linux-kernel - [PATCH V6 RESEND 4/5] cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode

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Message-Id: <20231120041422.75170-5-zhujia.zj@bytedance.com>
Date:   Mon, 20 Nov 2023 12:14:21 +0800
From:   Jia Zhu <zhujia.zj@...edance.com>
To:     dhowells@...hat.com, linux-cachefs@...hat.com
Cc:     linux-erofs@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, jefflexu@...ux.alibaba.com,
        hsiangkao@...ux.alibaba.com, Jia Zhu <zhujia.zj@...edance.com>,
        Xin Yin <yinxin.x@...edance.com>
Subject: [PATCH V6 RESEND 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>
Reviewed-by: Jingbo Xu <jefflexu@...ux.alibaba.com>
---
 fs/cachefiles/daemon.c   | 14 ++++++++++++--
 fs/cachefiles/internal.h | 12 ++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index aa4efcabb5e3..70caa1946207 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -355,14 +355,24 @@ static __poll_t cachefiles_daemon_poll(struct file *file,
 					   struct poll_table_struct *poll)
 {
 	struct cachefiles_cache *cache = file->private_data;
+	XA_STATE(xas, &cache->reqs, 0);
+	struct cachefiles_req *req;
 	__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(&cache->reqs)) {
+			rcu_read_lock();
+			xas_for_each_marked(&xas, req, ULONG_MAX, CACHEFILES_REQ_NEW) {
+				if (!cachefiles_ondemand_is_reopening_read(req)) {
+					mask |= EPOLLIN;
+					break;
+				}
+			}
+			rcu_read_unlock();
+		}
 	} else {
 		if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
 			mask |= EPOLLIN;
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index b9a90f1a0c01..26e5f8f123ef 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -329,6 +329,13 @@ cachefiles_ondemand_set_object_##_state(struct cachefiles_object *object) \
 CACHEFILES_OBJECT_STATE_FUNCS(open, OPEN);
 CACHEFILES_OBJECT_STATE_FUNCS(close, CLOSE);
 CACHEFILES_OBJECT_STATE_FUNCS(reopening, 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
 static inline ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
 					char __user *_buffer, size_t buflen)
@@ -359,6 +366,11 @@ static inline int cachefiles_ondemand_init_obj_info(struct cachefiles_object *ob
 static inline void cachefiles_ondemand_deinit_obj_info(struct cachefiles_object *obj)
 {
 }
+
+static inline bool cachefiles_ondemand_is_reopening_read(struct cachefiles_req *req)
+{
+	return false;
+}
 #endif
 
 /*
-- 
2.20.1