[PATCH AUTOSEL 5.0 077/262] btrfs: save drop_progress if we drop refs at all

[PATCH AUTOSEL 5.0 077/262] btrfs: save drop_progress if we drop refs at all

[Sasha Levin]

From: Josef Bacik <josef@toxicpanda.com>

[ Upstream commit aea6f028d01d629eda2e958ccd1133e805cda159 ]

Previously we only updated the drop_progress key if we were in the
DROP_REFERENCE stage of snapshot deletion.  This is because the
UPDATE_BACKREF stage checks the flags of the blocks it's converting to
FULL_BACKREF, so if we go over a block we processed before it doesn't
matter, we just don't do anything.

The problem is in do_walk_down() we will go ahead and drop the roots
reference to any blocks that we know we won't need to walk into.

Given subvolume A and snapshot B.  The root of B points to all of the
nodes that belong to A, so all of those nodes have a refcnt > 1.  If B
did not modify those blocks it'll hit this condition in do_walk_down

if (!wc->update_ref ||
    generation <= root->root_key.offset)
	goto skip;

and in "goto skip" we simply do a btrfs_free_extent() for that bytenr
that we point at.

Now assume we modified some data in B, and then took a snapshot of B and
call it C.  C points to all the nodes in B, making every node the root
of B points to have a refcnt > 1.  This assumes the root level is 2 or
higher.

We delete snapshot B, which does the above work in do_walk_down,
free'ing our ref for nodes we share with A that we didn't modify.  Now
we hit a node we _did_ modify, thus we own.  We need to walk down into
this node and we set wc->stage == UPDATE_BACKREF.  We walk down to level
0 which we also own because we modified data.  We can't walk any further
down and thus now need to walk up and start the next part of the
deletion.  Now walk_up_proc is supposed to put us back into
DROP_REFERENCE, but there's an exception to this

if (level < wc->shared_level)
	goto out;

we are at level == 0, and our shared_level == 1.  We skip out of this
one and go up to level 1.  Since path->slots[1] < nritems we
path->slots[1]++ and break out of walk_up_tree to stop our transaction
and loop back around.  Now in btrfs_drop_snapshot we have this snippet

if (wc->stage == DROP_REFERENCE) {
	level = wc->level;
	btrfs_node_key(path->nodes[level],
		       &root_item->drop_progress,
		       path->slots[level]);
	root_item->drop_level = level;
}

our stage == UPDATE_BACKREF still, so we don't update the drop_progress
key.  This is a problem because we would have done btrfs_free_extent()
for the nodes leading up to our current position.  If we crash or
unmount here and go to remount we'll start over where we were before and
try to free our ref for blocks we've already freed, and thus abort()
out.

Fix this by keeping track of the last place we dropped a reference for
our block in do_walk_down.  Then if wc->stage == UPDATE_BACKREF we know
we'll start over from a place we meant to, and otherwise things continue
to work as they did before.

I have a complicated reproducer for this problem, without this patch
we'll fail to fsck the fs when replaying the log writes log.  With this
patch we can replay the whole log without any fsck or mount failures.

The steps to reproduce this easily are sort of tricky, I had to add a
couple of debug patches to the kernel in order to make it easy,
basically I just needed to make sure we did actually commit the
transaction every time we finished a walk_down_tree/walk_up_tree combo.

The reproducer:

1) Creates a base subvolume.
2) Creates 100k files in the subvolume.
3) Snapshots the base subvolume (snap1).
4) Touches files 5000-6000 in snap1.
5) Snapshots snap1 (snap2).
6) Deletes snap1.

I do this with dm-log-writes, and then replay to every FUA in the log
and fsck the fs.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ copy reproducer steps ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/extent-tree.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d81035b7ea7d..def48123eaa9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8690,6 +8690,8 @@ struct walk_control {
 	u64 refs[BTRFS_MAX_LEVEL];
 	u64 flags[BTRFS_MAX_LEVEL];
 	struct btrfs_key update_progress;
+	struct btrfs_key drop_progress;
+	int drop_level;
 	int stage;
 	int level;
 	int shared_level;
@@ -9028,6 +9030,16 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
 					     ret);
 			}
 		}
+
+		/*
+		 * We need to update the next key in our walk control so we can
+		 * update the drop_progress key accordingly.  We don't care if
+		 * find_next_key doesn't find a key because that means we're at
+		 * the end and are going to clean up now.
+		 */
+		wc->drop_level = level;
+		find_next_key(path, level, &wc->drop_progress);
+
 		ret = btrfs_free_extent(trans, root, bytenr, fs_info->nodesize,
 					parent, root->root_key.objectid,
 					level - 1, 0);
@@ -9378,12 +9390,14 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
 		}
 
 		if (wc->stage == DROP_REFERENCE) {
-			level = wc->level;
-			btrfs_node_key(path->nodes[level],
-				       &root_item->drop_progress,
-				       path->slots[level]);
-			root_item->drop_level = level;
-		}
+			wc->drop_level = wc->level;
+			btrfs_node_key_to_cpu(path->nodes[wc->drop_level],
+					      &wc->drop_progress,
+					      path->slots[wc->drop_level]);
+		}
+		btrfs_cpu_key_to_disk(&root_item->drop_progress,
+				      &wc->drop_progress);
+		root_item->drop_level = wc->drop_level;
 
