[PATCH 28/29] xfs: support nowait semantics for xc_ctx_lock in xlog_cil_commit()

[Hao Xu]

From: Hao Xu <howeyxu at tencent.com>

Apply trylock logic for xc_ctx_lock in xlog_cil_commit() in nowait
case and error out -EAGAIN for xlog_cil_commit().

Signed-off-by: Hao Xu <howeyxu at tencent.com>
---
 fs/xfs/xfs_log_cil.c  | 12 ++++++++++--
 fs/xfs/xfs_log_priv.h |  2 +-
 fs/xfs/xfs_trans.c    |  4 +++-
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index b31830ee36dd..6d054359bbb5 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -1613,7 +1613,7 @@ xlog_cil_process_intents(
  * background commit, returns without it held once background commits are
  * allowed again.
  */
-void
+int
 xlog_cil_commit(
 	struct xlog		*log,
 	struct xfs_trans	*tp,
@@ -1623,6 +1623,7 @@ xlog_cil_commit(
 	struct xfs_cil		*cil = log->l_cilp;
 	struct xfs_log_item	*lip, *next;
 	uint32_t		released_space = 0;
+	bool			nowait = tp->t_flags & XFS_TRANS_NOWAIT;
 
 	/*
 	 * Do all necessary memory allocation before we lock the CIL.
@@ -1632,7 +1633,12 @@ xlog_cil_commit(
 	xlog_cil_alloc_shadow_bufs(log, tp);
 
 	/* lock out background commit */
-	down_read(&cil->xc_ctx_lock);
+	if (nowait) {
+		if (!down_read_trylock(&cil->xc_ctx_lock))
+			return -EAGAIN;
+	} else {
+		down_read(&cil->xc_ctx_lock);
+	}
 
 	if (tp->t_flags & XFS_TRANS_HAS_INTENT_DONE)
 		released_space = xlog_cil_process_intents(cil, tp);
@@ -1668,6 +1674,8 @@ xlog_cil_commit(
 
 	/* xlog_cil_push_background() releases cil->xc_ctx_lock */
 	xlog_cil_push_background(log);
+
+	return 0;
 }
 
 /*
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 41edaa0ae869..eb7a1241deab 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -580,7 +580,7 @@ int	xlog_cil_init(struct xlog *log);
 void	xlog_cil_init_post_recovery(struct xlog *log);
 void	xlog_cil_destroy(struct xlog *log);
 bool	xlog_cil_empty(struct xlog *log);
-void	xlog_cil_commit(struct xlog *log, struct xfs_trans *tp,
+int	xlog_cil_commit(struct xlog *log, struct xfs_trans *tp,
 			xfs_csn_t *commit_seq, bool regrant);
 void	xlog_cil_set_ctx_write_state(struct xfs_cil_ctx *ctx,
 			struct xlog_in_core *iclog);
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index f1f84a3dd456..e5beda636a37 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -1037,7 +1037,9 @@ __xfs_trans_commit(
 		xfs_trans_apply_sb_deltas(tp);
 	xfs_trans_apply_dquot_deltas(tp);
 
-	xlog_cil_commit(log, tp, &commit_seq, regrant);
+	error = xlog_cil_commit(log, tp, &commit_seq, regrant);
+	if (error)
+		goto out_unreserve;
 
 	xfs_trans_free(tp);
 
-- 
2.25.1