On 7/8/20 2:24 AM, Qu Wenruo wrote:
[PROBLEM]
Before this patch, when btrfs_qgroup_reserve_data() fails, we free all
reserved space of the changeset.
For example:
ret = btrfs_qgroup_reserve_data(inode, changeset, 0, SZ_1M);
ret = btrfs_qgroup_reserve_data(inode, changeset, SZ_1M, SZ_1M);
ret = btrfs_qgroup_reserve_data(inode, changeset, SZ_2M, SZ_1M);
If the last btrfs_qgroup_reserve_data() failed, it will release all [0,
3M) range.
This behavior is kinda OK for now, as when we hit -EDQUOT, we normally
go error handling and need to release all reserved ranges anyway.
But this also means the following call is not possible:
ret = btrfs_qgroup_reserve_data();
if (ret == -EDQUOT) {
/* Do something to free some qgroup space */
ret = btrfs_qgroup_reserve_data();
}
As if the first btrfs_qgroup_reserve_data() fails, it will free all
reserved qgroup space.
[CAUSE]
This is because we release all reserved ranges when
btrfs_qgroup_reserve_data() fails.
[FIX]
This patch will implement a new function, qgroup_revert(), to iterate
through the ulist nodes, to find any nodes in the failure range, and
remove the EXTENT_QGROUP_RESERVED bits from the io_tree, and decrease
the extent_changeset::bytes_changed, so that we can revert to previous
status.
This allows later patches to retry btrfs_qgroup_reserve_data() if EDQUOT
happens.
Suggested-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
fs/btrfs/qgroup.c | 90 +++++++++++++++++++++++++++++++++++++++--------
1 file changed, 75 insertions(+), 15 deletions(-)
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index ee0ad33b659c..84a452dea3f9 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3447,6 +3447,71 @@ btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info)
}
}
+static int qgroup_revert(struct btrfs_inode *inode,
+ struct extent_changeset *reserved, u64 start,
+ u64 len)
+{
+ struct rb_node *n = reserved->range_changed.root.rb_node;
+ struct ulist_node *entry = NULL;
+ int ret = 0;
+
+ while (n) {
+ entry = rb_entry(n, struct ulist_node, rb_node);
+ if (entry->val < start)
+ n = n->rb_right;
+ else if (entry)
+ n = n->rb_left;
+ else
+ break;
+ }
+ /* Empty changeset */
+ if (!entry)
+ goto out;
Don't need the goto out here, just return ret;
+
+ if (entry->val > start && rb_prev(&entry->rb_node))
+ entry = rb_entry(rb_prev(&entry->rb_node), struct ulist_node,
+ rb_node);
+
+ n = &entry->rb_node;
+ while (n) {
for (n = &entry->rb_node; n; n = rb_next(n)) {
Thanks,
Josef
