xfs: trace what memory backs a buffer

Add three trace points for the different backing memory allocators for
buffers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

Author: Christoph Hellwig

fs/xfs/xfs_buf.c

@@ -240,6 +240,7 @@ xfs_buf_alloc_kmem(
 		return -ENOMEM;
 	}
 	bp->b_flags |= _XBF_KMEM;
+	trace_xfs_buf_backing_kmem(bp, _RET_IP_);
 	return 0;
 }
 
@@ -319,9 +320,11 @@ xfs_buf_alloc_backing_mem(
 	if (!folio) {
 		if (size <= PAGE_SIZE)
 			return -ENOMEM;
+		trace_xfs_buf_backing_fallback(bp, _RET_IP_);
 		goto fallback;
 	}
 	bp->b_addr = folio_address(folio);
+	trace_xfs_buf_backing_folio(bp, _RET_IP_);
 	return 0;
 
 fallback:
@@ -335,6 +338,7 @@ xfs_buf_alloc_backing_mem(
 		memalloc_retry_wait(gfp_mask);
 	}
 
+	trace_xfs_buf_backing_vmalloc(bp, _RET_IP_);
 	return 0;
 }
 

fs/xfs/xfs_trace.h

@@ -692,6 +692,10 @@ DEFINE_BUF_EVENT(xfs_buf_iodone_async);
 DEFINE_BUF_EVENT(xfs_buf_error_relse);
 DEFINE_BUF_EVENT(xfs_buf_drain_buftarg);
 DEFINE_BUF_EVENT(xfs_trans_read_buf_shut);
+DEFINE_BUF_EVENT(xfs_buf_backing_folio);
+DEFINE_BUF_EVENT(xfs_buf_backing_kmem);
+DEFINE_BUF_EVENT(xfs_buf_backing_vmalloc);
+DEFINE_BUF_EVENT(xfs_buf_backing_fallback);
 
 /* not really buffer traces, but the buf provides useful information */
 DEFINE_BUF_EVENT(xfs_btree_corrupt);