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btrfs: ensure releasing squota reserve on head refs

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A reservation goes through a 3 step lifetime:

- generated during delalloc
- released/counted by ordered_extent allocation
- freed by running delayed ref

That third step depends on must_insert_reserved on the head ref, so the
head ref with that field set owns the reservation. Once you prepare to
run the head ref, must_insert_reserved is unset, which means that
running the ref must free the reservation, whether or not it succeeds,
or else the reservation is leaked. That results in either a risk of
spurious ENOSPC if the fs stays writeable or a warning on unmount if it
is readonly.

The existing squota code was aware of these invariants, but missed a few
cases. Improve it by adding a helper function to use in the cleanup
paths and call it from the existing early returns in running delayed
refs. This also simplifies btrfs_record_squota_delta and struct
btrfs_quota_delta.

This fixes (or at least improves the reliability of) generic/475 with
"mkfs -O squota". On my machine, that test failed ~4/10 times without
this patch and passed 100/100 times with it.

Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Boris Burkov 2023-12-01 13:00:13 -08:00 committed by David Sterba
parent a86805504b
commit e85a0adacf
3 changed files with 46 additions and 19 deletions
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48
fs/btrfs/extent-tree.c
View File

@ -1547,6 +1547,23 @@ out:
return ret;
}
static void free_head_ref_squota_rsv(struct btrfs_fs_info *fs_info,
struct btrfs_delayed_ref_head *href)
{
u64 root = href->owning_root;
/*
* Don't check must_insert_reserved, as this is called from contexts
* where it has already been unset.
*/
if (btrfs_qgroup_mode(fs_info) != BTRFS_QGROUP_MODE_SIMPLE ||
!href->is_data || !is_fstree(root))
return;
btrfs_qgroup_free_refroot(fs_info, root, href->reserved_bytes,
BTRFS_QGROUP_RSV_DATA);
}
static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_head *href,
struct btrfs_delayed_ref_node *node,
@ -1569,7 +1586,6 @@ static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
struct btrfs_squota_delta delta = {
.root = href->owning_root,
.num_bytes = node->num_bytes,
.rsv_bytes = href->reserved_bytes,
.is_data = true,
.is_inc = true,
.generation = trans->transid,
@ -1586,11 +1602,9 @@ static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
flags, ref->objectid,
ref->offset, &key,
node->ref_mod, href->owning_root);
free_head_ref_squota_rsv(trans->fs_info, href);
if (!ret)
ret = btrfs_record_squota_delta(trans->fs_info, &delta);
else
btrfs_qgroup_free_refroot(trans->fs_info, delta.root,
delta.rsv_bytes, BTRFS_QGROUP_RSV_DATA);
} else if (node->action == BTRFS_ADD_DELAYED_REF) {
ret = __btrfs_inc_extent_ref(trans, node, parent, ref->root,
ref->objectid, ref->offset,
@ -1742,7 +1756,6 @@ static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
struct btrfs_squota_delta delta = {
.root = href->owning_root,
.num_bytes = fs_info->nodesize,
.rsv_bytes = 0,
.is_data = false,
.is_inc = true,
.generation = trans->transid,
@ -1774,8 +1787,10 @@ static int run_one_delayed_ref(struct btrfs_trans_handle *trans,
int ret = 0;
if (TRANS_ABORTED(trans)) {
if (insert_reserved)
if (insert_reserved) {
btrfs_pin_extent(trans, node->bytenr, node->num_bytes, 1);
free_head_ref_squota_rsv(trans->fs_info, href);
}
return 0;
}
@ -1871,6 +1886,8 @@ u64 btrfs_cleanup_ref_head_accounting(struct btrfs_fs_info *fs_info,
struct btrfs_delayed_ref_root *delayed_refs,
struct btrfs_delayed_ref_head *head)
{
u64 ret = 0;
/*
* We had csum deletions accounted for in our delayed refs rsv, we need
* to drop the csum leaves for this update from our delayed_refs_rsv.
@ -1885,14 +1902,13 @@ u64 btrfs_cleanup_ref_head_accounting(struct btrfs_fs_info *fs_info,
btrfs_delayed_refs_rsv_release(fs_info, 0, nr_csums);
return btrfs_calc_delayed_ref_csum_bytes(fs_info, nr_csums);
ret = btrfs_calc_delayed_ref_csum_bytes(fs_info, nr_csums);
}
if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE &&
head->must_insert_reserved && head->is_data)
btrfs_qgroup_free_refroot(fs_info, head->owning_root,
head->reserved_bytes, BTRFS_QGROUP_RSV_DATA);
/* must_insert_reserved can be set only if we didn't run the head ref. */
if (head->must_insert_reserved)
free_head_ref_squota_rsv(fs_info, head);
return 0;
return ret;
}
static int cleanup_ref_head(struct btrfs_trans_handle *trans,
@ -2033,6 +2049,12 @@ static int btrfs_run_delayed_refs_for_head(struct btrfs_trans_handle *trans,
* spin lock.
*/
must_insert_reserved = locked_ref->must_insert_reserved;
/*
* Unsetting this on the head ref relinquishes ownership of
* the rsv_bytes, so it is critical that every possible code
* path from here forward frees all reserves including qgroup
* reserve.
*/
locked_ref->must_insert_reserved = false;
extent_op = locked_ref->extent_op;
@ -3292,7 +3314,6 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
struct btrfs_squota_delta delta = {
.root = delayed_ref_root,
.num_bytes = num_bytes,
.rsv_bytes = 0,
.is_data = is_data,
.is_inc = false,
.generation = btrfs_extent_generation(leaf, ei),
@ -4937,7 +4958,6 @@ int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans,
.root = root_objectid,
.num_bytes = ins->offset,
.generation = trans->transid,
.rsv_bytes = 0,
.is_data = true,
.is_inc = true,
};

