linux-kernel - [RFC PATCH 5/5] cachefiles: add restore command to recover inflight ondemand read requests

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Message-Id: <20220818135204.49878-6-zhujia.zj@bytedance.com>
Date:   Thu, 18 Aug 2022 21:52:04 +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>,
        Gao Xiang <hsiangkao@...ux.alibaba.com>
Subject: [RFC PATCH 5/5] cachefiles: add restore command to recover inflight ondemand read requests

Previously, in ondemand read scenario, if the anonymous fd was closed by
user daemon, inflight and subsequent read requests would return EIO.
As long as the device connection is not released, user daemon can hold
and restore inflight requests by setting the request flag to
CACHEFILES_REQ_NEW.

Suggested-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
Signed-off-by: Jia Zhu <zhujia.zj@...edance.com>
Signed-off-by: Xin Yin <yinxin.x@...edance.com>
---
 fs/cachefiles/daemon.c   |  1 +
 fs/cachefiles/internal.h |  3 +++
 fs/cachefiles/ondemand.c | 23 +++++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index c74bd1f4ecf5..014369266cb2 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -77,6 +77,7 @@ static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
 	{ "tag",	cachefiles_daemon_tag		},
 #ifdef CONFIG_CACHEFILES_ONDEMAND
 	{ "copen",	cachefiles_ondemand_copen	},
+	{ "restore",	cachefiles_ondemand_restore	},
 #endif
 	{ "",		NULL				}
 };
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index b4af67f1cbd6..d504c61a5f03 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -303,6 +303,9 @@ extern ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
 extern int cachefiles_ondemand_copen(struct cachefiles_cache *cache,
 				     char *args);
 
+extern int cachefiles_ondemand_restore(struct cachefiles_cache *cache,
+					char *args);
+
 extern int cachefiles_ondemand_init_object(struct cachefiles_object *object);
 extern void cachefiles_ondemand_clean_object(struct cachefiles_object *object);
 
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 79ffb19380cd..5b1c447da976 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -178,6 +178,29 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
 	return ret;
 }
 
+int cachefiles_ondemand_restore(struct cachefiles_cache *cache, char *args)
+{
+	struct cachefiles_req *req;
+
+	XA_STATE(xas, &cache->reqs, 0);
+
+	if (!test_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags))
+		return -EOPNOTSUPP;
+
+	/*
+	 * Search the requests which being processed before
+	 * the user daemon crashed.
+	 * Set the CACHEFILES_REQ_NEW flag and user daemon will reprocess it.
+	 */
+	xas_lock(&xas);
+	xas_for_each(&xas, req, ULONG_MAX)
+		xas_set_mark(&xas, CACHEFILES_REQ_NEW);
+	xas_unlock(&xas);
+
+	wake_up_all(&cache->daemon_pollwq);
+	return 0;
+}
+
 static int cachefiles_ondemand_get_fd(struct cachefiles_req *req)
 {
 	struct cachefiles_object *object;
-- 
2.20.1