[Cluster-devel] [GFS2 PATCH] GFS2: Add new debug trace point and evict code path

[Bob Peterson <rpeterso@redhat.com>]

Hi,

This patch adds a new kernel trace point for general gfs2 debugging.
Its first use is to trace which codepath is taken when an inode is
evicted. This helped me debugging some nasty problems.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 2a9a830..ae70bcf 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -41,6 +41,7 @@
 #include "recovery.h"
 #include "rgrp.h"
 #include "super.h"
+#include "trace_gfs2.h"
 #include "trans.h"
 #include "util.h"
 #include "sys.h"
@@ -815,6 +816,7 @@ static void gfs2_dirty_inode(struct inode *inode, int flags)
 	}
 
 	ret = gfs2_meta_inode_buffer(ip, &bh);
+	trace_gfs2_debug(ip->i_gl, ret, "gfs2_dirty_inode");
 	if (ret == 0) {
 		gfs2_trans_add_meta(ip->i_gl, bh);
 		gfs2_dinode_out(ip, bh->b_data);
@@ -1528,12 +1530,15 @@ static void gfs2_evict_inode(struct inode *inode)
 	int error;
 
 	if (test_bit(GIF_FREE_VFS_INODE, &ip->i_flags)) {
+		trace_gfs2_debug(ip->i_gl, inode->i_nlink, "evict_case_3a");
 		clear_inode(inode);
 		return;
 	}
 
-	if (inode->i_nlink || (sb->s_flags & MS_RDONLY))
+	if (inode->i_nlink || (sb->s_flags & MS_RDONLY)) {
+		trace_gfs2_debug(ip->i_gl, inode->i_state, "evict_case_3");
 		goto out;
+	}
 
 	/* Must not read inode block until block type has been verified */
 	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_SKIP, &gh);
@@ -1541,19 +1546,24 @@ static void gfs2_evict_inode(struct inode *inode)
 		ip->i_iopen_gh.gh_flags |= GL_NOCACHE;
 		gfs2_glock_dq_wait(&ip->i_iopen_gh);
 		gfs2_holder_uninit(&ip->i_iopen_gh);
+		trace_gfs2_debug(ip->i_gl, error, "evict_case_glerr");
 		goto out;
 	}
 
 	if (!test_bit(GIF_ALLOC_FAILED, &ip->i_flags)) {
 		error = gfs2_check_blk_type(sdp, ip->i_no_addr, GFS2_BLKST_UNLINKED);
-		if (error)
+		if (error) {
+			trace_gfs2_debug(ip->i_gl, error, "evict_case_2a");
 			goto out_truncate;
+		}
 	}
 
 	if (test_bit(GIF_INVALID, &ip->i_flags)) {
 		error = gfs2_inode_refresh(ip);
-		if (error)
+		if (error) {
+			trace_gfs2_debug(ip->i_gl, error, "evict_case_2b");
 			goto out_truncate;
+		}
 	}
 
 	if (gfs2_holder_initialized(&ip->i_iopen_gh) &&
@@ -1563,8 +1573,10 @@ static void gfs2_evict_inode(struct inode *inode)
 		gfs2_holder_reinit(LM_ST_EXCLUSIVE, LM_FLAG_TRY_1CB | GL_NOCACHE,
 				   &ip->i_iopen_gh);
 		error = gfs2_glock_nq(&ip->i_iopen_gh);
-		if (error)
+		if (error) {
+			trace_gfs2_debug(ip->i_gl, error, "evict_case_2c");
 			goto out_truncate;
+		}
 	}
 
 	/* Case 1 starts here */
@@ -1572,22 +1584,29 @@ static void gfs2_evict_inode(struct inode *inode)
 	if (S_ISDIR(inode->i_mode) &&
 	    (ip->i_diskflags & GFS2_DIF_EXHASH)) {
 		error = gfs2_dir_exhash_dealloc(ip);
-		if (error)
+		if (error) {
+			trace_gfs2_debug(ip->i_gl, error, "evict_case_1a");
 			goto out_unlock;
+		}
 	}
 
 	if (ip->i_eattr) {
 		error = gfs2_ea_dealloc(ip);
-		if (error)
+		if (error) {
+			trace_gfs2_debug(ip->i_gl, error, "evict_case_1b");
 			goto out_unlock;
+		}
 	}
 
 	if (!gfs2_is_stuffed(ip)) {
 		error = gfs2_file_dealloc(ip);
-		if (error)
+		if (error) {
+			trace_gfs2_debug(ip->i_gl, error, "evict_case_1c");
 			goto out_unlock;
+		}
 	}
 
+	trace_gfs2_debug(ip->i_gl, error, "evict_case_1");
 	error = gfs2_dinode_dealloc(ip);
 	goto out_unlock;
 
diff --git a/fs/gfs2/trace_gfs2.h b/fs/gfs2/trace_gfs2.h
index 49ac55d..3d24bbb 100644
--- a/fs/gfs2/trace_gfs2.h
+++ b/fs/gfs2/trace_gfs2.h
@@ -548,6 +548,38 @@ TRACE_EVENT(gfs2_rs,
 		  rs_func_name(__entry->func), (unsigned long)__entry->free)
 );
 
+/* Generic debug messages */
+TRACE_EVENT(gfs2_debug,
+
+	TP_PROTO(struct gfs2_glock *gl, int ret, const char *msg),
+
+	TP_ARGS(gl, ret, msg),
+
+	TP_STRUCT__entry(
+		__field(        dev_t,  dev                     )
+		__field(	u64,	glnum			)
+		__field(	u32,	gltype			)
+		__field(	int,	ret			)
+		__field(	int,	nrpages			)
+		__string(	msg,	msg			)
+	),
+
+	TP_fast_assign(
+		__entry->dev	= gl->gl_name.ln_sbd->sd_vfs->s_dev;
+		__entry->glnum	= gl->gl_name.ln_number;
+		__entry->gltype	= gl->gl_name.ln_type;
+		__entry->ret = ret;
+		__entry->nrpages = (gfs2_glock2aspace(gl) ?
+				    gfs2_glock2aspace(gl)->nrpages : 0);
+		__assign_str(msg, msg);
+	),
+
+	TP_printk("%u,%u %u:%llu rc:%d pgs: %d %s",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->gltype,
+		  (unsigned long long)__entry->glnum, __entry->ret,
+		  __entry->nrpages, __get_str(msg))
+);
+
 #endif /* _TRACE_GFS2_H */
 
 /* This part must be outside protection */