Use an inode flag, I_PINNING_FSCACHE_WB, to indicate that a cookie is
pinned in use by that inode for the purposes of writeback.
Pinning is necessary because the in-use pin from the open file is released
before the writeback takes place, but if the resources aren't pinned, the
dirty data can't be written to the cache.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/fs-writeback.c | 8 ++++++++
fs/fscache/io.c | 38 ++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 3 +++
include/linux/fscache.h | 22 ++++++++++++++++++++++
include/linux/writeback.h | 1 +
5 files changed, 72 insertions(+)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index e6005c78bfa9..f7fb7fb37337 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1506,6 +1506,13 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
inode->i_state |= I_DIRTY_PAGES;
+ else if (unlikely(inode->i_state & I_PINNING_FSCACHE_WB)) {
+ if (!(inode->i_state & I_DIRTY_PAGES)) {
+ inode->i_state &= ~I_PINNING_FSCACHE_WB;
+ wbc->unpinned_fscache_wb = true;
+ dirty |= I_PINNING_FSCACHE_WB; /* Cause write_inode */
+ }
+ }
spin_unlock(&inode->i_lock);
@@ -1517,6 +1524,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
if (ret == 0)
ret = err;
}
+ wbc->unpinned_fscache_wb = false;
trace_writeback_single_inode(inode, wbc, nr_to_write);
return ret;
}
diff --git a/fs/fscache/io.c b/fs/fscache/io.c
index 7ad13900b281..87ffe84c9f27 100644
--- a/fs/fscache/io.c
+++ b/fs/fscache/io.c
@@ -142,3 +142,41 @@ int __fscache_begin_operation(struct fscache_cookie *cookie,
return -ENOBUFS;
}
EXPORT_SYMBOL(__fscache_begin_operation);
+
+/**
+ * fscache_set_page_dirty - Mark page dirty and pin a cache object for writeback
+ * @page: The page being dirtied
+ * @cookie: The cookie referring to the cache object
+ *
+ * Set the dirty flag on a page and pin an in-use cache object in memory when
+ * dirtying a page so that writeback can later write to it. This is intended
+ * to be called from the filesystem's ->set_page_dirty() method.
+ *
+ * Returns 1 if PG_dirty was set on the page, 0 otherwise.
+ */
+int fscache_set_page_dirty(struct page *page, struct fscache_cookie *cookie)
+{
+ struct inode *inode = page->mapping->host;
+ bool need_use = false;
+
+ _enter("");
+
+ if (!__set_page_dirty_nobuffers(page))
+ return 0;
+ if (!fscache_cookie_valid(cookie))
+ return 1;
+
+ if (!(inode->i_state & I_PINNING_FSCACHE_WB)) {
+ spin_lock(&inode->i_lock);
+ if (!(inode->i_state & I_PINNING_FSCACHE_WB)) {
+ inode->i_state |= I_PINNING_FSCACHE_WB;
+ need_use = true;
+ }
+ spin_unlock(&inode->i_lock);
+
+ if (need_use)
+ fscache_use_cookie(cookie, true);
+ }
+ return 1;
+}
+EXPORT_SYMBOL(fscache_set_page_dirty);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f6dad577ea07..fdbac1252381 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2151,6 +2151,8 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
* Used to detect that mark_inode_dirty() should not move
* inode between dirty lists.
*
+ * I_PINNING_FSCACHE_WB Inode is pinning an fscache object for writeback.
+ *
* Q: What is the difference between I_WILL_FREE and I_FREEING?
*/
#define I_DIRTY_SYNC (1 << 0)
@@ -2173,6 +2175,7 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
#define I_CREATING (1 << 15)
#define I_DONTCACHE (1 << 16)
#define I_SYNC_QUEUED (1 << 17)
+#define I_PINNING_FSCACHE_WB (1 << 18)
#define I_DIRTY_INODE (I_DIRTY_SYNC | I_DIRTY_DATASYNC)
#define I_DIRTY (I_DIRTY_INODE | I_DIRTY_PAGES)
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 8d47c7a08456..d2fc98a5755a 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -19,6 +19,7 @@
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/list_bl.h>
+#include <linux/writeback.h>
#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
#define __fscache_available (1)
@@ -580,4 +581,25 @@ int fscache_write(struct fscache_op_resources *opr,
return ops->write(opr, start_pos, iter, term_func, term_func_priv);
}
+#if __fscache_available
+extern int fscache_set_page_dirty(struct page *page, struct fscache_cookie *cookie);
+#else
+#define fscache_set_page_dirty(PAGE, COOKIE) (__set_page_dirty_nobuffers((PAGE)))
+#endif
+
+/**
+ * fscache_unpin_writeback - Unpin writeback resources
+ * @wbc: The writeback control
+ * @cookie: The cookie referring to the cache object
+ *
+ * Unpin the writeback resources pinned by fscache_set_page_dirty(). This is
+ * intended to be called by the netfs's ->write_inode() method.
+ */
+static inline void fscache_unpin_writeback(struct writeback_control *wbc,
+ struct fscache_cookie *cookie)
+{
+ if (wbc->unpinned_fscache_wb)
+ fscache_unuse_cookie(cookie, NULL, NULL);
+}
+
#endif /* _LINUX_FSCACHE_H */
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 8e5c5bb16e2d..5e7d1d38f261 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -69,6 +69,7 @@ struct writeback_control {
unsigned for_reclaim:1; /* Invoked from the page allocator */
unsigned range_cyclic:1; /* range_start is cyclic */
unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
+ unsigned unpinned_fscache_wb:1; /* Cleared I_PINNING_FSCACHE_WB */
/*
* When writeback IOs are bounced through async layers, only the