 		BUG_ON(wc->level == 0);
 		if (btrfs_should_end_transaction(trans) ||
-- 
2.19.1

[PATCH AUTOSEL 5.0 090/262] btrfs: qgroup: Make qgroup async transaction commit more aggressive

[Sasha Levin]

From: Qu Wenruo <wqu@suse.com>

[ Upstream commit f5fef4593653dfa2a865c485bb81415de51d5c99 ]

[BUG]
Btrfs qgroup will still hit EDQUOT under the following case:

  $ dev=/dev/test/test
  $ mnt=/mnt/btrfs
  $ umount $mnt &> /dev/null
  $ umount $dev &> /dev/null

  $ mkfs.btrfs -f $dev
  $ mount $dev $mnt -o nospace_cache

  $ btrfs subv create $mnt/subv
  $ btrfs quota enable $mnt
  $ btrfs quota rescan -w $mnt
  $ btrfs qgroup limit -e 1G $mnt/subv

  $ fallocate -l 900M $mnt/subv/padding
  $ sync

  $ rm $mnt/subv/padding

  # Hit EDQUOT
  $ xfs_io -f -c "pwrite 0 512M" $mnt/subv/real_file

[CAUSE]
Since commit a514d63882c3 ("btrfs: qgroup: Commit transaction in advance
to reduce early EDQUOT"), btrfs is not forced to commit transaction to
reclaim more quota space.

Instead, we just check pertrans metadata reservation against some
threshold and try to do asynchronously transaction commit.

However in above case, the pertrans metadata reservation is pretty small
thus it will never trigger asynchronous transaction commit.

[FIX]
Instead of only accounting pertrans metadata reservation, we calculate
how much free space we have, and if there isn't much free space left,
commit transaction asynchronously to try to free some space.

This may slow down the fs when we have less than 32M free qgroup space,
but should reduce a lot of false EDQUOT, so the cost should be
acceptable.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/qgroup.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 4e473a998219..f7a7ac82c86a 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2842,16 +2842,15 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
 /*
  * Two limits to commit transaction in advance.
  *
- * For RATIO, it will be 1/RATIO of the remaining limit
- * (excluding data and prealloc meta) as threshold.
+ * For RATIO, it will be 1/RATIO of the remaining limit as threshold.
  * For SIZE, it will be in byte unit as threshold.
  */
-#define QGROUP_PERTRANS_RATIO		32
-#define QGROUP_PERTRANS_SIZE		SZ_32M
+#define QGROUP_FREE_RATIO		32
+#define QGROUP_FREE_SIZE		SZ_32M
 static bool qgroup_check_limits(struct btrfs_fs_info *fs_info,
 				const struct btrfs_qgroup *qg, u64 num_bytes)
 {
-	u64 limit;
+	u64 free;
 	u64 threshold;
 
 	if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_RFER) &&
@@ -2870,20 +2869,21 @@ static bool qgroup_check_limits(struct btrfs_fs_info *fs_info,
 	 */
 	if ((qg->lim_flags & (BTRFS_QGROUP_LIMIT_MAX_RFER |
 			      BTRFS_QGROUP_LIMIT_MAX_EXCL))) {
-		if (qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_EXCL)
-			limit = qg->max_excl;
-		else
-			limit = qg->max_rfer;
-		threshold = (limit - qg->rsv.values[BTRFS_QGROUP_RSV_DATA] -
-			    qg->rsv.values[BTRFS_QGROUP_RSV_META_PREALLOC]) /
-			    QGROUP_PERTRANS_RATIO;
-		threshold = min_t(u64, threshold, QGROUP_PERTRANS_SIZE);
+		if (qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_EXCL) {
+			free = qg->max_excl - qgroup_rsv_total(qg) - qg->excl;
+			threshold = min_t(u64, qg->max_excl / QGROUP_FREE_RATIO,
+					  QGROUP_FREE_SIZE);
+		} else {
+			free = qg->max_rfer - qgroup_rsv_total(qg) - qg->rfer;
+			threshold = min_t(u64, qg->max_rfer / QGROUP_FREE_RATIO,
+					  QGROUP_FREE_SIZE);
+		}
 
 		/*
 		 * Use transaction_kthread to commit transaction, so we no
 		 * longer need to bother nested transaction nor lock context.
 		 */
-		if (qg->rsv.values[BTRFS_QGROUP_RSV_META_PERTRANS] > threshold)
+		if (free < threshold)
 			btrfs_commit_transaction_locksafe(fs_info);
 	}
 
-- 
2.19.1

[PATCH AUTOSEL 5.0 091/262] btrfs: don't enospc all tickets on flush failure

[Sasha Levin]

From: Josef Bacik <josef@toxicpanda.com>

[ Upstream commit f91587e4151e84f798f37839dddd3e4152fb4c76 ]

With the introduction of the per-inode block_rsv it became possible to
have really really large reservation requests made because of data
fragmentation.  Since the ticket stuff assumed that we'd always have
relatively small reservation requests it just killed all tickets if we
were unable to satisfy the current request.