14
fs/btrfs/qgroup.c
View File

@ -4661,6 +4661,17 @@ void btrfs_qgroup_destroy_extent_records(struct btrfs_transaction *trans)
*root = RB_ROOT;
}
void btrfs_free_squota_rsv(struct btrfs_fs_info *fs_info, u64 root, u64 rsv_bytes)
{
if (btrfs_qgroup_mode(fs_info) != BTRFS_QGROUP_MODE_SIMPLE)
return;
if (!is_fstree(root))
return;
btrfs_qgroup_free_refroot(fs_info, root, rsv_bytes, BTRFS_QGROUP_RSV_DATA);
}
int btrfs_record_squota_delta(struct btrfs_fs_info *fs_info,
struct btrfs_squota_delta *delta)
{
@ -4705,8 +4716,5 @@ int btrfs_record_squota_delta(struct btrfs_fs_info *fs_info,
out:
spin_unlock(&fs_info->qgroup_lock);
if (!ret && delta->rsv_bytes)
btrfs_qgroup_free_refroot(fs_info, root, delta->rsv_bytes,
BTRFS_QGROUP_RSV_DATA);
return ret;
}

3
fs/btrfs/qgroup.h
View File

@ -274,8 +274,6 @@ struct btrfs_squota_delta {
u64 root;
/* The number of bytes in the extent being counted. */
u64 num_bytes;
/* The number of bytes reserved for this extent. */
u64 rsv_bytes;
/* The generation the extent was created in. */
u64 generation;
/* Whether we are using or freeing the extent. */
@ -422,6 +420,7 @@ int btrfs_qgroup_trace_subtree_after_cow(struct btrfs_trans_handle *trans,
struct btrfs_root *root, struct extent_buffer *eb);
void btrfs_qgroup_destroy_extent_records(struct btrfs_transaction *trans);
bool btrfs_check_quota_leak(struct btrfs_fs_info *fs_info);
void btrfs_free_squota_rsv(struct btrfs_fs_info *fs_info, u64 root, u64 rsv_bytes);
int btrfs_record_squota_delta(struct btrfs_fs_info *fs_info,
struct btrfs_squota_delta *delta);