2021-04-08 14:07:15

by David Howells

[permalink] [raw]
Subject: [PATCH v6 09/30] netfs, mm: Add set/end/wait_on_page_fscache() aliases

Add set/end/wait_on_page_fscache() as aliases of
set/end/wait_page_private_2(). These allow a page to marked with
PG_fscache, the flag to be removed and waiters woken and waiting for the
flag to be cleared. A ref on the page is also taken and dropped.

[Linus suggested putting the fscache-themed functions into the
caching-specific headers rather than pagemap.h[1]]

Changes:
v5:
- Mirror the changes to the core routines[2].

Signed-off-by: David Howells <[email protected]>
cc: Linus Torvalds <[email protected]>
cc: Matthew Wilcox <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]/
Link: https://lore.kernel.org/r/[email protected]om/ [1]
Link: https://lore.kernel.org/r/[email protected]rg.uk/ # v3
Link: https://lore.kernel.org/r/[email protected]g.uk/ # v4
Link: https://lore.kernel.org/r/[email protected]/ [2]
Link: https://lore.kernel.org/r/[email protected]org.uk/ # v5
---

include/linux/netfs.h | 57 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 57 insertions(+)

diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index cc1102040488..8479d63406f7 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -26,4 +26,61 @@
#define TestSetPageFsCache(page) TestSetPagePrivate2((page))
#define TestClearPageFsCache(page) TestClearPagePrivate2((page))

+/**
+ * set_page_fscache - Set PG_fscache on a page and take a ref
+ * @page: The page.
+ *
+ * Set the PG_fscache (PG_private_2) flag on a page and take the reference
+ * needed for the VM to handle its lifetime correctly. This sets the flag and
+ * takes the reference unconditionally, so care must be taken not to set the
+ * flag again if it's already set.
+ */
+static inline void set_page_fscache(struct page *page)
+{
+ set_page_private_2(page);
+}
+
+/**
+ * end_page_fscache - Clear PG_fscache and release any waiters
+ * @page: The page
+ *
+ * Clear the PG_fscache (PG_private_2) bit on a page and wake up any sleepers
+ * waiting for this. The page ref held for PG_private_2 being set is released.
+ *
+ * This is, for example, used when a netfs page is being written to a local
+ * disk cache, thereby allowing writes to the cache for the same page to be
+ * serialised.
+ */
+static inline void end_page_fscache(struct page *page)
+{
+ end_page_private_2(page);
+}
+
+/**
+ * wait_on_page_fscache - Wait for PG_fscache to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_fscache (aka PG_private_2) to be cleared on a page.
+ */
+static inline void wait_on_page_fscache(struct page *page)
+{
+ wait_on_page_private_2(page);
+}
+
+/**
+ * wait_on_page_fscache_killable - Wait for PG_fscache to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_fscache (aka PG_private_2) to be cleared on a page or until a
+ * fatal signal is received by the calling task.
+ *
+ * Return:
+ * - 0 if successful.
+ * - -EINTR if a fatal signal was encountered.
+ */
+static inline int wait_on_page_fscache_killable(struct page *page)
+{
+ return wait_on_page_private_2_killable(page);
+}
+
#endif /* _LINUX_NETFS_H */