[RFC PATCH 06/11] shmem: trace shmem_add_to_page_cache folio order

[Daniel Gomez <da.gomez@xxxxxxxxxxx>]

To be able to trace and account for order of the folio.

Based on include/trace/filemap.h.

Update MAINTAINERS file list for SHMEM.

Signed-off-by: Daniel Gomez <da.gomez@xxxxxxxxxxx>
---
 MAINTAINERS                  |  1 +
 include/trace/events/shmem.h | 52 ++++++++++++++++++++++++++++++++++++
 mm/shmem.c                   |  4 +++
 3 files changed, 57 insertions(+)
 create mode 100644 include/trace/events/shmem.h

diff --git a/MAINTAINERS b/MAINTAINERS
index bdc4638b2df5..befa63e7cb28 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21923,6 +21923,7 @@ M:	Hugh Dickins <hughd@xxxxxxxxxx>
 L:	linux-mm@xxxxxxxxx
 S:	Maintained
 F:	include/linux/shmem_fs.h
+F:	include/trace/events/shmem.h
 F:	mm/shmem.c
 
 TOMOYO SECURITY MODULE
diff --git a/include/trace/events/shmem.h b/include/trace/events/shmem.h
new file mode 100644
index 000000000000..223f78f11457
--- /dev/null
+++ b/include/trace/events/shmem.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM shmem
+
+#if !defined(_TRACE_SHMEM_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SHMEM_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(mm_shmem_op_page_cache,
+
+	TP_PROTO(struct folio *folio),
+
+	TP_ARGS(folio),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, pfn)
+		__field(unsigned long, i_ino)
+		__field(unsigned long, index)
+		__field(dev_t, s_dev)
+		__field(unsigned char, order)
+	),
+
+	TP_fast_assign(
+		__entry->pfn = folio_pfn(folio);
+		__entry->i_ino = folio->mapping->host->i_ino;
+		__entry->index = folio->index;
+		if (folio->mapping->host->i_sb)
+			__entry->s_dev = folio->mapping->host->i_sb->s_dev;
+		else
+			__entry->s_dev = folio->mapping->host->i_rdev;
+		__entry->order = folio_order(folio);
+	),
+
+	TP_printk("dev %d:%d ino %lx pfn=0x%lx ofs=%lu order=%u",
+		MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+		__entry->i_ino,
+		__entry->pfn,
+		__entry->index << PAGE_SHIFT,
+		__entry->order)
+);
+
+DEFINE_EVENT(mm_shmem_op_page_cache, mm_shmem_add_to_page_cache,
+	TP_PROTO(struct folio *folio),
+	TP_ARGS(folio)
+	);
+
+#endif /* _TRACE_SHMEM_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/mm/shmem.c b/mm/shmem.c
index ab31d2880e5d..e2893cf2287f 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -84,6 +84,9 @@ static struct vfsmount *shm_mnt __ro_after_init;
 
 #include "internal.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/shmem.h>
+
 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
 
 /* Pretend that each entry is of this size in directory's i_size */
@@ -1726,6 +1729,7 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
 		}
 	}
 
+	trace_mm_shmem_add_to_page_cache(folio);
 	shmem_recalc_inode(inode, pages, 0);
 	folio_add_lru(folio);
 	return folio;
-- 
2.39.2