[PATCH 10/35] btrfs: fix truncate throttling

Josef Bacik
2018-08-30T21:46:02Z

We have a bunch of magic to make sure we're throttling delayed refs when
truncating a file. Now that we have a delayed refs rsv and a mechanism
for refilling that reserve simply use that instead of all of this magic.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/inode.c | 78 ++++++++++++--------------------------------------------
1 file changed, 16 insertions(+), 62 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 212fa71317d6..10455d0aa71c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4493,31 +4493,6 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
return err;
}

-static int truncate_space_check(struct btrfs_trans_handle *trans,
- struct btrfs_root *root,
- u64 bytes_deleted)
-{
- struct btrfs_fs_info *fs_info = root->fs_info;
- int ret;
-
- /*
- * This is only used to apply pressure to the enospc system, we don't
- * intend to use this reservation at all.
- */
- bytes_deleted = btrfs_csum_bytes_to_leaves(fs_info, bytes_deleted);
- bytes_deleted *= fs_info->nodesize;
- ret = btrfs_block_rsv_add(root, &fs_info->trans_block_rsv,
- bytes_deleted, BTRFS_RESERVE_NO_FLUSH);
- if (!ret) {
- trace_btrfs_space_reservation(fs_info, "transaction",
- trans->transid,
- bytes_deleted, 1);
- trans->bytes_reserved += bytes_deleted;
- }
- return ret;
-
-}
-
/*
* Return this if we need to call truncate_block for the last bit of the
* truncate.
@@ -4562,7 +4537,6 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
u64 bytes_deleted = 0;
bool be_nice = false;
bool should_throttle = false;
- bool should_end = false;

BUG_ON(new_size > 0 && min_type != BTRFS_EXTENT_DATA_KEY);

@@ -4775,15 +4749,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
btrfs_abort_transaction(trans, ret);
break;
}
- if (btrfs_should_throttle_delayed_refs(trans, fs_info))
- btrfs_async_run_delayed_refs(fs_info,
- trans->delayed_ref_updates * 2,
- trans->transid, 0);
if (be_nice) {
- if (truncate_space_check(trans, root,
- extent_num_bytes)) {
- should_end = true;
- }
if (btrfs_should_throttle_delayed_refs(trans,
fs_info))
should_throttle = true;
@@ -4795,7 +4761,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,

if (path->slots[0] == 0 ||
path->slots[0] != pending_del_slot ||
- should_throttle || should_end) {
+ should_throttle) {
if (pending_del_nr) {
ret = btrfs_del_items(trans, root, path,
pending_del_slot,
@@ -4807,23 +4773,23 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
pending_del_nr = 0;
}
btrfs_release_path(path);
- if (should_throttle) {
- unsigned long updates = trans->delayed_ref_updates;
- if (updates) {
- trans->delayed_ref_updates = 0;
- ret = btrfs_run_delayed_refs(trans,
- updates * 2);
- if (ret)
- break;
- }
- }
+
/*
- * if we failed to refill our space rsv, bail out
- * and let the transaction restart
+ * We can generate a lot of delayed refs, so we need to
+ * throttle every once and a while and make sure we're
+ * adding enough space to keep up with the work we are
+ * generating. Since we hold a transaction here we can
+ * only FLUSH_LIMIT, if this fails we just return EAGAIN
+ * and let the normal space allocation stuff do it's
+ * work.
*/
- if (should_end) {
- ret = -EAGAIN;
- break;
+ if (should_throttle) {
+ ret = btrfs_refill_delayed_refs_rsv(fs_info,
+ BTRFS_RESERVE_FLUSH_LIMIT);
+ if (ret) {
+ ret = -EAGAIN;
+ break;
+ }
}
goto search_again;
} else {
@@ -4849,18 +4815,6 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
}

btrfs_free_path(path);
-
- if (be_nice && bytes_deleted > SZ_32M && (ret >= 0 || ret == -EAGAIN)) {
- unsigned long updates = trans->delayed_ref_updates;
- int err;
-
- if (updates) {
- trans->delayed_ref_updates = 0;
- err = btrfs_run_delayed_refs(trans, updates * 2);
- if (err)
- ret = err;
- }
- }
return ret;
}

--
2.14.3