return xa_empty(&mapping->i_pages);
}
+/*
+ * mapping_shrinkable - test if page cache state allows inode reclaim
+ * @mapping: the page cache mapping
+ *
+ * This checks the mapping's cache state for the pupose of inode
+ * reclaim and LRU management.
+ *
+ * The caller is expected to hold the i_lock, but is not required to
+ * hold the i_pages lock, which usually protects cache state. That's
+ * because the i_lock and the list_lru lock that protect the inode and
+ * its LRU state don't nest inside the irq-safe i_pages lock.
+ *
+ * Cache deletions are performed under the i_lock, which ensures that
+ * when an inode goes empty, it will reliably get queued on the LRU.
+ *
+ * Cache additions do not acquire the i_lock and may race with this
+ * check, in which case we'll report the inode as shrinkable when it
+ * has cache pages. This is okay: the shrinker also checks the
+ * refcount and the referenced bit, which will be elevated or set in
+ * the process of adding new cache pages to an inode.
+ */
+static inline bool mapping_shrinkable(struct address_space *mapping)
+{
+ void *head;
+
+ /*
+ * On highmem systems, there could be lowmem pressure from the
+ * inodes before there is highmem pressure from the page
+ * cache. Make inodes shrinkable regardless of cache state.
+ */
+ if (IS_ENABLED(CONFIG_HIGHMEM))
+ return true;
+
+ /* Cache completely empty? Shrink away. */
+ head = rcu_access_pointer(mapping->i_pages.xa_head);
+ if (!head)
+ return true;
+
+ /*
+ * The xarray stores single offset-0 entries directly in the
+ * head pointer, which allows non-resident page cache entries
+ * to escape the shadow shrinker's list of xarray nodes. The
+ * inode shrinker needs to pick them up under memory pressure.
+ */
+ if (!xa_is_node(head) && xa_is_value(head))
+ return true;
+
+ return false;
+}
+
/*
* Bits in mapping->flags.
*/
return folio_mapping(folio);
}
+/**
+ * folio_inode - Get the host inode for this folio.
+ * @folio: The folio.
+ *
+ * For folios which are in the page cache, return the inode that this folio
+ * belongs to.
+ *
+ * Do not call this for folios which aren't in the page cache.
+ */
+static inline struct inode *folio_inode(struct folio *folio)
+{
+ return folio->mapping->host;
+}
+
static inline bool page_cache_add_speculative(struct page *page, int count)
{
VM_BUG_ON_PAGE(PageTail(page), page);
folio_set_private(folio);
}
+/**
+ * folio_change_private - Change private data on a folio.
+ * @folio: Folio to change the data on.
+ * @data: Data to set on the folio.
+ *
+ * Change the private data attached to a folio and return the old
+ * data. The page must previously have had data attached and the data
+ * must be detached before the folio will be freed.
+ *
+ * Return: Data that was previously attached to the folio.
+ */
+static inline void *folio_change_private(struct folio *folio, void *data)
+{
+ void *old = folio_get_private(folio);
+
+ folio->private = data;
+ return old;
+}
+
/**
* folio_detach_private - Detach private data from a folio.
* @folio: Folio to detach data from.