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Subject: [PATCH 28/67] cachefiles: Trace truncations
From:   David Howells <dhowells@redhat.com>
To:     linux-cachefs@redhat.com
Cc:     dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Steve French <sfrench@samba.org>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Jeff Layton <jlayton@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Omar Sandoval <osandov@osandov.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
        linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
        v9fs-developer@lists.sourceforge.net,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Mon, 18 Oct 2021 15:57:42 +0100
Message-ID: <163456906284.2614702.7451773731985568258.stgit@warthog.procyon.org.uk>
In-Reply-To: <163456861570.2614702.14754548462706508617.stgit@warthog.procyon.org.uk>
References: <163456861570.2614702.14754548462706508617.stgit@warthog.procyon.org.uk>
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Add a tracepoint to trace truncation operations.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/cachefiles/interface.c         |    9 +++++++-
 include/trace/events/cachefiles.h |   40 +++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 4edb3a09932a..8f98e5c27d66 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -341,9 +341,16 @@ static void cachefiles_invalidate_object(struct cachefiles_object *object)
 		ASSERT(d_is_reg(file->f_path.dentry));
 
 		cachefiles_begin_secure(cache, &saved_cred);
+		trace_cachefiles_trunc(object, file_inode(file),
+				       i_size_read(file_inode(file)), 0,
+				       cachefiles_trunc_invalidate);
 		ret = vfs_truncate(&file->f_path, 0);
-		if (ret == 0)
+		if (ret == 0) {
+			trace_cachefiles_trunc(object, file_inode(file),
+					       0, ni_size,
+					       cachefiles_trunc_set_size);
 			ret = vfs_truncate(&file->f_path, ni_size);
+		}
 		cachefiles_end_secure(cache, saved_cred);
 
 		if (ret != 0) {
diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h
index 6e9f6462833d..09d76c160451 100644
--- a/include/trace/events/cachefiles.h
+++ b/include/trace/events/cachefiles.h
@@ -37,6 +37,11 @@ enum cachefiles_coherency_trace {
 	cachefiles_coherency_set_ok,
 };
 
+enum cachefiles_trunc_trace {
+	cachefiles_trunc_invalidate,
+	cachefiles_trunc_set_size,
+};
+
 #endif
 
 /*
@@ -72,6 +77,10 @@ enum cachefiles_coherency_trace {
 	EM(cachefiles_coherency_set_fail,	"SET fail")		\
 	E_(cachefiles_coherency_set_ok,		"SET ok  ")
 
+#define cachefiles_trunc_traces						\
+	EM(cachefiles_trunc_invalidate,		"INVAL ")		\
+	E_(cachefiles_trunc_set_size,		"SETSIZ")
+
 /*
  * Export enum symbols via userspace.
  */
@@ -83,6 +92,7 @@ enum cachefiles_coherency_trace {
 cachefiles_obj_kill_traces;
 cachefiles_obj_ref_traces;
 cachefiles_coherency_traces;
+cachefiles_trunc_traces;
 
 /*
  * Now redefine the EM() and E_() macros to map the enums to the strings that
@@ -292,6 +302,36 @@ TRACE_EVENT(cachefiles_coherency,
 		      __entry->content)
 	    );
 
+TRACE_EVENT(cachefiles_trunc,
+	    TP_PROTO(struct cachefiles_object *obj, struct inode *backer,
+		     loff_t from, loff_t to, enum cachefiles_trunc_trace why),
+
+	    TP_ARGS(obj, backer, from, to, why),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,			obj	)
+		    __field(unsigned int,			backer	)
+		    __field(enum cachefiles_trunc_trace,	why	)
+		    __field(loff_t,				from	)
+		    __field(loff_t,				to	)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->obj	= obj->debug_id;
+		    __entry->backer	= backer->i_ino;
+		    __entry->from	= from;
+		    __entry->to		= to;
+		    __entry->why	= why;
+			   ),
+
+	    TP_printk("o=%08x b=%08x %s l=%llx->%llx",
+		      __entry->obj,
+		      __entry->backer,
+		      __print_symbolic(__entry->why, cachefiles_trunc_traces),
+		      __entry->from,
+		      __entry->to)
+	    );
+
 #endif /* _TRACE_CACHEFILES_H */
 
 /* This part must be outside protection */