ff64ebe 100644
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -540,6 +540,14 @@ zvol_write(void *arg)
 	dmu_tx_t *tx;
 	rl_t *rl;
 
+	/*
+	 * Annotate this call path with a flag that indicates that it is
+	 * unsafe to use KM_SLEEP during memory allocations due to the
+	 * potential for a deadlock.  KM_PUSHPAGE should be used instead.
+	 */
+	ASSERT(!(current->flags & PF_NOFS));
+	current->flags |= PF_NOFS;
+
 	if (req->cmd_flags & VDEV_REQ_FLUSH)
 		zil_commit(zv->zv_zilog, ZVOL_OBJ);
 
@@ -548,7 +556,7 @@ zvol_write(void *arg)
 	 */
 	if (size == 0) {
 		blk_end_request(req, 0, size);
-		return;
+		goto out;
 	}
 
 	rl = zfs_range_lock(&zv->zv_znode, offset, size, RL_WRITER);
@@ -562,7 +570,7 @@ zvol_write(void *arg)
 		dmu_tx_abort(tx);
 		zfs_range_unlock(rl);
 		blk_end_request(req, -error, size);
-		return;
+		goto out;
 	}
 
 	error = dmu_write_req(zv->zv_objset, ZVOL_OBJ, req, tx);
@@ -578,6 +586,8 @@ zvol_write(void *arg)
 		zil_commit(zv->zv_zilog, ZVOL_OBJ);
 
 	blk_end_request(req, -error, size);
+out:
+	current->flags &= ~PF_NOFS;
 }
 
 #ifdef HAVE_BLK_QUEUE_DISCARD
@@ -592,14 +602,22 @@ zvol_discard(void *arg)
 	int error;
 	rl_t *rl;
 
+	/*
+	 * Annotate this call path with a flag that indicates that it is
+	 * unsafe to use KM_SLEEP during memory allocations due to the
+	 * potential for a deadlock.  KM_PUSHPAGE should be used instead.
+	 */
+	ASSERT(!(current->flags & PF_NOFS));
+	current->flags |= PF_NOFS;
+
 	if (offset + size > zv->zv_volsize) {
 		blk_end_request(req, -EIO, size);
-		return;
+		goto out;
 	}
 
 	if (size == 0) {
 		blk_end_request(req, 0, size);
-		return;
+		goto out;
 	}
 
 	rl = zfs_range_lock(&zv->zv_znode, offset, size, RL_WRITER);
@@ -613,6 +631,8 @@ zvol_discard(void *arg)
 	zfs_range_unlock(rl);
 
 	blk_end_request(req, -error, size);
+out:
+	current->flags &= ~PF_NOFS;
 }
 #endif /* HAVE_BLK_QUEUE_DISCARD */