linux-kernel - [RFC PATCH 4/5] cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode

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Message-Id: <20220818135204.49878-5-zhujia.zj@bytedance.com>
Date:   Thu, 18 Aug 2022 21:52:03 +0800
From:   Jia Zhu <zhujia.zj@...edance.com>
To:     dhowells@...hat.com, xiang@...nel.org, jefflexu@...ux.alibaba.com
Cc:     linux-cachefs@...hat.com, linux-erofs@...ts.ozlabs.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        yinxin.x@...edance.com, Jia Zhu <zhujia.zj@...edance.com>
Subject: [RFC PATCH 4/5] cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode

Don't trigger EPOLLIN when there are only reopening read requests in
xarray.

Suggested-by: Xin Yin <yinxin.x@...edance.com>
Signed-off-by: Jia Zhu <zhujia.zj@...edance.com>
---
 fs/cachefiles/daemon.c   | 13 +++++++++++--
 fs/cachefiles/internal.h | 12 ++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index aa4efcabb5e3..c74bd1f4ecf5 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -355,14 +355,23 @@ static __poll_t cachefiles_daemon_poll(struct file *file,
 					   struct poll_table_struct *poll)
 {
 	struct cachefiles_cache *cache = file->private_data;
+	struct xarray *xa = &cache->reqs;
+	struct cachefiles_req *req;
+	unsigned long index;
 	__poll_t mask;
 
 	poll_wait(file, &cache->daemon_pollwq, poll);
 	mask = 0;
 
 	if (cachefiles_in_ondemand_mode(cache)) {
-		if (!xa_empty(&cache->reqs))
-			mask |= EPOLLIN;
+		if (!xa_empty(xa)) {
+			xa_for_each_marked(xa, index, req, CACHEFILES_REQ_NEW) {
+				if (!cachefiles_ondemand_is_reopening_read(req)) {
+					mask |= EPOLLIN;
+					break;
+				}
+			}
+		}
 	} else {
 		if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
 			mask |= EPOLLIN;
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 66bbd4f1d22a..b4af67f1cbd6 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -344,6 +344,13 @@ cachefiles_ondemand_set_object_##_state(struct cachefiles_object *object) \
 CACHEFILES_OBJECT_STATE_FUNCS(open);
 CACHEFILES_OBJECT_STATE_FUNCS(close);
 CACHEFILES_OBJECT_STATE_FUNCS(reopening);
+
+static inline bool cachefiles_ondemand_is_reopening_read(struct cachefiles_req *req)
+{
+	return cachefiles_ondemand_object_is_reopening(req->object) &&
+			req->msg.opcode == CACHEFILES_OP_READ;
+}
+
 #else
 #define CACHEFILES_ONDEMAND_OBJINFO(object)	NULL
 
@@ -373,6 +380,11 @@ static inline int cachefiles_ondemand_init_obj_info(struct cachefiles_object *ob
 {
 	return 0;
 }
+
+static inline bool cachefiles_ondemand_is_reopening_read(struct cachefiles_req *req)
+{
+	return false;
+}
 #endif
 
 /*
-- 
2.20.1