[PATCH v5 15/18] btrfs: check generation when recording simple quota delta

Boris Burkov
2023-07-27T22:15:49Z

Simple quotas count extents only from the moment the feature is enabled.
Therefore, if we do something like:
1. create subvol S
2. write F in S
3. enable quotas
4. remove F
5. write G in S

then after 3. and 4. we would expect the simple quota usage of S to be 0
(putting aside some metadata extents that might be written) and after
5., it should be the size of G plus metadata. Therefore, we need to be
able to determine whether a particular quota delta we are processing
predates simple quota enablement.

To do this, store the transaction id when quotas were enabled. In
fs_info for immediate use and in the quota status item to make it
recoverable on mount. When we see a delta, check if the generation of
the extent item is less than that of quota enablement. If so, we should
ignore the delta from this extent.

Signed-off-by: Boris Burkov <boris@bur.io>
---
fs/btrfs/accessors.h | 2 ++
fs/btrfs/extent-tree.c | 4 ++++
fs/btrfs/fs.h | 2 ++
fs/btrfs/qgroup.c | 14 ++++++++++++--
fs/btrfs/qgroup.h | 1 +
include/uapi/linux/btrfs_tree.h | 7 +++++++
6 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/accessors.h b/fs/btrfs/accessors.h
index a23045c05937..513f8edbd98e 100644
--- a/fs/btrfs/accessors.h
+++ b/fs/btrfs/accessors.h
@@ -970,6 +970,8 @@ BTRFS_SETGET_FUNCS(qgroup_status_flags, struct btrfs_qgroup_status_item,
flags, 64);
BTRFS_SETGET_FUNCS(qgroup_status_rescan, struct btrfs_qgroup_status_item,
rescan, 64);
+BTRFS_SETGET_FUNCS(qgroup_status_enable_gen, struct btrfs_qgroup_status_item,
+ enable_gen, 64);

/* btrfs_qgroup_info_item */
BTRFS_SETGET_FUNCS(qgroup_info_generation, struct btrfs_qgroup_info_item,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1b5efd03ef83..395ab46e520b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1513,6 +1513,7 @@ static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
.rsv_bytes = href->reserved_bytes,
.is_data = true,
.is_inc = true,
+ .generation = trans->transid,
};

if (extent_op)
@@ -1676,6 +1677,7 @@ static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
.rsv_bytes = 0,
.is_data = false,
.is_inc = true,
+ .generation = trans->transid,
};

BUG_ON(!extent_op || !extent_op->update_flags);
@@ -3217,6 +3219,7 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
.rsv_bytes = 0,
.is_data = is_data,
.is_inc = false,
+ .generation = btrfs_extent_generation(leaf, ei),
};

/* In this branch refs == 1 */
@@ -4850,6 +4853,7 @@ int btrfs_alloc_logged_file_extent(struct btrfs_trans_handle *trans,
struct btrfs_simple_quota_delta delta = {
.root = root_objectid,
.num_bytes = ins->offset,
+ .generation = trans->transid,
.rsv_bytes = 0,
.is_data = true,
.is_inc = true,
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index f76f450c2abf..da7b623ff15f 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -802,6 +802,8 @@ struct btrfs_fs_info {
spinlock_t eb_leak_lock;
struct list_head allocated_ebs;
#endif
+
+ u64 quota_enable_gen;
};

static inline void btrfs_set_last_root_drop_gen(struct btrfs_fs_info *fs_info,
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 58e9ed0deedd..a8a603242431 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -454,6 +454,8 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
}
fs_info->qgroup_flags = btrfs_qgroup_status_flags(l, ptr);
simple = fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_SIMPLE;
+ if (simple)
+ fs_info->quota_enable_gen = btrfs_qgroup_status_enable_gen(l, ptr);
if (btrfs_qgroup_status_generation(l, ptr) !=
fs_info->generation && !simple) {
qgroup_mark_inconsistent(fs_info);
@@ -1107,10 +1109,12 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info,
btrfs_set_qgroup_status_generation(leaf, ptr, trans->transid);
btrfs_set_qgroup_status_version(leaf, ptr, BTRFS_QGROUP_STATUS_VERSION);
fs_info->qgroup_flags = BTRFS_QGROUP_STATUS_FLAG_ON;
- if (simple)
+ if (simple) {
fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_SIMPLE;
- else
+ btrfs_set_qgroup_status_enable_gen(leaf, ptr, trans->transid);
+ } else {
fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+ }
btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags &
BTRFS_QGROUP_STATUS_FLAGS_MASK);
btrfs_set_qgroup_status_rescan(leaf, ptr, 0);
@@ -1202,6 +1206,8 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info,
goto out_free_path;
}

+ fs_info->quota_enable_gen = trans->transid;
+
mutex_unlock(&fs_info->qgroup_ioctl_lock);
/*
* Commit the transaction while not holding qgroup_ioctl_lock, to avoid
@@ -4622,6 +4628,10 @@ int btrfs_record_simple_quota_delta(struct btrfs_fs_info *fs_info,
if (!is_fstree(root))
return 0;

+ /* If the extent predates enabling quotas, don't count it. */
+ if (delta->generation < fs_info->quota_enable_gen)
+ return 0;
+
spin_lock(&fs_info->qgroup_lock);
qgroup = find_qgroup_rb(fs_info, root);
if (!qgroup) {
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index ce6fa8694ca7..ae1ce14b365c 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -241,6 +241,7 @@ struct btrfs_simple_quota_delta {
u64 rsv_bytes; /* The number of bytes reserved for this extent */
bool is_inc; /* Whether we are using or freeing the extent */
bool is_data; /* Whether the extent is data or metadata */
+ u64 generation; /* The generation the extent was created in */
};

static inline u64 btrfs_qgroup_subvolid(u64 qgroupid)
diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index eacb26caf3c6..1120ce3dae42 100644
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -1242,6 +1242,13 @@ struct btrfs_qgroup_status_item {
* of the scan. It contains a logical address
*/
__le64 rescan;
+
+ /*
+ * the generation when quotas are enabled. Used by simple quotas to
+ * avoid decrementing when freeing an extent that was written before
+ * enable.
+ */
+ __le64 enable_gen;
} __attribute__ ((__packed__));

struct btrfs_qgroup_info_item {
--
2.41.0