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Be sure not to overfill a segment with items

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The segment writing loop was assuming that the currently dirty items
will fit in a segment.  That's not true.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2017-01-02 11:59:37 -08:00
parent be497f3fcf
commit 157b9294fa
1 changed files with 19 additions and 6 deletions
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25
kmod/src/item.c
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@@ -977,6 +977,17 @@ static void count_seg_items(struct item_cache *cac, u32 *nr_items,
*
* The caller is responsible for the consistency of the dirty items once
* they're in its seg. We can consider them clean once we store them.
*
* Today entering a transaction doesn't ensure that there's never more
* than a segment's worth of dirty items. As we release a trans we kick
* off an async sync. By the time we get here we can have a lot more
* than a segments worth of dirty items.
*
* XXX This is unacceptable because multiple segment writes are not
* atomic. We can have the items that make up an atomic change span
* segments and can be partially visible if we only write the first
* segment. We probably want to throttle trans enters once we have as
* many dirty items as our atomic segment updates can write.
*/
int scoutfs_item_dirty_seg(struct super_block *sb, struct scoutfs_segment *seg)
{
@@ -987,16 +998,18 @@ int scoutfs_item_dirty_seg(struct super_block *sb, struct scoutfs_segment *seg)
u32 nr_items;
count_seg_items(cac, &nr_items, &key_bytes);
if (nr_items) {
item = first_dirty(cac->items.rb_node);
item = first_dirty(cac->items.rb_node);
if (item) {
scoutfs_seg_first_item(sb, seg, item->key, item->val,
nr_items, key_bytes);
clear_item_dirty(cac, item);
nr_items--;
}
while ((item = next_dirty(item))) {
scoutfs_seg_append_item(sb, seg, item->key, item->val);
clear_item_dirty(cac, item);
}
while (nr_items-- && (item = next_dirty(item))) {
scoutfs_seg_append_item(sb, seg, item->key, item->val);
clear_item_dirty(cac, item);
}
return 0;