On 7/28/21 6:42 AM, Chandan Babu R wrote:

On 27 Jul 2021 at 11:50, Allison Henderson wrote:

quoted

This is a quick patch to add a new xfs_attr_*_return tracepoints.  We
use these to track when ever a new state is set or -EAGAIN is returned

Signed-off-by: Allison Henderson <redacted>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
---
  fs/xfs/libxfs/xfs_attr.c        | 28 ++++++++++++++++++++++++++--
  fs/xfs/libxfs/xfs_attr_remote.c |  1 +
  fs/xfs/xfs_trace.h              | 24 ++++++++++++++++++++++++
  3 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index 5040fc1..b0c6c62 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c

@@ -335,6 +335,7 @@ xfs_attr_sf_addname(
  	 * the attr fork to leaf format and will restart with the leaf
  	 * add.
  	 */
+	trace_xfs_attr_sf_addname_return(XFS_DAS_UNINIT, args->dp);
  	dac->flags |= XFS_DAC_DEFER_FINISH;
  	return -EAGAIN;
  }

@@ -394,6 +395,8 @@ xfs_attr_set_iter(
  				 * handling code below
  				 */
  				dac->flags |= XFS_DAC_DEFER_FINISH;
+				trace_xfs_attr_set_iter_return(
+					dac->dela_state, args->dp);
  				return -EAGAIN;
  			} else if (error) {
  				return error;

@@ -418,6 +421,7 @@ xfs_attr_set_iter(
  
  			dac->dela_state = XFS_DAS_FOUND_NBLK;
  		}
+		trace_xfs_attr_set_iter_return(dac->dela_state,	args->dp);
  		return -EAGAIN;
  	case XFS_DAS_FOUND_LBLK:
  		/*

@@ -445,6 +449,8 @@ xfs_attr_set_iter(
  			error = xfs_attr_rmtval_set_blk(dac);
  			if (error)
  				return error;
+			trace_xfs_attr_set_iter_return(dac->dela_state,
+						       args->dp);
  			return -EAGAIN;
  		}
  

@@ -479,6 +485,7 @@ xfs_attr_set_iter(
  		 * series.
  		 */
  		dac->dela_state = XFS_DAS_FLIP_LFLAG;
+		trace_xfs_attr_set_iter_return(dac->dela_state, args->dp);
  		return -EAGAIN;
  	case XFS_DAS_FLIP_LFLAG:
  		/*

@@ -496,6 +503,9 @@ xfs_attr_set_iter(
  		dac->dela_state = XFS_DAS_RM_LBLK;
  		if (args->rmtblkno) {
  			error = __xfs_attr_rmtval_remove(dac);
+			if (error == -EAGAIN)
+				trace_xfs_attr_set_iter_return(
+					dac->dela_state, args->dp);
  			if (error)
  				return error;

if __xfs_attr_rmtval_remove() successfully removes all the remote blocks, we
transition over to XFS_DAS_RD_LEAF state and return -EAGAIN. A tracepoint
is probably required for this as well?

quoted

@@ -549,6 +559,8 @@ xfs_attr_set_iter(
  				error = xfs_attr_rmtval_set_blk(dac);
  				if (error)
  					return error;
+				trace_xfs_attr_set_iter_return(
+					dac->dela_state, args->dp);
  				return -EAGAIN;
  			}
  

@@ -584,6 +596,7 @@ xfs_attr_set_iter(
  		 * series
  		 */
  		dac->dela_state = XFS_DAS_FLIP_NFLAG;
+		trace_xfs_attr_set_iter_return(dac->dela_state, args->dp);
  		return -EAGAIN;
  
  	case XFS_DAS_FLIP_NFLAG:

@@ -603,6 +616,10 @@ xfs_attr_set_iter(
  		dac->dela_state = XFS_DAS_RM_NBLK;
  		if (args->rmtblkno) {
  			error = __xfs_attr_rmtval_remove(dac);
+			if (error == -EAGAIN)
+				trace_xfs_attr_set_iter_return(
+					dac->dela_state, args->dp);
+
  			if (error)
  				return error;

