afs: Trace page dirty/clean

Add a trace event that logs the dirtying and cleaning of pages attached to
AFS inodes.
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/file.c

@@ -583,6 +583,9 @@ static int afs_readpages(struct file *file, struct address_space *mapping,
 static void afs_invalidatepage(struct page *page, unsigned int offset,
 			       unsigned int length)
 {
+	struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
+	unsigned long priv;
+
 	_enter("{%lu},%u,%u", page->index, offset, length);
 
 	BUG_ON(!PageLocked(page));
@@ -598,6 +601,9 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 #endif
 
 		if (PagePrivate(page)) {
+			priv = page_private(page);
+			trace_afs_page_dirty(vnode, tracepoint_string("inval"),
+					     page->index, priv);
 			set_page_private(page, 0);
 			ClearPagePrivate(page);
 		}
@@ -613,6 +619,7 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
 static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 {
 	struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
+	unsigned long priv;
 
 	_enter("{{%x:%u}[%lu],%lx},%x",
 	       vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
@@ -628,6 +635,9 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)
 #endif
 
 	if (PagePrivate(page)) {
+		priv = page_private(page);
+		trace_afs_page_dirty(vnode, tracepoint_string("rel"),
+				     page->index, priv);
 		set_page_private(page, 0);
 		ClearPagePrivate(page);
 	}

fs/afs/write.c

@@ -17,19 +17,6 @@
 #include <linux/pagevec.h>
 #include "internal.h"
 
-/*
- * We use page->private to hold the amount of the page that we've written to,
- * splitting the field into two parts.  However, we need to represent a range
- * 0...PAGE_SIZE inclusive, so we can't support 64K pages on a 32-bit system.
- */
-#if PAGE_SIZE > 32768
-#define AFS_PRIV_MAX	0xffffffff
-#define AFS_PRIV_SHIFT	32
-#else
-#define AFS_PRIV_MAX	0xffff
-#define AFS_PRIV_SHIFT	16
-#endif
-
 /*
  * mark a page as having been made dirty and thus needing writeback
  */
@@ -145,6 +132,8 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 
 	priv = (unsigned long)t << AFS_PRIV_SHIFT;
 	priv |= f;
+	trace_afs_page_dirty(vnode, tracepoint_string("begin"),
+			     page->index, priv);
 	SetPagePrivate(page);
 	set_page_private(page, priv);
 	_leave(" = 0");
@@ -386,6 +375,7 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 					   struct page *primary_page,
 					   pgoff_t final_page)
 {
+	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
 	struct page *pages[8], *page;
 	unsigned long count, priv;
 	unsigned n, offset, to, f, t;
@@ -407,8 +397,13 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 	priv = page_private(primary_page);
 	offset = priv & AFS_PRIV_MAX;
 	to = priv >> AFS_PRIV_SHIFT;
+	trace_afs_page_dirty(vnode, tracepoint_string("store"),
+			     primary_page->index, priv);
 
 	WARN_ON(offset == to);
+	if (offset == to)
+		trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
+				     primary_page->index, priv);
 
 	if (start >= final_page || to < PAGE_SIZE)
 		goto no_more;
@@ -452,6 +447,9 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
 			}
 			to = t;
 
+			trace_afs_page_dirty(vnode, tracepoint_string("store+"),
+					     page->index, priv);
+
 			if (!clear_page_dirty_for_io(page))
 				BUG();
 			if (test_set_page_writeback(page))
@@ -657,6 +655,7 @@ int afs_writepages(struct address_space *mapping,
 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
 {
 	struct pagevec pv;
+	unsigned long priv;
 	unsigned count, loop;
 	pgoff_t first = call->first, last = call->last;
 
@@ -676,6 +675,9 @@ void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call)
 		ASSERTCMP(pv.nr, ==, count);
 
 		for (loop = 0; loop < count; loop++) {
+			priv = page_private(pv.pages[loop]);
+			trace_afs_page_dirty(vnode, tracepoint_string("clear"),
+					     pv.pages[loop]->index, priv);
 			set_page_private(pv.pages[loop], 0);
 			end_page_writeback(pv.pages[loop]);
 		}
@@ -783,6 +785,8 @@ int afs_page_mkwrite(struct vm_fault *vmf)
 
 	priv = (unsigned long)PAGE_SIZE << AFS_PRIV_SHIFT; /* To */
 	priv |= 0; /* From */
+	trace_afs_page_dirty(vnode, tracepoint_string("mkwrite"),
+			     vmf->page->index, priv);
 	SetPagePrivate(vmf->page);
 	set_page_private(vmf->page, priv);
 
@@ -840,9 +844,13 @@ int afs_launder_page(struct page *page)
 			t = priv >> AFS_PRIV_SHIFT;
 		}
 
+		trace_afs_page_dirty(vnode, tracepoint_string("launder"),
+				     page->index, priv);
 		ret = afs_store_data(mapping, page->index, page->index, t, f);
 	}
 
+	trace_afs_page_dirty(vnode, tracepoint_string("laundered"),
+			     page->index, priv);
 	set_page_private(page, 0);
 	ClearPagePrivate(page);
 

include/trace/events/afs.h

@@ -402,6 +402,45 @@ TRACE_EVENT(afs_dir_check_failed,
 		      __entry->vnode, __entry->off, __entry->i_size)
 	    );
 
+/*
+ * We use page->private to hold the amount of the page that we've written to,
+ * splitting the field into two parts.  However, we need to represent a range
+ * 0...PAGE_SIZE inclusive, so we can't support 64K pages on a 32-bit system.
+ */
+#if PAGE_SIZE > 32768
+#define AFS_PRIV_MAX	0xffffffff
+#define AFS_PRIV_SHIFT	32
+#else
+#define AFS_PRIV_MAX	0xffff
+#define AFS_PRIV_SHIFT	16
+#endif
+
+TRACE_EVENT(afs_page_dirty,
+	    TP_PROTO(struct afs_vnode *vnode, const char *where,
+		     pgoff_t page, unsigned long priv),
+
+	    TP_ARGS(vnode, where, page, priv),
+
+	    TP_STRUCT__entry(
+		    __field(struct afs_vnode *,		vnode		)
+		    __field(const char *,		where		)
+		    __field(pgoff_t,			page		)
+		    __field(unsigned long,		priv		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->vnode = vnode;
+		    __entry->where = where;
+		    __entry->page = page;
+		    __entry->priv = priv;
+			   ),
+
+	    TP_printk("vn=%p %lx %s %lu-%lu",
+		      __entry->vnode, __entry->page, __entry->where,
+		      __entry->priv & AFS_PRIV_MAX,
+		      __entry->priv >> AFS_PRIV_SHIFT)
+	    );
+
 #endif /* _TRACE_AFS_H */
 
 /* This part must be outside protection */