This new function will do all the hard work to reserve precious space
for a write.
The overall work flow will be the following.
File A already has some dirty pages:
0 4K 8K 12K 16K
|///////| |///////|
And then, someone want to write some data into range [4K, 16K).
|<------desired-------->|
Unlike the old and wrong implement, which reserve 12K, this function
will only reserve space for newly dirty part:
|\\\\\\\| |\\\\\\\|
Which only takes 8K reserve space, as other part has already allocated
their own reserve space.
So the final reserve map will be:
|///////////////////////////////|
This provides the basis to resolve the long existing qgroup limit bug.
Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
---
v2:
Add needed parameter for later trace functions
---
fs/btrfs/qgroup.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/qgroup.h | 1 +
2 files changed, 58 insertions(+)
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 3bdf28e..e840f5c 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2796,6 +2796,63 @@ insert:
}
/*
+ * Make sure the data space for [start, start + len) is reserved.
+ * It will either reserve new space from given qgroup or reuse the already
+ * reserved space.
+ *
+ * Return 0 for successful reserve.
+ * Return <0 for error.
+ *
+ * TODO: to handle nocow case, like NODATACOW or write into prealloc space
+ * along with other mixed case.
+ * Like write 2M, first 1M can be nocowed, but next 1M is on hole and need COW.
+ */
+int btrfs_qgroup_reserve_data(struct inode *inode, u64 start, u64 len)
+{
+ struct btrfs_inode *binode = BTRFS_I(inode);
+ struct btrfs_root *root = binode->root;
+ struct btrfs_qgroup_data_rsv_map *reserve_map;
+ struct data_rsv_range *tmp = NULL;
+ struct ulist *insert_list;
+ int ret;
+
+ if (!root->fs_info->quota_enabled || !is_fstree(root->objectid) ||
+ len == 0)
+ return 0;
+
+ if (!binode->qgroup_rsv_map) {
+ ret = btrfs_qgroup_init_data_rsv_map(inode);
+ if (ret < 0)
+ return ret;
+ }
+ reserve_map = binode->qgroup_rsv_map;
+ insert_list = ulist_alloc(GFP_NOFS);
+ if (!insert_list)
+ return -ENOMEM;
+ tmp = kzalloc(sizeof(*tmp), GFP_NOFS);
+ if (!tmp) {
+ ulist_free(insert_list);
+ return -ENOMEM;
+ }
+
+ spin_lock(&reserve_map->lock);
+ ret = reserve_data_range(root, reserve_map, tmp, insert_list, start,
+ len, NULL);
+ /*
+ * For error and already exists case, free tmp memory.
+ * For tmp used case, set ret to 0, as some careless
+ * caller consider >0 as error.
+ */
+ if (ret <= 0)
+ kfree(tmp);
+ else
+ ret = 0;
+ spin_unlock(&reserve_map->lock);
+ ulist_free(insert_list);
+ return ret;
+}
+
+/*
* Init data_rsv_map for a given inode.
*
* This is needed at write time as quota can be disabled and then enabled
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index c87b7dc..366b853 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -87,4 +87,5 @@ int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
/* for qgroup reserve */
int btrfs_qgroup_init_data_rsv_map(struct inode *inode);
void btrfs_qgroup_free_data_rsv_map(struct inode *inode);
+int btrfs_qgroup_reserve_data(struct inode *inode, u64 start, u64 len);
#endif /* __BTRFS_QGROUP__ */
--
2.6.1
--
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