A transition to XFS_DAS_CLR_FLAG state probably requires a tracepoint call.

quoted

@@ -1183,6 +1200,8 @@ xfs_attr_node_addname(
  			 * this point.
  			 */
  			dac->flags |= XFS_DAC_DEFER_FINISH;
+			trace_xfs_attr_node_addname_return(
+					dac->dela_state, args->dp);
  			return -EAGAIN;
  		}
  

@@ -1429,10 +1448,13 @@ xfs_attr_remove_iter(
  			 * blocks are removed.
  			 */
  			error = __xfs_attr_rmtval_remove(dac);
-			if (error == -EAGAIN)
+			if (error == -EAGAIN) {
+				trace_xfs_attr_remove_iter_return(
+						dac->dela_state, args->dp);
  				return error;
-			else if (error)
+			} else if (error) {
  				goto out;
+			}

if the call to __xfs_attr_rmtval_remove() is successful, we transition over to
XFS_DAS_RM_NAME state and return -EAGAIN. Maybe tracepoint is required here as
well?

Yes, I think these three are good additions.  I think this patch was 
written before those extra states were added, and likley forgot to add 
the corresponding traces.  Will update.  Thanks for the review!

Allison

quoted

  			/*
  			 * Refill the state structure with buffers (the prior

@@ -1473,6 +1495,8 @@ xfs_attr_remove_iter(
  
  			dac->flags |= XFS_DAC_DEFER_FINISH;
  			dac->dela_state = XFS_DAS_RM_SHRINK;
+			trace_xfs_attr_remove_iter_return(
+					dac->dela_state, args->dp);
  			return -EAGAIN;
  		}
  

diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
index 0c8bee3..70f880d 100644
--- a/fs/xfs/libxfs/xfs_attr_remote.c
+++ b/fs/xfs/libxfs/xfs_attr_remote.c

@@ -696,6 +696,7 @@ __xfs_attr_rmtval_remove(
  	 */
  	if (!done) {
  		dac->flags |= XFS_DAC_DEFER_FINISH;
+		trace_xfs_attr_rmtval_remove_return(dac->dela_state, args->dp);
  		return -EAGAIN;
  	}
  

diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index f9d8d60..f9840dd 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h

@@ -3987,6 +3987,30 @@ DEFINE_ICLOG_EVENT(xlog_iclog_want_sync);
  DEFINE_ICLOG_EVENT(xlog_iclog_wait_on);
  DEFINE_ICLOG_EVENT(xlog_iclog_write);
  
+DECLARE_EVENT_CLASS(xfs_das_state_class,
+	TP_PROTO(int das, struct xfs_inode *ip),
+	TP_ARGS(das, ip),
+	TP_STRUCT__entry(
+		__field(int, das)
+		__field(xfs_ino_t, ino)
+	),
+	TP_fast_assign(
+		__entry->das = das;
+		__entry->ino = ip->i_ino;
+	),
+	TP_printk("state change %d ino 0x%llx",
+		  __entry->das, __entry->ino)
+)
+
+#define DEFINE_DAS_STATE_EVENT(name) \
+DEFINE_EVENT(xfs_das_state_class, name, \
+	TP_PROTO(int das, struct xfs_inode *ip), \
+	TP_ARGS(das, ip))
+DEFINE_DAS_STATE_EVENT(xfs_attr_sf_addname_return);
+DEFINE_DAS_STATE_EVENT(xfs_attr_set_iter_return);
+DEFINE_DAS_STATE_EVENT(xfs_attr_node_addname_return);
+DEFINE_DAS_STATE_EVENT(xfs_attr_remove_iter_return);
+DEFINE_DAS_STATE_EVENT(xfs_attr_rmtval_remove_return);
  #endif /* _TRACE_XFS_H */
  
  #undef TRACE_INCLUDE_PATH