Illumos 4950 - files sometimes can't be removed from a full filesystem

4950 files sometimes can't be removed from a full filesystem
Reviewed by: Adam Leventhal <[email protected]>
Reviewed by: George Wilson <[email protected]>
Reviewed by: Sebastien Roy <[email protected]>
Reviewed by: Boris Protopopov <[email protected]>
Approved by: Dan McDonald <[email protected]>

References:
  https://www.illumos.org/issues/4950
  https://github.com/illumos/illumos-gate/commit/4bb7380

Porting notes:
- ZoL currently does not log discards to zvols, so the portion of
  this patch that modifies the discard logging to mark it as
  freeing space has been discarded.

2. may_delete_now had been removed from zfs_remove() in ZoL.
   It has been reintroduced.

3. We do not try to emulate vnodes, so the following lines are
   not valid on Linux:

	mutex_enter(&vp->v_lock);
	may_delete_now = vp->v_count == 1 && !vn_has_cached_data(vp);
	mutex_exit(&vp->v_lock);

  This has been replaced with:

	mutex_enter(&zp->z_lock);
	may_delete_now = atomic_read(&ip->i_count) == 1 && !(zp->z_is_mapped);
	mutex_exit(&zp->z_lock);

Ported-by: Richard Yao <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>

1 files changed, 14 insertions, 1 deletions

diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 311613ae5..2f003de9f 100644
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
  * Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2015 by Chunwei Chen. All rights reserved.
  */
@@ -1525,6 +1525,7 @@ zfs_remove(struct inode *dip, char *name, cred_t *cr)
 	uint64_t	obj = 0;
 	zfs_dirlock_t	*dl;
 	dmu_tx_t	*tx;
+	boolean_t	may_delete_now;
 	boolean_t	unlinked;
 	uint64_t	txtype;
 	pathname_t	*realnmp = NULL;
@@ -1584,6 +1585,10 @@ top:
 		dnlc_remove(dvp, name);
 #endif /* HAVE_DNLC */
 
+	mutex_enter(&zp->z_lock);
+	may_delete_now = atomic_read(&ip->i_count) == 1 && !(zp->z_is_mapped);
+	mutex_exit(&zp->z_lock);
+
 	/*
 	 * We never delete the znode and always place it in the unlinked
 	 * set.  The dentry cache will always hold the last reference and
@@ -1609,6 +1614,14 @@ top:
 	/* charge as an update -- would be nice not to charge at all */
 	dmu_tx_hold_zap(tx, zsb->z_unlinkedobj, FALSE, NULL);
 
+	/*
+	 * Mark this transaction as typically resulting in a net free of
+	 * space, unless object removal will be delayed indefinitely
+	 * (due to active holds on the vnode due to the file being open).
+	 */
+	if (may_delete_now)
+		dmu_tx_mark_netfree(tx);
+
 	error = dmu_tx_assign(tx, waited ? TXG_WAITED : TXG_NOWAIT);
 	if (error) {
 		zfs_dirent_unlock(dl);