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XArray: Redesign xa_alloc API

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It was too easy to forget to initialise the start index.  Add an
xa_limit data structure which can be used to pass min & max, and
define a couple of special values for common cases.  Also add some
more tests cribbed from the IDR test suite.  Change the return value
from -ENOSPC to -EBUSY to match xa_insert().

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox 2018-12-31 10:41:01 -05:00
parent 3ccaf57a6a
commit a3e4d3f97e
3 changed files with 135 additions and 60 deletions
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29
lib/xarray.c
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@ -1615,23 +1615,23 @@ EXPORT_SYMBOL(xa_store_range);
* __xa_alloc() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @max: Maximum ID to allocate (inclusive).
* @limit: Range for allocated ID.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Allocates an unused ID in the range specified by @id and @max.
* Updates the @id pointer with the index, then stores the entry at that
* index. A concurrent lookup will not see an uninitialised @id.
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
* Context: Any context. Expects xa_lock to be held on entry. May
* release and reacquire xa_lock if @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory allocation fails or -ENOSPC if
* there is no more space in the XArray.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
* -EBUSY if there are no free entries in @limit.
*/
int __xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, gfp_t gfp)
int __xa_alloc(struct xarray *xa, u32 *id, void *entry,
struct xa_limit limit, gfp_t gfp)
{
XA_STATE(xas, xa, 0);
int err;
if (WARN_ON_ONCE(xa_is_advanced(entry)))
return -EINVAL;
@ -1642,18 +1642,17 @@ int __xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, gfp_t gfp)
entry = XA_ZERO_ENTRY;
do {
xas.xa_index = *id;
xas_find_marked(&xas, max, XA_FREE_MARK);
xas.xa_index = limit.min;
xas_find_marked(&xas, limit.max, XA_FREE_MARK);
if (xas.xa_node == XAS_RESTART)
xas_set_err(&xas, -ENOSPC);
xas_set_err(&xas, -EBUSY);
else
*id = xas.xa_index;
xas_store(&xas, entry);
xas_clear_mark(&xas, XA_FREE_MARK);
} while (__xas_nomem(&xas, gfp));
err = xas_error(&xas);
if (!err)
*id = xas.xa_index;
return err;
return xas_error(&xas);
}
EXPORT_SYMBOL(__xa_alloc);