[PATCH 02/25] vm: Add wait/unlock functions for PG_fscache

David Howells
2021-01-21T06:40:20Z

Add functions to unlock and wait for unlock of PG_fscache analogously with
those for PG_lock.

Signed-off-by: David Howells <dhowells@redhat.com>
---

include/linux/pagemap.h | 14 ++++++++++++++
mm/filemap.c | 18 ++++++++++++++++++
2 files changed, 32 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index d5570deff400..1fa160e682fa 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -591,6 +591,7 @@ extern int __lock_page_async(struct page *page, struct wait_page_queue *wait);
extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags);
extern void unlock_page(struct page *page);
+extern void unlock_page_fscache(struct page *page);

/*
* Return true if the page was successfully locked
@@ -681,6 +682,19 @@ static inline int wait_on_page_locked_killable(struct page *page)
return wait_on_page_bit_killable(compound_head(page), PG_locked);
}

+/**
+ * wait_on_page_fscache - Wait for PG_fscache to be cleared on a page
+ * @page: The page
+ *
+ * Wait for the fscache mark to be removed from a page, usually signifying the
+ * completion of a write from that page to the cache.
+ */
+static inline void wait_on_page_fscache(struct page *page)
+{
+ if (PagePrivate2(page))
+ wait_on_page_bit(compound_head(page), PG_fscache);
+}
+
extern void put_and_wait_on_page_locked(struct page *page);

void wait_on_page_writeback(struct page *page);
diff --git a/mm/filemap.c b/mm/filemap.c
index 5c9d564317a5..91fcae006d64 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1466,6 +1466,24 @@ void unlock_page(struct page *page)
}
EXPORT_SYMBOL(unlock_page);

+/**
+ * unlock_page_fscache - Unlock a page pinned with PG_fscache
+ * @page: The page
+ *
+ * Unlocks the page and wakes up sleepers in wait_on_page_fscache(). Also
+ * wakes those waiting for the lock and writeback bits because the wakeup
+ * mechanism is shared. But that's OK - those sleepers will just go back to
+ * sleep.
+ */
+void unlock_page_fscache(struct page *page)
+{
+ page = compound_head(page);
+ VM_BUG_ON_PAGE(!PagePrivate2(page), page);
+ clear_bit_unlock(PG_fscache, &page->flags);
+ wake_up_page_bit(page, PG_fscache);
+}
+EXPORT_SYMBOL(unlock_page_fscache);
+
/**
* end_page_writeback - end writeback against a page
* @page: the page