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scoutfs: allow btree update with different lengths

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The previous _btree_update implementation required that the new value be
the same length as the old value.  This change allows a new updated item
to be a different length.  It performs the btree walk assuming that the
item will be larger so that there's room for the difference.   It
doesn't search for the size of the existing item so it doesn't know if
the new item is smaller.  It might leave the dirty leaf under the low
water mark, which is fine.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2019-09-29 22:12:52 -07:00
committed by Zach Brown
parent 4265ecedb0
commit f3a8a5110e
1 changed files with 14 additions and 12 deletions
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26
kmod/src/btree.c
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@@ -1356,10 +1356,17 @@ int scoutfs_btree_insert(struct super_block *sb, struct scoutfs_btree_root *root
}
/*
* Update a btree item. The key and value must be of the same length (though
* it would be easy enough for us to change that if a caller cared).
* Update a btree item. -ENOENT is returned if the item didn't exist.
*
* We don't know the existing item's value length as we first descend.
* We assume that the new value is longer and try to split so that we
* can insert if that's true. If the new value is shorter than the
* existing then the leaf might fall under the minimum watermark, but at
* least we can do that while we simply can't insert a new longer value
* which doesn't fit.
*/
int scoutfs_btree_update(struct super_block *sb, struct scoutfs_btree_root *root,
int scoutfs_btree_update(struct super_block *sb,
struct scoutfs_btree_root *root,
void *key, unsigned key_len,
void *val, unsigned val_len)
{
@@ -1372,19 +1379,14 @@ int scoutfs_btree_update(struct super_block *sb, struct scoutfs_btree_root *root
if (invalid_item(key, key_len, val_len))
return -EINVAL;
ret = btree_walk(sb, root, BTW_DIRTY, key, key_len, 0, &bt, NULL, NULL);
ret = btree_walk(sb, root, BTW_DIRTY | BTW_INSERT, key, key_len,
val_len, &bt, NULL, NULL);
if (ret == 0) {
pos = find_pos(bt, key, key_len, &cmp);
if (cmp == 0) {
item = pos_item(bt, pos);
if (item_key_len(item) != key_len ||
item_val_len(item) != val_len) {
ret = -EINVAL;
} else {
memcpy(item_key(item), key, key_len);
memcpy(item_val(item), val, val_len);
ret = 0;
}
delete_item(bt, pos);
create_item(bt, pos, key, key_len, val, val_len);
ret = 0;
} else {
ret = -ENOENT;