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xarray: Extract entries from an XArray
The xa_extract function combines the functionality of radix_tree_gang_lookup() and radix_tree_gang_lookup_tagged(). It extracts entries matching the specified filter into a normal array. Signed-off-by: Matthew Wilcox <willy@infradead.org>
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@ -284,6 +284,8 @@ void *xa_find(struct xarray *xa, unsigned long *index,
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unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
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void *xa_find_after(struct xarray *xa, unsigned long *index,
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unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
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unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
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unsigned long max, unsigned int n, xa_mark_t);
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/**
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* xa_init() - Initialise an empty XArray.
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80
lib/xarray.c
80
lib/xarray.c
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@ -1444,6 +1444,86 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp,
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}
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EXPORT_SYMBOL(xa_find_after);
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static unsigned int xas_extract_present(struct xa_state *xas, void **dst,
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unsigned long max, unsigned int n)
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{
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void *entry;
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unsigned int i = 0;
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rcu_read_lock();
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xas_for_each(xas, entry, max) {
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if (xas_retry(xas, entry))
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continue;
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dst[i++] = entry;
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if (i == n)
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break;
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}
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rcu_read_unlock();
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return i;
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}
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static unsigned int xas_extract_marked(struct xa_state *xas, void **dst,
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unsigned long max, unsigned int n, xa_mark_t mark)
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{
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void *entry;
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unsigned int i = 0;
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rcu_read_lock();
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xas_for_each_marked(xas, entry, max, mark) {
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if (xas_retry(xas, entry))
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continue;
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dst[i++] = entry;
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if (i == n)
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break;
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}
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rcu_read_unlock();
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return i;
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}
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/**
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* xa_extract() - Copy selected entries from the XArray into a normal array.
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* @xa: The source XArray to copy from.
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* @dst: The buffer to copy entries into.
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* @start: The first index in the XArray eligible to be selected.
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* @max: The last index in the XArray eligible to be selected.
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* @n: The maximum number of entries to copy.
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* @filter: Selection criterion.
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*
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* Copies up to @n entries that match @filter from the XArray. The
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* copied entries will have indices between @start and @max, inclusive.
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*
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* The @filter may be an XArray mark value, in which case entries which are
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* marked with that mark will be copied. It may also be %XA_PRESENT, in
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* which case all entries which are not NULL will be copied.
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*
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* The entries returned may not represent a snapshot of the XArray at a
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* moment in time. For example, if another thread stores to index 5, then
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* index 10, calling xa_extract() may return the old contents of index 5
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* and the new contents of index 10. Indices not modified while this
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* function is running will not be skipped.
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*
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* If you need stronger guarantees, holding the xa_lock across calls to this
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* function will prevent concurrent modification.
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*
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* Context: Any context. Takes and releases the RCU lock.
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* Return: The number of entries copied.
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*/
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unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
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unsigned long max, unsigned int n, xa_mark_t filter)
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{
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XA_STATE(xas, xa, start);
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if (!n)
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return 0;
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if ((__force unsigned int)filter < XA_MAX_MARKS)
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return xas_extract_marked(&xas, dst, max, n, filter);
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return xas_extract_present(&xas, dst, max, n);
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}
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EXPORT_SYMBOL(xa_extract);
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#ifdef XA_DEBUG
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void xa_dump_node(const struct xa_node *node)
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{
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