• sundb's avatar
    Fix crash due to delete entry from compress quicklistNode and wrongly split quicklistNode (#11242) · 01358df3
    sundb authored
    This PR mainly deals with 2 crashes introduced in #9357,
    and fix the QUICKLIST-PACKED-THRESHOLD mess in external test mode.
    
    1. Fix crash due to deleting an entry from a compress quicklistNode
       When inserting a large element, we need to create a new quicklistNode first,
       and then delete its previous element, if the node where the deleted element is
       located is compressed, it will cause a crash.
       Now add `dont_compress` to quicklistNode, if we want to use a quicklistNode
       after some operation, we can use this flag like following:
    
        ```c
        node->dont_compress = 1; /* Prevent to be compressed */
        some_operation(node); /* This operation might try to compress this node */
        some_other_operation(node); /* We can use this node without decompress it */
        node->dont_compress = 0; /* Re-able compression */
        quicklistCompressNode(node);
        ```
    
       Perhaps in the future, we could just disable the current entry from being
       compressed during the iterator loop, but that would require more work.
    
    2. Fix crash due to wrongly split quicklist
       before #9357, the offset param of _quicklistSplitNode() will not negative.
       For now, when offset is negative, the split extent will be wrong.
       following example:
        ```c
        int orig_start = after ? offset + 1 : 0;
        int orig_extent = after ? -1 : offset;
        int new_start = after ? 0 : offset;
        int new_extent = after ? offset + 1 : -1;
        # offset: -2, after: 1, node->count: 2
        # current wrong range: [-1,-1] [0,-1]
        # correct range: [1,-1] [0, 1]
        ```
    
       Because only `_quicklistInsert()` splits the quicklistNode and only
       `quicklistInsertAfter()`, `quicklistInsertBefore()` call _quicklistInsert(), 
       so `quicklistReplaceEntry()` and `listTypeInsert()` might occur this crash.
       But the iterator of `listTypeInsert()` is alway from head to tail(iter->offset is
       always positive), so it is not affected.
       The final conclusion is this crash only occur when we insert a large element
       with negative index into a list, that affects `LSET` command and `RM_ListSet`
       module api.
         
    3. In external test mode, we need to restore quicklist packed threshold after
       when the end of test.
    4. Show `node->count` in quicklistRepr().
    5. Add new tcl proc `config_get_set` to support restoring config in tests.
    
    (cherry picked from commit 13d25dd9)
    01358df3
debug.c 81.2 KB