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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>
This commit is contained in:
Matthew Wilcox 2017-11-14 16:42:22 -05:00
parent b803b42823
commit 80a0a1a9a3
2 changed files with 82 additions and 0 deletions
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2
include/linux/xarray.h
View File

@ -284,6 +284,8 @@ void *xa_find(struct xarray *xa, unsigned long *index,
unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
void *xa_find_after(struct xarray *xa, unsigned long *index,
unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
unsigned long max, unsigned int n, xa_mark_t);
/**
* xa_init() - Initialise an empty XArray.

80
lib/xarray.c
View File

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