Add tracepoints to dax_pmd_insert_mapping(), following the same logging
conventions as the tracepoints in dax_iomap_pmd_fault().

Here is an example PMD fault showing the new tracepoints:

big-1504  [001] ....   326.960743: xfs_filemap_pmd_fault: dev 259:0 ino
0x1003

big-1504  [001] ....   326.960753: dax_pmd_fault: dev 259:0 ino 0x1003
shared WRITE|ALLOW_RETRY|KILLABLE|USER address 0x10505000 vm_start
0x10200000 vm_end 0x10700000 pgoff 0x200 max_pgoff 0x1400

big-1504  [001] ....   326.960981: dax_pmd_insert_mapping: dev 259:0 ino
0x1003 shared write address 0x10505000 length 0x200000 pfn 0x100600 DEV|MAP
radix_entry 0xc000e

big-1504  [001] ....   326.960986: dax_pmd_fault_done: dev 259:0 ino 0x1003
shared WRITE|ALLOW_RETRY|KILLABLE|USER address 0x10505000 vm_start
0x10200000 vm_end 0x10700000 pgoff 0x200 max_pgoff 0x1400 NOPAGE

Signed-off-by: Ross Zwisler <ross.zwis...@linux.intel.com>
Reviewed-by: Jan Kara <j...@suse.cz>
---
 fs/dax.c                      | 12 +++++++---
 include/linux/pfn_t.h         |  6 +++++
 include/trace/events/fs_dax.h | 51 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 61b3080..d3fe880 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1232,15 +1232,16 @@ static int dax_pmd_insert_mapping(struct vm_area_struct 
*vma, pmd_t *pmd,
 {
        struct address_space *mapping = vma->vm_file->f_mapping;
        struct block_device *bdev = iomap->bdev;
+       struct inode *inode = mapping->host;
        struct blk_dax_ctl dax = {
                .sector = dax_iomap_sector(iomap, pos),
                .size = PMD_SIZE,
        };
        long length = dax_map_atomic(bdev, &dax);
-       void *ret;
+       void *ret = NULL;
 
        if (length < 0) /* dax_map_atomic() failed */
-               return VM_FAULT_FALLBACK;
+               goto fallback;
        if (length < PMD_SIZE)
                goto unmap_fallback;
        if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
@@ -1253,13 +1254,18 @@ static int dax_pmd_insert_mapping(struct vm_area_struct 
*vma, pmd_t *pmd,
        ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
                        RADIX_DAX_PMD);
        if (IS_ERR(ret))
-               return VM_FAULT_FALLBACK;
+               goto fallback;
        *entryp = ret;
 
+       trace_dax_pmd_insert_mapping(inode, vma, address, write, length,
+                       dax.pfn, ret);
        return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
 
  unmap_fallback:
        dax_unmap_atomic(bdev, &dax);
+fallback:
+       trace_dax_pmd_insert_mapping_fallback(inode, vma, address, write,
+                       length, dax.pfn, ret);
        return VM_FAULT_FALLBACK;
 }
 
diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
index a3d90b9..033fc7b 100644
--- a/include/linux/pfn_t.h
+++ b/include/linux/pfn_t.h
@@ -15,6 +15,12 @@
 #define PFN_DEV (1ULL << (BITS_PER_LONG_LONG - 3))
 #define PFN_MAP (1ULL << (BITS_PER_LONG_LONG - 4))
 
+#define PFN_FLAGS_TRACE \
+       { PFN_SG_CHAIN, "SG_CHAIN" }, \
+       { PFN_SG_LAST,  "SG_LAST" }, \
+       { PFN_DEV,      "DEV" }, \
+       { PFN_MAP,      "MAP" }
+
 static inline pfn_t __pfn_to_pfn_t(unsigned long pfn, u64 flags)
 {
        pfn_t pfn_t = { .val = pfn | (flags & PFN_FLAGS_MASK), };
diff --git a/include/trace/events/fs_dax.h b/include/trace/events/fs_dax.h
index 43f1263..c3b0aae 100644
--- a/include/trace/events/fs_dax.h
+++ b/include/trace/events/fs_dax.h
@@ -104,6 +104,57 @@ DEFINE_EVENT(dax_pmd_load_hole_class, name, \
 DEFINE_PMD_LOAD_HOLE_EVENT(dax_pmd_load_hole);
 DEFINE_PMD_LOAD_HOLE_EVENT(dax_pmd_load_hole_fallback);
 
+DECLARE_EVENT_CLASS(dax_pmd_insert_mapping_class,
+       TP_PROTO(struct inode *inode, struct vm_area_struct *vma,
+               unsigned long address, int write, long length, pfn_t pfn,
+               void *radix_entry),
+       TP_ARGS(inode, vma, address, write, length, pfn, radix_entry),
+       TP_STRUCT__entry(
+               __field(unsigned long, ino)
+               __field(unsigned long, vm_flags)
+               __field(unsigned long, address)
+               __field(long, length)
+               __field(u64, pfn_val)
+               __field(void *, radix_entry)
+               __field(dev_t, dev)
+               __field(int, write)
+       ),
+       TP_fast_assign(
+               __entry->dev = inode->i_sb->s_dev;
+               __entry->ino = inode->i_ino;
+               __entry->vm_flags = vma->vm_flags;
+               __entry->address = address;
+               __entry->write = write;
+               __entry->length = length;
+               __entry->pfn_val = pfn.val;
+               __entry->radix_entry = radix_entry;
+       ),
+       TP_printk("dev %d:%d ino %#lx %s %s address %#lx length %#lx "
+                       "pfn %#llx %s radix_entry %#lx",
+               MAJOR(__entry->dev),
+               MINOR(__entry->dev),
+               __entry->ino,
+               __entry->vm_flags & VM_SHARED ? "shared" : "private",
+               __entry->write ? "write" : "read",
+               __entry->address,
+               __entry->length,
+               __entry->pfn_val & ~PFN_FLAGS_MASK,
+               __print_flags_u64(__entry->pfn_val & PFN_FLAGS_MASK, "|",
+                       PFN_FLAGS_TRACE),
+               (unsigned long)__entry->radix_entry
+       )
+)
+
+#define DEFINE_PMD_INSERT_MAPPING_EVENT(name) \
+DEFINE_EVENT(dax_pmd_insert_mapping_class, name, \
+       TP_PROTO(struct inode *inode, struct vm_area_struct *vma, \
+               unsigned long address, int write, long length, pfn_t pfn, \
+               void *radix_entry), \
+       TP_ARGS(inode, vma, address, write, length, pfn, radix_entry))
+
+DEFINE_PMD_INSERT_MAPPING_EVENT(dax_pmd_insert_mapping);
+DEFINE_PMD_INSERT_MAPPING_EVENT(dax_pmd_insert_mapping_fallback);
+
 #endif /* _TRACE_FS_DAX_H */
 
 /* This part must be outside protection */
-- 
2.7.4

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