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Subject: [PATCH 27/67] cachefiles: trace: Log coherency checks
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 15:57:30 +0100
Message-ID: <163456905064.2614702.902644495518051262.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 cachefiles tracepoint that logs the result of coherency management
when the coherency data on a file in the cache is checked or committed.

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

 fs/cachefiles/xattr.c             |   44 +++++++++++++++++++++--------
 include/trace/events/cachefiles.h |   56 +++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+), 12 deletions(-)

diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
index 2f14618d9a36..bfb2f4d605af 100644
--- a/fs/cachefiles/xattr.c
+++ b/fs/cachefiles/xattr.c
@@ -53,12 +53,21 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object,
 	ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
 			   buf, sizeof(struct cachefiles_xattr) + len,
 			   xattr_flags);
-	kfree(buf);
-	if (ret < 0 && ret != -ENOMEM)
-		cachefiles_io_error_obj(
-			object,
-			"Failed to set xattr with error %d", ret);
+	if (ret < 0) {
+		trace_cachefiles_coherency(object, file_inode(file)->i_ino,
+					   0,
+					   cachefiles_coherency_set_fail);
+		if (ret != -ENOMEM)
+			cachefiles_io_error_obj(
+				object,
+				"Failed to set xattr with error %d", ret);
+	} else {
+		trace_cachefiles_coherency(object, file_inode(file)->i_ino,
+					   0,
+					   cachefiles_coherency_set_ok);
+	}
 
+	kfree(buf);
 	_leave(" = %d", ret);
 	return ret;
 }
@@ -72,21 +81,32 @@ int cachefiles_check_auxdata(struct cachefiles_object *object)
 	struct dentry *dentry = object->file->f_path.dentry;
 	unsigned int len = object->cookie->aux_len, tlen;
 	const void *p = fscache_get_aux(object->cookie);
-	ssize_t ret;
+	enum cachefiles_coherency_trace why;
+	ssize_t xlen;
+	int ret = -ESTALE;
 
 	tlen = sizeof(struct cachefiles_xattr) + len;
 	buf = kmalloc(tlen, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
 
-	ret = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, tlen);
-	if (ret == tlen &&
-	    buf->type == object->cookie->type &&
-	    memcmp(buf->data, p, len) == 0)
+	xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, tlen);
+	if (xlen != tlen) {
+		if (xlen == -EIO)
+			cachefiles_io_error_obj(
+				object,
+				"Failed to read aux with error %zd", xlen);
+		why = cachefiles_coherency_check_xattr;
+	} else if (buf->type != object->cookie->type) {
+		why = cachefiles_coherency_check_type;
+	} else if (memcmp(buf->data, p, len) != 0) {
+		why = cachefiles_coherency_check_aux;
+	} else {
+		why = cachefiles_coherency_check_ok;
 		ret = 0;
-	else
-		ret = -ESTALE;
+	}
 
+	trace_cachefiles_coherency(object, file_inode(object->file)->i_ino, 0, why);
 	kfree(buf);
 	return ret;
 }
diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h
index 10ad5305d1c5..6e9f6462833d 100644
--- a/include/trace/events/cachefiles.h
+++ b/include/trace/events/cachefiles.h
@@ -24,6 +24,19 @@ enum cachefiles_obj_ref_trace {
 	cachefiles_obj_ref__nr_traces
 };
 
+enum cachefiles_coherency_trace {
+	cachefiles_coherency_check_aux,
+	cachefiles_coherency_check_content,
+	cachefiles_coherency_check_dirty,
+	cachefiles_coherency_check_len,
+	cachefiles_coherency_check_objsize,
+	cachefiles_coherency_check_ok,
+	cachefiles_coherency_check_type,
+	cachefiles_coherency_check_xattr,
+	cachefiles_coherency_set_fail,
+	cachefiles_coherency_set_ok,
+};
+
 #endif
 
 /*
@@ -47,6 +60,18 @@ enum cachefiles_obj_ref_trace {
 	EM(cachefiles_obj_put_wait_retry,	"PUT wait_retry")	\
 	E_(cachefiles_obj_put_wait_timeo,	"PUT wait_timeo")
 
+#define cachefiles_coherency_traces					\
+	EM(cachefiles_coherency_check_aux,	"BAD aux ")		\
+	EM(cachefiles_coherency_check_content,	"BAD cont")		\
+	EM(cachefiles_coherency_check_dirty,	"BAD dirt")		\
+	EM(cachefiles_coherency_check_len,	"BAD len ")		\
+	EM(cachefiles_coherency_check_objsize,	"BAD osiz")		\
+	EM(cachefiles_coherency_check_ok,	"OK      ")		\
+	EM(cachefiles_coherency_check_type,	"BAD type")		\
+	EM(cachefiles_coherency_check_xattr,	"BAD xatt")		\
+	EM(cachefiles_coherency_set_fail,	"SET fail")		\
+	E_(cachefiles_coherency_set_ok,		"SET ok  ")
+
 /*
  * Export enum symbols via userspace.
  */
@@ -57,6 +82,7 @@ enum cachefiles_obj_ref_trace {
 
 cachefiles_obj_kill_traces;
 cachefiles_obj_ref_traces;
+cachefiles_coherency_traces;
 
 /*
  * Now redefine the EM() and E_() macros to map the enums to the strings that
@@ -236,6 +262,36 @@ TRACE_EVENT(cachefiles_mark_inactive,
 		      __entry->obj, __entry->inode)
 	    );
 
+TRACE_EVENT(cachefiles_coherency,
+	    TP_PROTO(struct cachefiles_object *obj,
+		     ino_t ino,
+		     int content,
+		     enum cachefiles_coherency_trace why),
+
+	    TP_ARGS(obj, ino, content, why),
+
+	    /* Note that obj may be NULL */
+	    TP_STRUCT__entry(
+		    __field(unsigned int,			obj	)
+		    __field(enum cachefiles_coherency_trace,	why	)
+		    __field(int,				content	)
+		    __field(u64,				ino	)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->obj	= obj->debug_id;
+		    __entry->why	= why;
+		    __entry->content	= content;
+		    __entry->ino	= ino;
+			   ),
+
+	    TP_printk("o=%08x %s i=%llx c=%u",
+		      __entry->obj,
+		      __print_symbolic(__entry->why, cachefiles_coherency_traces),
+		      __entry->ino,
+		      __entry->content)
+	    );
+
 #endif /* _TRACE_CACHEFILES_H */
 
 /* This part must be outside protection */