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Message-Id: <20220818135204.49878-2-zhujia.zj@bytedance.com>
Date: Thu, 18 Aug 2022 21:52:00 +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 1/5] cachefiles: introduce object ondemand state
Previously, @ondemand_id field was used not only to identify ondemand
state of the object, but also to represent the index of the xarray.
This commit introduces @state field to decouple the role of @ondemand_id
and adds helpers to access it.
Signed-off-by: Jia Zhu <zhujia.zj@...edance.com>
Reviewed-by: Xin Yin <yinxin.x@...edance.com>
---
fs/cachefiles/internal.h | 33 +++++++++++++++++++++++++++++++++
fs/cachefiles/ondemand.c | 15 +++++++++------
2 files changed, 42 insertions(+), 6 deletions(-)
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 6cba2c6de2f9..6661b3e361da 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -17,6 +17,7 @@
#include <linux/security.h>
#include <linux/xarray.h>
#include <linux/cachefiles.h>
+#include <linux/atomic.h>
#define CACHEFILES_DIO_BLOCK_SIZE 4096
@@ -44,6 +45,11 @@ struct cachefiles_volume {
struct dentry *fanout[256]; /* Fanout subdirs */
};
+enum cachefiles_object_state {
+ CACHEFILES_ONDEMAND_OBJSTATE_close, /* Anonymous fd closed by daemon or initial state */
+ CACHEFILES_ONDEMAND_OBJSTATE_open, /* Anonymous fd associated with object is available */
+};
+
/*
* Backing file state.
*/
@@ -62,6 +68,7 @@ struct cachefiles_object {
#define CACHEFILES_OBJECT_USING_TMPFILE 0 /* Have an unlinked tmpfile */
#ifdef CONFIG_CACHEFILES_ONDEMAND
int ondemand_id;
+ enum cachefiles_object_state state;
#endif
};
@@ -295,6 +302,32 @@ extern void cachefiles_ondemand_clean_object(struct cachefiles_object *object);
extern int cachefiles_ondemand_read(struct cachefiles_object *object,
loff_t pos, size_t len);
+#define CACHEFILES_OBJECT_STATE_FUNCS(_state) \
+static inline bool \
+cachefiles_ondemand_object_is_##_state(const struct cachefiles_object *object) \
+{ \
+ /*
+ * Pairs with smp_store_release() in set_object_##_state()
+ * I.e. another task can publish state concurrently, by executing
+ * a RELEASE barrier. We need to use smp_load_acquire() here
+ * to safely ACQUIRE the memory the other task published.
+ */ \
+ return smp_load_acquire(&object->state) == CACHEFILES_ONDEMAND_OBJSTATE_##_state; \
+} \
+ \
+static inline void \
+cachefiles_ondemand_set_object_##_state(struct cachefiles_object *object) \
+{ \
+ /*
+ * Pairs with smp_load_acquire() in object_is_##_state()
+ * I.e. here we publish a state with a RELEASE barrier
+ * so that concurrent tasks can ACQUIRE it.
+ */ \
+ smp_store_release(&object->state, CACHEFILES_ONDEMAND_OBJSTATE_##_state); \
+}
+
+CACHEFILES_OBJECT_STATE_FUNCS(open);
+CACHEFILES_OBJECT_STATE_FUNCS(close);
#else
static inline ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
char __user *_buffer, size_t buflen)
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 1fee702d5529..e3155a5f32e4 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -15,6 +15,7 @@ static int cachefiles_ondemand_fd_release(struct inode *inode,
xa_lock(&cache->reqs);
object->ondemand_id = CACHEFILES_ONDEMAND_ID_CLOSED;
+ cachefiles_ondemand_set_object_close(object);
/*
* Flush all pending READ requests since their completion depends on
@@ -172,6 +173,8 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags);
trace_cachefiles_ondemand_copen(req->object, id, size);
+ cachefiles_ondemand_set_object_open(req->object);
+
out:
complete(&req->done);
return ret;
@@ -353,7 +356,8 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
/* coupled with the barrier in cachefiles_flush_reqs() */
smp_mb();
- if (opcode != CACHEFILES_OP_OPEN && object->ondemand_id <= 0) {
+ if (opcode != CACHEFILES_OP_OPEN &&
+ !cachefiles_ondemand_object_is_open(object)) {
WARN_ON_ONCE(object->ondemand_id == 0);
xas_unlock(&xas);
ret = -EIO;
@@ -420,7 +424,6 @@ static int cachefiles_ondemand_init_close_req(struct cachefiles_req *req,
void *private)
{
struct cachefiles_object *object = req->object;
- int object_id = object->ondemand_id;
/*
* It's possible that object id is still 0 if the cookie looking up
@@ -428,10 +431,10 @@ static int cachefiles_ondemand_init_close_req(struct cachefiles_req *req,
* sending CLOSE request for CACHEFILES_ONDEMAND_ID_CLOSED, which means
* anon_fd has already been closed.
*/
- if (object_id <= 0)
+ if (!cachefiles_ondemand_object_is_open(object))
return -ENOENT;
- req->msg.object_id = object_id;
+ req->msg.object_id = object->ondemand_id;
trace_cachefiles_ondemand_close(object, &req->msg);
return 0;
}
@@ -450,7 +453,7 @@ static int cachefiles_ondemand_init_read_req(struct cachefiles_req *req,
int object_id = object->ondemand_id;
/* Stop enqueuing requests when daemon has closed anon_fd. */
- if (object_id <= 0) {
+ if (!cachefiles_ondemand_object_is_open(object)) {
WARN_ON_ONCE(object_id == 0);
pr_info_once("READ: anonymous fd closed prematurely.\n");
return -EIO;
@@ -475,7 +478,7 @@ int cachefiles_ondemand_init_object(struct cachefiles_object *object)
* creating a new tmpfile as the cache file. Reuse the previously
* allocated object ID if any.
*/
- if (object->ondemand_id > 0)
+ if (cachefiles_ondemand_object_is_open(object))
return 0;
volume_key_size = volume->key[0] + 1;
--
2.20.1
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