However, this is generally not the case anymore.  So fix this logic to
instead see if we had a ticket that we were able to give some
reservation to, and if we were continue the flushing loop again.

Likewise we make the tickets use the space_info_add_old_bytes() method
of returning what reservation they did receive in hopes that it could
satisfy reservations down the line.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/extent-tree.c | 45 +++++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 20 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index def48123eaa9..a4eef51e2942 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4808,6 +4808,7 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
 }
 
 struct reserve_ticket {
+	u64 orig_bytes;
 	u64 bytes;
 	int error;
 	struct list_head list;
@@ -5030,7 +5031,7 @@ static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
 		!test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
 }
 
-static void wake_all_tickets(struct list_head *head)
+static bool wake_all_tickets(struct list_head *head)
 {
 	struct reserve_ticket *ticket;
 
@@ -5039,7 +5040,10 @@ static void wake_all_tickets(struct list_head *head)
 		list_del_init(&ticket->list);
 		ticket->error = -ENOSPC;
 		wake_up(&ticket->wait);
+		if (ticket->bytes != ticket->orig_bytes)
+			return true;
 	}
+	return false;
 }
 
 /*
@@ -5094,8 +5098,12 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 		if (flush_state > COMMIT_TRANS) {
 			commit_cycles++;
 			if (commit_cycles > 2) {
-				wake_all_tickets(&space_info->tickets);
-				space_info->flush = 0;
+				if (wake_all_tickets(&space_info->tickets)) {
+					flush_state = FLUSH_DELAYED_ITEMS_NR;
+					commit_cycles--;
+				} else {
+					space_info->flush = 0;
+				}
 			} else {
 				flush_state = FLUSH_DELAYED_ITEMS_NR;
 			}
@@ -5147,10 +5155,11 @@ static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
 
 static int wait_reserve_ticket(struct btrfs_fs_info *fs_info,
 			       struct btrfs_space_info *space_info,
-			       struct reserve_ticket *ticket, u64 orig_bytes)
+			       struct reserve_ticket *ticket)
 
 {
 	DEFINE_WAIT(wait);
+	u64 reclaim_bytes = 0;
 	int ret = 0;
 
 	spin_lock(&space_info->lock);
@@ -5171,14 +5180,12 @@ static int wait_reserve_ticket(struct btrfs_fs_info *fs_info,
 		ret = ticket->error;
 	if (!list_empty(&ticket->list))
 		list_del_init(&ticket->list);
-	if (ticket->bytes && ticket->bytes < orig_bytes) {
-		u64 num_bytes = orig_bytes - ticket->bytes;
-		update_bytes_may_use(space_info, -num_bytes);
-		trace_btrfs_space_reservation(fs_info, "space_info",
-					      space_info->flags, num_bytes, 0);
-	}
+	if (ticket->bytes && ticket->bytes < ticket->orig_bytes)
+		reclaim_bytes = ticket->orig_bytes - ticket->bytes;
 	spin_unlock(&space_info->lock);
 
+	if (reclaim_bytes)
+		space_info_add_old_bytes(fs_info, space_info, reclaim_bytes);
 	return ret;
 }
 
@@ -5204,6 +5211,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
 {
 	struct reserve_ticket ticket;
 	u64 used;
+	u64 reclaim_bytes = 0;
 	int ret = 0;
 
 	ASSERT(orig_bytes);
@@ -5239,6 +5247,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
 	 * the list and we will do our own flushing further down.
 	 */
 	if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
+		ticket.orig_bytes = orig_bytes;
 		ticket.bytes = orig_bytes;
 		ticket.error = 0;
 		init_waitqueue_head(&ticket.wait);
@@ -5279,25 +5288,21 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
 		return ret;
 
 	if (flush == BTRFS_RESERVE_FLUSH_ALL)
-		return wait_reserve_ticket(fs_info, space_info, &ticket,
-					   orig_bytes);
+		return wait_reserve_ticket(fs_info, space_info, &ticket);
 
 	ret = 0;
 	priority_reclaim_metadata_space(fs_info, space_info, &ticket);
 	spin_lock(&space_info->lock);
 	if (ticket.bytes) {
-		if (ticket.bytes < orig_bytes) {
-			u64 num_bytes = orig_bytes - ticket.bytes;
-			update_bytes_may_use(space_info, -num_bytes);
-			trace_btrfs_space_reservation(fs_info, "space_info",
-						      space_info->flags,
-						      num_bytes, 0);
-
-		}
+		if (ticket.bytes < orig_bytes)
+			reclaim_bytes = orig_bytes - ticket.bytes;
 		list_del_init(&ticket.list);
 		ret = -ENOSPC;
 	}
 	spin_unlock(&space_info->lock);
+
+	if (reclaim_bytes)
+		space_info_add_old_bytes(fs_info, space_info, reclaim_bytes);
 	ASSERT(list_empty(&ticket.list));
 	return ret;
 }
-- 
2.19.1